Analysis of year-long drifter trajectories and records of simulated surface Lagrangian Coherent Structures (LCSs) have suggested the presence of a resilient Cross-Shelf Transport Barrier (CSTB) on the West Florida Shelf (WFS). The CSTB was conjectured to provide a large degree of isolation, which is consequential for the fueling of red tides on the southern WFS by nutrients possibly released by rivers and canals directly on the region. Here this conjecture is thoroughly tested by identifying LCSs as well as performing tracer advection calculations based on seven-year-long records of surface and subsurface currents produced by a HYbrid-Coordinate Ocean Model (HYCOM) simulation of the Gulf of Mexico (GoM). The identified LCSs suggest that the CSTB extends downward in the water column. The tracer calculations suggest that, while the majority of the nutrients possibly released by rivers and canals directly on the southern WFS are retained within the region for long times, only a small fraction of the nutrients possibly released by rivers outside the WFS reach the southern WFS, mainly accompanying shoreward excursions of the CSTB. These results add importance to the role played by the CSTB in controlling red tide development on the WFS. Implications of the results for the dispersal of pollutants, such as oil, in the GoM are discussed.

中文翻译：

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西佛罗里达大陆架的隔离对墨西哥湾赤潮和污染物扩散的影响

长达一年的漂移轨迹分析和模拟表面拉格朗日相干结构 (LCS) 的记录表明，西佛罗里达大陆架 (WFS) 上存在弹性跨架运输屏障 (CSTB)。据推测，CSTB 提供了很大程度的隔离，这对于可能由该地区的河流和运河直接释放的营养物质加剧了 WFS 南部的赤潮产生了影响。在这里，通过识别 LCS 以及基于墨西哥湾 (GoM) 的混合坐标海洋模型 (HYCOM) 模拟产生的长达七年的地表和地下洋流记录进行示踪平流计算，彻底检验了这一猜想。已识别的 LCS 表明 CSTB 在水体中向下延伸。示踪剂计算表明，虽然直接在 WFS 南部的河流和运河可能释放的大部分养分在区域内长期保留，但 WFS 以外的河流可能释放的养分只有一小部分到达 WFS 南部，主要伴随着CSTB。这些结果增加了 CSTB 在控制 WFS 赤潮发展方面的作用的重要性。讨论了结果对 GoM 中污染物（例如石油）扩散的影响。这些结果增加了 CSTB 在控制 WFS 赤潮发展方面的作用的重要性。讨论了结果对 GoM 中污染物（例如石油）扩散的影响。这些结果增加了 CSTB 在控制 WFS 赤潮发展方面的作用的重要性。讨论了结果对 GoM 中污染物（例如石油）扩散的影响。