Tropical Cyclones and Transient Upper-Ocean Warming

Strong winds affect mixing and heat distribution in the upper ocean. In turn, upper-ocean heat content affects the evolution of tropical cyclones. Here the authors explore the global effects of the interplay between tropical cyclones and upper-ocean heat content. The modeling study suggests that, for given atmospheric thermodynamic conditions, regimes characterized by intense (with deep mixing and large upper-ocean heat content) and by weak (with shallow mixing and small heat content) tropical cyclone activity can be sustained. A global general circulation ocean model is used to study the transient evolution of a heat anomaly that develops following the strong mixing induced by the passage of a tropical cyclone. The results suggest that at least one-third of the anomaly remains in the tropical region for more than one year. A simple atmosphere–ocean model is then used to study the sensitivity of maximum wind speed in a cyclone to the oceanic vertical temperature profile. The feedback between cyclone activity and upper-ocean heat content amplifies the sensitivity of modeled cyclone power dissipation to atmospheric thermodynamic conditions.