Collaborative Research: The Antarctic Circumpolar Current: A Conduit or Blender of Antarctic Bottom Waters?

南极底水（AABW）是地球上最冷、最咸、密度最大的水，因为它是在南极冰层的高纬度地区形成的。全球环流通常通过二维纬度/深度坐标空间的输运来量化。然而，AABW的形成、向北流动以及大西洋、印度洋和太平洋盆地之间的分布基本上是三维过程。AABW形成于南极海岸附近的几个不同的地点，特别是威德尔海南部，罗斯海西部，沿着Ad’elie海岸和Prydz湾。AABW是全球海洋翻转环流的关键组成部分之一，在几十年到千年的时间尺度上对地球气候的调节起着关键作用。第2部分：AABW向北部盆地输运的映射没有得到很好的约束，在以前的研究中得出的结论相互矛盾。在一个极端的情况下，ACC被认为是一个“管道”，允许各种AABW直接向北移动。在另一个极端，有人认为ACC在陆架AABW源到达北部盆地之前将它们“混合”在一起。为了缩小理解上的差距，该合作项目利用了三种互补的分析工具：横跨ACC的AABW输出的面向过程的建模、高分辨率全球海洋模型和全球环流的观测约束估计。AABW途径的鉴定和机制理解。该项目还将促进三名博士后研究人员和两名早期职业教师的职业发展，并将继续PI与一名外国研究者之间的合作联系。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。

Part 1: Because of the manner in which it is formed at high latitudes in the Antarctic ice, Antarctic Bottom Water (AABW) is the coldest, saltiest and densest water on the planet. The global circulation of is often quantified via the transport in a two-dimensional, latitude/depth coordinate space. However, AABW formation, northward flow and distribution between the Atlantic, Indian and Pacific basins are fundamentally three-dimensional processes. AABW is formed in a handful of distinct sites around the Antarctic coast, notably the southern Weddell Sea, the western Ross Sea, along the Ad´elie coast, and in Prydz Bay. AABW is one of the key components of the global ocean overturning circulation, and plays a critical role in regulating Earth's climate, on multi-decadal-to-millennial time scales. Part 2: Mapping of AABW transport to northern basins is not well constrained, with conflicting conclusions drawn in previous studies. At one extreme the ACC has been suggested to be a “conduit" that simply allows each variety of AABW to transit directly northward. At the other extreme, it has been suggested that the ACC “blends" all shelf AABW sources together before they reach the northern basins. To close the gap in understanding, this collaborative project draws on three complementary analytical tools: process-oriented modeling of AABW export across the ACC, a high-resolution global ocean model, and an observationally-constrained estimate of the global circulation. The proposed identification and mechanistic understanding of AABW pathways. This project will also advance the careers of three postdoctoral researchers and two early-career faculty members, and will continue collaborative links between the PI and a foreign investigator.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.