Vulnerability of the Antarctic Ice Sheet to a changing thermocline

南极冰盖对温跃层变化的脆弱性

• 批准号: 442927134
• 负责人: Professorin Dr. Ricarda Winkelmann
• 金额: --
• 依托单位: Forschungsbereich Erdsystemanalyse
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/442927134?language=en
• 关键词: Vulnerability; Antarctic; Ice; Sheet; changing

The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Even small changes in its mass balance have enormous global impacts, which makes the question of its future evolution highly relevant for society. Over the past decades, the Antarctic Ice Sheet has been losing mass at an accelerating pace. The imbalance of the ice sheet is caused by - partially abrupt - changes in parts of West Antarctica where speed-up, thinning, retreat and discharge of the inland ice is driven by enhanced basal melting of the ice shelves. The amount of warm water which can access the ice shelf cavities, fueling basal ice-shelf melt, is regulated by the depth of the thermocline. Observations and numerical atmosphere-ocean modeling suggest that the thermocline is strongly driven by winds over the Southern Ocean, which connects it to global-scale climate variability. There is evidence that wind patterns that cause an elevated thermocline and thus facilitate warm-water penetration of the ice-shelf cavities will continue to strengthen in the future. However, the future evolution of the dynamics of the Antarctic Ice Sheet and its sea-level contribution in response to the expected wind-driven shifts in the thermocline remain unexplored.To overcome this knowledge gap, we propose a thorough investigation of the vulnerability of the Antarctic Ice Sheet to thermocline variations, guiding a first-order assessment of the ice-sheet’s mass changes in response to large-scale climate variability and change. For this purpose, we first plan to carry out an in-depth analysis of how the circum-antarctic thermocline depth depends on changes in wind speed and direction, putting their relation into functional form. Based on that, we aim to find critical wind-stress thresholds, indicating the regional potential of future warm-water intrusion into the different ice-shelf cavities around Antarctica. Further, we plan to implement this process of wind-driven thermocline changes into the sophisticated, yet computationally efficient ice-sheet model PISM. For the first time this will allow for simulations of the flow dynamics of the entire Antarctic Ice Sheet in response to basal ice-shelf melting that is sensitive to wind-driven thermocline changes. Conducting an ensemble of simulations, we plan to provide projections of the future Antarctic sea-level contribution, associated with projected regional changes in the atmosphere. In further sets of experiments, we intend to systematically vary the thermocline depth to conceptually explore the ice-sheet’s sensitivity to changes in larger-scale atmospheric variability, e.g., to changes in frequency, amplitude and trend of recurring El-Niño events. In a final step, we envisage to generate an Antarctic risk map that indicates the regional impact of potential warm-water entrainment with respect to the long-term ice-flow response and ice-sheet stability.

南极冰盖是未来海平面上升的最大潜在来源。即使是其质量平衡的微小变化也会产生巨大的全球影响，这使得其未来演变的问题与社会高度相关。在过去的几十年里，南极冰盖一直在以加速的速度失去质量。冰盖的不平衡是由南极洲西部部分地区的部分突然变化造成的，在这些变化中，内陆冰的加速、变薄、退缩和排放是由冰架底部融化加剧造成的。能够进入冰架洞穴的温水的数量，为基础冰架融化提供燃料，由温跃层的深度调节。观测和大气-海洋数值模拟表明，温跃层强烈地受到南大洋上空风的驱动，这将其与全球尺度的气候变化联系起来。有证据表明，造成温跃层升高从而促进暖水渗透冰架空洞的风型今后将继续加强。然而，南极冰盖的动态和海平面的贡献，以响应预期的风驱动的温跃层的变化的未来演变仍然unexplored.To克服这一知识差距，我们提出了一个彻底的调查南极冰盖温跃层变化的脆弱性，指导一阶评估冰盖的质量变化，以响应大规模的气候变率和变化。为此，我们首先计划进行一个深入的分析，如何环南极温跃层深度取决于风速和风向的变化，把它们的关系到函数形式。在此基础上，我们的目标是找到临界风应力阈值，表明未来暖水入侵到南极洲周围不同冰架空腔的区域潜力。此外，我们计划将风驱动的温跃层变化过程实施到复杂但计算效率高的冰盖模型PISM中。这将首次允许模拟整个南极冰盖的流动动力学，以应对对风力驱动的温跃层变化敏感的基底冰架融化。进行一系列模拟，我们计划提供未来南极海平面贡献的预测，与预测的区域大气变化有关。在进一步的实验中，我们打算系统地改变温跃层深度，以从概念上探索冰盖对大尺度大气变化的敏感性，例如，厄尔尼诺事件的频率、幅度和趋势的变化。在最后一步中，我们设想生成一个南极风险图，表明潜在的温水夹带对长期冰流响应和冰盖稳定性的区域影响。