Pathways to the Denmark Strait Overflow: A Lagrangian Study in the Iceland Sea

智力优势：丹麦海峡溢出是全球经向翻转环流深支的重要贡献者。然而，关于溢出水的来源及其迁移和温度/盐度变化的原因，仍然存在相当大的不确定性。为了更好地了解并预测进入北大西洋的高密度水进入丹麦海峡的变化，需要更好地描述高密度水通过冰岛海的路径。最近的研究提出，高密度水进入丹麦海峡有两条路径：一条是通过东格陵兰海流从格陵兰海进入，另一条是通过北冰岛急流从冰岛海内部进入。最近的一项模拟研究表明，这些路径可能会随着风力条件的变化而交替变化，特别是冰岛周围地区的风应力旋度。在风应力旋度高（低）的年份，东格陵兰海流（北冰岛急流）被认为是主要的路径。次表层拉格朗日观测，直接测量流体包裹路径，目前还没有在冰岛海。该项目将在丹麦海峡底床深度以上500米处部署声学跟踪浮标，在两年期间直接观察冰岛海密集的水道。总共有35个浮子轨迹，跟踪一个阵列的六个声源，将结合大气，水文和测高数据，以确定之间的关系，观察到的路径和强迫条件在实验期间。在冰岛海的粒子轨迹的海洋环流模型模拟，被迫与实验期间观察到的条件下，将与浮子轨迹进行比较。实地工作得到了很大的利用，挪威卑尔根海洋研究所提供了声源阵列、声源和浮标部署的船舶时间以及大约40%的浮标。总体而言，这项研究将有助于更好地了解丹麦海峡溢出和它的变化，以及阐明了一般的地下环流的冰岛海。更广泛的影响：这个项目的影响，经翻转环流的下肢的变化，因此是有关更广泛的主题的海洋？在全球气候变化中的作用。这项研究是与几个国际伙伴高度合作的，包括挪威卑尔根海洋研究所、冰岛雷克雅未克海洋研究所和德国汉堡海洋学研究所。这个实验也将为一个早期的职业科学家提供一个机会，领导她的第一个实地项目。

Intellectual Merit: The Denmark Strait overflow is an important contributor to the deep limb of the global Meridional Overturning Circulation. However, considerable uncertainty remains regarding the source(s) of the overflow water, and the causes of its transport and temperature/salinity variability. A better description of the dense water pathways leading to Denmark Strait through the Iceland Sea is needed to understand, and ultimately predict, changes in the overflow entering the North Atlantic Ocean.Recent studies have proposed that there are two pathways for dense water to enter the Denmark Strait: one from the Greenland Sea via the East Greenland Current, and another from the interior Iceland Sea via the North Icelandic Jet. A recent modeling study suggests that these pathways may alternate with changing wind conditions, in particular the wind stress curl in the region around Iceland. During years with high (low) wind stress curl, the East Greenland Current (North Icelandic Jet) is thought to be the dominant pathway.Subsurface Lagrangian observations, which directly measure fluid parcel pathways, are not presently available in the Iceland Sea. This project will deploy acoustically tracked floats set at a depth of 500 m, just above the sill depth of Denmark Strait, to directly observe dense water pathways in the Iceland Sea over a two-year period. A total of 35 float trajectories, tracked with an array of six sound sources, will be combined with atmospheric, hydrographic and altimetry data to define the relationship between the observed pathways and the forcing conditions during the experiment. An ocean general circulation model simulation of particle trajectories in the Iceland Sea, forced with the conditions observed during the experiment, will be compared with the float trajectories. The field work is heavily leveraged, with the Institute for Marine Research in Bergen, Norway providing the sound source array, the ship time for sound source and float deployment and about 40% of the floats. Overall, this study will help to better understand the Denmark Strait overflow and its variability as well as shed light on the general subsurface circulation of the Iceland Sea.Broader impacts: This project has bearing on the variability of the lower limb of the Meridional Overturning Circulation, and thus is relevant to the broader topic of the ocean?s role in global climate change. The research is highly collaborative with several international partners, including the Institute of Marine Research in Bergen, Norway, the Marine Research Institute in Reykjavik, Iceland and the Institute of Oceanography in Hamburg, Germany. This experiment will also provide an opportunity for an early career scientist to lead her first field project.