NSF-NERC: Thwaites-Amundsen Regional Survey and Network (TARSAN) Integrating Atmosphere-Ice-Ocean Processes affecting the Sub-Ice-Shelf Environment

该项目是美国国家科学基金会（NSF）和英国自然环境研究委员会（NERC）联合发起的一项倡议的一部分，该倡议旨在实质性地改进西南极洲思韦茨冰川的冰损失和海平面上升的十年和长期预测。由于最近的气候变暖和海洋环流的相关变化，阿蒙森海海湾的斯韦茨和邻近的冰川正在迅速失去质量。阿蒙森海爆炸造成的物质损失可能导致南极西部冰盖的最终崩塌，在短短500年内，全球海平面将上升2.5米（8英尺）。导致冰川消融的过程似乎是海洋环流变暖以及冰川宽度和流速的变化，但需要更好地了解这些变化，才能精确预测冰川将如何演变。一个高度敏感的过程是冰川冰从陆地到海洋的过渡流，成为一个浮动的冰架。这种从地面到浮冰的流动受到地表气温变化和降雪的影响；上游入冰的速度和厚度；海洋温度，盐度，水深，以及冰流入的洋流。该项目团队将收集这些当地环境条件的新测量数据，以便更好地预测未来空气、海洋或冰的变化将如何影响该地区海洋中冰的损失。目前和预计近期Thwaites冰川和附近阿蒙森海海湾地区的质量损失主要是由于相对温暖的环极深水侵入亚冰架空洞，导致亚冰架融化，导致冰架支撑减少。然而，这种对质量损失的预测仍然缺乏对地面及其附近的主要过程的了解，特别是它们的空间和时间变异性，以及这些过程的大气和海洋驱动因素。该项目旨在约束和比较Thwaites冰架和Dotson冰架的这些过程，这两个冰架通过上游冰动力学连接，但受到不同海底槽的影响。该团队的具体目标是：1)在冰架上安装大气-冰-海洋多传感器远程自主站，为期两年，提供亚每日连续的海洋、冰川学和大气条件同步观测；2)测量冰架锋面附近大陆架上的海洋特性（使用海豹标记、滑翔机和船舶调查，以及现有的系泊和电导率-温度-深度数据）；3)测量亚冰架空腔的海洋特性（使用自主水下航行器），以详细描述海洋运输和热通量；4)约束当前冰架和亚冰架空腔的几何形状、冰流和冰架的温度特性（使用雷达、有源地震和重力方法），以更好地了解海洋和大气对冰盖变化的影响。该团队还将通过“冰上直播”社交媒体活动吸引公众，提高公众对冰冻圈这一快速变化的组成部分的认识，公众可以从带标签的海豹和自动站的角度关注行动和数据收集。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project contributes to the joint initiative launched by the U.S. National Science Foundation (NSF) and the U.K. Natural Environment Research Council (NERC) to substantially improve decadal and longer-term projections of ice loss and sea-level rise originating from Thwaites Glacier in West Antarctica. Thwaites and neighboring glaciers in the Amundsen Sea Embayment are rapidly losing mass in response to recent climate warming and related changes in ocean circulation. Mass loss from the Amundsen Sea Embayment could lead to the eventual collapse of the West Antarctic Ice Sheet, raising the global sea level by up to 2.5 meters (8 feet) in as short as 500 years. The processes driving the loss appear to be warmer ocean circulation and changes in the width and flow speed of the glacier, but a better understanding of these changes is needed to refine predictions of how the glacier will evolve. One highly sensitive process is the transitional flow of glacier ice from land onto the ocean to become a floating ice shelf. This flow of ice from grounded to floating is affected by changes in air temperature and snowfall at the surface; the speed and thickness of ice feeding it from upstream; and the ocean temperature, salinity, bathymetry, and currents that the ice flows into. The project team will gather new measurements of each of these local environmental conditions so that it can better predict how future changes in air, ocean, or the ice will affect the loss of ice to the ocean in this region. Current and anticipated near-future mass loss from Thwaites Glacier and nearby Amundsen Sea Embayment region is mainly attributed to reduction in ice-shelf buttressing due to sub-ice-shelf melting by intrusion of relatively warm Circumpolar Deep Water into sub-ice-shelf cavities. Such predictions for mass loss, however, still lack understanding of the dominant processes at and near grounding zones, especially their spatial and temporal variability, as well as atmospheric and oceanic drivers of these processes. This project aims to constrain and compare these processes for the Thwaites and the Dotson Ice Shelves, which are connected through upstream ice dynamics, but influenced by different submarine troughs. The team's specific objectives are to: 1) install atmosphere-ice-ocean multi-sensor remote autonomous stations on the ice shelves for two years to provide sub-daily continuous observations of concurrent oceanic, glaciologic, and atmospheric conditions; 2) measure ocean properties on the continental shelf adjacent to ice-shelf fronts (using seal tagging, glider-based and ship-based surveys, and existing moored and conductivity-temperature-depth-cast data), 3) measure ocean properties into sub-ice-shelf cavities (using autonomous underwater vehicles) to detail ocean transports and heat fluxes; and 4) constrain current ice-shelf and sub-ice-shelf cavity geometry, ice flow, and firn properties for the ice-shelves (using radar, active-source seismic, and gravimetric methods) to better understand the impact of ocean and atmosphere on the ice-sheet change. The team will also engage the public and bring awareness to this rapidly changing component of the cryosphere through a "Live from the Ice" social media campaign in which the public can follow the action and data collection from the perspective of tagged seals and autonomous stations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.