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SPRI Review 2010: Polar Physical Science

Polar Physical Science

Detecting lake change in the permafrost-influenced wetlands of northern Alaska

This project aims to determine whether lakes in Alaskan wetlands are changing in response to warming of permafrost, which has been 3-4°C since 1985 in this region. An automatic method has been developed to determine the number and cumulative area of wetland lakes in satellite imagery; the results show major recent change. The number of lakes and their cumulative area were similar in 1980 and 1990, but lakes grew and became more frequent in 2000. In the drainage basin of the Kuparuk River, our main study site, we found cumulative lake area growth from 694 km2 in 1990 to 819 km2 in 2000; an 18% increase. Overall, more than 5,000 lakes had shrunk, whereas almost 30,000 had increased in size. We are currently mapping lake changes after 2000 to determine whether such growth continues. A numerical model of permafrost is being developed which will be used to establish whether lake growth is a result of permafrost thaw. Degradation of permafrost and lake growth may result in significant methane emissions due to the carbon-rich nature of Arctic wetlands. The project is funded by Eni S.p.A.

Poul Christoffersen, Julian Dowdeswell, Toby Benham and Ruth Mugford

Under-wing antenna for ice-pentrating 60 MHz radar system, McMurdo Station, Antarctica

Under-wing antenna for ice-pentrating 60 MHz radar system, McMurdo Station, Antarctica

Hydrology of the Greenland Ice Sheet

There is growing interest in the “plumbing” of the Greenland Ice Sheet; in particular, how meltwater is delivered from the surface into the ice sheet and how it influences basal water pressures and ice sheet dynamics as the water makes its way to the ice sheet margin. We are currently developing an ice sheet hydrology model and applying it to the Paakitsoq / Swiss Camp region of West Greenland. Our model uses local climate data to calculate patterns of snow accumulation and, using an energy-balance approach, patterns of melt. Snow hydrology and open channel flow theory are then used to route the water through snow and across ice to surface lakes. We are currently testing the surface melt / routing component of our model against existing field data and satellite imagery. Field data include long-term measurements of surface lowering from which we calculate snow and ice melt. Satellite data consist of Landsat and MODIS imagery to classify patterns of snow and ice cover. We are also developing algorithms to calculate lake surface areas and water depths from satellite imagery. The work is being undertaken with PhD student Alison Banwell and Masters student Alex Messerli, and in collaboration with Andreas Ahlstrøm (Geological Survey of Denmark and Greenland) and Marco Tedesco (City College of New York).

Ian Willis and Neil Arnold

Past ice-sheet flow east of Svalbard inferred from streamlined subglacial landforms

The pattern of full-glacial ice flow about 20,000 years ago in the northern Barents Sea is not well known, due mainly to a lack of marine data east of Svalbard. Several years with little summer sea ice have allowed acquisition of swath-bathymetric imagery of well-preserved subglacial landforms characterising Late Weichselian ice-flow directions over ~150,000 km2 of the northwestern Barents Sea. A major ice dome was located on easternmost Spitsbergen or southern Hinlopen Strait, at least 500 km west of its previously inferred position in the northern Barents Sea. This dome controlled the regional flow pattern; ice flowed eastward around Kong Karls Land into Franz Victoria Trough and north through Hinlopen Strait. An ice dome west of Kong Karls Land is required to explain the observed ice-flow pattern, but does not preclude an additional ice dome to the southeast. Discrepancies with earlier ice-sheet reconstructions reflect the lack of previous seafloor observations, with evidence limited mainly to past ice loading and postglacial rebound. The new pattern of ice-flow directions shows predominantly eastward rather than northward flow, with Franz Victoria Trough a major drainage pathway with a full-glacial balance flux of >40 km3 per year. This work is collaborative with Colm Ó Cofaigh (Durham), Jeff Evans (Loughborough), Riko Noormets (UNIS) and Dag Ottesen (Norwegian Geological Survey).

