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Research seminars in Polar Social Science and Humanities: previous seminars

Research seminars in Polar Social Science and Humanities: previous seminars

Here is an archive of previous seminar listings:

Scott Polar Research Institute - Physical Sciences Seminar: archive

Return to the list of forthcoming seminars.

# Wednesday 15th March 2017, 4.30pm - Dr. Jerome A. Neufeld, Department of Earth Sciences & DAMTP, University of Cambridge
Controls on the rapid drainage of supraglacial lakes
Venue: Scott Polar Research Institute, main lecture theatre

TBC

# Wednesday 1st March 2017, 4.30pm - Dr. David Amblas, Scott Polar Research Institute, University of Cambridge
Submarine canyons in polar and temperate margins: shaping mechanisms and long-term evolution
Venue: Scott Polar Research Institute, main lecture theatre

Submarine canyons are deep incisions observed along most of the world’s continental margins. Their topographic relief is as dramatic as that of any canyon or river valley on land but is hidden beneath the surface of the ocean. Our knowledge of canyons has therefore come primarily from remote sensing and sampling, and has involved contributions from various oceanographic disciplines. Canyons represent a critical link between coastal and shelf waters and abyssal depths; water masses, sediment, nutrients, and even litter and pollutants are carried through them. Advances in technology continue to provide new insights into canyon environments by pushing the frontier of deep marine observations and measurements. In this talk we will describe the main geomorphic features of submarine canyons and what is known about their formation and the fundamental processes controlling their long-term form and dynamics. We will present a simple model for the long-profile curvature of submarine canyons, inspired in fluvial systems, that includes the combined effects of turbidity currents and background (i.e. hemipelagic) sedimentation, and compare the range of model profile shapes with those observed in present-day continental slopes, 3D seismic data and experimental models. Finally we will introduce a relatively poorly known geomorphic agent in submarine slopes: the cascading of dense shelf waters. This oceanographic phenomenon occurs seasonally and only in certain polar and temperate margins through cooling, evaporation, sea-ice freezing and/or deep sub-ice shelf melting. It involves the massive transfer of energy and matter from shallow to deep waters and can result in appreciable sediment erosion and downslope transport. We will discuss about the distribution and hydrodynamics of these flows, its far-reaching effects on the seafloor relief, and whether it should be included in the classic turbidity current and mass-gravity transport continuum of processes and deposits formulated more than 70 years ago.

# Wednesday 23rd November 2016, 4.30pm - Daniel Goldberg (University of Edinburgh)
Ice shelf-ocean interactions: self-organisation and instability
Venue: Scott Polar Research Institute, main lecture theatre

The ice shelves bordering the Antarctic coastline play an important role in both the hydrography of the Southern Ocean and the mass balance and configuration of the Antarctic Ice Sheet. On the oceanographic side, ice shelves provide a surface boundary condition that is different than either open ocean or sea ice, with melting and freezing rates determined by small-scale turbulence and shelf-scale circulation, the latter in turn influenced by melting and freezing rates as well as ice shelf thickness. In some instances under-shelf processes significantly influence open-ocean hydrological and biogeochemical properties.

On the glaciological side, the ice shelves control the distribution of normal stresses at the grounding line, which in turn affects ice mass flux from the continent. Thus ice shelves provide a pathway for the heat content of the ocean to cause changes in continental ice sheets — which in turn feeds back on circulation by modifying the shape of the ice shelf cavity. In the case of rapidly-evolving ice shelves exposed to warm Circumpolar Deep Water, numerical modelling of such interaction presents a large challenge, since most ocean general circulation models (OGCMs) are not designed to allow for changing boundaries.

I will first present results from my own studies which examined such interactions using an old method of ice-ocean coupling — an “asynchronous” (or “dump-and-restart”) approach, and discuss the results of the study as well as strengths and weaknesses of the asynchronous approach and why it is not ideal as we move forward from process modelling to global predictions of coupled ice-ocean behaviour. I will then discuss the development of a new, synchronously-coupled ice sheet-ocean model, the difficulties and what is done to address them, and some preliminary experiments with this framework, yielding interesting results.

A common theme arising from the old work and new is the fact that, from the ice sheet stability perspective, ice shelf thinning due to melting is not solely important close the grounding line, as commonly thought, and may be vitally important to constrain and model in other regions of ice shelves commonly overlooked. Luckily, new observing platforms are being developed that may enable us to do just this.

# Tuesday 8th November 2016, 1.00pm - Twila Moon (University of Bristol)
NOTE!!! UNUSUAL DAY (TUE) AND TIME (1-2 pm)
Greenland Ice Sheet motion, ice-ocean interactions, and other ambitions to understand the cryosphere
Venue: Scott Polar Research Institute, Seminar Room

Ice sheet mass loss has wide-ranging impacts, from increasing global sea level to changing regional ocean characteristics via heightened freshwater flux to influencing local ecosystem function. The modern satellite era provides unprecedented opportunities to understand ice sheet behaviour and its associated effects. Dr. Moon will discuss on-going work to understand fast moving outlet glaciers that connect the interior of the Greenland Ice Sheet to the ocean and new research determining the near-glacier fingerprint of freshwater flux once ice is lost from the ice sheet. Her research explores seasonal to decadal timescales, taking advantage of remote sensing instruments to understand changes across the entire ice sheet on the level of detail of individual glaciers and fjord systems. Along with discussing connections between rapidly changing ice sheet areas and broader environmental system, she will highlight new datasets that continue to increase scientists’ skill at characterizing, understanding, and predicting ice sheet change in a warming world.

# Wednesday 26th October 2016, 4.30pm - Antonio Abellan
Linking ice-cliff and rock-slope failures
Venue: Scott Polar Research Institute, Seminar Room

Shear failure of ice during glacier frontal calving events shares many characteristics of rock-slope failures (RSFs) in high mountain areas; Nevertheless, the investigation of gravity-driven instabilities that shape rock cliffs and glacier fronts have been dissociated research topics so far.

The dynamic processes shaping the termini of glacier fronts – and thus directly a major contribution to sea level rise – have attracted the attention of the scientific community. Although recent research has shed light on the dynamics of tidewater glaciers, a full understanding of the calving phenomena is still elusive. This epistemic uncertainty may be related not only to the highly non-linear dynamics of the calving phenomena, but also to the 2D nature and the limited spatial and temporal resolution of the techniques typically used for investigating the rapidly evolving glacier front.

Through my two year Marie-Curie H2020 project, I am progressively adapting my previous research interests (4D investigation of RSF using Terrestrial LiDAR and Structure-from-Motion photogrammetry) to the investigation of glacier front dynamics, aiming to gain understanding of the processes leading to discrete calving events, to adapt landslide modelling techniques for investigating glacier response to external forces and to explore the apparent randomness of calving events. Working in the reverse direction, this research project will allow me to analyse a plethora of recorded calving events in order to shed light on natural slope evolution.

# Wednesday 12th October 2016, 4.30pm - Nial Peters
A journey into Erebus volcano, Antarctica
Venue: Scott Polar Research Institute, Seminar Room

Erebus volcano is a 3794 m high stratovolcano located on Ross Island in Antarctica. It is the most southerly active volcano in the world, exhibiting persistent degassing and occasional Strombolian eruptions. Additionally, Erebus hosts one of the few active lava lakes in the world making it a prime site for scientific study. The Mount Erebus Volcano Observatory is a long running project to study and monitor the volcano. In this talk I will give an overview of how fieldwork is conducted at Erebus and introduce some of the research that has been undertaken by Mount Erebus Volcano Observatory in recent years.

# Tuesday 15th March 2016, 4.30pm - Brice Noël (Utrecht University)
NOTE UNUSUAL DAY AND ROOM
High-resolution modelling of polar climates using the regional climate model RACMO2.3
Venue: Scott Polar Research Institute, Seminar Room

Monitoring the current climate in polar regions such as the Greenland (GrIS) and Antarctic ice sheets (AIS), encompasses many limitations. Automatic weather stations, stake sites, firn and ice cores located all over the accumulation and ablation zones of the GrIS and AIS only measure point climate conditions, not necessarily representative of larger areas. Since the late 50s, airborne and satellite measurements provide spatially continuous coverage of the ice sheets at relatively low resolutions. These limitations can be solved using regional climate models (RCMs), covering the entire ice sheets at high spatial and temporal resolutions, typically 5 km to 30 km at a hourly-to-daily time scale. The polar version of the Regional Atmospheric Climate Model (RACMO2) is adapted to specifically model the surface mass balance (SMB) and energy budget (SEB) over Greenland, Antarctica and other glaciated regions. RACMO2 incorporates a multilayer snow module, interactively coupled to the atmosphere, that simulates meltwater percolation, refreezing and runoff; an albedo scheme based on prognostic snow grain size, and a drifting snow routine, accounting for interactions between drifting snow, the surface and the lower atmosphere. RACMO2 has been thoroughly evaluated in many glaciated regions including Greenland, Canadian Arctic, Svalbard, Patagonia and Antarctica.

Recently, RACMO2 has been updated from version 2.1 to 2.3. These updates include major modifications in the description of cloud microphysics, surface and boundary layer turbulence, and radiation transport. Most notably, the new cloud scheme enables ice supersaturation, which prolongs the vapour phase at low temperatures and delays cloud formation at higher elevations. Furthermore, the auto-conversion coefficient, controlling the conversion rate of water-vapour into precipitation in convective clouds, has been modified to favour solid at the expense of liquid precipitation. The implications of these physics updates on modelled SMB components are discussed for Greenland (1958-2014, 11 km) and Antarctica (1979-2014, 27 km). In addition, RACMO2.3 performances improve on the previous version 2.1; the evaluation against observations shows a better agreement for both the GrIS and AIS.

Despite physics improvements, the current spatial resolution in RACMO2.3 remains too coarse to represent the local variability in SMB components, especially over narrow glaciated features, i.e. the Antarctic Peninsula (AP), the GrIS and surrounding ice caps (GICs). The relatively low-resolution surface elevation prescribed in RACMO2.3 contributes to underestimate topographically-forced precipitation over the mountainous regions of the AP. In Greenland, underestimated elevation and thus near-surface temperature result in too low surface melt and runoff at the GrIS rough margins. To address these issues, a high-resolution simulation at 5 km is carried out over the AP for the period 1979-2014, allowing for a better representation of local precipitation patterns. Another approach is applied in Greenland, where the data of RACMO2.3 at 11 km (1958-2014) are statistically downscaled to the topography and ice mask of a down-sampled version of the GIMP DEM at 1 km, using a daily specific elevation dependent technique. This method allows to provide more realistic SMB patterns over Greenland narrow ablation zones, marginal outlet glaciers and peripheral ice caps, owing to enhanced runoff at the GrIS margins. These high-resolution SMB products are evaluated against ablation/accumulation measurements collected in the AP and Greenland. Finally, the current GICs contribution to the total GrIS mass loss is estimated based on the 1 km dataset of daily downscaled SMB components.

# Wednesday 2nd March 2016, 4.30pm - Donald Slater (University of Edinburgh)
Modelling ice-ocean interaction at Greenland’s tidewater glaciers
Venue: Scott Polar Research Institute, main lecture theatre

Observations of the mass balance of the Greenland Ice Sheet over recent decades have shown significant losses at the coastal margins, much of which has been attributed to the thinning, speed-up and retreat of tidewater glaciers. The synchronous and widespread nature of these changes is indicative of a common climatic forcing, and due to a roughly simultaneous subsurface warming of the ocean around Greenland, the ocean is the leading candidate for driving the changes observed at marine-terminating glaciers around Greenland. However the processes by which the ocean interacts with these glaciers are poorly understood, severely hampering efforts to project glacier behaviour into the future and ultimately to predict Greenland’s future contribution to sea level rise. Here, we take an ocean modelling approach to exploring the processes by which the ocean interacts with tidewater glaciers.
We use both a simple theoretical model (buoyant plume theory) and a complex numerical model (MITgcm) to explore controls on submarine melt rates at tidewater glaciers, identifying fjord stratification, subglacial discharge and subglacial hydrology as the key variables which determine the rate and pattern of submarine melting. Of the three variables, subglacial hydrology is the least understood and we describe a novel attempt to constrain subglacial hydrology at Kangiata Nunata Sermia, a large tidewater glacier in southwest Greenland. We finally consider the effect of submarine melting on glacier dynamics by implementing a tidewater glacier as a moving boundary within MITgcm. Results show melt undercutting of the calving front which may drive calving and glacier dynamics at smaller tidewater glaciers. However at large tidewater glaciers this process may not proceed sufficiently quickly to influence glacier dynamics, suggesting we need to consider other processes to explain the recent changes observed at Greenland’s largest and fastest flowing tidewater glaciers.

