Loop Current and Eddy-Driven Salinity Variability in the Gulf of Mexico
Loop Current and Eddy-Driven Salinity Variability in the Gulf of Mexico
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DOI：
10.1029/2019gl082931
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发表时间：
2019-06-16
影响因子：
5.2
通讯作者：
Morey, Steven L.
中科院分区：
文献类型：
--
作者：
Brokaw, Richard J.;Subrahmanyam, Bulusu;Morey, Steven L.
环流系统，包括环流和环流涡流，是墨西哥湾的主要环流特征，由于密西西比河系统的淡水排放和季节性时间尺度上的大盐度变化，墨西哥湾呈现盐度梯度。本研究利用NASA的土壤水分主动被动任务和ESA的土壤水分和海洋盐度任务卫星获取的海面盐度数据，通过测高海面高度数据，观察和量化环流系统相互作用下低盐度水的再分布。该地区夏季几个月的淡水通量由环流系统配置调制，分为三种状态。延伸的环流将低盐度的水向南输送到佛罗里达海峡。路易斯安那-德克萨斯大陆架附近的环流涡流使海湾中部的低盐度水循环。在收缩环流期间，不发生相互作用，低盐度的水保持在海湾北部海岸附近。墨西哥湾从密西西比河和阿查法拉亚河接收淡水，每年春季由于流域上部的融雪而达到峰值。淡水形成了一个低盐度的水羽，它根据当地的风强迫以及环流系统相关的环流特征而演变。环流将加勒比海的海水向北带入墨西哥湾，并通过佛罗里达海峡将海水带出墨西哥湾，在那里流入墨西哥湾流。在墨西哥湾内部，环流可以向北延伸到密西西比-阿拉巴马海岸。当向北延伸时，环流沿着密西西比/阿拉巴马/佛罗里达大陆架向东平流低盐度水，沿着西佛罗里达大陆架向南。这种低盐度的水然后通过佛罗里达海峡流出海湾。此外，环流偶尔会释放反气旋涡流，向西迁移到德克萨斯州海岸，并能在墨西哥湾中部重新循环低盐度的水。对近十年卫星盐度数据的分析表明，在夏末的几个月里，淡水通量倾向于流向墨西哥湾东南部的事件，其年际变化与环流系统的配置有关。
The Loop Current System, involving the Loop Current and Loop Current Eddies, is the principal circulation feature in the Gulf of Mexico, which exhibits salinity gradients due to Mississippi River system freshwater discharge and large salinity variability on seasonal timescales. This research uses satellite-derived sea surface salinity from NASA's Soil Moisture Active Passive and ESA's Soil Moisture and Ocean Salinity missions with altimetric sea surface height data to observe and quantify the redistribution of low-salinity water by Loop Current System interaction. Freshwater flux in this region during summer months is modulated by Loop Current System configuration as classified by three states. An extended Loop Current transports low-salinity water southward to the Florida Straits. A Loop Current eddy near the Louisiana-Texas shelf recirculates low-salinity water within the central Gulf. During a retracted Loop Current, no interaction occurs and low-salinity water remains close to the coast in the northern Gulf.Plain Language Summary The Gulf of Mexico receives freshwater from the Mississippi and Atchafalaya Rivers with an annual peak during spring due to snow melt over the upper part of the watershed. The fresh water forms a low-salinity water plume, which evolves based on local wind forcing as well as circulation features associated with the Loop Current System. The Loop Current brings Caribbean Sea water northward into the Gulf of Mexico and transports waters out of the Gulf through the Florida Straits where it feeds into the Gulf Stream. While inside the Gulf, the Loop Current can extend northward to the Mississippi-Alabama coast. When extended northward, the Loop Current advects low-salinity water eastward along the Mississippi/Alabama/Florida shelf, and southward along the West Florida Shelf. This low-salinity water then exits the Gulf through the Florida Straits. Additionally, the Loop Current occasionally sheds anticyclonic eddies which migrate westward to the Texas coast, and can recirculate low-salinity water in the central Gulf of Mexico. Analysis of nearly a decade of satellite salinity data shows a preference for events of freshwater flux toward the southeastern Gulf of Mexico during the late summer months with substantial interannual variability linked with the configuration of the Loop Current System.