Holocene Glacial Retreat at Walgreen Coast, West Antarctica
Abstract
The Walgreen Coast of West Antarctica represents one of the most rapidly changing sectors of the West Antarctic Ice Sheet (WAIS). With the fastest ice streams in the whole Antarctic, the WAIS is characterised by rapid thinning and grounding line retreat. Airborne and satellite-based short-term observations show a doubling of the negative net mass balance between 1996-2006 (Rignot et al., 2008). Furthermore, because the WAIS is largely grounded below sea level, continued inland thinning and grounding line retreat could result in rapid ice sheet collapse, which would raise global sea level by between 3-5 m. However, due to remoteness and challenging accessibility, onshore data is limited to a few isolated nunataks making it difficult to assess the long-term evolution of the glacial dynamics along Walgreen Coast. To address this we present new data from two key areas of the Walgreen Coast; the Kohler Range and the Pine Island Bay. Our 10Be surface exposure ages from erratic boulders in the Kohler Range are the first and reveal that this area became ice-free between 8.3 and 12.3 ka. This implies a long-term thinning rate of 3.3 cm/yr and agrees with similar data published from glaciers eastward. Our ages are also consistent with recent deglaciation models which suggest strong thinning after 15 ka and off-shore sediments shows a concurrent lateral ice-shelf front retreat. Our results suggest an ice-cover at least 300 m thicker in the Kohler Range during the early Holocene and that subsequent average thinning occurred on rates one order of magnitude slower than recent satellite measurements show. This implies that the recent trend in ice-sheet thinning results from a recent dynamic changes rather than a response to long-term thinning. To further constrain the lateral deglaciation history along the eastern Walgreen Coast, namely the Pine Island Glacier, we collected additional samples from a chain of islands, located flow-parallel and downstream of the ice-shelf front. We will use this new 10Be surface exposure data to infer whether the uncovering of these islands results from glacial retreat and/or subsequent isostatic rebound. Together, our new data will contribute to a better understanding of long-term glacial thinning along the West Antarctic coast, and thus provides new constraints for ice sheet models helping to predict the future behaviour of the WAIS. Rignot, E., Bamber, J. L., Van den Broeke, M. R., Davis, C., Li, Y., Van de Berg, W. J., van Meijgaard, E., 2008: Recent Antarctic ice mass loss from radar interferometry and regional climate modelling. Nature Geoscience. 1, 106-110.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP23C2074L
- Keywords:
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- 0726 CRYOSPHERE / Ice sheets;
- 1150 GEOCHRONOLOGY / Cosmogenic-nuclide exposure dating;
- 9310 GEOGRAPHIC LOCATION / Antarctica