# Wednesday 27th May 2015, 4.30pm - Mai Winstrup (University of Wahington)
Ice cores: development of time scales and some applications
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Wednesday 13th May 2015, 4.30pm - Brice Rea (University of Aberdeen)
Evidence for, and implications of, a grounded ice sheet in the Central North Sea during the Pleistocene
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Thursday 19th March 2015, 4.30pm - Olivier Gagliardini (Laboratoire de glaciologie et géophysique de l’environnement)
NOTE: THIS TALK IS ON A THURSDAY
Marine terminating glaciers within Elmer/Ice: model and applications
Venue: Scott Polar Research Institute, main lecture theatre

Over the last two decades, new observing systems have shown that the Greenland and Antarctic ice sheets have contributed 20% of the global sea level rise (SLR). Ice sheets impact sea level through variations of their surface mass balance and their ice discharge. For Antarctica, no trend in snow accumulation has been identified for the entire Antarctic ice sheet over the recent decades. In contrast, a number of outlet glaciers have continuously accelerated, particularly in Western Antarctica. A consensus has emerged on the role of the ocean as a driver of the observed acceleration: marine melt underneath the ice shelves drives changes in ice dynamics by decreasing the buttressing. Upon a retreat has been initiated, the bedrock configuration plays also a key role in controlling the rate and extend of the grounding line retreat.

Prediction of the dynamical contribution to SLR of ice-sheets require the development of ice flow models capable to account for these various processes. In this presentation, I will make an overview of the modelling effort performed these last years using the ice-sheet / ice flow finite element model Elmer/Ice. I will focus on the grounding line dynamics and associated processes: basal melting below the ice-shelf, basal friction, calving. I will present the processes already included in Elmer/Ice and the corresponding applications. I will then present the missing processes that should be implemented in the near future developments.

# Wednesday 25th February 2015, 4.30pm - Coen Hodstede (Alfred Wegener Institute)
Seismic survey considerations in glaciology
Venue: Scott Polar Research Institute, main lecture theatre

Seismic surveying of glaciers give both englacial and subglacial physical information and is as such an important tool in glaciology. In comparison with the collection of radar data, mainly performed from airborne platforms, seismic data acquisition is a time consuming process practiced in small survey areas and used less frequent. Over the last six years, Alfred Wegener Institute developed an effective strategy to collect seismic data on glaciers, ice sheets and ice shelves, at a high production rate with a small team (three to five persons) at relatively little effort. The survey areas varied from a 4500m high Alpine saddle to several hundreds of kilometers long transects on the Antarctic ice sheet and adjacent ice shelf. Each survey area has its own possibilities and limitations in the survey set-up. I will reflect upon the hardware, methods, advantages and shortcomings of the performed surveys and will discuss some results. In particular I will focus on the results of two seismic surveys performed in the ablation zone on the West coast of the Greenland Ice Sheet. The main objective here was to characterize the subglacial conditions of the glacier. One site was Russell glacier where ice terminates on land, a second site was Store Glacier, a tidewater glacier in Uummannaq Fjord. In both areas the subglacial hydrology probably plays a key role in the ice dynamics as ice velocities pick up in summer.

# Wednesday 11th February 2015, 4.30pm - Christoph Mayer (Bavarian Academy of Sciences and Humanities)
The last ten years of glacier observation in the Karakoram
Venue: Scott Polar Research Institute, main lecture theatre

TBA

# Wednesday 28th January 2015, 4.30pm - Tom Cowton (University of Sheffield)
Controls on the stability of Greenland’s tidewater glaciers: the impact of runoff on fjord circulation and termini melt rates
Venue: Scott Polar Research Institute, main lecture theatre

Observations suggest that oceanic warming may cause phases of rapid retreat and acceleration at Greenland’s marine-terminating outlet glaciers, significantly increasing the rate of mass loss from the ice sheet. In this scenario, retreat may be triggered by increased submarine melting at the glacier termini. Due to the inaccessibility of this submarine environment however, little is known about the rate of melting or how it is influenced by oceanic and atmospheric processes. This seminar will focus on the potential role of meltwater runoff from these glaciers in stimulating submarine melting. Firstly, a high resolution general circulation model (MITgcm) is used to explore the role of near-terminus hydrology on submarine melt rate. It has been shown previously that freshwater input increases melting by driving a vigorous upwelling circulation; we find that the importance of this process is strongly dependent on the subglacial drainage morphology, with more distributed drainage systems driving dramatically higher melt rates. We then explore the influence of glacial runoff on the wider circulation of the fjords. Through simulation of Kangerdlugssuaq Fjord, east Greenland, we find that this freshwater input drives a strong, two-celled overturning circulation capable of transporting warm ocean waters to the fjord head on sub-seasonal timescales. This circulation may play a significant role in maintaining the connection between the ocean and the ice sheet, permitting glaciers to respond rapidly to changing ocean properties despite long and complex fjord systems.

# Wednesday 26th November 2014, 4.30pm - Martin Siegert (Imperial College)
Assessing the vulnerability of the Weddell Sea sector of West Antarctic Ice Sheet to future changes
Venue: Scott Polar Research Institute, main lecture theatre

Institute and Möller Ice Streams (IMIS) drain 20% of the ice from West Antarctica, forming major contributors to the Weddell Sea Sector (WSS) of Antarctica. Before 2010, relative to the other major West Antarctic drainage basins feeding the Ross and Amundsen Seas, the WSS rated as West Antarctica’s “pole of ignorance” concerning past and present glaciological conditions and sensitivity to change. Underpinned by the hypothesis that IMIS may be underlain by deformable marine sediments analogous to the Siple Coast ice streams, and may therefore be prone to similar ice-dynamical
instabilities, a comprehensive aerogeophysical survey of IMIS was undertaken in the austral summer 2010/11 under the auspices of NERC’s Antarctic Funding Initiative. I will present a synthesis of
findings from the new data.

We now know that the lower portion of IMIS is underlain by a deep basin filled with marine sediments and sloping inland, rendering much of the region vulnerable to the marine ice-sheet instability. Inland of the marine basin, the subglacial terrain is composed of mixed roughness. This reflects, in part, a significant tectonic signature of faults, structural lineaments and Jurassic intrusions likely emplaced during opening of the Weddell Sea Rift.

Superimposed is a geomorphological signature testifying to the
basin’s experience of waxing and waning ice cover over glacial cycles. An extensive plateau inland of the deep basin was likely created under ice-free conditions during the mid-Miocene (17-15 Ma), while large channels cut into the bedrock testify to the presence of thinner, temperate ice cover which allowed supraglacial subglacial connections during the Pliocene (5.3 – 2.6 Ma).

Today the regional ice cover is thinning steadily from the Last Glacial Maximum (20 ka). Patterns of englacial layering suggest that in the less topographically constrained western and southern parts of IMIS the spatial configuration of ice has changed considerably, likely in response to thinning and increased grounding of the Bungenstock Ice Rise and a proportional increased to drainage of IMIS via Institute Ice Stream. Multiple lines of evidence show that IMIS is today underlain by a highly dynamic subglacial hydrological system which may facilitate further changes to ice flow. Modelling suggests that of all the WSS ice
streams, IMIS may be particularly susceptible to considerable change after only a projected moderate
increase in ice-shelf melt at its grounding zone.

# Wednesday 12th November 2014, 1.00pm - Peter Talling (National Oceanography Centre, Southampton)
NOTE UNUSUAL TIME: 1-2 PM
Frequency and triggers of huge underwater landslides - and their relationship to climate change and sediment delivery from ice streams
Venue: Scott Polar Research Institute, main lecture theatre

Submarine landslides can be far larger than even the largest terrestrial landslide. For instance, the Storegga Slide that occurred 8,200 years ago offshore Norway contained over 3,000 cubic kilometers of material, and is bigger than Scotland. It generated a major tsunami that inundated surrounding coastlines to heights of up to 3-20m above sea level. The Storegga Slide coincided with the last major abrupt climate change – the so called 8.2ka event. This talk will explore the evidence for (and against) the links between major submarine landslides and climate change, and pulses of sediment delivery by cross-shelf ice streams. Perhaps the most remarkable feature of these huge underwater slides is that they occur on slopes of <2 degrees, which are about as flat as a Premiership soccer pitch. The talk will also explore how such widespread slope failure can be triggered on such remarkably low gradients. The talk will contain preliminary results from a NERC funded research cruise in July 2014, which successfully collected 88 cores and > 1,200km of swath bathymetry lines from the Nordic Seas. It will conclude with recent work on direct monitoring of other types of sediment mass flow (turbidity currents), which it is hoped to extend to glacially fed systems.

# Wednesday 29th October 2014, 4.30pm - Sam Doyle (University of Aberystwyth)
Supraglacial lake drainage and ice flow acceleration in Greenland
Venue: Scott Polar Research Institute, main lecture theatre

The rapid in situ drainage of supraglacial lakes drives transient accelerations in ice flow on the Greenland Ice Sheet and creates the surface-to-bed hydraulic pathways that deliver surface melt water to the ice-bed interface throughout the remainder of the melt season. Records of lake discharge, ice motion and passive seismicity capture the rapid drainage of a ∼ 4 km2 supraglacial lake through 1.1-km-thick ice in West Greenland. These observations allow detailed insight into the opening and closure of hydraulically-driven fractures and the transient acceleration in ice flow caused by the delivery of large volumes of water to the bed. Furthermore, the observed expansion of surface melt and supraglacial lakes to higher elevations in recent warm summers correlates with an acceleration in annually-averaged ice flow in the Greenland ice sheet’s interior. These observations contrast with the prevailing hypothesis that annually-averaged flow in the ablation area is regulated by slower winter flow following warmer, faster summers.

# Wednesday 15th October 2014, 4.30pm - Alv Egeland (Department of Physics, University of Oslo)
The Importance to Solar-Terrestrial Physics of Amundsen’s and Scott’s Conjugate Observations of the Earth’s Magnetic Field
Venue: Scott Polar Research Institute, main lecture theatre

The ships Gjøa and Discovery sailed to the opposite ends of the Earth during the years 1902-06. Among the scientific goals of the two expeditions, was that of documenting the nature of the high latitude geomagnetic field and especially the location of the respective north and south magnetic dip poles (MDP). Both expeditions overwintered within 200 km of their respective poles, and, unwittingly, at nearly the same geomagnetic longitude, 240°. Thus, they were camped at opposite ends of the same geomagnetic field line. Their unique magnetic observations at Gjøahavn and Cape Armitage more than 100 years ago were at the same local geomagnetic time, but they were separated in local solar time by ~6 hours because of the tilt of the geomagnetic axis with respect to the geographic axis. This is important to the interpretation of the data, especially when the relationship of the high latitude geomagnetic field to the interplanetary magnetic field (IMF), is examined.

Indeed, the combined observations offer a glimpse of the solar wind fifty years before it was known to exist. After a brief review of the characteristics of the Earth’s magnetic field, the main facts found on diurnal and seasonal variations of the field at Gjøahavn will be compared with similar observations at Cape Armitage. These are unique observations of the geomagnetic field in the polar-regions decades before modern polar observatories were established. After comparing the data sets of the two expeditions and subjecting the data to modern analysis, we reached the following conclusions:

Amundsen and Scott were the first to demonstrate that the north and south magnetic dip-poles do not have a permanent location, but move their position in a regular manner on average. The activity was more intense in the local summer than in the local winter. The wavelike, diurnal variation in the field at Cape Armitage mimics the Gjøahavn data almost exactly.

The quality of these magnetic observations may be shown to be equal to that of the late 20th century observations by subjecting them to analytical techniques showing the newly discovered relationship between the diurnal variation of high latitude magnetic observations and the direction of the interplanetary magnetic field in the solar wind called the .Svalgard-Mansurov effect (SME). From this comparison, we found that the solar wind and its temporal variations were similar to what we observe today. For stations near 80 degrees magnetic latitude we conclude that the SME is not a UT effect, but maximizes near magnetic noon.

Our motivation for this study has been to illuminate the contributions of Amundsen and Scott as scientists. Their contributions are important to the world-wide survey of the Earth’s magnetic field in the early 20th century.

# Thursday 8th May 2014, 4.30pm - Susan Conway
The martian Cryosphere: there’s more ice than we thought!
Venue: Scott Polar Research Institute, main lecture theatre

I will give a general introduction to the martian cryosphere, from the large polar caps, to kilometre-scale glacier-like features down to the mid-latitude ground-ice. I’ll talk about some new discoveries that have revealed that Mars has more ice outside the polar regions than previously thought: including evidence from orbital ground penetrating radar, high resolution images and topographic data. These discoveries are important for understanding the nature of Mars’ recent climate oscillations and generating liquid water at its surface.

# Wednesday 23rd April 2014, 4.30pm - Dr Mauro Werder, University of Bristol
The pressure melting point of ice and Jakobshavn Isbrae's fast flow
Venue: Scott Polar Research Institute, main lecture theatre

Jakobshavn Isbrae and many other outlet glaciers of present and past ice sheets lie in deep troughs which often have several over deepened sections. The subglacial drainage system of such glaciers is heavily influenced by two effects caused by the pressure dependence of the melting point of water. The melting point decreases with increasing water pressure, this enhances wall-melt in downward sloping channels and diminishes wall-melt in upward sloping channels. Thus the first effect is the well known shutdown of channels on steep adverse bed slopes of overdeepenings and the associated high water pressure/low effective pressure. The second effect is a 2D effect and has not received much/any attention so far: the orientation of a channel will be deflected from the direction of the (negative) hydraulic potential gradient (which drives the water flow) towards the steepest slope of the bed. This leads to the enhanced formation of side channels dipping into the trough at about a 45° angle. This efficient connection between the
margin and the trough equalizes the hydraulic potential and increases the water pressure in the trough even further.

