Scott Polar Research Institute - Physical Sciences Seminar: archive

Return to the list of forthcoming seminars.

# 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.