The Effect of Lower Sea Level on Volume Transport Through the Florida Straits During the Last Glacial Maximum

In this study we investigate the effect of sea level change on the volume transport through the Caribbean Sea and the Florida Straits during the Last Glacial Maximum (LGM) relative to the present. During the LGM, the sea level was lower by approximately 120 meters, which reduced the Florida Straits sill depth of 760 meters to 640 meters. The sea level's effect on the Florida Current volume transport has not been previously investigated and has been assumed to be negligible. A geostrophic transport estimate for the Florida Straits suggests that the Florida Current was weaker by one third during the LGM relative to today, associated with a corresponding decrease in the North Atlantic overturning circulation. It is important to investigate a possible simultaneous impact of a shallower Florida Straits on the Florida Current. The Regional Ocean Modeling System (ROMS) with the Intra American Seas bathymetry grid of the Gulf of Mexico, the Caribbean Sea, and the Bahamas is used in a sensitivity study to assess the impact of lowered sea level on the flow distribution through the various channels in the Florida Straits and the Caribbean Sea. The bathymetry has a 10 km horizontal resolution and the sill depths for various straits have been adjusted to agree with observations. Based on preliminary results, the volume transport through the Florida Straits is expected to be slightly reduced in the lower sea level run compared to the control run, with most of the difference exiting the Caribbean Sea through the Windward Passage and joining the Florida Current north of the Bahamas. The sill depth's limitation on the Florida Current transport during the LGM is likely to be small relative to the decrease in the North Atlantic overturning circulation, which is believed to account for most of the observed flow reduction.