I investigate these two effects with the 2D subglacial drainage system model GlaDS using Jakobshavn Isbrae as an example. I compare model runs with the pressure melt term disabled and enabled. With the term disabled the main channel situated in the trough is continuous and produces a large depression in the hydraulic potential and consequently high effective pressure in the trough (1-2MPa). Conversely, with the term enabled the main channel becomes discontinuous on steep adverse bed slopes and many side channels form on the margins of the trough. This
leads to a hydraulic potential in the trough which is higher than in the surrounding area and consequently the effective pressure is low
(0-1MPa).

Low effective pressure leads to reduced basal drag and thus to more
basal sliding. This work suggests that the pressure dependence of the melting point of water may be one of the leading causes for the fast flow of Jakobshavn Isbrae and other glaciers in deep troughs.

# Wednesday 12th March 2014, 4.30pm - Hamish Pritchard (British Antarctic Survey)
Patterned ground stories: wars, disasters and ice sheets
Venue: Scott Polar Research Institute, main lecture theatre

Are maps just pictures, or analytical tools? Are they graphics or science? Analysis of patterns in data is at the core of science, and analysis of spatial patterns is at the core of geographical research. Never have spatial data been more available and never have we been better equipped to use them. Using examples from the Antarctic and Greenland ice sheets and from Syria to the Congo, I’ll make a case for the map as a valuable scientific tool, a key asset in disaster management and a powerful way to tell important stories.

# Wednesday 26th February 2014, 4.30pm - Poul Christoffersen (Scott Polar Research Insitute)
Are rapid ice losses in Greenland caused by atmosphere or ocean?
Venue: Scott Polar Research Institute, main lecture theatre

Studies of mass balance show that the Greenland Ice Sheet is losing mass at a growing rate, and that that the contribution to sea level rise could reach 1 mm per year within a decade. Part of this loss is caused by increased surface melting, which is widespread, but limited to the ice sheet’s ablation zone. The other part is caused by faster rates of ice flow, a localised mechanism linked to glaciers terminating in fjords, but with potential far-reaching consequences for the flow of the entire ice sheet. The key question, which has yet to be fully resolved, is whether these two mechanisms are coupled in a positive feedback. This talk will present outcomes from a 3D higher-order ice sheet model, with soft bed and hydrology included in novel new parameterizations. The results demonstrate that a resilient characteristic of ice flow, corresponding to recent observations, may be linked to the storage of surface melt-water in subglacial sediment. This stable mechanism may, however, vanish as climate warms and be limited to regions where the ice sheet terminates on land.

# Wednesday 12th February 2014, 4.30pm - Neil Glasser (Aberystwyth University)
The glaciation of the Antarctic Peninsula: a journey through time
Venue: Scott Polar Research Institute, main lecture theatre

The Antarctic Peninsula is warming rapidly. This warming is responsible for increased glacier and ice-shelf melting, ice-shelf collapse, glacier retreat and acceleration. If we want to put these much-publicised recent events into their wider context, we have to look back in time through the Quaternary for evidence of former ice volume, controls on ice-volume changes and past rates and magnitudes of change. The Antarctic Peninsula is a good place to do this because it contains a well-preserved record of marine and terrestrial glaciations. In this talk, I will present new evidence from fieldwork on James Ross Island about the location and extent of former ice-steams that impinged on the island. I will also present new cosmogenic isotope dates from erratic boulders transported onto James Ross Island from the Antarctic Peninsula and comment on when this former ice stream existed.

# Wednesday 29th January 2014, 4.30pm - Jason Box (Geological Survey of Denmark and Greenland)
Dark Snow in Greenland
Venue: Scott Polar Research Institute, main lecture theatre

Sunlight is the primary energy source for Greenland snow and ice melt. Key in modulating this energy source is surface reflectivity. Snow reflectivity changes not only in response to ice crystal shape and liquid water, but a host of light absorbing “impurities” including mineral dust, black carbon, and even microbes. Quantifying the importance of black carbon and microbial abundance are the subject of the Dark Snow Project, a science project and and experiment in internet crowd funding. This presentation recaps the experience and science of the Dark Snow Project. In the meantime, do join Dark Snow Project at https://www.facebook.com/DarkSnowProject, https://twitter.com/DarkSnowProject, and http://darksnow.org/.

# Wednesday 27th November 2013, 4.30pm - Duncan Quincey (University of Leeds)
Are Karakoram glacier surges linked with climate?
Venue: Scott Polar Research Institute, main lecture theatre

Glaciers in the Karakoram are of particular current interest because many are in balance or are gaining mass, and the majority have either stable terminus positions or are advancing. A number of studies have cited recent (decadal) climatic patterns as being responsible for this anomalous behaviour, but the picture is somewhat complicated by the large number of surging glaciers in the region, about which little is known. This talk will present remotely sensed data that demonstrate glacier velocities can reach as high as 5 km/yr during a surge and that surge return periods may be as short as two decades. Such data can help to shed light on glacier thermal conditions, the processes that trigger surges in this region, and how their characteristics may change in different climatic conditions. Better knowledge of Karakoram surges is critical if accurate assessments of the mass balance of western Himalayan glaciers are to be made.

# Thursday 14th November 2013, 4.30pm - David G. Vaughan (British Antarctic Survey)
Note unusual time (THURSDAY)
Ice sheets, glaciers and sea-level rise: a perspective from the 5th Assessment Report by the IPCC
Venue: Scott Polar Research Institute, main lecture theatre

This seminar will summarise recent changes on ice sheets and glaciers worldwide, and discuss the impact these have on global sea-level. Prof. David Vaughan is the coordinating lead author of the Cryosphere section in the 5th Assessment report by the Intergovernmental Panel on Climate Change, published in 2013, and a contributor to the section on sea level change.

# Wednesday 30th October 2013, 4.30pm - Malcolm McMillan (University of Leeds)
Antarctic elevation change from satellite radar altimetry
Venue: Scott Polar Research Institute, main lecture theatre

It is 50 years since the first scientific observations of Antarctica were made from space. Since then, satellites have revolutionised our ability to monitor the Antarctic Ice Sheet on a continent-wide scale; detailing the diverse behaviour of a vast ice sheet. One of the longest continuous satellite records of Antarctica comes from the series of radar altimeters flown on-board the ERS-1, ERS-2 and Envisat satellites. For the past two decades, these instruments have documented changes in ice sheet elevation, and helped to improve our understanding of the mechanisms and time-scales of Antarctica’s evolution. Now, with the recent retirement of ERS-2 and the loss of Envisat, ESA’s CryoSat-2 mission offers the potential to further extend this record.

This talk will provide an overview of this 20 year dataset; its value, its limitations and its contribution to recent estimates of ice sheet mass balance. I will then discuss current analysis of CryoSat-2 observations, focusing upon data acquired in it’s novel interferometric mode of operation. This instrument is the first of its kind to be flown on an Earth observation satellite, and presents both opportunities and challenges for mapping ongoing changes to the Antarctic Ice Sheet.

# Wednesday 16th October 2013, 4.30pm - Stephen J. Livingstone (University of Sheffield)
Predicting subglacial lake locations and meltwater drainage pathways in Antarctica, Greenland and North America
Venue: Scott Polar Research Institute, main lecture theatre

There is increasing recognition that subglacial lakes act as key components within the ice sheet system, capable of influencing ice-sheet topography, ice volume and ice flow. At present, much glaciological research is concerned with the role of modern subglacial lake systems in Antarctica. Another approach to the exploration of subglacial lakes involves identification of the geological record of subglacial lakes that once existed beneath ice sheets of the last glaciation. Investigation of such palaeo-subglacial lakes offers significant advantages because we have comprehensive information about the bed properties, they are much more accessible and we can examine and sample the sediments with ease. However, their identification in the geological record remains controversial.

We therefore present a simple diagnostic approach based on the Shreve equation, for predicting and investigating likely (palaeo-)subglacial lake locations. Data on the current topography and seafloor bathymetry, and elevation models of the ice and ground surface topography from data-calibrated glaciological modelling are used to calculate the hydraulic potential surface at the ice-sheet bed. Meltwater routing algorithms and the flooding of local hydraulic minima allow us to predict subglacial routeways and lakes respectively.

Discovered subglacial lakes beneath the Antarctic Ice Sheet present an opportunity to verify the model using the BEDMAP2 dataset. Using a lake threshold of 5 km2 we identify 12,767 subglacial lakes occurring over 4% of the grounded bed and are able to recover >60% of the discovered subglacial lakes. Applying the same approach to the Greenland Ice Sheet produces 1,607 potential subglacial lakes, covering 1.3% of the bed. These lake localities will make suitable targets for radar surveys attempting to find subglacial lakes.

Finally, we apply the Shreve equation to the North American Ice Sheet to try and predict likely palaeo-subglacial lake locations. Given that specific ice surface elevations of the former North American Ice Sheet are only inferred from modelling, and thus contain significant uncertainty, we utilise results from an ensemble of models to examine where on the bed subglacial lakes are likely to have occurred. Predictions are calculated at discrete time-slices through deglaciation to assess the temporal variability and persistence of subglacial lakes and drainage networks. These lake likelihood predictions could usefully form targets for detailed field investigations.

# Wednesday 12th June 2013, 4.30pm - Dr Lorna Linch, University of Brighton
The ‘fingerprint’ left by icebergs that plough through sediment: Glacial Lake Agassiz, Manitoba, Canada
Venue: Scott Polar Research Institute, main lecture theatre

Icebergs plough through unconsolidated lake/sea sediments gouging out kilometre long grooves, 100s of metres wide and tens of metres deep. Although the surface morphology of iceberg scours is well-documented, little is known about what scours look like in stratigraphic section, particularly where surface characteristics are absent (e.g. through decay or burial). This investigation establishes a definitive suite of diagnostic criteria for identifying iceberg scours in clays by macroscopically and microscopically (2D thin sections) examining sediment deformation below iceberg scours in former Glacial Lake Agassiz, Manitoba, Canada. This suite of structures is unlike those found in subglacial tills and mass-wasting deposits. This research will be particularly valuable in palaeoenvironmental reconstruction and in predicting glacial dynamics. In addition, it may eventually aid structural engineering on polar shelves, which could be of great value to oil and gas companies.

# Wednesday 5th June 2013, 4.30pm - Dr Suzanne Bevan, Swansea University
Remote sensing of Greenland tidewater glaciers
Venue: Scott Polar Research Institute, main lecture theatre

Recent years have seen large losses in the mass balance of the Greenland ice sheet, with flux lost at the calving margins of tidewater outlet glaciers a significant component of these losses. Ice-sheet calving processes and interactions between ice and ocean, however, are still not well understood and in-situ observations in the critical ice-front regions are difficult and dangerous to obtain. This seminar will show the various roles that satellite observations have to play in underpinning attempts to advance understanding of calving processes.
To begin with I will summarise some recent work which made use of data from the early LandSAT archive through to more recent Envisat SAR imagery. The results highlight the onset of changing tidewater glacier dynamics around Greenland, and the coincidence of change with warming atmosphere and ocean temperatures. These long time series of broad-scale data can provide empirical evidence for the influence of atmosphere and ocean on glacier dynamics.
Next I will present some data of much higher temporal sampling – Envisat ASAR Wide Swath Mode data. These data begin to capture continuous observations of calving and allow differences in calving characteristics to be identified between, for example, Helheim and Kangerdugssuq glaciers in east Greenland. This type of data can be used to inform empirical or parametrised models of calving behaviour.
Progressing towards a mechanistic calving model requires improved spatial resolution. TanDEM-X (launched in 2010) and TerraSAR-X (2007) are providing extremely high-spatial resolution SAR data. These data will ultimately be used to generate an interferometric global digital elevation model (DEM). However, by processing data ourselves we are able to create DEM time series at 11-day repeat intervals and an extraordinary 2 m spatial resolution over ‘supersites’ such as Helheim and Kangerdlugssuaq. I will conclude by presenting some of these DEMs and also feature-tracked surface velocity fields based on the same data.

# Wednesday 22nd May 2013, 4.30pm - Dr Jonathan Carrivick, Leeds University
Glacier outburst floods: spatial and temporal evolution
Venue: Scott Polar Research Institute, main lecture theatre

Glacial lake outburst floods affect ice dynamics, produce distinctive and widespread onshore and offshore geomorphological impacts and are a hazard to populations and infrastructure. This presentation will firstly review the status of research into the occurrence of glacier outburst floods; those in alpine mountain ranges, those from ice sheet margins and those from subglacial volcanic eruptions. It will then detail quantification of the evolution of a single outburst flood from flume, field and numerical model analyses. It will be shown that glacier outburst floods are initially controlled by a short acceleration due to the depth of impounded water. Channel flow quickly converges to an inertial regime and thence to a viscous regime dominated by channel bed friction. Outburst floods that enter intermediary lakes are dramatically attenuated in terms of propagation whilst basin filling proceeds to the outlet level, dissipated of energy due to considerable flow recirculation during the rising stage of the flood, and after overtopping of the outlet are moderated in terms of peak discharge. Outburst floods can have kinematic waves that are introduced to a flood via hydraulic ponding. A partitioning of flow regimes occurs due to time-transgressive changes in channel cross-section; specifically between inner channel and overbank regions. Furthermore, net erosion along a reach can be related to hydraulic persistence above a marker value and net deposition can be related to a ‘time to peak’ value. These findings shed light on the diversity and complexity of the Quaternary record of outburst floods, provoke consideration of the requirements for modern hazard management strategies and quantify the controls on rapid landscape change due to outburst floods.

