Collaborative Research: Shelf-Basin Exchange South of Denmark Strait: Forcing, Dynamics, and Large-Scale Impact

位于格陵兰岛南部和雷克雅未克海脊之间的伊尔明格海是北冰洋与北大西洋第一次相遇的重要区域。在丹麦海峡以南，冷的、新鲜的流出的北极水与温暖的、含盐的亚热带水相遇，形成了一个尖锐的锋面。这一锋面及其相关的急流，东格陵兰/伊尔明格海流，是再循环的亚热带起源的北极水输出到北大西洋的主要途径。与格陵兰高原附近的下锋面屏障风的应力，以及锋面和Irminger海流的不稳定性和时变性，在这一地区发生了与开阔大西洋的强烈陆架-海盆交换。作为这一交换过程的一部分，密集的陆架水瀑布在陆架断裂，形成一个“溢出射流”，居住在东格陵兰/Irminger电流。这导致了拉布拉多海下游的大量下沉，并影响了次极地环流和流向北方淡水源的赤道翻转环流。目前，科学家们对这个复杂的陆架断裂流系统的理解很差，因此不确定其运输，淡水通量，季节演变以及导致跨流质量和属性交换的中尺度变化的性质和动力学。通过一项联合观测/模拟研究，来自伍兹霍尔海洋研究所和约翰霍普金斯大学的海洋学家建议量化推动格陵兰岛以东发生陆架-盆地交换的水动力不稳定性和大气强迫。通过研究东格陵兰/Irminger海流系统的平均和季节性变化的运输，结构和运动学，并确定导致陆架盆地交换的中尺度变化的性质和动力学，他们将能够探索陆架盆地交换对亚极地北大西洋的影响在过去几十年中如何变化，以及它在未来可能如何演变。这项研究的更广泛的影响解决了北大西洋纬向翻转环流相对于北方淡水资源的敏感性的关注。北极淡水输出总量的大约一半经过格陵兰以东，在拟议的研究区与开阔的大西洋汇合，因此，了解该区域陆架-海盆交换的动态对于预测北大西洋对未来气候变化的反应至关重要。这项研究包括资助教育推广活动，包括在格陵兰南部偏远地区的活动，以及在美国的科学中心展览。还包括资助研究生和本科生的教育和培训。

The Irminger Sea, situated between southern Greenland and the Reykjanes Ridge, is a critically important area where the Arctic Sea first meets the North Atlantic Ocean. South of the Denmark Strait, a sharp front is formed where cold, fresh outflowing Arctic water meets the warm, salty subtropical-origin water. This front and its associated jet, the East Greenland/Irminger Current, act as the main pathway that recirculating subtropical-origin Arctic water is exported to the North Atlantic. With the stress of the down-front barrier winds adjacent to the Greenland plateau in addition to the instability and time-variability of both the front and the Irminger Current, intense shelf-basin exchange with the open Atlantic occurs in this region. As part of this exchange process, dense shelf water cascades over the shelf-break to form a "Spill Jet" which resides below the East Greenland/Irminger Current. This results in substantial sinking, which occurs downstream in the Labrador Sea and impacts the sub-polar gyre and the meridional overturning circulation to northern freshwater sources. Currently, scientists have a poor understanding of this complex shelf-break current system, and thus are unsure of its transport, freshwater flux, seasonal evolution, and the nature and dynamics of the mesoscale variability that lead to the cross-stream exchange of mass and properties. Through a joint observational/modeling study, oceanographers from Woods Hole Oceanographic Institution and Johns Hopkins University propose to quantify the hydrodynamic instability and atmospheric forcing that drive shelf-basin exchange to occur east of Greenland. By examining the mean and seasonally varying transport, structure, and kinematics of the East Greenland/Irminger Current system and determining the nature and dynamics of the mesoscale variability that leads to shelf-basin exchange, they will be able to explore how the impact of shelf-basin exchange on the sub-polar North Atlantic has changed in the last few decades and how it may evolve in the future. The broader impacts of this study address the concern about the sensitivity of the North Atlantic meridional overturning circulation with respect to northern freshwater sources. Approximately one half of the total Arctic export of freshwater passes east of Greenland and meets the open Atlantic in the proposed study area, therefore understanding the dynamics of the shelf-basin exchange in this region is essential to potentially predict the response of the North Atlantic to future changes in climate. This research includes funding to support educational outreach including activities in a remote location in southern Greenland, as well as science center exhibits in the United States. Funding is also included to support education and training at both the graduate and undergraduate level.