A SEISMIC ANALYSIS OF HVÍTÁRVATN, ICELAND TO DETERMINE DOMINANT SEDIMENT SOURCES INTO THE GLACIAL LAKE BASIN DURING THE HOLOCENE

Iceland is situated at the boundary between cold, polar air masses and relatively warm air masses of tropical origin. Iceland is also at the boundary between the cold, relatively fresh East Greenland Current and the warm, salty North Atlantic Drift. Subtle shifts in either atmospheric or oceanic circulation are expected to produce strong changes in the terrestrial environment of Iceland. As a consequence, the impact of North Atlantic Holocene circulation variability is likely to be stronger on Iceland than most other North Atlantic landmasses. Despite the large amplitude of climate change expected for Iceland during the Holocene, and numerous large ice caps that would respond to these changes, there are no complete records of terrestrial environmental change for the Holocene of Iceland, and the status of Icelandic glaciers in the early Holocene remains debated. It is not known whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew.

To address these questions, continuous cores from a deep, high-sedimentation-rate lake basin will be taken to provide high-resolution, quantitative evidence of environmental change over the past 10 ka. To determine the best position of the continuous sediment cores, an initial seismic survey of sediment fill in Hvítárvatn (a glacial dominated lake located at 420 m elevation on the eastern margin of Langjökull Ice Cap in central western Iceland) was completed. Analysis of the seismic data reveals over 30 m of finely stratified postglacial sediment in the north basin, and shifting locations of primary sediment sources during the Holocene. The approximate sediment volumes for each of these periods have been determined. The shifting sediment sources are indications of possible environmental changes in Hvítárvatn basin and shifts in Langjökull Ice Cap.