# Wednesday 8th May 2013, 4.30pm - Dr Camilla Andresen, Geological Survey of Denmark and Greenland
Using sediment archives from glacial fjords to reconstruct past glacier and ocean variability
Venue: Scott Polar Research Institute, main lecture theatre

Since major outlet glaciers on Greenland started to accelerate, thin and retreat in the early 2000s, the causes and significance of this change has been debated, however, it is widely believed that the combined effects of surface and submarine melting and loss of buttressing ice mélange play a significant role. The understanding of the climatic influence on outlet glacier behaviour is hampered by the short time span for which satellite observations of glacier changes and instrumental records of ocean variability exist. The purpose of the SEDIMICE project (‘linking sediments with ice sheet retreat’) is to extend the glacier and ocean changes back in time by analysing sediment cores obtained from the fjords into which the outlet glaciers terminate and thus leave sedimentary traces from icebergs and melt water. In this presentation some studies from Sermilik Fjord are presented. The investigated time span covers the last c. 1000 years and thus shed light on oceanographic conditions during and after the LIA and the concordant outlet glacier behaviour. With this presentation I will also take the opportunity to outline some other scientific activities from the Department of Marine Geology and Glaciology at GEUS.

# Wednesday 24th April 2013, 4.30pm - Dr Neil Ross, Newcastle University
Unveiling the glacial and landscape evolution of West Antarctica: subglacial insights from ice-penetrating radar and satellite imagery
Venue: Scott Polar Research Institute, main lecture theatre

Antarctic subglacial highlands are where the Antarctic ice sheets first developed and the ‘pinning points’ where retreat phases of the marine-based sectors of the ice sheet are impeded. Due to low ice velocities and limited present-day change in the ice sheet interior, West Antarctic subglacial highlands have been overlooked for detailed study. These regions have considerable potential, however, for establishing from where the West Antarctic Ice Sheet (WAIS) originated and grew, and its likely configuration and glaciology in a warmer climate. Here, we characterise the subglacial morphology of the Ellsworth Subglacial Highlands (ESH), West Antarctica, using radio-echo sounding (RES) surveys and satellite-derived ice surface imagery. We document numerous, well-preserved classic glaciated valley landforms (e.g. large overdeepened troughs, hanging tributary valleys, and fjord-mouth threshold bars) indicative of warm-based marine-proximal alpine glaciation. The landscape predates the present ice sheet, and was formed by a small dynamic ice-field(s) with tidewater-terminating margins, at times when the marine sections of the WAIS were absent and the deep former marine basins of the WAIS (e.g. Bentley Subglacial Trench) were inundated. ESH represents a major seeding centre of the palaeo-WAIS, and its margins represent the pinning point at which future retreat of the marine-based WAIS would be arrested.

# Wednesday 13th March 2013, 4.30pm - Dr Eero Rinne, Finnish Meteorological Institute
Sea Ice Research at Finnish Meteorological Institute – from Ice Charts to Climate Studies
Venue: Scott Polar Research Institute, main lecture theatre

Every Finnish harbor gets ice blocked even during a mild winter. Thus understanding sea ice is extremely important and there is a call for high quality sea ice research. The sea ice research group at Finnish Meteorological Institute (FMI) conducts research on remote sensing and forecast models for sea ice, and develops charting methods and ice forecasts. Our core objective is to produce reliable and user relevant information on sea ice. The end users range from those involved in winter navigation and offshore activities to policymakers and the general public in ice-covered sea regions.

For ice charting, we use earth observation data obtained from current EO satellites as well as develop new methods for future satellites. I will present some of our currently operational products, such as Baltic Sea ice charts and forecasts. I will also introduce novel sea ice thickness retrieval methods combining data from satellite synthetic aperture radar, passive microwave and optical sensors and ice models. I will also give a short overview of model development concerning sea ice dynamics – particularly from the viewpoint of ice compression felt by a ship navigating through ice.

FMI is also involved in reanalysis of long satellite data series. As part of the European Space Agency’s Climate Change Initiative we will reprocess the radar altimeter measurements from ERS-1, ERS-2 and EnviSAT satellites. We will build an “Essential Climate Variable” product of sea ice thickness covering the Arctic and spanning the winters 1993 – 2012. I will present the algorithms used in altimeter sea ice thickness retrieval, introduce our prototype sea ice thickness processor and finally seek answers to some open questions concerning the sea ice thickness retrieval.

# Wednesday 27th February 2013, 4.30pm - Dr Kathryn Rose, British Antarctic Survey
Early East Antarctic Ice Sheet Growth Recorded in the Landscape of the Gamburtsev Subglacial Mountains
Venue: Scott Polar Research Institute, main lecture theatre

The Gamburtsev Subglacial Mountains are regarded as a key nucleation site for the Antarctic ice sheet and, as such, may retain a unique long-term record of pre-glacial and early glacial landscape evolution. Here, we use a range of morphometric analyses to constrain the nature of early glaciation and subsequent ice sheet evolution in the interior of East Antarctica, using a new digital elevation model of the Gamburtsev Subglacial Mountains, derived from an extensive airborne radar survey. We find that an inherited fluvial landscape confirms the existence of the Gamburtsev Subglacial Mountains prior to the onset of glaciation at the Eocene-Oligocene climate boundary (ca. 34 Ma). Features characteristic of glaciation, at a range of scales, are evident across the mountains. High elevation alpine valley heads, akin to cirques, identified along the mountain ridge, are interpreted as evidence for early phases of glaciation in East Antarctica. The equilibrium line altitudes associated with these features, combined with information from fossil plant assemblages, suggests that they formed at, or prior to, 34 Ma. It cannot be ruled out that they may have been eroded by ephemeral ice between the Late Cretaceous and the Eocene (100-34 Ma). Hanging valleys, overdeepenings, truncated spurs and steep-sided, linear valley networks are indicative of a more widespread alpine glaciation in this region. These features represent ice growth at the latest 33.7 Ma and provide a minimum estimate for the scale of the East Antarctic Ice Sheet between ca. 34-14 Ma, when dynamic fluctuations in ice extent are recorded at the coast of Antarctica. The implications are that the early East Antarctic Ice Sheet grew rapidly and developed a cold-based core that preserved the alpine landscape. The patterns of landscape evolution identified provide the earliest evidence for the development of the East Antarctic Ice Sheet and can be used to test coupled ice-climate evolution models.

# Wednesday 30th January 2013, 4.30pm - Professor David Evans, Durham University
Glacial landsystems: modern polar and alpine analogues for Quaternary palaeoglaciology
Venue: Scott Polar Research Institute, main lecture theatre

Accelerated historical recession of glacier snouts throughout the world has resulted in the exposure of large areas of former glacier beds and the abandonment of substantial ice-marginal landforms such as moraines and glacifluvial depocenters. Inset sequences of these landforms document the pattern, pace, and timing of glacier recession and also readvances triggered by regional climate oscillations. In high latitude and high altitude regions, glacier recession has resulted in the development of substantial ice-cored terrain, which demonstrates the importance of retarded deglaciation in the evolution of glacial landforms. Therefore, the wide range of landform assemblages that characterizes these deglaciated landscapes provides a set of invaluable modern analogues or process-form models for use in paleoglaciological reconstruction, especially where spatial and temporal variability in glacier dynamics and thermal characteristics results in the juxtaposition of different diagnostic terrain types. A landsystem framework is used to classify a range of deglaciated terrains, focusing specifically on moraines and glacifluvial depo-centers as the most significant landforms charting glacier recession. Landsystem signatures vary according to glacier morphology and dynamics and therefore the initial focus of this presentation is on the role of glacier thermal regimes in moraine/till construction and the operation of the glacifluvial depositional system.

# Wednesday 16th January 2013, 4.30pm - Dr Stewart Jamieson, Durham University
N.B. re-scheduled from earlier date
Reproducing unexpected LGM ice-stream retreat behaviour in a dynamic numerical model of Marguerite Bay, Antarctica
Venue: Scott Polar Research Institute, main lecture theatre

Geophysical mapping of the sea floor in Marguerite Bay, Antarctica, has led to the identification of a series of grounding zone wedges which represent the locations of palaeo grounding lines during retreat from maximum ice stream extent. This data indicates that during rapid retreat following the LGM, the ice stream grounding line stabilised multiple times on a bed that deepens inland. According to the marine ice sheet instability theory, these stabilisations should not be expected. We use a numerical flowband model which can robustly calculate groundine line behaviour over time to reproduce the retreat pattern inferred from the seafloor. We conduct a series of sensitivity tests to determine what controlled grounding line motion and stability, and to understand what drove wider retreat behaviour in Marguerite Bay. Our findings have implications for understanding past retreat dynamics in other regions, and for making future predictions of ice sheet stability.

# Wednesday 28th November 2012, 4.30pm - Dr Alun Hubbard, Aberystwyth University
N.B. Change of date
What's going on in Greenland?
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Monday 29th October 2012, 4.30pm - Dr Maryline Vautravers, Earth Sciences, University of Cambridge
Note: not usual day
Palaeoenvironmental records from the West Antarctic Peninsula drift sediments over the last 75 ka.
Venue: Scott Polar Research Institute, main lecture theatre

We present results of a multi-proxy study on marine sediment core JR179-PC466 recovered from the crest of a sediment drift off the west Antarctic Peninsula at roughly 2300 m water depth. The 10.45-m long core consists dominantly of glaciomarine terrigenous sediments with only traces of calcium carbonate (<1 wt.%). Despite the very low abundance of calcareous foraminifera, planktonic shell numbers are sufficient for stable isotope analyses in 2/3 of the samples studied. The core chronology is based on oxygen isotope stratigraphy and correlation of its relative palaeomagnetic intensity (RPI) with a stacked reference curve. Planktonic foraminifera are present in the Holocene, but more abundant in sediments deposited during MIS3 (29-57 ka BP), owing to less dilution by terrigenous detritus and/or better carbonate preservation. During MIS3, foraminifera maxima correlate with Antarctic warming events as recorded in the d18O signal of the EPICA Dronning Maud Land (EDML) ice core. They indicate higher planktonic foraminifera production and better carbonate preservation west of the Antarctic Peninsula during that time. The abundance of Ice Rafted Detritus (IRD) in core PC466 increased during the last deglaciation between ~19 and 11 ka BP, when numerous icebergs drifted across the core site, thereby releasing IRD. During this time sea-level rise destabilized the Antarctic Peninsula (APIS) and West Antarctic (WAIS) ice sheets that had advanced onto the shelf during the sea-level low-stand of the Last Glacial Maximum (LGM; ~19-23 ka BP). Overall, our results demonstrate that it is possible to establish an age model and reconstruct palaeoceanographic and climatologic changes at high temporal resolution from sedimentary sequences recovered at 2300 m water depth from a West Antarctic drift.

# Wednesday 17th October 2012, 4.30pm - Christine Batchelor, SPRI
Reflection seismic investigations of the Beaufort Sea margin, Arctic Ocean: Variable history of Quaternary ice-sheet advance
Venue: Scott Polar Research Institute, main lecture theatre

The seismic stratigraphy and sedimentary architecture of the Beaufort Sea shelf and adjacent continental slope are investigated using a comprehensive grid of high-resolution 2-D seismic reflection data. Three cross-shelf troughs, representing the locations of former ice streams draining a 1000 km-long section of the Laurentide Ice Sheet are examined; the Mackenzie, Amundsen Gulf and M’Clure Strait systems. Significant contrasts are identified between the Mackenzie Trough on the western Beaufort Sea margin and the Amundsen Gulf and M’Clure Strait troughs to the east, both in terms of their glacial history and the resulting architecture of the shelf and slope. These observations are considered in relation to the dynamics of the Laurentide Ice Sheet and the glacial history of the Beaufort Sea margin.

# Tuesday 12th June 2012, 4.30pm - Professor Pat Quilty, University of Tasmania
Note unusual day
Robert Falcon Scott: the Tasmanian links and an appreciation.
Venue: Scott Polar Research Institute, main lecture theatre

Scott is not normally recognised as having a strong Tasmanian association, but he spent an afternoon on Macquarie Island in 1901, thus meaning he was in Tasmania. Perhaps odd is the existence at St Alban’s Anglican church in the northern Hobart suburb of Claremont, a very high quality three panel stained glass window dedicated to Scott. Over the last 20 years, I have been trying find out who designed and made the window. It is now believed it was Auguste Fischer (sometimes Fisher) who was a close asociate of the designer of the church Alan Cameron Walker, a renowned architect and silversmith, whio also designed the General Post Office from which Amundsen sent the information of his successful attempt on the South Pole. When Scott’s death was made known to the world in 1913, Scott’s sister Ettie was the wife of the newly appointed governor of Tasmania, and many other members of Scott’s family also lived in Government House. The appreciation will be my personal positive view of the achievements of Scott’s expedition.

