Response of sea surface properties to Hurricane Dennis in the eastern Gulf of Mexico

Abstract

Sea Surface Reflectance (SSR) and Sea Surface Temperature (SST) were assessed in the eastern Gulf of Mexico in early July 2005 after passage of Hurricane Dennis, a category 4 storm, using data from the MODIS, Sea WiFS, and AVHRR satellite sensors, historical hydrographic: and nutrient surveys, and a simple vertical water column mixing model. The bathymetric gradient across the shelf break, the offshore deep nutricline, and nearby Loop Current eddies led to unique SSR and SST changes after the passage of Dennis. In waters shallower than 50 m, a strong sediment resuspension event led to higher SSR in the visible and an increase in the MODIS fluorescence line height (FLH). These variables returned to pre-storm conditions after about 10 days. The FLH change indicates increasing biomass in the short response time (<2 days), which might have been due to resuspended benthic and/or near-bottom algae, as opposed to simply new primary production in the overlying water column. The SST changes occurred almost entirely along the right side of the hurricane track (-1.96 ± 0.66°C for an area of 158,600 km2). Waters >50 m deep cooled down significantly, but there was no apparent change in SSR, presumably because the nutricline was too deep to be affected by vertical mixing due to the storm. The three-dimensional hydrographic and nutrient structure in waters near the west Florida shelf defines what changes may be detected at the surface with remote sensing. Copyright 2007 by the American Geophysical Union.