Deep oceanic convection: the outsized role of small-scale processes

在高纬度地区，特别是北大西洋次极地的拉布拉多海，深水形成（对流）形成了大尺度海洋环流的关键部分。这使得大气和深海之间的气体交换成为可能，从而有助于全球海洋的碳封存。在气候变暖的情况下，进入拉布拉多海的淡水量增加，加上格陵兰冰盖和北极海冰的融化加剧，预计会减少或停止对流，这将降低海洋减缓气候变化的潜力。在拉布拉多海西部，淡水在盆地边界和内部之间的交换部分是由于小尺度（亚中尺度<10公里）过程。最近的证据表明，漩涡、海冰和大气（风和浮力）强迫都能影响这些小尺度过程。然而，由于极端的冬季条件，拉布拉多海的高分辨率观测很少。因此，对流停止的机制仍然知之甚少，并且在很大程度上被气候模式所忽略。该项目将使用自主平台（滑翔机）的多年测量来研究对流停止时小尺度过程的作用。学生将确定涡旋、大气强迫和海冰对对流生命周期的竞争效应。

Deep-water formation (convection) at high-latitudes, and more specifically in the Labrador Sea in the subpolar North Atlantic, forms a key part of the large-scale ocean circulation. This enables the exchange of gases between the atmosphere and deep ocean, and thus contributes to the global oceanic sequestration of carbon. In a warming climate, added volumes of freshwater into the Labrador Sea, associated with the increased melting of Greenland ice sheet and of Arctic sea-ice, are expected to reduce or shutdown convection, which would reduce the ocean's potential to mitigate climate change. In the western Labrador Sea, freshwater is exchanged between the basin boundary and interior due in part to small-scale (submesoscale <10 km) processes. Recent evidence revealed that eddies, sea-ice, and atmospheric (wind and buoyancy) forcing can all influence these small-scale processes. However, high-resolution observations in the Labrador Sea are scarce due to extreme winter conditions. Thus, the mechanisms responsible for the cessation of convection remain poorly understood and are largely neglected by climate models.This project will use multi-year measurements from autonomous platforms (gliders) to investigate the role of small-scale processes on the cessation of convection. The student will determine the competing effects of eddies, atmospheric forcing, and sea-ice on the lifecycle of convection.