# Wednesday 6th June 2012, 4.30pm - Amber Leeson & Dr Kate Briggs, School of Earth & Environment, University of Leeds
Double bill: Modelling the evolution of supra-glacial lakes in the Russell glacier region of the Greenland Ice Sheet / IMBIE - Ice sheet Mass Balance Inter-comparison Exercise
Venue: Scott Polar Research Institute, main lecture theatre

Modelling the evolution of supra-glacial lakes in the Russell glacier region of the Greenland Ice Sheet

We present a new 2 dimensional model of supra-glacial lake evolution at the western Greenland ice sheet margin which uses a digital elevation model (DEM) to route meltwater runoff simulated by the regional climate model MAR (Modele Atmospherique Regional) across the ice sheet surface. The resulting water drainage network and supra-glacial lake distribution are compared to optical satellite imagery derived from the MODIS satellite. Our simulations of lake evolution in 2003-2007 confirm that the locations of supra-glacial lakes coincide with intransient depressions in the ice surface topography, and that the onset date of lakes coincides with local runoff availability. We also attempt to constrain a practical limit to the area occupied by modelled supra-glacial lakes (6 ) in our simulation and volume which they contain (12 all runoff produced) which is not exceeded, even when double the estimated runoff amount is supplied.

IMBIE – Ice sheet Mass Balance Inter-comparison Exercise

Accurate monitoring of ice sheet mass balance is critical for understanding the interaction of climate and ice sheets, and for forecasting sea level rise. Over the past 20 years or so the measurement of ice sheet mass balance has been revolutionised by the advent of three geodetic techniques- altimetry, gravimetry and the mass budget method. There are now more than 30 published results of mass balance for the Greenland and Antarctica Ice Sheets. However, disagreements between many of the published results have limited the confidence in the measurements. Over the past year, a group of over 30 scientists have worked together on the IMBIE project with the aim of understanding the causes for these disagreements and reconciling the measurements of ice sheet mass balance from the different geodetic techniques. In my presentation, I will outline the approach and experiments of the IMBIE group, and some of our key findings.

# Wednesday 30th May 2012, 4.30pm - Dr Jemma Wadham, University of Bristol
Microbial activity beneath the Antarctic Ice Sheet: impacts beyond the ice margin?
Venue: Scott Polar Research Institute, main lecture theatre

Once thought to be devoid of life, the Antarctic Ice Sheet is now known to be a dynamic reservoir of organic carbon and metabolically active microbial cells. At the ice-bed interface, subglacial lake environments and till are believed to support low diversity microbial populations, adapted to perennial cold, anoxia and lack of light. The dynamic exchange of water between these shallow environments sustains nutrient and organic carbon supply to the subglacial zone, and ultimately conveys meltwaters and sediments into the coastal ocean. The latter may be important for fertilizing the Southern Ocean with N, P and Fe, with potential implications for marine productivity and associated CO2 drawdown. Beyond the subglacial lakes and the subglacial till complex are deep sedimentary basins up to 14km thick located largely around the Antarctic periphery. Here, sustained microbial activity over Myr timescales is likely to be important for the cycling of organic carbon and elements in the deep sub-surface. These sedimentary basins may be hydrologically decoupled from shallower lake and till environments by the presence of highly consolidated sediments which limit the penetration of glacial meltwaters to depth. Organic carbon buried in these basins (e.g. marine sediments) during ice sheet formation is thought to be microbially cycled to methane gas, which is stored as hydrate within sediments, stabilized by the high pressure/low temperature conditions. It has been demonstrated via numerical modeling that this methane store could be of a similar order of magnitude to that present as hydrate in other globally significant reserves. In summary, microbial activity beneath the Antarctic ice sheet is likely to have far reaching impacts beyond the ice margin and may be important to consider in future global models of biogeochemical cycling.

# Wednesday 23rd May 2012, 4.30pm - Anna-Maria Trofaier & Dr Steven Palmer, Scott Polar Research Institute.
Double bill: "Monitoring Arctic water bodies using active microwave data" / "Airborne glacier geophysics in Greenland"
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Wednesday 16th May 2012, 4.30pm - Dr Andy Smith, British Antarctic Survey
Subglacial conditions on Pine Island Glacier, West Antarctica: Results from ground-based geophysical surveys; and plans for future activities with the iSTAR Programme
Venue: Scott Polar Research Institute, main lecture theatre

Pine Island Glacier is changing; it is currently the single biggest contributor to global sea level rise from the whole of the West Antarctic Ice Sheet. The source of this change seems to be oceanographic, but it is glaciological factors, including interactions between the ice and its bed, which control the nature of the glacier’s response.

Two recent geophysical experiments illustrate the potential influence of subglacial conditions on the dynamics of Pine Island Glacier. The first experiment identified a subglacial geological boundary that appears to coincide with changes in ice flow and basal drag; the second experiment measured subglacial erosion of 32 m over a 49-year period. One conclusion from both experiments is the potential influence erosion can have on a glacier’s form and flow. Pine Island Glacier continues to be a focus for ice sheet stability research. Plans are evolving for the next phase of this research with NERC’s iSTAR Programme.

# Wednesday 9th May 2012, 4.30pm - Professor Bryn Hubbard, Aberystwyth University
Glaciers on Mars
Venue: Scott Polar Research Institute, main lecture theatre

It is well-known that ice exists within Mars’ polar caps. However, similar to Earth, numerous smaller ice masses appear to populate lower latitude regions on Mars. These glacier like forms (GLFs) form a subgroup of what have been identified as widespread viscous flow features throughout Mars’ mid-latitudes. In this seminar I will summarise Mars’ environmental history and focus on the geographic distribution, geometry and surface characteristics of mid-latitude GLFs. I will summarise the current situation in terms of what is known about the physical character and formation of GLFs and highlight outstanding research questions for future glaciological and geomorphological investigation.

# Wednesday 2nd May 2012, 4.30pm - Prof John Smellie, University of Leicester
Sub ice volcanism, ice sheets and global change
Venue: Scott Polar Research Institute, main lecture theatre

Other than in response to mitigating the impacts of modern eruptions (e.g. Eyjafjallajökull (Iceland) in 2010), the products of volcanism are generally neglected in environmental studies. This is also true for studies of palaeoenvironments, where volcanism is not often considered a first line of attack. However, Antarctica is host to numerous volcanoes that were constructed over the past 25 million years. They were erupted in association with a coeval ice sheet, and Antarctica contains the world’s largest and longest-lived glaciovolcanic province. Glaciovolcanic studies have advanced out of all recognition over the past 10 years and they are now a major new proxy methodology that can yield a much wider and more quantitative range of critical parameters of past ice sheets than any other palaeoenvironmental methodology. They provide a unique ultra-proximal terrestrial record of equal importance to results of more distally situated higher-resolution marine sedimentary studies, which are obtained by offshore drilling at a substantially higher cost. Historically, glaciovolcanic sequences provided the earliest evidence for a pre-Quaternary ice sheet in Antarctica, and subglacial volcano(es) might today be influencing ice sheet stability by lubricating sensitive parts of the West Antarctic Ice Sheet. This talk will use examples of selected mature studies of Antarctic glaciovolcanism to demonstrate how they are at last beginning to be used to reconstruct parts of the Neogene Antarctic Ice Sheet (AIS) in far greater detail than was previously possible. Critical parameters that can be routinely deduced include basal thermal regime and (uniquely) ice thickness, knowledge of which is a fundamental prerequisite for making accurate estimates of past ice volumes and showing how those volumes fluctuated with time. Studies such as these are important in assessing the stability of the AIS under the current phase of climate warming, and ultimately to calculate much more reliably the possible impacts on eustasy. Thus glaciovolcanic investigations in Antarctica are likely to make major contributions to our understanding of the global impact of the world’s largest & longest-lived ice sheet.

# Wednesday 28th March 2012, 1.00pm - Dr Marco Tedesco, Department of Earth and Atmospheric Sciences, City College of New York
Darker, wetter and faster: recent and projected trends of mass balance over the Greenland ice sheet and linkages to surface and sub-surface processes
Venue: Scott Polar Research Institute, main lecture theatre

Over the recent years, runoff and melting over Greenland have been increasing, confirming a long-term statistically significant trend and suggesting negative surface mass balance in the close future. Moreover, many glaciers along the edges have been retreating and thinning at higher elevations. New records were set in 2010 and close-to-record in 2011 for surface melt and albedo, runoff, the number of days when bare ice was exposed and surface mass balance of the Greenland ice sheet, especially over its west and southwest regions. Analyzing the causes and implications of these recently observed extremes and records is crucial to properly project the behavior of the Greenland ice sheet in future climate scenarios. In this talk I analyze recent and projected trends of surface mass balance over the Greenland ice sheet. I focus on some of the major causes and drivers of these events through a combination of remote sensing tools, fieldwork data and outputs of a regional climate model. In particular, I will show results from our fieldwork expeditions focusing on albedo changes, I will discuss the impact of supraglacial lakes on ice flow velocities and ice sheet dynamics, the role of accumulation and I will assess the impact of the biological activity on Greenlands ice.

# Wednesday 21st March 2012, 1.45pm - Dr Valentina Radic, Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada
Challenges in modeling future sea level rise from melting glaciers
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Wednesday 21st March 2012, 1.00pm - Professor Veli-Pekka Salonen, Dept. of Geosciences and Geography, University of Helsinki (and Visiting fellow at Clare Hall)
Pleistocene and Holocene in Murchisonforden area, Nordaustlandet, Svalbard.
Venue: Scott Polar Research Institute, main lecture theatre

The research campaign formed part of International Polar Year (2007-2009) activities (IPY-Kinnvika), which made it possible to run three expeditions to High Arctic terrains of Northaustlandet (Svalbard). These areas normally have very difficult access. The target was to reconstruct the glacier history of the Barents Ice Sheet within its north-westernmost sector which has thusfar been only little studied. The area is important palaeoclimatologically because influenced by relatively warm North Atlantic waters, and because the reactions of the glaciers to climate fluctuations are known to be fast and extreme.

Sediments from entire Weichselian glacial Stage were located and related with other similar records from all around Spitsbergen (Kaakinen et al. 2008). The Weichselian record found represented three stadials and two interstadials. The Mid-Weichselian stadial ca. 60-50 000 BP affected the area most heavily causing areal scouring of the landscape and depositing tills. During the latest glacial phase, 25000 – 15000 BP, frozen bed conditions prevailed leading to an almost non-existing erosion or deposition of strata. Deglaciation was dated to ca. 12 500 years ago.

Holocene foraminiferal assemblages from Isvika bay sediments indicate a transition from glacier-proximal to glacier-distal faunas with a clear indication of the inflow of warmer North Atlantic waters in the early Holocene (Kubischta et al. 2011). The climatic optimum was terminated by a glacier re-advance that occurred 6000 years ago. This event caused the deposition of waterlain till, that disturbed the glacio-isostatic emerging of the shores and changed local chironomid fauna to indicate generally colder lake temperatures (Luoto et al. 2011). Since the Mid-Holocene, foraminifera and ice rafted detritus (IRD-) record indicate a gradual cooling climatic trend. Lacustrine faunal changes testify to major environmental turnovers, including a total decline of a previously unknown endemic cladocera species (Nevalainen et al. 2011).

References
Kaakinen, A., Salonen, V.P., Kubischta, A., Eskola, K.O. ja Oinonen, M. 2009. Weichselian glacial stage in Murchisonfjorden, Nordaustlandet, Svalbard. Boreas 38:718-729.
Kubischta, F., Knudsen, K.L., Ojala, A. ja Salonen, V-P. 2011. Holocene benthic foraminiferal record from a high-arctic fjord, Nordaustlandet, Svalbard. Geographiska Annaler 93, 227-242.
Luoto, T.P., Nevalainen, L., Kubischta, F., Kultti, S., Knudsen, K.L., ja Salonen, V-P. 2011. Late Quaternary ecological turnover in a High Arctic Lake Einstaken, Nordaustlandet, Svalbard (80 °N). Geographiska Annaler, 93, 337-354.
Nevalainen, L., Van Damme, K., Luoto. T.P. ja Salonen, V-P. 2011.- Fossil remains of an unknown Alona species (Chydoridae, Aloninae) from a high arctic lake in Nordaustlandet, Svalbard, and its relation to glaciation and Holocene environmental history. Polar Biology, 35, 325–333.

# Wednesday 14th March 2012, 4.30pm - Dr Gwendolyn Leysinger-Vieli, University of Durham
Exploring radar data of ice sheets by means of numerical modelling
Venue: Scott Polar Research Institute, main lecture theatre

Radio echo sounding data of ice sheets reveals the ice thickness, the bed topography and the internal ice layers. Internal ice layers represent the paleo-ice surfaces, which were buried by surface accumulation and advected with time by ice flow. These reflecting layers can therefore be treated as layers of the same age (isochrones) and in combination with age layers calculated from numerical models can be used to learn more about ice dynamics and boundary conditions. Information extracted from radar layers are e.g. the temporal and spatial accumulation pattern over a large area, where previously only point information from boreholes was available. Furthermore the data allows to investigate the basal conditions of the ice sheet and its flow dynamics, and potentially to infer for its long-term history. In this talk I will show how numerical modelling can be used to explore radar layer architecture, thereby improving our understanding of ice sheet dynamics.

# Wednesday 7th March 2012, 4.30pm - Dr Fausto Ferraccioli, British Antarctic Survey
Revealing the Antarctic continent with recent aerogeophysical exploration
Venue: Scott Polar Research Institute, main lecture theatre

The Antarctic continent plays a pivotal role in global Earth System. The major ice sheets that cover the continent are a key influence on both global sea level rise and the climate system, and the underlying geology is a critical piece of the puzzle for studies of supercontinental evolution and processes.

