High-resolution simulation of the circulation in the Bahamas and Turks and Caicos Archipelagos

• We used ROMS to simulate the circulation in the Bahamas and Turks and Caicos.
• Salinity seasonal variations are driven by the north Atlantic sub-tropical gyre.
• Shallow banks singular short term dynamics is driven by atmospheric forcing.
• Deep basins local water masses are produced by wind and eddy driven upwelling.
• Deep basins oceanographic features and topography control their isolation degree.

We present the first high-resolution simulation of the Bahamas and Turks and Caicos archipelagos implemented with the Regional Oceanic Modeling System (ROMS). Our model resolves tides and our simulation consists of two nested grids of respectively 4 and 2 km horizontal resolution. This oceanic region is constituted of the juxtaposition of very large and shallow banks, and very deep basins. Our modeling study shows that the dominant influence is the salinity from the sub-tropical gyre, which varies latitudinally with seasons. Less salty surface waters entered the archipelago from September to November from the north and through the Old Bahama (OBC) and the North West Providence (NWPC) channels as the western Atlantic saline waters moved south. Saltier Atlantic waters arrived from the south in December and moved north till the next fall.This salinity flux is mitigated by the atmospheric forcing on the banks as well as the water temperature, which varied diurnally, what modified the water density causing this water to be unique to the banks, yielding its own seasonality as seen in their SST. The banks were colder in winter and warmer in summer than their surrounding waters. Fronts were formed at every ebb tide in winter, spring, and fall. However the influence of bank waters on the surrounding waters was shown to be limited because of the dominant influence of the large-scale flow and of the local production of water masses by wind and cyclone driven upwelling. Bank waters were contained at the front where they mixed with the surrounding waters as shown by the short time presence of the fronts. Local wind, in addition to the tide was also shown to be a significant forcing which is responsible for some of the short scale variability 5–30 days in Florida Current transport, the NWPC, the OBC, the Windward Passage (WP), and the Antilles Current (AC). Finally, the study also confirmed the mesoscale eddy influence at seasonal scales (100 days) on the AC transport as well as on the FC, through a possible leakage of eddy flux through the NWPC. A similar influence was found south of the archipelago, where mesoscale eddy could also influence WP transport.

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