Influence of tropical cyclones on sea surface temperature seasonal cycle and ocean heat transport
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- Vincent, E.M., Madec, G., Lengaigne, M. et al. Clim Dyn (2013) 41: 2019. doi:10.1007/s00382-012-1556-0
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Recent studies suggested that tropical cyclones (TCs) contribute significantly to the meridional oceanic heat transport by injecting heat into the subsurface through mixing. Here, we estimate the long-term oceanic impact of TCs by inserting realistic wind vortices along observed TCs tracks in a 1/2° resolution ocean general circulation model over the 1978–2007 period. Warming of TCs’ cold wakes results in a positive heat flux into the ocean (oceanic heat uptake; OHU) of ~480 TW, consistent with most recent estimates. However, ~2/5 of this OHU only compensates the heat extraction by the TCs winds during their passage. Another ~2/5 of this OHU is injected in the seasonal thermocline and hence released back to the atmosphere during the following winter. Because of zonal compensations and equatorward transport, only one-tenth of the OHU is actually exported poleward (46 TW), resulting in a marginal maximum contribution of TCs to the poleward ocean heat transport. Other usually neglected TC-related processes however impact the ocean mean state. The residual Ekman pumping associated with TCs results in a sea-level drop (rise) in the core (northern and southern flanks) of TC-basins that expand westward into the whole basin as a result of planetary wave propagation. More importantly, TC-induced mixing and air-sea fluxes cool the surface in TC-basins during summer, while the re-emergence of subsurface warm anomalies warms it during winter. This leads to a ~10 % reduction of the sea surface temperature seasonal cycle within TCs basins, which may impact the climate system.