Biophysical responses of the upper ocean to major Gulf of Mexico hurricanes in 2005

The biophysical responses of the upper ocean to three major Gulf of Mexico (GoM) hurricanes in 2005 were analyzed using satellite observations. The degree and orientation of the responses exhibited by Hurricanes Katrina, Rita, and Wilma were greatly affected by the oceanic processes that occur within the GoM, as well as the translation speed of each hurricane. Maximum sea surface temperature change was 6-7 degrees C, 4-5 degrees C, and 5-6 degrees C; whereas, chlorophyll-a (chl-a) enhancement was 3 mg m(-3), 2 mg m(-3),and 4 mg m(-3), respectively. Areas of chl-a enhancement (i.e., increases in phytoplankton biomass accumulation at the ocean's surface) were observed days after passage of each hurricane. Comparison of thermocline displacement estimates and depth approximations of the nitracline and deep chl-a maximum suggests that the increases in surface phytoplankton biomass associated with Hurricanes Katrina and Rita were the result of new production from nutrient influx, as well as entrainment of phytoplankton from the deep chlorophyll maximum, while chl-a enhancement linked with Hurricane Wilma appears to be attributable to the latter.