I will review some recent aerogeophysical exploration projects that the British Antarctic Survey has been performing together with its national and international collaborators over the last decade to help unveil both the geological structure of the continent and to assist in studying ice sheet behaviour, through an improved knowledge of basal conditions and englacial structures. In particular I will be focussing on our latest major aerogeophysical exploration campaign over the enigmatic Gamburtsev Subglacial Mountains in interior East Antarctica that was achieved by major international collaboration during the International Polar Year.

Although coupled climate and ice sheet models have suggested that the Gamburtsevs were a key nucleation site for the early formation and evolution of the Antarctic ice sheet the origin of this high elevation mountain range in an apparently stable Precambrian shield has remained an unresolved mystery ever since their first discovery some 50 years ago. With the aid of combined radar, gravity and magnetic measurements we investigated the structure and the processes that created the Gamburtsevs. We propose that a thick crustal root was formed under the Gamburtsevs province when different parts of East Antarctica came together (collided) perhaps a billion years ago or more. Normally these old roots are lost in the mantle, but here the root was preserved, probably becauseit was very dense and dry, as is the case for example in the Urals or the TransHudson Orogen. About 250 Ma ago, and then again about 100 Ma, a major rift system that extended for over 3,000 Km from India to South Pole reactivated the old root and through a processes known as flexure helped uplift the range. However, the modern Gambuirtsevs achieved their present day rugged Alpine topography through later valley incision processes that helped uplift the peaks. The remarkable preservation of the mountain range is linked to extremely low erosion rates that are due to the overlying cover by the East Antarctic Ice Sheet, as Antarctica plunged into an icehouse world some 34 Ma.

Testing the new geophysical models for the Gamburtsevs now require and even great challenge: drilling through several thousand meters thick ice (in places)to get samples. Ambitious plans for drilling are already on the Chinese research agenda, in particular to try and find the oldest ice of our planet and perhaps recover a rock sample!

# Wednesday 29th February 2012, 4.30pm - Dr Rob Bingham, University of Aberdeen
Inland thinning of West Antarctic Ice Sheet steered along subglacial rifts
Venue: Scott Polar Research Institute, main lecture theatre

Ice currently being liberated from the West Antarctic Ice Sheet (WAIS) accounts for ~10% of observed global sea-level rise. Losses are dominated by the accelerated draw-down and resultant “dynamic thinning” of ice along the coastline, forced by oceanic or atmospheric perturbations to the ice margin. Though key to improving projections of future ice-sheet contributions to sea-level, the incorporation of dynamic thinning into models has been restricted by lack of knowledge of basal topography so that, for much of WAIS, the fundamental controls on its dynamic losses, hence the rate and ultimate extent of its potential retreat, remain difficult to quantify. Here I detail the discovery of a subglacial trench up to 1.5 km deep and 20 km wide, connecting the ice-sheet interior to the Bellingshausen margin, whose existence impacts profoundly on current ice-dynamic losses. I report on use a suite of ice-penetrating radar, magnetic and gravity measurements to interpret the likely origins of the trench in rifting arising from crustal thinning in association with the wider development of the West Antarctic Rift System. Now deactivated, but exhumed by glacial erosion, the inferred rift represents a conduit through which a palaeo-ice stream was directed onto the continental shelf during glacial maxima, eroding the major “Belgica” trough across Eltanin Bay which today routes warm open-ocean water back to the ice front to reinforce dynamic thinning. I show that the inland propagation of dynamic thinning from the Bellingshausen margin is steered towards the ice-sheet interior directly along the rift axis. Expanding analysis to the wider WAIS, it appears that those basins that will most readily transmit coastally-perturbed change inland are those underlain by old rifts that cut across the modern ice-sheet margin.

# Wednesday 22nd February 2012, 4.30pm - Prof Elizabeth Morris, Scott Polar Research Insitute
Densification in the Greenland dry snow zone - implications for altimetry
Venue: Scott Polar Research Institute, main lecture theatre

As part of the cal/val experiments for the CryoSat radar altimeter, density profiles in the upper 10-14 m of snow have been measured along a 500 km traverse across the Greenland Ice Sheet, using a neutron scattering technique. Repeat measurements, over periods ranging from a few days to 5 years allow strain rates and densification rates to be determined as a function of depth. As expected, the strain rate decreases as the ratio of pore space to ice content decreases. Very large strain rates are observed in the surface layer of snow over summer periods. However, for multi-year snow, once the effect of porosity has been removed, the remaining mean response is constant with depth, that is the effect of increasing overburden pressure is counteracted by increasing strength of the material. The mean strain rate for multi-year snow at a given site is related to the mean annual accumulation rate and mean annual temperature by an expression consistent with the Herron and Langway equation for first-stage densification. However, there are fluctuations in strainrate associated with the annual layering which indicate that fine and coarse-grained snow have differing strengths. Futhermore, the temperature-dependent process equations proposed by previous workers are not consistent with the data. An alternative approach is suggested.

# Wednesday 8th February 2012, 4.30pm - Dr Kelly Hogan, Scott Polar Research Institute
The central-west sector of the Greenland Ice Sheet since the LGM - the story from offshore evidence
Venue: Scott Polar Research Institute, main lecture theatre

Recent reconstructions of the Greenland Ice Sheet (GrIS) during the LGM still have large uncertainties along much of the ice sheet’s
margin, particularly for the NW, NE and central-W sectors of the ice sheet. This is partly due to the scarcity of information from the offshore record that could confirm maximum ice-sheet extent and date the start of deglaciation in these areas. Here we present recent work that uses a
variety of seismic data to investigate sediments deposited by ice masses retreating in to Disko Bay and, ultimately, the Jakobshavn and Torssukatak fjord systems. The sub-bottom profiles show rapid ice-margin retreat through bathymetric troughs and embayments until topographic pinning points close to the present coastline. Once the ice margins were pinned at fjord mouths large volumes of sediment were deposited via rainout from turbid meltwater plumes and calculated subglacial sediment fluxes are relatively high when compared with existing estimates from West Antarctic ice streams. Using existing marine and terrestrial dates we place these standstills in a chronologic framework that support an earlier ice-margin retreat in northern Disko Bay (Torssukatak) than in southern Disko Bay (Jakobshavn). Using the newest radiocarbon dates available from the offshore record we can now present a deglacial chronology for the GrIS from the shelf break several hundred kilometres west of Disko Bay, through the bay to the fjord mouth, and then into the fjord itself at c. 7.8-7.6 cal ka BP. We will also present dates from Umanak Trough to the north for which there is an emerging picture of retreat from the shelf edge followed by a significant stillstand or readvance before c. 10 cal ka BP.

# Wednesday 1st February 2012, 4.30pm - Dr Bill Austin, University of St Andrews
The timing and rate of deglaciation along the north Svalbard margin
Venue: Scott Polar Research Institute, main lecture theatre

The changing Arctic environment is of particular interest at the present time, with important implications for marine ecosystem structure, biodiversity and functioning. In this seminar, I will outline some new work on faunal assemblages from the north Svalbard margin and present preliminary results from a marine sediment core (JM10-03GC) from the mouth of Wijdefjorden, NW Svalbard. I will focus on the challenges of building a chronology for the core based on 14C dating of marine shell material and pay particular attention to the evidence for Atlantic water incursion onto the north Svalbard shelf during the Younger Dryas – Holocene transition. I will then broaden the discussion of the seminar to look at the question of the timing and rate of change in other North Atlantic records which span this time interval, highlighting the significance of a mechanistic link between the strength of the Atlantic’s overturning circulation and the spatial-temporal changes in the 14C age of surface waters (e.g. Austin et al., 2011).

# Wednesday 25th January 2012, 4.30pm - Dr Poul Christoffersen, Scott Polar Research Institute
Ice-ocean interactions in Kangerdlugssuaq Fjord
Venue: Scott Polar Research Institute, main lecture theatre

The Greenland Ice Sheet is losing mass at an accelerating pace. This decline in mass is a result of increased runoff during longer and warmer summers as well as the interaction of the ice sheet with the surrounding seas. Whereas the effect of atmospheric warming is relatively well established, little is known about the latter effect since ice-ocean interactions in glaciated fjords are poorly documented. Here, we use hydrographic data acquired in Kangerdlugssuaq Fjord and adjacent seas in 1993 and 2004, together with reanalysis from the Nucleus for European Modelling of the Ocean (NEMO), to establish the connection between water mass change in the fjord and offshore air-sea interactions. The hydrographic data show that the fjord contains warm subtropical waters and that fjord waters in 2004 were considerably warmer than in 1993. The ocean reanalysis shows that the warm properties of fjord waters in 2004 are related to a major peak in oceanic shoreward heat flux into a cross-shelf trough on the outer continental shelf. The heat flux into this trough varies according to seasonal exchanges with the atmosphere as well as from deep seasonal intrusions of subtropical waters. Both mechanisms contribute to high (low) shoreward heat flux when winds from the northeast are weak (strong). The combined effect of surface heating and inflow of subtropical waters is seen in the hydrographic data, which were collected after periods when along-shore coastal winds from the north were strong (1993) and weak (2004). The latter data were furthermore acquired during the early phase of a prolonged retreat of Kangerdlugssuaq Glacier. We show that coastal winds vary according to a large scale pressure gradient defined by a semi-permanent atmospheric high-pressure system over Greenland and a persistent atmospheric low situated near Iceland, i.e. the Icelandic Low, which defines the northern state of the North Atlantic Oscillation. The magnitude of this pressure gradient is controlled by longitudinal variability in the position of the Icelandic Low.

# Wednesday 30th November 2011, 4.30pm - Dr Neil Harris, University of Cambridge
Polar ozone loss
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Wednesday 23rd November 2011, 4.30pm - Dr Mark Skidmore, Department of Earth Sciences, Montana State University
Microbial Communities in Antarctic Subglacial Aquatic Environments.
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Wednesday 16th November 2011, 4.30pm - Dr Marion Bougamont, Scott Polar Research Institute
Understanding contemporary change in West Antarctica: Insights from a higher order ice sheet model with dynamic subglacial processes
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Monday 14th November 2011, 1.00pm - Dr Ian Willis, Scott Polar Research Institute
Modelling melt, water routing and the filling and drainage of lakes on the Greenland Ice Sheet
Venue: MR4, Centre for Mathematical Sciences

Abstract not available

# Wednesday 2nd November 2011, 4.30pm - Dr Ed King, British Antarctic Survey
Imaging contemporary subglacial landscapes: detailed geophysical surveys of Antarctic ice streams
Venue: Scott Polar Research Institute, main lecture theatre

Abstract not available

# Wednesday 19th October 2011, 4.30pm - Martin O'Leary, Department of Atmospheric, Oceanic and Space Sciences, University of Michigan
Why do glaciers fall apart?
Venue: Scott Polar Research Institute, main lecture theatre

Most of the time, glaciologists treat ice as a highly viscous fluid, something quite different from our everyday experience of the material. However, near the
margins of ice sheets and glaciers, our intuitive ideas of ice as a brittle solid become more important. A broad family of processes lead to the breakup of the ice, and the calving of icebergs. While the details of the fracture process are still unknown, it is possible to say a lot about the sensitivity of calving by examining the response of the stress field within the glacier to changes at the margins. In this talk I will discuss some of these effects, focusing on the response of tidewater glaciers to frontal melting.

# Wednesday 16th March 2011, 4.30pm - Anne Le Brocq (University of Exeter)
Antarctic subglacial hydrology and topography
Venue: Scott Polar Research Institute, main lecture theatre

In this seminar I will talk about my previous modelling efforts for incorporating a representation of subglacial hydrology into a numerical ice sheet model and consider the challenges that are faced at present. I will also talk about recent developments in characterising the basal topography and how this is contributing to the subglacial hydrology debate.

# Wednesday 23rd February 2011, 4.30pm - Finlo Cottier (Scottish Association for Marine Science)
THIS SEMINAR HAS BEEN CANCELLED
Oceanography in Arctic fjords
Venue: Scott Polar Research Institute, main lecture theatre

Arctic fjords are rapidly becoming the focus of intense oceanographic activity, both physical and biological. The main sites of current research are the fjords in Svalbard and Greenland. The dynamics and exchanges of fjords are particularly important with respect to the delivery of heat to glacier fronts. There are also complex interactions on the adjacent shallow shelves that determine the input of oceanic waters to the fjords. Fjords are also recognised as sites for process based studies and this is particularly relevant to studying seasonality in biological systems. This talk will present examples of physical and biological research undertaken in arctic fjords demonstrating some of the key attributes and complexities of these coastal environments. It will include some very recent results from observational work undertaken during summer 2010 in southeast Greenland where we are starting to disentangle the complex dynamics of heat delivery to tidewater glaciers.

