Tropical Cyclone-Induced Thermocline Warming and its Regional and Global Impacts

Strong surface winds of a hurricane locally cool the surface and warm the subsurface waters via turbulent mixing processes. While the surface cool anomalies generally decay in roughly a month, the subsurface anomalies can persist over a much longer time scale. We use NOAA GFDL's Modular Ocean Model (MOM4), a global mesoscale eddy permitting ocean simulation, forced by historically observed tropical cyclones, to examine the magnitude and cumulative footprint of subsurface warm anomalies. The simulations are conducted with and without tropical cyclone wind forcing, blended with the Coordinated Ocean-Ice Reference Experiments (CORE) atmospheric dataset. We examine the spatial extent and magnitude of tropical cyclone forced subsurface warm anomalies in all ocean basins. We estimate the contribution of these anomalies to the ocean heat content and begin to determine the pathways by which this anomalous heating is redistributed by the large-scale ocean circulation. We find a maximum global annually accumulated heat uptake of ~4·10²¹J, with the greatest regional contributions found in the North Atlantic (~1.6·10²¹J), Western Pacific (~1.5·10²¹J), and Eastern Pacific (~1·10²¹J) ocean regions. While some attenuation of this global heat uptake occurs in mid-latitudes during boreal winter, the effect of mid-latitude reventilation of anomalous heat to the atmosphere is relatively small. Rather, we find an export of heat from the subtropics to the tropics via relatively rapid advective pathways, most notably emanating from the Western Pacific. These warm anomalies tend to remain in the equatorial band, with potential implications for the tropical climate system.