Observed ocean thermal response to Hurricanes Gustav and Ike
The 2008 Atlantic hurricane season featured two hurricanes, Gustav and Ike, crossing the Gulf of Mexico (GOM) within a 2 week period. Over 400 airborne expendable bathythermographs (AXBTs) were deployed in a GOM field campaign before, during, and after the passage of Gustav and Ike to measure the evolving upper ocean thermal structure. AXBT and drifter deployments specifically targeted the Loop Current (LC) complex, which was undergoing an eddy shedding event during the field campaign. Hurricane Gustav forced a 50 m deepening of the ocean mixed layer (OML) dramatically altering the prestorm ocean conditions for Hurricane Ike. Wind forced entrainment of colder thermocline water into the OML caused sea surface temperatures to cool by over 5degC in GOM common water, but only 1 2degC in the LC complex. Ekman pumping and a near inertial wake were identified by fluctuations in the 20degC isotherm field observed by AXBTs and drifters following Hurricane Ike. Satellite estimates of the 20deg and 26degC isotherm depths and ocean heat content were derived using a two layer model driven by sea surface height anomalies. Generally, the satellite estimates correctly characterized prestorm conditions, but the two layer model inherently could not resolve wind forced mixing of the OML. This study highlights the importance of a coordinated satellite and in situ measurement strategy to accurately characterize the ocean state before, during, and after hurricane passage, particularly in the case of two consecutive storms traveling through the same domain.