Cumulative Effect of Hurricanes on the Atlantic Ocean

Strong surface winds of a hurricane locally cools the surface and warm the subsurface waters via turbulent mixing processes. While the surface cool anomalies may decay on scales of days, the subsurface anomalies persist much longer. For individual hurricanes the response of local ocean temperatures to the surface wind field has been well described via observations and models. However, questions related to the cumulative effect of seasonal hurricane activity remain unanswered. For example, what is the magnitude and cumulative footprint of subsurface warm anomalies forced by all storms during an entire Atlantic hurricane season? On what time scales do the subsurface anomalies decay? In order to answer these questions, a study is being carried out utilizing a global, high resolution ocean model. The goals of this study are to (1) understand the spatial extend and magnitude of tropical cyclone forced subsurface warm anomalies over the course of an entire season and (2) to reach an estimate for the contribution of these anomalies to the ocean heat content and sea surface temperature. Simulations of the 2004 and 2005 Atlantic hurricane seasons are conducted using NOAA GFDL's Modular Ocean Model 4 with 25 km grid spacing. These simulations were carried out with and without the inclusion of hurricane wind forcing, blended with the daily NCAR heat and momentum fluxes. The ocean response was compared with the results from the Princeton Ocean Model and measurements for 2004's Hurricane Frances. By differencing models runs that do and do not include the contribution of hurricanes to surface wind fields during the 2004 and 2005 seasons, the physical characteristics of hurricane-forced surface and subsurface anomalies will be elucidated.