Julian Dowdeswell and Kelly Hogan

Modelling iceberg-rafted sedimentation in high-latitude fjords

A numerical model, SedBerg, has been developed to simulate sedimentation from icebergs in high-latitude glaciated fjords. Sediments deposited in fjords provide an important record of glaciological response to changing climatic conditions. The model simulates the formation, drift, and melt of a population of icebergs utilizing Monte Carlo based techniques with a number of underlying probability distributions to describe the behaviour of iceberg formation and dynamics. The model captures iceberg dynamics and melting in fjord environments and has been applied to Kangerlugssuaq Fjord in East Greenland; an example of an iceberg-dominated sedimentary environment. Sedimentation has been simulated over the past 1500 years, encompassing the climatic intervals of the Medieval Warm Period and the Little Ice Age of the past few centuries, which terminated about 100 years ago. Model results have been compared with the observed sedimentary record in the fjord. The model demonstrates that the glaciological regime plays a more important role than the direct influence of climate (such as ocean and air temperatures) on iceberg sedimentation. This research has been published recently in the Journal of Geophysical Research.

Ruth Mugford and Julian Dowdeswell

CryoSat

SPRI continues to participate in an international programme to calibrate data collected by a new radar altimeter (SIRAL) carried on the CryoSat-2 satellite, launched this year. The first of the post-launch field activities was a repeat traverse along the Expedition Glaciologique Internationale au Groenland (EGIG) line across the Greenland Ice Sheet. As in 2004 and 2006, measurements of snow density profiles were made using an automated neutron profiling system but, for the first time, an 800 km round trip from Summit Station was also undertaken. This allowed measurements of summer densification of surface snow over short time periods to be made. A paper on snow densification in Greenland was presented at the 2010 American Geophysical Union Fall Meeting and is being prepared for publication.

Liz Morris

Four C - 130 aircraft on the sea ice runway in McMurdo Sound, Antarctica

Four C - 130 aircraft on the sea ice runway in McMurdo Sound, Antarctica

Snow mechanics

Adrian McCallum is completing his doctoral thesis on the mechanical properties of snow. Field studies of the strength of snow on the Brunt Ice Shelf in Antarctica have shown that a commercial cone penetrometer system can provide useful data on the fracture strength of undisturbed polar snow and of snow roads and runways prepared using heavy machinery. Cone penetration tests reveal strong and weak layers in natural snow and the effect of various techniques for forming hard pavements by reworking and compressing the surface snow. The work has been presented at conferences in California and Perth, Australia.

Liz Morris

Spectral and physical characterisation of glacier surfaces

Airborne multispectral remote sensing data were used to determine spatial variations in the physical properties of glacier surfaces. Quantitative analysis has been carried out on multispectral imagery from Langjökull, Iceland, and from Midre Lovénbreen, Svalbard. In July and August we undertook fieldwork on Midre Lovénbreen, collecting detailed spectral reflectance data on a number of ice and snow surfaces using an ASD Fieldspec 3 spectroradiometer loaned to us by the Natural Environment Research Council.

We also collected data on the physical state of the glacier surface, particular snow density and grain size. These data are being used to link the physical and spectral properties of the ice surface and to scale up the results to the resolution of airborne imagery (a few metres) and, ultimately, to that of satellite data (tens of metres).

Allen Pope, Neil Arnold, Ian Willis and Gareth Rees

The validation of British Arctic whaling information, 1750-1850

During the 18th and 19th centuries, the British whaling industry was conducted from over 30 ports. Information from the industry is still scattered, unconsolidated and without a central repository. This project makes use of primary data extracted from contemporary documents such as ships’ logs, journals, voyage listings, maps and pictures sourced from archives, museums, public and private collections and port authorities throughout Britain. Data from voyages of the Whitby scientist and whaler William Scoresby Jr. provide a baseline for comparison with those of a contemporary group of other Hull whalers.

Scoresby’s navigational observations are matched against present-day charts. His seasonal ice drift observations are tested against his own records of wind vectors, confirming a high standard of reliability. A test sample of 20 logs from 1810 to 1820 is used to examine topics such as navigation, wind strengths and directions, sun, ice and weather observations. The vocabulary to express ice and wind observations shows a level of consistency indicating a similarity between ports and masters.

Dinah Molloy Thompson and Gareth Rees

Sediment corer used to sample the seafloor, deployed in a Greenland fjord

Sediment corer used to sample the seafloor, deployed in a Greenland fjord