Submesoscale currents in the northern Gulf of Mexico: Deep phenomena and dispersion over the continental slope
Submesoscale currents in the northern Gulf of Mexico: Deep phenomena and dispersion over the continental slope
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DOI：
10.1016/j.ocemod.2016.03.002
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发表时间：
2016-05-01
期刊：
影响因子：
3.2
通讯作者：
McWilliams, James C.
中科院分区：
文献类型：
--
作者：
Bracco, Annalisa;Choi, Jun;McWilliams, James C.
本研究探讨中尺度和亚中尺度环流沿着大陆坡在墨西哥湾北方的深度大于1000米。2010年1月至2012年12月，采用水平网格分辨率为5 km和1.6 km的区域模式，对大陆坡进行了为期3年的模拟。它们是由高度间歇性的、底部强化的、沿斜坡的边界流边缘的水平剪切层和这些流的核心形成的，在这些核心中，它们被限制在陡坡上。确定了两种不同的流态。第一个适用于德索托峡谷，其特点是弱的平均电流，并在高分辨率运行，由强烈的，但很少的次中尺度漩涡，形成附近优先沿着佛罗里达大陆坡。第二个是在区域的其余部分，其中平均气流较强，环流在空间和时间上都高度可变，并且涡度场被填充，在高分辨率情况下，大量的涡丝和短的拉格朗日示踪剂部署在不同的时间沿着大陆架低于10 0 0 m的深度，以量化的影响，亚中尺度流运输和混合。建模的绝对分散，平均而言，独立的水平分辨率，而混合，量化的有限大小的李雅普诺夫指数和垂直相对分散，增加时，亚中尺度过程。德索托峡谷的色散比模型域的其余部分小，受分辨率的影响较小。通过比较部署在Macondo前景附近的De Soto峡谷（深水地平线钻井平台于2010年在此爆炸）和北方海湾已知最大的天然烃渗漏（称为GC 600，位于钻井平台井口以西几百公里处）的被动染料场的演变，进一步证实了这一点。(C)2016爱思唯尔有限公司版权所有
This study examines the mesoscale and submesoscale circulations along the continental slope in the northern Gulf of Mexico at depths greater than 1000 m. The investigation is performed using a regional model run at two horizontal grid resolutions, 5 km and 1.6 km, over a 3 year period, from January 2010 to December 2012.Ageostrophic submesoscale eddies and vorticity filaments populate the continental slope, and they are stronger and more abundant in the simulation at higher resolution, as to be expected. They are formed from horizontal shear layers at the edges of highly intermittent, bottom-intensified, along-slope boundary currents and in the cores of those currents where they are confined to steep slopes. Two different flow regimes are identified. The first applies to the De Soto Canyon that is characterized by weak mean currents and, in the high-resolution run, by intense but few submesoscale eddies that form near preferentially along the Florida continental slope. The second is found in the remainder of the domain, where the mean currents are stronger and the circulation is highly variable in both space and time, and the vorticity field is populated, in the high-resolution case, by numerous vorticity filaments and short-lived eddies.Lagrangian tracers are deployed at different times along the continental shelf below 10 0 0 m depth to quantify the impact of the submesoscale currents on transport and mixing. The modeled absolute dispersion is, on average, independent of horizontal resolution, while mixing, quantified by finite-size Lyapunov exponents and vertical relative dispersion, increases when submesoscale processes are present. Dispersion in the De Soto Canyon is smaller than in the rest of the model domain and less affected by resolution. This is further confirmed comparing the evolution of passive dye fields deployed in De Soto Canyon near the Macondo Prospect, where the Deepwater Horizon rig exploded in 2010, and at the largest known natural hydrocarbon seep in the northern Gulf, known as GC600, located a few hundred kilometers to the west of the rig wellhead. (C) 2016 Elsevier Ltd. All rights reserved.