Impact of Marine Cold-Air Outbreaks on the Rate of Oceanic Heat Storage in the Gulf of Mexico

The Gulf of Mexico is among the most populated of coastlines threatened by tropical cyclones and has experienced some of the most destructive hurricanes in history. The importance of the warm ocean waters of the Gulf in providing optimal conditions for tropical cyclone intensification is becoming more clear with recent research; thus, understanding factors that affect the upper ocean heat content in the Gulf is essential to anticipating hurricane intensity. In this study, two reanalysis data sets, NASA's Modern Era Retrospective-analysis for Research Applications (MERRA) and the NCEP Climate Forecast System Reanalysis (CFSR), are used to calculate the surface heat flux budget and the upper ocean heat budget of the Gulf for 29 winter seasons (November – March), since the greatest spatial and temporal variability in the surface fluxes occurs during this season. The results of the heat budget analysis indicate that the turbulent fluxes largely drive the magnitude and the interannual variability of the rate of oceanic heat storage. Marine cold-air outbreaks (CAOs) bring cold, dry polar air over the Gulf throughout the winter season, forcing the release of extreme latent and sensible heat fluxes from the ocean to the atmosphere. To understand the impact of these events on the interannual variability in the rate of oceanic heat storage, we create a climatology of CAO event characteristics for 29 winter seasons. We find that on average, over half of the total winter season flux loss occurs due to surface fluxes during CAO events, the duration of which only accounts for about 15% of the winter season. Therefore, capturing the heat flux loss due to these events is essential to accurately determining the rate of change in upper ocean heat content throughout the winter season, as well as during the ensuing months. The possible impact of this extreme winter season heat flux loss on the following hurricane season is explored on a preliminary basis through comparison of the interannual variability in the July average upper ocean heat content to that of the CAO heat flux loss. My results suggest that the heat flux loss due to CAOs does affect the variability of the summer season ocean heat content. However, this variability is very small in comparison to the total ocean heat content. More in depth analysis must be done to better determine how long-lasting the effects of the winter season heat flux loss are, and to assess their influence on the thermal structure of the upper ocean during the hurricane season.