East Antartic ice sheet and ocean interactions during past warmer than present climates

政府间气候变化专门委员会最近发布的第六次评估报告指出，南极洲对海平面变化的贡献是未来几十年和几个世纪全球气候预测中最大的不确定性，也是气候变化科学面临的最优先问题。观测表明，目前海平面以下陆地上的冰盖(海基冰盖)很容易受到海洋引起的基底部融化的影响，从而导致不稳定和海平面上升。然而，推动大陆架上海洋热交换的确切机制，以及它们对海洋冰盖稳定性的影响，人们知之甚少。过去冰盖和海洋环流相互作用的高分辨率记录可以填补这一空白。特别有用的是研究过去比现在温暖的气候区间，当时的温度和二氧化碳浓度与现在相似，或者与本世纪末预测的相似。ICEAN项目将提供一个独特的大陆架，用于开放海洋横断面，记录中上新世暖期(约300万年前)水团、海洋温度和冰盖位置的地质记录。当时，大气中的二氧化碳浓度与现在差不多(约400ppm)，年平均表面温度比工业化前的值高约1.8-3.6摄氏度。这些条件导致冰盖范围缩小，海平面上升。ICEAN项目中产生的数据将首次允许限制在上新世中期南极洲附近的一个关键位置的冰消退的过程和驱动力。这一结果将是验证和测试当前冰盖模型的关键，该模型用于预测未来海平面的上升。

The recently published Sixth Assessment Report by the Intergovernmental Panel on Climate Change identified the Antarctica's contribution to sea-level change as the single greatest uncertainty in global climate predictions for the coming decades and centuries, and the highest priority issue facing climate change science. Observations show that ice sheets grounded on land below current sea level (marine-based ice sheets) are vulnerable to ocean-induced basal melting, resulting in destabilization and sea level rise. However, the exact mechanisms that drive oceanic heat exchange across the continental shelves, and their influence on the stability of the marine-based ice sheets are poorly known. High-resolution records of past ice sheet and ocean circulation interaction can fill this gap. Of particular use is the study of past warmer-than-present climate intervals, when temperatures and CO2 concentrations were similar to the present-day or those projected for the end of this century. The ICEAN project will deliver a unique shelf to open ocean transect of geological records on water masses, ocean temperature, and ice sheet position for the Mid-Pliocene warm period (~3 million years ago). Back then, atmospheric CO2 concentrations where similar to the present-day (ca. 400ppm), and mean annual surface temperatures were ca. 1.8-3.6C warmer than preindustrial values. These conditions led to reduced ice sheet extent and increased sea levels. The data produced in the ICEAN project will for the first time allow to constrain processes and drivers for ice retreat during the Mid-Pliocene warm period in a critical location off East Antarctica. The results will be key to validate and test current ice sheet models, which are used to project future seal level rise.