NSFGEO-NERC: Understanding the Response to Ocean Melting for Two of East Antarctica's Most Vulnerable Glaciers: Totten and Denman

落在南极洲的雪压缩成冰，以大片的形式流向海岸，在几个世纪到几千年的时间里回到海洋。在南极洲周围的许多地方，冰盖从陆地延伸到海洋上空，在外围形成了漂浮的冰架。如果这个周期处于平衡状态，冰盖有助于维持稳定的海平面。然而，当气候变冷或变暖时，海平面会随着冰盖的增加或消失而下降或上升。外围的冰架对调节海平面很重要，因为它们有助于阻止冰流入海洋。通过融化冰架底部使海水变暖，使冰层更快地流入海洋，并提高全球海平面。因此，一个重要的问题是，在下个世纪，随着海洋温度变暖，海平面将上升多少(S)，使南极洲的冰架进一步变薄。目前，西南极洲对大陆海平面的贡献主要来自西南极洲。尽管存在很大的不确定性，但冰盖模型表明，东南极的托滕和德曼冰川也可能在下个世纪导致海平面大幅上升(S)。这项国际研究将侧重于提高人们对这些冰川在不同变暖情况下对海平面的贡献程度的理解。该项目将使用受海洋和遥感观测约束的数值模型来确定托滕和德曼冰川将如何应对日益融化的冰川。遥感数据将对每个冰架的融化速度提供更新和改进的估计。英国和澳大利亚的合作伙伴将从飞机上部署两个浮标剖面仪，在每个冰架前重复测量水柱的温度和盐度，并通过卫星链路将结果遥测回来。融化和海洋数据将被用来约束冰架空洞融化的参数化传递函数，以响应海洋温度，改进目前基于有限数据的参数化。这些融化功能将与气候模型中的海洋温度一起使用，以迫使每个冰川的开放源码冰流数值模型确定各种情况下的百年尺度响应，有助于减少南极洲这一地区海平面贡献的不确定性。未来几个世纪可能进一步改变海平面贡献的熔融以外的其他过程也将被研究。在观测方面，从声纳浮标发射管在极地环境中示范部署浮标剖面仪将有助于提高对快速变化的极地陆架海进行现场监测的技术准备情况，为扩大对目前知之甚少的偏远地区海洋水文特性的观测铺平道路。海平面上升预测的不确定性减少除了具有科学价值外，对正在努力制定长期规划以减轻未来几十年至几个世纪海平面上升影响的沿海社区也有很大的社会效益。小组成员的外联活动将有助于提高公众对南极洲剧烈变化及其后果的认识。这是一个由国家科学基金会地球科学局(NSF/GEO)和英国国家环境研究委员会(NERC)通过NSF/GEO-NERC牵头机构协议共同资助的项目。该协定允许美国和英国提交一个单一的联合提案，并由该机构进行同行审查，该机构的调查员在预算中所占比例最大。在成功地共同确定奖项建议后，每个机构将为支持各自国家机构科学家的预算比例提供资金。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。

The snow that falls on Antarctica compresses to ice that flows toward the coast as a large sheet, returning it to the ocean over periods of centuries to millennia. In many places around Antarctica, the ice sheet extends from the land to over the ocean, forming floating ice shelves on the periphery. If this cycle is in balance, the ice sheets help maintain a stable sea level. When the climate cools or warms, however, sea level falls or rises as the ice sheet gains or loses ice. The peripheral ice shelves are important for regulating sea level because they help hold back the flow of ice to the ocean. Warming ocean waters thin ice shelves by melting their undersides, allowing ice to flow faster to the ocean, and raising sea level globally. Thus, an important question is how much sea level will rise in response to warming ocean temperatures over the next century(s) that further thin Antarctica’s ice shelves. Currently, West Antarctica produces the majority of the continent’s contribution to sea level. Albeit with large uncertainty, ice-sheet models indicate that Totten and Denman glaciers in East Antarctica could also produce substantial sea-level rise in the next century(s). This international study will focus on improving understanding of how much these glaciers will contribute to sea level under various warming scenarios.The project will use numerical models constrained by oceanographic and remote sensing observations to determine how Totten and Denman glaciers will respond to increased melting. Remote sensing data will provide updated and improved estimates of the melt rate for each ice shelf. Two float profilers will be deployed from aircraft by British and Australian partners in front of each ice shelf to repeatedly measure the temperature and salinity of the water column, with the results telemetered back via satellite link. The melt and oceanographic data will be used to constrain parameterized transfer functions for ice-shelf cavity melting in response to ocean temperature, improving on current parameterizations based on limited data. These melt functions will be used with ocean temperatures from climate models to force an open-source ice-flow numerical model for each glacier to determine the century-scale response for a variety of scenarios, helping to reduce uncertainty in sea level contributions from this part of Antarctica. Processes other than melt that might further alter the contribution to sea level over the next few centuries will also be examined. On the observational side, the demonstrated deployment of float profilers from a sonobuoy launch tube in polar settings would help raise the technology readiness of operational in-situ monitoring of the rapidly changing polar shelf seas, paving the way for an expansion of observations of ocean hydrographic properties from remote areas that currently are poorly understood. In addition to being of scientific value, reduced uncertainty in sea-level rise projections has strong societal benefit to coastal communities struggling with long-range planning to mitigate the effects of sea-level rise over the coming decades to centuries. Outreach activities by team members will help raise public awareness of Antarctica's dramatic changes and the resulting consequences. This is a project jointly funded by the National Science Foundation’s Directorate for Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award recommendation, each Agency funds the proportion of the budget that supports scientists at institutions in their respective countries.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.