Variable Nordic Seas Inflow Linked to Shifts in North Atlantic Circulation
Variable Nordic Seas Inflow Linked to Shifts in North Atlantic Circulation
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DOI：
10.1175/jcli-d-20-0917.1
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发表时间：
2021-09-01
影响因子：
4.9
通讯作者：
Arthun, Marius
中科院分区：
文献类型：
--
作者：
Asbjornsen, Helene;Johnson, Helen L.;Arthun, Marius
冰岛-苏格兰海脊的流入决定了北大西洋次极地(SPNA)向北欧海洋提供的热量。因此，海脊不同的流入特性和流量输送影响到更北边的海洋生态系统和海冰范围。在这里，我们确定了北欧海洋流入的上游路径，并评估了造成年际流入变化的机制。使用允许涡流的海洋模式后播和拉格朗日分析工具，在1986-2015年间在海脊释放数值粒子，并在时间上向后跟踪。我们发现，就其性质而言，流入的资金很好地混合在一起，其中%来自亚热带，26%来自亚极地或北极。对北大西洋涛动的本地瞬时响应对副热带和北冰洋起源的海脊水域的整体输送很重要。在到达脊线之前的几年里，副热带粒子受到环流边界区域和SPNA上大气环流异常的影响，迫使北大西洋洋流(NAC)和亚极锋发生变化。赤道上移的NAC和西移的亚极锋对应着更温暖、更多的盐分流入。SPNA上的大气环流异常也影响到从拉布拉多洋流改道到北欧海域的北极起源的水量。来自北极的水的高度输送与冰岛-苏格兰山脊上更冷、更新鲜的流入有关。结果表明，涡旋动力和风强迫在影响北欧海域的流入特性和流量输送方面具有重要意义。
The inflow across the Iceland-Scotland Ridge determines the amount of heat supplied to the Nordic seas from the subpolar North Atlantic (SPNA). Consequently, variable inflow properties and volume transport at the ridge influence marine ecosystems and sea ice extent farther north. Here, we identify the upstream pathways of the Nordic seas inflow and assess the mechanisms responsible for interannual inflow variability. Using an eddy-permitting ocean model hindcast and a Lagrangian analysis tool, numerical particles are released at the ridge during 1986-2015 and tracked backward in time. We find an inflow that is well mixed in terms of its properties, where 64% comes from the subtropics and 26% has a subpolar or Arctic origin. The local instantaneous response to the NAO is important for the overall transport of both subtropical and Arctic-origin waters at the ridge. In the years before reaching the ridge, the subtropical particles are influenced by atmospheric circulation anomalies in the gyre boundary region and over the SPNA, forcing shifts in the North Atlantic Current (NAC) and the Subpolar Front. An equatorward-shifted NAC and westward-shifted Subpolar Front correspond to a warmer, more saline inflow. Atmospheric circulation anomalies over the SPNA also affect the amount of Arctic-origin water rerouted from the Labrador Current toward the Nordic seas. A high transport of Arctic-origin water is associated with a colder, fresher inflow across the Iceland-Scotland Ridge. The results thus demonstrate the importance of gyre dynamics and wind forcing in affecting the Nordic seas inflow properties and volume transport.