Processes controlling cross shelf exchange in the Amundsen/Bellingshausen Seas

南极西部冰盖（WAIS）正在以越来越快的速度失去体积，这导致海平面上升。一个被提出的导致基底融化增加的原因是温暖的环极深水（CDW）的温度或数量的变化，这些水移动到冰架上并在漂浮的冰盖下流动。西太平洋大部分位于海平面以下的基岩上；所以，当冰融化时，海水可以侵入它的下面，使它漂浮起来，使更多的冰暴露在温暖的水中。冰山的崩解、径流和海水的基底融化是造成西海冰川体积损失的三个主要原因。其次是基底融化，但海水侵入的过程和驱动机制尚不清楚。可能的动力过程包括底部Ekman层输送、惯性-测深相互作用、热风引起的南极环极流（ACC）密度变化、ACC动力不稳定、大气强迫和冰架环流。研究人员建议分析这些过程对CDW沿阿蒙森海和别林斯豪森海的南极大陆架跨大陆架运输的重要性。研究的假设是大气对引起沿阿蒙森海和别令斯高森海陆架断裂的CDW交换的海洋过程没有直接或间接的影响。另一种假设是，大气对沿阿蒙森海和别令斯豪森海陆架断裂产生CDW交换的海洋过程起主导作用。过程模拟将使用代表阿蒙森冰架和别令斯豪森冰架特征的海洋-冰模型（具有动态海冰和冰架的区域海洋模拟系统）进行，以测试每种过程对冰架断裂交换、跨冰架运输和冰架基底融化的影响。根据高分辨率大气预报和使用大尺度海洋模式的边界信息，两个实际计算将分别代表别令斯豪森海和阿蒙森海陆架区域。每个模型将有一个2公里（或更小）的网格间距，以适当地表示斜压过程。对于每一个模拟，将分析CDW的跨冰架输送和到冰架底部的热通量。这些诊断与地表强迫和ACC速度以及大气指数（ENSO和SAM）的关系将被确定。更广泛的影响：南极半岛和南极洲西部的气候正在迅速变化。此外，WAIS的体积正在以惊人的速度减少，因此迫切需要了解温暖的海水在冰架下的冰架上移动并导致基底融化的过程，在某些情况下，还加速了附近冰盖的移动。这个模型研究将确定影响海水侵入大陆架的过程。它还将把该地区ACC的变率与气候指数联系起来，将这些结果预测到未来，以估计海洋变化对冰盖运动和融化的影响。一名博士后将接受海冰建模培训。

The West Antarctic Ice Sheet (WAIS) is losing volume at an increasing rate which is contributing to sea level rise. One proposed reason for the increased basal melt is a change in either the temperature or quantity of warm Circumpolar Deep Water (CDW) that moves onto the shelf and flows underneath the floating ice sheet. The WAIS rests largely on bedrock below sea level; so, as the ice melts, seawater can intrude under it causing it to float and exposing more ice to warm water. Calving of icebergs, runoff and basal melt due to oceanic water are the three major causes of volume loss for the WAIS. Basal melt is second in importance but the processes and driving mechanisms for the intrusion of oceanic water are not well understood. Possible dynamical processes are bottom Ekman layer transport, inertia-bathymetry interaction, Antarctic Circumpolar Current (ACC) density variation due to thermal wind, ACC dynamic instability, atmospheric forcing, and ice shelf circulation. Intellectual Merit: The investigators propose to analyze the importance of each of these processes on cross shelf transport of CDW along the Antarctic continental shelf of the Amundsen and Bellingshausen Seas. The research hypothesis is that there is no direct or indirect effect of the atmosphere on oceanic processes that cause exchange of CDW along the shelf break of the Amundsen and Bellingshausen Seas. The alternative hypothesis is that the atmosphere has a dominant effect on oceanic processes that produce exchange of CDW along the shelf break of the Amundsen and Bellingshausen Seas. Process simulations will be conducted with an ocean-ice model (the Regional Ocean Modeling System with dynamic sea ice and ice shelves) that represents the character of the Amundsen and Bellingshausen shelves to test the influence of each process on shelf break exchange, transport across the shelf and basal melt of the ice shelf. Two realistic calculations will represent the Bellingshausen Sea and Amundsen Sea shelf area, respectively, forced by high resolution atmospheric forecasts and using boundary information from the large scale ocean models. Each models will have a 2 km (or smaller) grid spacing to properly represent baroclinic processes. Cross shelf transport of CDW and heat flux to the base of the ice shelf will be analyzed for each of these simulations. The relationship of these diagnostics to surface forcing and ACC speed as well as to atmospheric indexes (ENSO and SAM) will be determined.Broader impacts: The climate of the Antarctic Peninsula and West Antarctica is changing rapidly. Furthermore, the WAIS is losing volume at an alarming rate, creating an urgent need to understand the processes by which warm oceanic water moves across the shelf under ice shelves and contributes to basal melting and, in some cases, to accelerate movement of the nearby ice sheets. This model study will identify processes affecting the intrusion of this oceanic water onto the shelf. It will also associate variability in the ACC in this region with climate indexes to project these results into the future to estimate the effect of oceanic changes on ice sheet movement and melting. A post-doctoral fellow will be train in ocean-ice modeling.