Fate of Freshwater and Heat in Baffin Bay: Basin-scale Circulation and Shelf/slope Processes

由于气候变暖，北极的浮冰正在快速融化，一些模型预测，在短短几十年内，北极将在夏季无冰。与此同时，格陵兰冰盖正在加速融冰，这在很大程度上是由于来自南方的温暖海水融化了海岸周围冰川的底部。与此相关的两个重要问题是：(1)增加的融水的最终命运是什么？(2)温暖的海水是如何如此接近格陵兰岛海岸的？2021年秋天，美国海岸警卫队的Cutter Healy对巴芬湾（格陵兰岛西侧）的环流和水特征进行了详细的船上调查。在这个项目中，我们将分析在Healy上收集的数据，以解决上述两个问题。我们将把船上的信息和一个小型的自动水下航行器收集的数据结合起来，这个水下航行器比希利号更接近海岸。我们还将使用其他船只最近和过去收集的数据，并将使用一个非常详细的数值模型的输出来补充我们的观测。该项目将促进我们对环流和风力如何帮助决定地表融水去向以及地下暖水如何被引导到岸上的理解。该项目将资助一名年轻研究人员与主要研究人员一起工作。我们将与巴芬岛上的土著社区分享我们的成果，并在格陵兰自然资源研究所组织一次科学讲习班。在过去的几十年里，北冰洋的淡水量一直在大幅增加，格陵兰冰盖的质量损失一直在加速。从弗拉姆海峡（格陵兰岛和斯瓦尔巴群岛之间）流出的大部分淡水，以及格陵兰岛的大部分融水，最终流入环绕格陵兰岛的边界流。此外，在洋流的表层之下，存在着温暖而咸的亚热带水，这种水与格陵兰冰川的基底融化有关。2021年秋季，USCGC Healy对巴芬湾进行了广泛的水文/速度调查。该项目将利用这些数据来解决海湾中热量和淡水的命运。除了Healy的数据外，我们还将使用CCS Amundsen的同期滑翔机数据和船上数据，以及历史水文数据和高分辨率数值模型的输出。该项目将从根本上促进我们对以下方面的理解：(1)围绕巴芬湾的边界流系统的演变；(2)热量从西格陵兰边界流经大陆架深槽向冰川峡湾转移的机制；(3)淡水在北极和格陵兰融水之间的划分以及这两个组成部分在海湾中的分布情况；(4)巴芬湾的环流和水文特征，包括季节特征。来自六个外国机构的研究人员参与了该项目。一名博士后研究员将与研究小组一起工作。在外联方面，我们将在巴芬岛之旅期间与社区成员和利益相关者接触，我们将在格陵兰自然资源研究所组织一次科学研讨会。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。

Due to the warming climate the Arctic pack-ice is melting at a fast rate, and some models predict that, in just a few decades, the Arctic will be ice-free during the summer months. At the same time, the Greenland ice sheet is undergoing accelerated ice loss, which is largely due to warm ocean waters from the south melting the undersides of the glaciers surrounding the coast. Two important questions associated with this are: (1) What is the ultimate fate of the increased meltwater? and (2) How are the warm waters able to get so close to the coast of Greenland? In fall of 2021, a detailed shipboard survey of the circulation and water characteristics in Baffin Bay (on the western side of Greenland) was carried out on the US Coast Guard Cutter Healy. In this project we will analyze the data collected on the Healy to address the two questions above. We will combine our shipboard information with data collected by a small, self-propelled underwater vehicle that was able to sample closer to the coast than the Healy could. We will also use recent and past data collected by other ships and will use output from a very detailed numerical model to complement our observations. The project will advance our understanding of how the circulation and wind forcing help dictate where the surface meltwater goes and how the subsurface warm waters are steered shoreward. The project will fund a young researcher to work with the principal investigators. We will share our results with indigenous communities on Baffin Island and organize a scientific workshop at the Greenland Institute of Natural Resources.During the past few decades, the amount of freshwater in the Arctic Ocean has been increasing substantially and the mass loss from the Greenland ice sheet has been accelerating. Much of the freshwater exiting Fram Strait (between Greenland and Svalbard), and most of the meltwater from Greenland, ends up in the boundary current encircling Greenland. Furthermore, beneath the surface layer in the current resides the warm and salty subtropical-origin water that has been implicated in causing basal melt in Greenland’s glaciers. In autumn 2021 the USCGC Healy carried out an extensive hydrographic/velocity survey of Baffin Bay. This project will use these data to address the fate of heat and freshwater in the bay. In addition to the Healy data, we will use contemporaneous glider data and shipboard data from the CCS Amundsen, as well as historical hydrographic data and output from a very high-resolution numerical model. The project will fundamentally advance our understanding of (1) the evolution of the boundary current system as it encircles Baffin Bay; (2) the mechanisms by which heat is transferred from the west Greenland boundary current to glacial fjords via deep troughs in the continental shelf; (3) the partitioning of freshwater between Arctic-origin and Greenland meltwaters and how these two components are distributed in the bay; and (4) the general circulation and hydrography of Baffin Bay, including its seasonality. Researchers from six foreign institutions are involved in the project. A postdoctoral investigator will work with the team of investigators. For outreach we will engage community members and stakeholders during a trip to Baffin Island, and we will organize a scientific workshop at the Greenland Institute of Natural Resources.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.