Processes controlling cross shelf exchange in the Amundsen/Bellingshausen Seas

阿蒙森/别林斯高晋海跨大陆架交换的控制过程

• 批准号: 0927797
• 负责人: John Klinck
• 金额: $ 55.96万
• 依托单位: Old Dominion University Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0927797&HistoricalAwards=false
• 关键词: Processes; controlling; cross; shelf; exchange

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.

西南极冰盖（WAIS）正在以越来越快的速度失去体积，这是导致海平面上升的原因。一个被提出的增加基底融化的原因是温度或温暖的绕极深水（CDW）的数量发生了变化，这些深水移动到大陆架上并在浮动冰盖下面流动。WAIS主要位于海平面以下的基岩上;因此，当冰融化时，海水可以侵入它下面，使它漂浮并使更多的冰暴露在温水中。冰山的崩解、径流和海水导致的基底融化是WAIS体积损失的三个主要原因。基底熔融是第二重要的，但海洋水入侵的过程和驱动机制还没有得到很好的理解。可能的动力过程是底部Ekman层传输，惯性测深相互作用，南极绕极流（ACC）密度变化由于热成风，ACC动力不稳定性，大气强迫和冰架环流。智力优势：研究人员建议分析这些过程中的每一个跨架运输的CDW沿着南极大陆架的阿蒙森海和别林斯高晋海的重要性。研究假设是，大气对海洋过程没有直接或间接的影响，这些海洋过程会导致沿着阿蒙森海和别林斯高晋海的陆架断裂交换CDW。另一种假设是，大气对海洋过程产生的CDW交换沿着阿蒙森海和别林斯高晋海的陆架断裂的主导作用。将用一个代表阿蒙森和别林斯高晋大陆架特征的海洋-冰模型（具有动态海冰和冰架的区域海洋模拟系统）进行过程模拟，以测试每个过程对大陆架断裂交换、跨大陆架迁移和冰架底部融化的影响。两个现实的计算将分别代表别林斯高晋海和阿蒙森海陆架区，由高分辨率的大气预报和使用大规模海洋模型的边界信息。每个模式将有一个2公里（或更小）的网格间距，以正确地代表斜压过程。将对这些模拟中的每一个进行分析CDW和热通量到冰架底部的跨大陆架运输。将确定这些诊断与地面强迫和ACC速度以及与大气指数（ENSO和SAM）的关系。更广泛的影响：南极半岛和西南极洲的气候正在迅速变化。此外，WAIS正在以惊人的速度失去体积，迫切需要了解温暖的海洋水在冰架下移动的过程，并有助于基底融化，在某些情况下，加速附近冰盖的移动。这一模型研究将查明影响海洋水侵入大陆架的过程。它还将把该地区ACC的变化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。一名博士后研究员将接受海洋冰模拟培训。