# Wednesday 16th February 2011, 4.30pm - Cameron Rye (University of Oxford)
Quantifying the predictive uncertainty of numerical mass balance models
Venue: Scott Polar Research Institute, main lecture theatre

Spatially distributed, physically based mass balance models are valuable tools for exploring the detailed spatial and temporal responses of glaciers and ice sheets to climate forcing. Indeed, the last two decades have seen their application become increasingly widespread, partly due to the increased availability of computational resources, and partly because scientists have a natural tendency to adopt realistic descriptions of real-world processes. However, while considerable progress has been made in the development of sophisticated numerical models, very little attention has been given to their predictive uncertainty. In particular, mass balance models have traditionally been calibrated (or “tuned”) in order to identify a single set of model parameters (e.g. snow density, surface albedo, temperature lapse rate) such that the model’s behaviour closely matches that of the real system it represents. But, as will be demonstrated for a case study in Svalbard, it is often difficult (if not impossible) to find a single “best” set of parameter values that reproduce all the characteristics of real-world observations. Instead, multiple equally plausible parameter sets will usually exist, which undoubtedly introduces a degree of uncertainty into model forecasts. Despite knowledge of this problem within the environmental science community, there has yet to be a rigorous attempt to quantify the predictive uncertainty of glacier mass balance models. The present work will address this limitation through the novel application of a calibration technique previously not employed in glacial modelling – multi-objective optimisation – designed to identify multiple optimal parameter sets that fit different characteristics of the real-world observations, thereby enabling an assessment of the uncertainty associated with predictions. This is a generic methodology that can be applied to any type of mass balance model and to both glaciers and ice sheets. Overall it is argued that a new calibration paradigm is urgently required to provide more useful information on the uncertainty associated with ongoing and future projections of ice volume and sea level rise.

# Wednesday 26th January 2011, 4.30pm - Adrian Jenkins (British Antarctic Survey)
Ocean forcing of ice sheet change in West Antarctica
Venue: Scott Polar Research Institute, main lecture theatre

The part of the West Antarctic Ice Sheet that drains into the Amundsen Sea is currently thinning at such a rate that it contributes nearly 10% of the observed rise in global mean sea level. Acceleration of the outlet glaciers means that the sea level contribution has grown over the past decades, while the likely future contribution remains a key unknown. The synchronous response of several independent glaciers, coupled with the observation that thinning is most rapid at their downstream ends, where the ice goes afloat, is generally taken as an indicator that the changes are being forced by the ocean. On Pine Island Glacier (PIG), in particular, the signatures of acceleration, thinning and inland retreat of the
grounding line, where the ice goes afloat, have been almost monotonic in the admittedly short and patchy observational record. Understanding the causes of these changes and their relationship to climate variability is imperative if we are to make quantitative estimates of sea level into the future. Observations made since the mid‐1990s on the Amundsen Sea continental shelf have revealed that the deep troughs, carved by previous
glacial advances, are flooded by almost unmodified Circumpolar Deep Water (CDW) with temperatures around 3‐4°C above the freezing point, and that this water mass drives rapid melting of the floating ice. This talk summarises the results of recent work, including both observations made by an Autonomous Underwater Vehicle beneath the floating tongue of PIG and numerical modelling of ocean circulation in the Amundsen Sea. The results give us important insight into the processes that could cause variability of CDW inflows and how the impact of any such variability on PIG would have been influenced by the seabed topography beneath the floating glacier tongue.

# Wednesday 1st December 2010, 7.00pm - Paul A. Berkman (University of Cambridge) & David W. H. Walton (British Antarctic Survey)
Note unusual time (7 PM)
ANTARCTICA DAY Inaugural Lecture
Venue: Scott Polar Research Institute, main lecture theatre

This year marks the 51st anniversary of a landmark treaty — the planet’s first nuclear arms-control agreement, and the first institution to govern all human activities in a region beyond sovereign jurisdictions. Adopted in Washington DC on 1 December 1959, the Antarctic Treaty recognized that “it is in the interest of all mankind that Antarctica shall continue forever to be used exclusively for peaceful purposes and shall not become the scene or object of international discord”.

ANTARCTICA DAY is conceived as an enduring legacy
to celebrate the 1st December 1959 signature of the Antarctic Treaty, which was adopted “with the interests of science and the progress of all mankind.” Paul A. Berkman and David W. H. Walton, co-chairs of the Antarctic Treaty Summit, will highlight lessons from the first fifty years of the Antarctic Treaty that have enabled humanity to manage nearly 10% of the Earth for “peaceful purposes only,” establishing precedents for our children to share as they build a world with hope and inspiration for future generations.

# Wednesday 17th November 2010, 4.30pm - Douglas Benn (University Centre in Svalbard and the University of St. Andrews)
Calving Laws for Ice Sheet Models - Recent Progress and Future Prospects
Venue: Scott Polar Research Institute, main lecture theatre

Calving accounts for most ice losses from the Antarctic Ice Sheet, around half of the losses from the Greenland Ice Sheet, and a substantial amount of the ablation from many high-latitude glaciers and ice caps. Despite this, calving processes are still poorly represented in prognostic ice sheet models, limiting our ability to predict ice-sheet response to climate change. A new approach to quantifying calving losses has been developed, based on the depth of penetration of surface crevasses, which in turn is a function of the velocity field near the glacier margin. The potential of this new approach has been demonstrated in two recent papers, which incorporate crevasse-depth calving laws (CDCLs) in glacier models. First, Nick et al. (2010) conducted a series of experiments with a higher-order flow-line model, and showed that CDCLs allow a much broader range of glacier behaviour than other ‘calving laws’. Second, Otero et al. (2009) used a static, three-dimensional, higher-order model to successfully predict the calving front position of a small Antarctic glacier. While the success of these implementations is very encouraging, the incorporation of CDCLs in a time-evolving, three-dimensional higher-order model remains an important goal for the future.

Future development of calving models requires both systematic observations of calving margins and improved modeling routines. Empirical data are urgently needed to determine how well models represent real calving processes and ice-front behaviour, and to identify key areas where improvements are needed. Many issues remain with modeling calving glaciers, but perhaps the most fundamental challenge is to find robust methods of incorporating basal motion (sliding) in higher-order models. It is clear that there are intimate links between calving and glacier dynamics, but realistic, workable ‘sliding laws’ remain elusive. This problem is closely linked with another of glaciology’s ‘last great problems’ – the calculation of evolving subglacial water-pressure fields.

# Monday 1st November 2010, 4.30pm - Hilmar Gudmundsson (British Antarctic Survey)
Note unusual time (MONDAY)
Ice Stream Tides
Venue: Scott Polar Research Institute, main lecture theatre

The ice streams of Antarctica are fast flowing glaciers that move large amount of ice from the interior of the ice sheet towards the ocean. Despite being grounded, and therefore not directly subjected to oceanic tides, ice-stream flow is sometimes tidally modulated. These ice-stream tides are caused by oceanic tides, but the relationship between oceanic and ice-streams tides can be complex. As an example, on Rutford Ice Stream (RIS), one of the large ice streams of West Antarctica, ice flow speeds increase by 10 % in the course of about one week, and then decreases again in the following week. Despite being subjected to strong diurnal tides, there is little or no diurnal modulation in the flow of RIS. Response of ice streams to tides is critically affected by the mechanical conditions at the base of the ice stream. Observations and modelling of ice-stream tides can therefore be used establish constrains on basal processes and to test theoretical concepts about the flow of large ice masses.

# Wednesday 20th October 2010, 4.30pm - Daniel Nývlt (Czech Geological Survey)
Northernmost Antarctic Peninsula glacial and climate changes
Venue: Scott Polar Research Institute, main lecture theatre

Present climate changes in Antarctica are documented by disintegration of ice shelves along the Antarctic Peninsula (Prince Gustav, Larsen, or Wilkins Ice Shelves), by West Antarctic ice sheet decay connected with enhanced ice flow velocities, by minor East Antarctic ice build-up and by temperature rise evidenced by meteorological measurements in West Antarctica and Antarctic Peninsula. However, it was shown by different geological and palaeoclimatological studies that the climate has not been stable in Antarctica since the Antarctic massive ice built-up in the early Cenozoic. Three different windows in the northernmost Antarctic Peninsula glacial and climate history will be shown. The first one includes changes that appeared some 5–6 million years ago; the second shows the melting of the Antarctic Peninsula ice at the end of the last Ice Age 12 thousand years ago and the Holocene glacial changes; and the third one documents direct field and remote data of glacier changes during the last 3–4 decades.

# Thursday 7th October 2010, 4.30pm - Lisle A. Rose
Note unusual time: this seminar is on a Thursday
Lives on The Ice - Changing Patterns of Antarctic Experience from Scott to Byrd
Venue: Scott Polar Research Institute, main lecture theatre

Lisle A. Rose, author of ‘Explorer: The Life of Richard E. Byrd’ (University of Missouri Press, 2008) will talk on Byrd’s Antarctic expeditions, comparing them with those of the Heroic Age of Scott and others. Together with the aeroplane, motorized vehicles and long-range radio communications, Richard E. Byrd and his men also introduced a new lifestyle to polar exploration in the 1920s and ‘30s, one less disciplined and deferential to authority than the earlier expeditions. Byrd’s two Antarctic winter camps were beset by dissention, frequent turmoil, and often risky behavior that bordered on the foolhardy. Animosities and rivalries were suppressed during the austral summer field seasons. Byrd and his men thus accomplished their goals and emerged from their ordeals unscathed and triumphant. But as so often is the case in Antarctica, good fortune was as great an element in their success as dedication and skill.

Lisle Rose is the first biographer to have had complete and full access to Byrd’s extensive personal papers at The Ohio State University archives. Rose first went to Antarctica in 1956-57 as a twenty year old petty officer aboard a U.S. Navy icebreaker. He subsequently served (1978-82) as the U.S. State Department’s polar affairs officer. Author of eleven other books, Rose lives in Edmonds, Washington.

Picture: Byrd’s Little America II camp on the Ross Ice Shelf, 1934 (from National Geographic).

# Wednesday 3rd March 2010, 4.30pm - Bernd Kulessa (Swansea University)
Flow, fracture and modelled stability of the Larsen C ice shelf
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR), doors open for general access

We modelled the flow of the Larsen C ice shelf using an adapted continuum-mechanical model, and applied a fracture criterion to the simulated velocities to investigate its present-day stability. Constraints come from satellite data and geophysical measurements in the 2008-09 austral summer. We obtained excellent agreements between modelled and measured ice-flow velocities, and inferred and observed distributions of rifts and crevasses. Ice-shelf thickness was derived from BEDMAP and ICESat data and depth-density profiles inferred from our seismic data. Notable exceptions occur in regions of modelled basal accretion down flow of promontories, thus placing the first quantitative constraints on their mechanical effects. Anomalously soft marine ice, advected into the ice shelf in flow-parallel bands, controls rates of rift propagation downstream. In this presentation I will assess the implications of these findings for the current stability of the Larsen C ice shelf, as compared with the pre-collapse dynamic evolution of the Larsen B ice shelf. I will also present initial analyses and findings from extensive ground-penetrating radar surveys in the 2009-10 austral summer in a prominent zone of basal accretion down-flow of the Joerg Peninsula.

# Wednesday 17th February 2010, 4.30pm - Anthony Seale (University of Cambridge)
Automatic satellite monitoring of East Greenland's calving glacier fronts: seasonal signals and southern retreat
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR), doors open for general access

Whilst completing my M.Phil at SPRI I developed a new automated system for tracking Greenland tidewater glacier frontal positions using MODIS (satellite) data. By reducing the amount of researcher labour required to gather glacier positions, the method allowed data to be collected from 105,536 glacier images, giving a detailed account of East Greenland glacier retreat and other behaviour during the rapid speed-up events of the past decade. Large scale retreat was found on southern glaciers, with little change further north. Widespread seasonal patterns were also found to exist on many glaciers. The role of the ocean in controlling retreat is considered, attempting to explain the observations. This talk will be of interest to remote sensors, glaciologists and M.Phil students beginning their research.

# Wednesday 3rd February 2010, 4.30pm - Paul Berkman (University of Cambridge)
Environmental Protection in the Arctic Ocean
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR), doors open for general access

The Arctic Ocean is crossing an environmental threshold expected to transform it from a perpetually ice-covered region to a seasonally ice-free sea within the next few decades. This environmental change has awakened global interests in Arctic energy, fishing, shipping, and tourism. The Arctic could slide into a new era featuring jurisdictional conflicts, increasingly severe clashes over the extraction of natural resources, and the emergence of a new “great game” among the global powers. However, the environment provides a physical and a conceptual framework to link government interests in the Arctic Ocean, as well as a template for addressing transboundary security risks cooperatively.

# Wednesday 20th January 2010, 4.30pm - Andrew Sole (University of Aberdeen)
The effects of coastal ocean warming and increased supra-glacial run-off on water temperature and circulation in Kangerdlugssuaq Fjord, East Greenland
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR), doors open for general access

Recent studies have suggested that regional changes in ocean temperatures could be a potential trigger for retreat and acceleration of Greenland tidewater outlet glaciers. There is therefore a need to understand how these changes are propagated along fjords to the glaciers’ calving termini. We use the Bergen Ocean Model to simulate ocean circulation in Kangerdlugssuaq Fjord to assess the impact that warmer coastal waters and increased supra-glacial run-off could have on the submarine melt rate of Kangerdlugssuaq Gletscher. The model includes tidal and freshwater runoff forcing and is able to replicate well observed temperature and salinity profiles. We find that warm coastal water flows into the fjord at several distinct depths as a result of freshwater outflow near the surface and at intermediate depth. The deeper (~400m) warm water plume reaches the terminus of Kangerdlugssuaq Gletscher and increases submarine melt rates. The magnitude of supraglacial runoff is crucial in controlling the penetration of warm water into the fjord because of the compensatory inflow at depth.

