Reconstruction of the latest 100 years of iceberg calving from Helheim Glacier, Southeast Greenland, on basis of marine sediment cores from Sermilik Fjord
Abstract
Evidence is emerging that rising temperatures of subsurface ocean currents may play a vital role in the recent acceleration of large fast flowing glaciers, such as Jakobshavn Isbrae in West Greenland and Helheim Glacier in Southeast Greenland. An important question is whether these incursions of warmer waters are part of a recurrent phenomenon and indeed how exactly they influence the glaciers. In this study, sedimentary deposits from Sermilik Fjord in front of Helheim Glacier are analysed in order to reconstruct past hydrographic and glacier calving variability. All together 19 cores ranging between 0.5-1.5 m length were retrieved on a cruise conducted in the fjord in August 2009 and four cores positioned in a distal to proximal transect were chosen for further analyses. The cores were x-ray photographed and analysed with regard to sedimentological variability and the sea ice proxy IP25. The lithofacies is glaciomarine mud with sand content varying along-transect and within-core and this variability is interpreted to reflect variability in iceberg rafting. In the distal cores layers of decreased sand content are interpreted to reflect periods with increased occurrence of shore fast sea ice in the fjord, stabilizing the glacier and preventing icebergs from drifting out of the fjord, whereas increases in the flux of sand are interpreted to represent periods of increased iceberg calving from Helheim Glacier. The record spanning the latest 100 years shows that variability in iceberg calving from Helheim Glacier has been a recurrent phenomenon on decadal timescales and that the 2003-2005 acceleration is not outstanding. A comparison of our data with a record of SST from the North Atlantic Ocean strengthens the hypothesis of a coupling between calving rates and oceanic variability in that, for example, calving decreased during the Great Salinity Anomalies around 1910’s and 1970’s and increased during following warming episodes during the 1920’s and 1980’s. However, the data also suggest that negative feedback processes play an important role in stabilizing the glacier.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.C23C0635A
- Keywords:
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- 0730 CRYOSPHERE / Ice streams;
- 0732 CRYOSPHERE / Icebergs;
- 3022 MARINE GEOLOGY AND GEOPHYSICS / Marine sediments: processes and transport;
- 4926 PALEOCEANOGRAPHY / Glacial