Let’s get to the bottom of West Antarctic Ice Sheet evolution: An initiative to drill sediment drifts on the Amundsen Sea continental rise

Gabriele.Uenzelmann-Neben [ at ] awi.de


The Antarctic ice sheets have moved into the focus of public and scientific interest because of modern global warming and their possible contribution to sea level rise and resulting flooding of low lying coastal areas. Research has predominantly concentrated on recent short-term dynamics of the ice sheets in order to understand their vulnerability to a changing climate by collecting multi-disciplinary data. However, little is known about their long-term evolution, especially about that of the West Antarctic Ice Sheet (WAIS). The WAIS is a marine based ice sheet and assumed to respond more sensitively to both atmospheric and oceanic warming than the largely terrestrial East Antarctic Ice Sheet (EAIS). Information on the early stage of WAIS formation and the Cenozoic glacial history in its Amundsen Sea sector is scarce. Drilling offshore from the George V. and Adelie Land drainage sectors of the EAIS has shown that mid Eocene cooling there was initiated by early flow of the cold Antarctic Counter Current across the Tasman Gateway (IODP Expedition 318). Seismic data indicate that this cold Antarctic Counter Current has also bathed the Amundsen Sea continental margin implying a cold climate in this area during the Palaeogene. The timing of WAIS formation and possible collapse events thereafter are still under debate, and little is known about the Cenozoic WAIS dynamics in the Amundsen Sea region, where the east setting Antarctic Circumpolar Current (ACC) bathes the continental rise. The on-going discussions about the glacial history of West Antarctica resulting from both on- and off-shore studies include topics such as (i) the first appearance of mountain glaciers, ice shelves and local ice caps, (ii) the build up of a large WAIS, (iii) the cooling of surface waters, (iv) the variability of bottom water circulation, and (v) the (in-)stability of the WAIS during the Neogene. Ground truthing is difficult because most of the corresponding palaeo-records were recovered in the Ross Sea sector, thus providing an integrated picture of WAIS and EAIS history, while the only available deep-sea drill site from the Amundsen Sea, DSDP Site 324, extends back to not more than 4 Ma. We suggest the development of an IODP proposal to address the following objectives: 1. Develop a general age-depth model for the whole sedimentary column on the Amundsen Sea continental rise down to the oceanic basement, identify its basal age and reconstruct changes in depositional regimes in response to palaeoenvironmental changes from sedimentological analyses on the drill cores 2. Identify the first supply of glaciogenic sediments to the Amundsen Sea for reconstructing WAIS formation 3. Search for indicators for WAIS collapses during the Neogene 4. Identify the oldest documented bottom current activity on the continental rise and study its relation to WAIS formation 5. Decipher the history and southward protrusions of Circumpolar Deep Water (CDW) 6. Document the interaction of along-slope and down-slope sediment transport and distinguish between times with high detrital input from the continent and times with low material input for reconstructing ice sheet advance and retreat and changes in bed conditions (temperate vs. polar) on land through time and for determining forcing mechanisms 7. Reconstruct the variability in the direction and velocity of bottom current flow in the Amundsen Sea and infer changes in bottom water production in the source areas (Ross and Weddell seas) We invite and welcome further ideas and contributions.

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Conference (Talk)
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XII International Symposium on Antarctic Earth Sciences, 13 Jul 2015 - 17 Jul 2015, Goa, India.
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Uenzelmann-Neben, G. and Hillenbrand, C. D. (2015): Let’s get to the bottom of West Antarctic Ice Sheet evolution: An initiative to drill sediment drifts on the Amundsen Sea continental rise , XII International Symposium on Antarctic Earth Sciences, Goa, India, 13 July 2015 - 17 July 2015 .

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