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

该项目为美国国家科学基金会(NSF)和英国自然环境研究理事会(NERC)发起的联合倡议做出了贡献，该倡议旨在大幅改善对南极洲西部斯韦茨冰川造成的冰流失和海平面上升的十年和更长期的预测。由于最近气候变暖和海洋环流的相关变化，阿蒙森海湾的Thwaite和邻近的冰川正在迅速失去质量。阿蒙森海湾的质量损失可能导致西南极冰盖最终崩溃，在短短500年内使全球海平面上升多达2.5米(8英尺)。造成冰川减少的原因似乎是海洋环流变暖，以及冰川宽度和流速的变化，但需要更好地理解这些变化，才能完善对冰川将如何演变的预测。一个高度敏感的过程是冰川冰从陆地流向海洋的过渡过程，成为漂浮的冰架。冰流从搁浅到漂浮受到以下因素的影响：气温和表面降雪量的变化；从上游流入的冰的速度和厚度；以及冰流入的海洋温度、盐度、水深和洋流。项目团队将收集这些当地环境条件的每一个新的测量数据，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的冰向海洋流失。目前和预计在不久的将来，Thwaites冰川和附近的阿蒙森海湾区的质量损失主要是由于相对温暖的环极深水侵入次冰架洞穴而导致的次冰架融化导致的冰架支撑减少。然而，这种对质量损失的预测仍然缺乏对接地带及其附近的主要过程，特别是其空间和时间变异性，以及这些过程的大气和海洋驱动因素的了解。该项目旨在限制和比较Thwaites和Dotson冰架的这些过程，这两个冰架通过上游冰动力学连接在一起，但受到不同的海底槽的影响。该小组的具体目标是：1)在冰架上安装大气-冰-海洋多传感器远程自治站，为期两年，以提供同步的海洋、冰川和大气条件的次日连续观测；2)测量冰架前缘附近大陆架上的海洋特性(使用海豹标记、基于滑翔机和基于船舶的调查以及现有的系泊和电导率-温度-深度投射数据)，3)测量冰架下洞穴的海洋特性(使用自主水下航行器)，以详细说明海洋传输和热通量；4)约束当前冰架和次冰架洞穴的几何形状、冰流和冰架的降雪特性(使用雷达、有源地震和重力测量方法)，以更好地了解海洋和大气对冰盖变化的影响。该团队还将通过一项名为“冰雪中的生活”的社交媒体活动，让公众了解冰冻圈中这一快速变化的部分，公众可以从标记海豹和自主站的角度来跟踪行动和数据收集。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.