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

落在南极洲的雪被压缩成冰，形成大片的冰盖流向海岸，经过几个世纪到几千年的时间，这些冰又回到海洋中。在南极洲周围的许多地方，冰原从陆地延伸到海洋之上，在边缘形成了漂浮的冰架。如果这个循环是平衡的，那么冰盖有助于维持一个稳定的海平面。然而，当气候变冷或变暖时，海平面会随着冰盖的增减而下降或上升。外围冰架对调节海平面很重要，因为它们有助于阻止冰流向海洋。海水变暖使冰架底部融化，从而使冰架变薄，使冰更快地流向海洋，并使全球海平面上升。因此，一个重要的问题是，随着下个世纪海洋温度的升高，海平面将上升多少，这将使南极洲冰架进一步变薄。目前，南极洲西部对海平面的贡献主要来自南极大陆。尽管存在很大的不确定性，但冰盖模型表明，东南极洲的Totten和Denman冰川也可能在下个世纪导致海平面大幅上升。这项国际研究的重点是提高人们对这些冰川在各种变暖情景下对海平面的影响程度的理解。该项目将使用受海洋学和遥感观测约束的数值模型来确定Totten和Denman冰川将如何应对日益加剧的融化。遥感数据将提供对每个冰架融化速率的最新和改进的估计。英国和澳大利亚的合作伙伴将在飞机上部署两台浮子分析器，在每个冰架前反复测量水柱的温度和盐度，并将结果通过卫星链路遥测回来。融化和海洋学数据将用于约束冰架空洞融化响应海洋温度的参数化传递函数，改进目前基于有限数据的参数化。这些融水函数将与气候模型中的海洋温度结合使用，为每个冰川建立一个开源的冰流数值模型，以确定各种情景下的世纪尺度响应，从而帮助减少南极洲这部分地区对海平面贡献的不确定性。在接下来的几个世纪里，除了融化之外，其他可能进一步改变海平面变化的过程也将被研究。在观测方面，在极地环境中部署声纳浮标发射管的浮子剖面仪将有助于提高对迅速变化的极地大陆架海洋进行现场监测的技术准备程度，为扩大对目前知之甚少的偏远地区的海洋水文特性的观测铺平道路。除了具有科学价值外，降低海平面上升预测的不确定性对沿海社区具有强大的社会效益，这些社区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的影响。科考队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。这是一个由美国国家科学基金会地球科学理事会（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。该协议允许美国/英国提交一份联合提案，并由其调查员拥有最大比例预算的机构进行同行评审。在成功地共同确定一个奖项推荐后，每个机构资助预算的比例，以支持各自国家机构的科学家。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。

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.