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SPRI Review 1996: Research Overviews

Research Overviews

Glacier Geophysics Group

Dr G. de Q. Robin, Dr C.W.M. Swithinbank
J. Evans, M.R. Gorman, Dr R. Hodgkins

Professor Julian Dowdeswell moved to Aberystwyth in October 1994 to start a centre for Glaciology within the Department of Earth Studies, University of Wales, followed by Dr Martin J. Siegert in December 1994 and two others from the Institute in 1995. Another member of this group, Mr Michael Gorman (Research Associate), continued his research and instrument development in SPRI.

The outstanding feature of the year for both groups was the coordinated reassessment of all radio-echo sounding (RES) around the large sub-ice lake of 10,000 km2 beneath 4 km of ice of central East Antarctica, reported in 1974. Reassessment followed publication of the first satellite altimetry data from the European Satellite ERS1 in 1993. The relevant programming had been developed at a series of meetings in Europe from 1982 to 1990 to which Institute staff (Dr D.J. Drewry and others) contributed. The 1993 altimetric data showed a surface topography in general agreement with the 1974 RES data. This led to a workshop in Cambridge in November 1993 between Institute, British Antarctic Survey, and Russian scientists who planned an extensive reassessment of all data relevant to the ice and lake dynamics. Extensive satellite altimetry giving 2 m contours over the Antarctic ice sheet north of 82°S became available in January 1996. Agreement between the lake boundary along RES flight lines and slope changes shown by 2 m contours was then used to define the lake boundary in detail. The lake area, now 14,300 km2, extends southwards beneath Vostok station. A new interpretation of seismic soundings made in 1964 using a vertical seismometer line to 49 m depth, gave a water depth of 510 m beneath 3.7 km of ice, the first deep lake beneath an ice sheet to be identified. RES showed that the lake occupies a deep rift valley extending more than 200 km north of Vostok Station, where grounded ice showed the valley bed at 700 m below sea level, as beneath Vostok.

The estimated time from depositon of snow on the surface to melting into the sub-ice lake of around one million years created considerable interest among microbiologists. The sub-ice lake and lake bed sediments are likely to contain micro-biological molecules that have been preserved and isolated from the atmosphere for an even longer period. The outline of these results in Nature in June 1996 received considerable attention from the press and media in several countries.

Dr Siegert made five visits to the Intitute during the year for further processing and research on the Institute's RES data. This led to a list of locations of 77 sub-ice lakes identified along RES flight lines from 1967 to 1979. Siegert and Dr Richard Hodgkins (Research Associate) linked RES layering beneath Vostok station due to widespread deposition of volcanic dust on the ice sheet with that at the future European ice coring site on Dome C some 500 km distant. This indicates that the continuous stratigraphy of the Dome C ice cores should extend over at least the last three glacial cycles, a significantly longer period than is likely in the Vostok core.

Radio-echo sounding equipment built by Gorman in 1993-94 was used successfully by the Italian Antarctic expedition in 1995-96 to sound the Dome C area. Gorman also helped Italians analyse these data to select the best site for the planned European ice coring project. In addition to further analysis of RES data, Gorman spent much time during 1995-96 developing equipment for the joint Aberystwyth-Russian study entitled 'Form and flow of the ice caps on Severnaya Zemlya (80°N, 100°E) in the Russian high Arctic.'

Mr Jeff Evans (Research Student) moved from the Institute to Aberystwyth in October 1995 to complete his PhD thesis on 'Late Quaternary ice rafted debris on East Greenland fjords and continental shelf.'

Dr Gordon Robin continued his revision of polar ice sheet dynamics.

The appointment of a glaciologist, Dr Neil Arnold, to a joint lectureship in the Department of Geography and the Institute from 1 October 1996 will develop new activities of the group.