Surface Heating and Restratification of the Ocean after a Tropical Cyclone

Ocean transport of heat is a substantial component of the climate system but its characteristics and dynamic causes are still somewhat unknown. Prior research has shown that global observations from the ocean and atmosphere indicate that the ocean and atmosphere transport about 6 PW of energy from the equatorial regions towards the poles. Studies have shown that approximately 2 PW of that transport are carried by the ocean. It has been proposed that global tropical cyclone activity could account for a large amount of the mixing needed to explain the thermohaline circulation driving this transport. However, there remain insufficient observations to conclusively prove this hypothesis. After a tropical cyclone moves across the ocean it leaves behind a wake of colder temperatures in the upper ocean. The cold wake is primarily caused by mixing, upwelling and an enthalpy flux into the atmosphere. This study makes use of the JASON-1, and TOPEX/POSEIDON satellite altimeters to investigate the amount of heating of the ocean required to re-stratify the ocean to pre storm conditions. Argo floats are also used to validate results found from the sea surface height anomalies from satellite. In order to attain the necessary spatial and temporal resolution, the Climate System Forecast Reanalysis (CFSR) model is used. Given that CFSR is a coupled atmospheric and ocean model, it enabled this study to compare the modeled storms and then the impact of storms on the ocean. After the storm passed through the area, surface heating fluxes could be determined over the duration of the storm thus providing a direct comparison of heat loss and net heat gain over the entire duration of the storm. It was found that during the time period of the cold wake, the surface heating imbalance was high enough to account for all of the rewarming of the cold wake. Therefore it is possible that global cyclone activity could account for the large amount of mixing required to explain the thermohaline circulation.