Observational evidence for an ocean heat pump induced by tropical cyclones

Cyclones in the mix Tropical cyclones are known to mix the upper layers of the ocean, a process that 'pumps' heat downwards and thereby cools the ocean surface on local scales. It has been suggested that they may play an important role in ocean mixing at the global scale, and new calculations suggest that tropical cyclones are indeed responsible for significant cooling and vertical mixing of the surface ocean in tropical regions. Heat pumped downwards must be balanced by heat transport towards the poles, so some 15% of peak poleward oceanic heat transport may be associated with tropical cyclone-induced mixing. The amount of mixing induced by tropical cyclones is also related to sea surface temperature, suggesting that future changes in tropical sea surface temperatures may have significant effects on ocean circulation and ocean heat transport, as both processes are affected by ocean mixing. Climate change models could benefit from taking these effects into account. See also last week's Concepts essay, in which Martin Visbeck argues that the 'pulling power' of upwardly mobile ocean waters is an increasing factor in ocean mixing. Elsewhere in this issue, Quirin Schiermeier takes a broad view of recent work on ocean mixing and the US National Hurricane Center releases its latest storm predictions.