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

在过去的5500万年里，地球的气候从温室变成了冰窖。自3400万年前以来，南极洲一直（部分）被冰川覆盖。最初，南极冰盖的面积可能比现在更大。然而，在今天，南极大陆是“满的”，冰盖不能再扩大了。因此，南极大陆储存冰的能力在过去一定发生了变化。这种情况最有可能发生在西南极洲，那里的冰盖现在是（浅）海洋基础，但在其形成时被重建为主要是大陆基础。这种变化的日期目前尚不清楚，这是本提案的关键问题之一：这种所谓的过度深化是什么时候发生的？为了解决这个问题，该提案将为2018年1月至3月从罗斯海（南极洲西部）回收的新岩芯提供准确的年龄模型。这些冰芯还将有助于评估南极西部冰盖的不稳定性。一项新的气候模型表明，南极西部冰盖并不像原先认为的那样稳定。如果我们在一切照旧的情况下继续排放二氧化碳，到本世纪末，这可能导致全球海平面上升2米。评估这个新模型的最好方法是看看它对过去气候的准确性。在过去的数百万年里，由于气候变化，南极西部冰盖的大小一直在增长和缩小，这可能是未来人为变暖的类比。在本建议中，我们将为回收的岩心提供精确的地层和年龄模型。然后，我们可以准确地重建南极西部冰盖的大小和位置，并将其与模型预测的大小和位置进行比较。因此，我们可以测试在一切照常的二氧化碳排放情景下，全球海平面将升高2米的预测的准确性。

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.