# Wednesday 2nd December 2009, 4.30pm - Christopher Talbot (Earth Sciences, University of Uppsala)
Image caption: view across the northern namakier at Kuh-e-namak (Dashti), Iran Zagros. Salt is > 500 my old.
Subaerial salt extrusions in Iran as analogues of ice sheets, streams & glaciers
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR)

Ice (H20) and salt (halite, NaCl) form by different processes in mutually exclusive environments but share many physical properties and resemble each other in hand specimens and en-masse. Layyers of salt have to be buried by kilometres of other rocks over millions of years before they rise to the surface in piercing structures (diapirs) many of which extrude flows that simulate glaciers. Seismic profiles have revealed 1000s such salt sheets in over 35 basins worldwide in the last 25 years. As most of these are submarine the focus here will be on subaerial rivers of salt (namakiers) exposed in the deserts of Iran. Glaciers and namakiers will be compared and contrasted. Clear grain shape fabrics map streamlines that help understand how folds develop inside namakiers. Namakiers surge like glaciers but within 20 minutes of their TOP surfaces being wet by rain that cannot reach the basal contact.

# Wednesday 18th November 2009, 4.30pm - Alan Ashworth (Department of Geosciences, North Dakota State University)
Neogene terrestrial environment of Antarctica
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR)

The discovery of terrestrial fossil assemblages at several locations in the Transantarctic Mountains is transforming our understanding of the late Cenozoic environment of Antarctica. The most southerly fossil assemblage is at lat. 85.1°S, about 500 km from the South Pole. The environment was an active glacial margin in which plants, insects and freshwater mollusks inhabited sand and gravel bars and small lakes on an outwash plain. Initially the deposits were assigned a Pliocene age (3.5 Ma) but a mid- to early Miocene age is more probable (c. 14 – 25 Ma) based on correlation of fossil pollen from the deposits with 39Ar/40Ar dated pollen assemblages from the McMurdo Dry Valleys. Within the McMurdo Dry Valleys, the oldest fossiliferous beds are at least 19.76 Ma based on the 39Ar/40Ar age of a volcanic ash bed interbedded within a valley fill of diamictites, paleosols and lacustrine deposits. The valley floor during the non-glacial phases had poorly-drained soils and the extensive development of mossy mires. Wood and leaves of Nothofagus are abundant in lacustrine deposits. The silts of shallow fluvial channels contain abundant megaspores and spiky leaves of the aquatic lycopod Isoetes (Quillwort). The youngest fossiliferous beds within the Dry Valleys are 14.07 Ma. The fossils are mostly those of freshwater organisms including numerous species of diatoms and an ostracod species in which the soft anatomy is preserved. The base of the lake is marked by a moss bed with exceptionally well-preserved stems and leaves of the extant species Drepanocladus longifolius. Pollen evidence from marine cores in the Ross Sea basin suggests that tundra existed from the Oligocene to the Mid-Miocene. Fossil evidence from the Dry Valleys locations indicates organisms with complex life histories persisted in Antarctica until c. 14 Ma. At 14 Ma there was a shift in glacial regimes from wet- to cold-based, marking a profound and abrupt climatic shift likely causing widespread extinction. It seems probable that at least some of the mid-Miocene fossils had ancestors that evolved in Antarctica during the Paleogene or earlier. An important consequence of these studies is that the Cenozoic climate of Antarctica was warm enough until the mid-Miocene to support vascular plants and insects.

# Wednesday 11th November 2009, 4.30pm - Alex Piotrowski (Earth Sciences, University of Cambridge)
Linking North and South Atlantic deep water circulation using Nd isotopes
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR)

Understanding changes in ocean circulation during the last deglaciation is crucial to unravelling the dynamics of glacial-interglacial and millennial climate shifts. Neodymium (Nd) isotope records measured on Fe-Mn oxide leaches from marine sediment cores have been used to reconstruct changes in Atlantic deep water mixing and structure. We present new tests of marine Nd extraction, and new widely distributed records. Taken as a whole, these records provide a coherent reconstruction of glacial Atlantic deep circulation, which is consistent with benthic d13C reconstructions, and suggests major changes in water mass strength and structure during the last deglaciation. Neodymium isotope measurements from deep western North Atlantic at the Bermuda Rise allow comparison of our deep water source record with overturning strength proxies. This comparison shows that both deep water mass source and overturning rate shifted rapidly and synchronously during the last deglacial transition. In contrast any freshwater perturbation caused by Heinrich event 1, could have only affected shallow overturning illustrating the difference between changes in upper-ocean overturning associated with millennial-scale events, and whole ocean deglacial climate events.

# Wednesday 28th October 2009, 4.30pm - Paul Holland (British Antarctic Survey)
Note: unusual venue
Marine Ice in Larsen Ice Shelf
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR)
It is argued that Larsen Ice Shelf contains marine ice formed by oceanic freezing and other mechanisms. Missing basal returns in airborne radar soundings and observations of a smooth and healed surface coincide downstream of regions where an ocean model predicts freezing. Visible imagery suggests that marine ice currently stabilizes Larsen C Ice Shelf and implicates failure of marine flow bands in the 2002 Larsen B Ice Shelf collapse. Ocean modeling indicates that any regime change towards the incursion of warmer Modified Weddell Deep Water into the Larsen C cavity could curtail basal freezing and its stabilizing influence.
# Wednesday 20th May 2009, 4.30pm - Chris Woodworth-Lynas (NW Atlantic Ocean Observing System Partnership)
Where Have All the Icebergs Gone?
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR)

The Greenland Ice Sheet is annually producing nearly 50% more icebergs, volumetrically, than it did prior to 1995. This volumetric increase should be reflected in a similar increase in the numbers of icebergs. However, the increase in numbers is not seen along the iceberg drift route further south on the Grand Banks of Newfoundland. The presentation examines the reasons for this unanticipated and massive increase in iceberg production into the NW Atlantic and discusses possible reasons why the increase is not seen further south.

# Wednesday 22nd April 2009, 4.30pm - Speaker to be confirmed
Mechanisms of englacial conduit formation and their implications for subglacial recharge
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR)

Ideas about the character and evolution of englacial drainage systems have been deeply influenced by the theoretical model developed by Shreve (1972). The Shreve model is based on three main assumptions: (1) englacial drainage is in steady state; (2) englacial water will flow along the steepest hydraulic gradient within the glacier; and (3) pressure head equals the pressure of the surrounding ice minus a small component due to melting of the walls. The Shreve model has been widely adopted as a fundamental component of englacial drainage theory.

To evaluate Shreve’s theory, we used speleological techniques to directly survey englacial conduits. We have explored more than 45 distinct englacial conduits to ice depths of 110 m and mapped a total of 9.5 km of passage in 28 conduits in temperate, polythermal, cold-based and debris-covered glaciers between 2005 and 2009. New information reported here is supplemented by published data on 40 other englacial conduits located worldwide and surveyed to ice depths of 203 m using speleological techniques. In all cases, englacial drainage systems consisted of a single unbranching conduit. Englacial conduit morphologies were found to be intimately linked to the orientation of a glacier’s principal stresses or the presence of pre-existing lines of high hydraulic conductivity. If a sufficient supply of water is available, hydrofracturing forms vertical conduits in zones of longitudinal extension and subhorizontal conduits where longitudinal stresses are compressive. On unfractured glacier surfaces, relatively shallow subhorizontal conduits with migrating nickpoints form by cut-and-closure provided channel incision is significantly faster than surface lowering. Conduits can also form along permeable debris-filled crevasse traces that connect supraglacial lake basins of different potential. Only conduits formed by extensional hydrofracture were found to be connected to glacier beds. Our results suggest that a Shreve-type englacial drainage system probably does not exist and implies that englacial conduits can only penetrate through thick ice to recharge the bed of the Greenland Ice Sheet where supraglacial water bodies either intersect, or are advected through, zones of acceleration.

# Wednesday 4th March 2009, 4.30pm - John Woodward, Northumbria University
Geophysical surveys of Subglacial Lake Ellsworth, West Antarctica: implications for in-situ exploration
Venue: Scott Polar Research Institute, LIBRARY (1ST FLOOR)

In addition to exerting a significant impact on ice sheet dynamics, subglacial lakes are expected to contain unique life forms and records of ice sheet history. To date, none of the ~150 Antarctic lakes discovered from radio echo sounding surveys have been accessed directly. The Ellsworth Consortium has recently received funding to access Subglacial Lake Ellsworth (SLE) in West Antarctica in 2012/13. In order to plan for lake access we have completed a geophysical reconnaissance of SLE. A series of airborne and ground-based radar surveys have mapped: a) the lake outline, b) the ice thickness in the region and c) the internal structure of the ice sheet. Radar surveys reveal that SLE lies beneath 3.2 km of ice in a deep, topographically controlled fjord-like valley, is 11.9 km long and has a maximum width of 2.9 km. Between November 2007 and February 2008 five seismic reflection survey lines were collected perpendicular to the long axis of the lake at 1.4 km intervals. The seismic profiles show the steep valley side-walls, lake water depths and the morphology and composition of the lakebed. The seismic profiles indicate that the thickness of the water-body increases down-lake from a maximum depth of 50 m on the up-flow profile to a maximum depth of nearly 160 m on the down-flow profile, producing a water volume of 1.4 km3, suggesting that SLE is a substantial body of water. The lake bed is composed of high-porosity, low-density sediments with acoustic properties very similar to material found on the deep ocean floor. Seismic reflections indicate a substantial thickness of this soft sedimentary material, accumulated at the lake bed in a low-energy environment. Modelled basal mass balance suggests that nearly 80% of the ice water interface is at the melting point. A thin 15 m thickness of accretion ice forms at the down-ice-flow end of the lake. Geophysical results confirm that SLE is an ideal target for in-situ sampling and indicate significant practical implications for the lake access operation.

# Wednesday 18th February 2009, 4.30pm - Clive Oppenheimer, Department of Geography, University of Cambridge
Erebus volcano, Antarctica: eruption dynamics and atmospheric impacts
Venue: Scott Polar Research Institute, main lecture theatre

Erebus is an exceptional volcano. It rises nearly 4 km above sea-level, dominating Ross Island, and continuously erupts an unusual magma (phonolite) via a persistent lava lake in the summit crater. But it also goes through phases, lasting months, in which this peaceful behaviour is punctuated by violent explosive eruptions that occur a few times a day. Erebus also represents the largest point source of several reactive gases and particles to the Antarctic troposphere. The volcano is monitored more or less year-round by a network of seismometers and other instruments, and is subject to intense field campaigns each year during the austral summer. Drawing on the results of measurements of gas and heat emissions from the volcano, I will review progress in the development of conceptual models for the evolution, transport and degassing of magma beneath Erebus, discuss the origins of the explosive activity, and examine the evidence for impacts of the emissions of NOx, halogens and sulfur on the atmospheric environment.

# Wednesday 26th November 2008, 4.30pm - Robert Bingham (British Antarctic Survey)
In situ glacial geophysical investigations of Pine Island Glacier, West Antarctica
Venue: Scott Polar Research Institute, main lecture theatre

Remote sensing observations since the 1990s have exposed Pine Island Glacier as one of the most rapidly thinning and accelerating ice streams in Antarctica, and therefore the world. Flowing into the Amundsen Sea embayment, thought to be an area of potential ocean warming, and grounded well below isostatically rebounded sea levels, there is concern that the astonishing changes witnessed across the region from space reflect the onset of a major response of the West Antarctic Ice Sheet to global warming. Attempts to model the behaviour of the ice sheet in this region have been hindered by a dearth of subsurface information, with fieldwork hampered by the extreme remoteness of the catchment. This talk will report on the first in situ glacial geophysical investigations ever conducted on Pine Island Glacier. Punctuated with photographic material from the speaker’s first visit to the continent, the talk will outline the range of geophysical methods used to investigate change across this extremely remote, yet highly dynamic region; and will focus on the use of over snow radar to image the internal and basal conditions beneath the surface of Pine Island Glacier.

# Wednesday 12th November 2008, 4.30pm - Adrian Luckman (Swansea University)
TBA
Venue: Scott Polar Research Institute, main lecture theatre

TBA

# Wednesday 29th October 2008, 4.30pm - Anne Le Brocq (University of Durham)
Antarctic subglacial hydrology
Venue: Scott Polar Research Institute, main lecture theatre

Investigations into the subglacial hydrology network beneath the Antarctic Ice Sheet have shown that it is a dynamic system which is highly sensitive to small changes in the surface morphology. However, the role of subglacial water in controlling the dynamics of ice flow is not fully understood, and hence a physically realistic numerical model of the Antarctic Ice Sheet does not presently exist. This seminar will describe the nature of Antarctic subglacial hydrology, highlighting the locations which may be highly sensitive to surface changes, and discuss previous and potential modelling efforts which have attempted to link the two dynamic systems.

# Wednesday 15th October 2008, 4.30pm - Murray Mitchell (OPUS Engineering - New Zealand)
Antarctic Engineering
Venue: Scott Polar Research Institute, main lecture theatre

Structural engineering in Antarctica presents unique technical and logistical challenges. With more than twenty-five years of experience, Murray Mitchell has been the lead structural engineer in New Zealand’s Antarctic programme. Projects include rebuilding of the Scott Base, structural assessments of Scott’s and Shackleton’s huts and wind turbines for Arrival Heights. This illustrated talk will focus on the technical challenges of ANDRILL , an international Antarctic drilling project where sedimentary cores are collected from beneath moving ice. The talk will also outline some of the general engineering techniques that New Zealand has utilised in one of the world’s most extreme environments.

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