Influence of the Loop Current ocean heat content on hurricanes Katrina, Rita, and Wilma

The Loop Current (LC) transports warm subtropical water into the Gulf of Mexico with markedly different temperatures and salinities compared to the background Gulf Common water. This warm subtropical water is characterized by deep isotherms where the 26^oC water extends to depths of 120-150 m, which increases oceanic heat content (OHC) of the Loop Current with values from 125-150 KJ cm^-2. Given the importance of the warm subtropical water in the Loop Current and the warm core eddies in the Gulf of Mexico on rapid hurricane intensification (such as Katrina, Rita and Wilma), in situ measurements acquired from the deployment of airborne expendable current, temperature and salinity profilers are used together with satellite-based measurements to evaluate changes in isotherm depths and OHC during the passages of hurricanes Katrina, Rita, and Wilma.

It is shown that the ballooning of the LC -ring genesis process- built a large reservoir of oceanic heat that was available during the passage of Katrina, Rita, and Wilma. Shear-induced mixing in the deep layers does not significantly cool the upper ocean, and horizontal advection of thermal structure play an important role in replenishing the heat of the upper ocean. The development of cold-core rings (CCR) along the LC rim during ring separation affected Rita intensity, since she encountered one CCR prior to landfall, which was juxtaposed with an eyewall replacement cycle that contributed to her weakening from category five to three. Therefore, understanding the LC cycle is an important part for hurricanes entering the Gulf of Mexico during the summer months and for hurricane intensity forecasting.