Variation of the fresh water in the western Nordic Seas

该项目的目标是捕捉和分析北欧海西部的淡水波动，确定其来源并了解其基本机制。在东格陵兰洋流（EGC）中，大西洋咸水沿其东缘向北流动，极淡水沿其西缘向南流动，形成了强烈的盐度对比，从而形成了北欧海。从大陆径流和太平洋流入北冰洋的大量淡水，以及通过海冰形成在地表积累的淡水，都被排到北大西洋。其中一部分以液态海冰的形式携带在EGC中。在北欧海，淡水因格陵兰岛径流的增加而加入到EGC中。这些淡水的一小部分通过分支和中尺度特征从EGC流入北欧海中部。这种淡水的数量和垂直分布影响了北欧海的密度分层，从而影响了对流深度和深水的形成。近几十年来，北欧海淡水产量和分布以及对流活动发生了显著变化。最近的研究，以及FOR1740第一阶段的研究表明，大部分海冰是内北欧海的淡水来源。在这个项目中，我们将通过长期（月到季节）的滑翔机任务，调查从EGC到西北欧海内部的淡水泄漏的结构，并分析潜在的过程及其变化。我们将在Argo浮标引起的内部盆地淡水变化的背景下分析这种泄漏，并使用TP2.1的输入来评估净降水的贡献，与EGC的泄漏相比。

The goal of this project is to capture and analyse the freshwater fluctuations in the western Nordic Seas, to identify their sources and to understand the underlying mechanisms. The Nordic Seas are shaped by the strong salinity contrast arising from the northward flow of saline Atlantic Water along their eastern rim and the southward flow of very fresh Polar Water along their western rim in the East Greenland Current (EGC). The huge import of freshwater to the Arctic Ocean from continental runoff and from the Pacific Ocean, and the freshwater accumulated at the surface through sea ice formation is drained to the North Atlantic. Part of it is carried in the EGC as sea ice and in liquid form. In the Nordic Seas freshwater is added to the EGC by an increasing rate of runoff from Greenland. A fraction of this freshwater drains from the EGC via branching and through mesoscale features into the central Nordic Seas. The amount and the vertical distribution of this freshwater influence the density stratification in the Nordic Seas and thus the convection depth and the formation of deep waters. The last decades showed significant changes of the freshwater yield and distribution in the Nordic Seas and of the convective activity. Recent studies, also those of the first phase of FOR1740, indicate that mostly sea ice is the source of freshwater for the inner Nordic Seas. In this project we will investigate the structure of the freshwater leakage from the EGC to the inner western Nordic Seas by long-term (months to seasons) glider missions, and analyse the underlying processes and their variability. We will analyse this leakage in the context of freshwater changes in the inner basins derived from Argo floats and use input from TP2.1 for assessing the contribution of net precipitation as compared to the leakage from the EGC.