Stratigraphy and chronology of IODP Exp. 374 (Ross Sea West Antarctic Ice Sheet History) drill cores: implications for West Antarctic glaciations

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Over the past 55 million years, Earth's climate changed from a greenhouse into an icehouse world. Antarctica has been (partially) glaciated since ~34 million years ago. Initially, the Antarctic ice sheet probably grew to a larger size than it is at present-day. At present-day, however, the Antarctic continent is 'full' and the ice sheet cannot grow much larger anymore. Therefore the capacity of the Antarctic continent to store ice must have changed in the past. This has most likely happened in West Antarctica, where the ice sheet is now (shallow-)marine based, but is reconstructed to have been predominantly continental-based at its formation. The date of this change is currently unknown, and that is one of the key questions of this proposal: when did this so-called overdeepening occur?To address this question, this proposal will provide accurate age models for new cores, to be recovered from the Ross Sea (West Antarctica) in January-March 2018. These cores will also help with the evaluation of the instability of the West Antarctic ice sheet. A new climate model suggests that the West Antarctic ice sheet is not as stable as originally thought. This can result in global sea level of up to ~2 m by the end of this century, if we continue CO2 emissions under the business-as-usual scenario. The best way to evaluate this new model is by looking at its accuracy for past climates. Over the past millions of years, the size of the West Antarctic ice sheet has grown and shrunk due to climatic variations, which may be an analogy for future anthropogenic warming. In this proposal we will provide an accurate stratigraphy and age model for the recovered cores. We can then accurately reconstruct the size and position of the West Antarctic ice sheet and compare these to the predicted size and position from the model. Therefore, we can test the accuracy of the prediction that global sea levels will be up to ~2 m higher under business-as-usual CO2 emission scenarios.