Warm and saline events embedded in the meridional circulation of the northern North Atlantic
Warm and saline events embedded in the meridional circulation of the northern North Atlantic
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DOI：
10.1029/2010jc006275
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发表时间：
2011-03-04
影响因子：
3.6
通讯作者：
Worthen, Denise L.
中科院分区：
文献类型：
--
作者：
Haekkinen, Sirpa;Rhines, Peter B.;Worthen, Denise L.
本文分析了SODA系统1958 - 2005年的海洋状态估计，以了解副热带和亚极地大西洋环流及其与大气强迫的关系。这一分析显示了三个时期（20世纪60年代、1980年前后和2000年代），高纬度地区的温暖咸水增多，与源自高纬度地区的淡水事件交替发生。它补充了地表漂移和测高数据，表明亚热带-亚极交换导致2001年后东北大西洋的温度和盐度显著增加。以SODA为代表的大西洋经向翻转环流暖水分支在密度/盐度空间上有所扩大。使用SODA速度的示踪模拟也显示了墨西哥湾流到达亚极地环流和北欧海的年代际变化。北大西洋涛动指数的负相位（通常在这种变率中被引用）无法预测本世纪初的变暖和盐碱化，盐度自20世纪60年代以来从未出现过。风应力旋度变率为副热带/亚极环流交换提供了联系，如理想化的双层环流模式所示。海洋对气候风应力旋度模式调制的响应是，当风应力旋度幅值较弱时，副热带示踪剂的北侵增强。在这种情况下，副热带和次极环流减弱，次极密度面松弛；因此，极锋向西移动，在东部边界流中为副热带水域的北进打开了一个增强通道。
Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand circulation between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced warm, saline waters reaching high latitudes, alternating with freshwater events originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical-subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The warm water limb of the Atlantic meridional overturning cell represented by SODA expanded in density/salinity space during these warm events. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the warming and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two-layer circulation model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.