The response of the circulation in the Faroe-Shetland Channel to the North Atlantic Oscillation
The response of the circulation in the Faroe-Shetland Channel to the North Atlantic Oscillation
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DOI：
10.3402/tellusa.v64i0.18423
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发表时间：
2012-01-01
影响因子：
2
通讯作者：
Chafik, Leon
中科院分区：
文献类型：
--
作者：
Chafik, Leon
这项研究基于卫星获取的海面高度和温度以及水文数据，试图阐明北大西洋涛动（NAO）的极端阶段对法罗-设得兰海峡（FSC）局部动力的作用。在2009- 2010年低nao事件期间，设得兰斜坡流在测深最大梯度以上的通常路径上显示出明显的偏转，最终导致反气旋。这导致北大西洋水（NAW）在海峡较深的部分积聚，表现为盐斜的明显加深。一个源自法罗群岛北部（因此是由经过改造的北大西洋海水组成）的与盐跃层的圆顶有关的气旋涡旋，在海峡中向南移动，在它的南部入口停了下来，导致了斜坡流的偏转大约两周。利用1992-2010年的高程资料评估了NAO对这些区域动态的影响，发现在NAO的正相位，地表环流倾向于强烈的水深对称约束，因此与区域平均环流相似。NAO的负相位与风应力旋度的区域减弱有关，这导致挪威海环流的收缩和FSC再环流的北移，涉及设得兰斜坡流的偏转路径。这种负NAO条件下环流的变化可能通过咸化NAW在通道内的积累对区域海洋气候产生影响。
This study, based on satellite-derived sea-surface heights and temperatures as well as hydrographic data, attempts to shed some light on the role of the extreme phases of the North Atlantic Oscillation (NAO) for the local dynamics of the Faroe-Shetland Channel (FSC). During the low-NAO event 2009-10 the Shetland-slope current showed a significant deflection from its usual path above the maximal gradient of the bathymetry, ultimately resulting in an anticyclone. This led to an accumulation of North Atlantic Water (NAW) over the deeper parts of the channel, manifested as a pronounced deepening of the halocline. Leading this deflection of the slope current by around 2 weeks, a cyclonic eddy associated with a doming of the halocline and originating from north of the Faroes (and hence constituted by Modified North Atlantic Waters) had moved southwards in the channel, coming to rest at its southern entrance. Assessing the influence of the NAO on these regional dynamics using 1992-2010 altimetric data, it was found that for positive phases of the NAO, the surface circulation tended to be strongly bathymetrically constrained and thus resembles the mean regional circulation. The negative phases of the NAO are associated with a regional weakening of the wind-stress curl, which leads to a contraction of the Norwegian-Sea gyre and a linked northward migration of the FSC recirculation involving a deflected path of the Shetland-slope current. This change in the circulation under negative NAO conditions may have an impact on the regional ocean climate through the accumulation of saline NAW in the channel.