Warm pool variability and heat flux change in the global oceans

In this study, we investigate the temperature and size variability of the areas with sea surface temperature (SST) higher than 20 °C in the global oceans. The SST and surface heat flux data from 1982 to 2008 are used as a baseline. The SST in the global oceans is binned into 1 °C interval. Observations at the warm pools (SST > 29 °C) show larger area increase rates than that in lower SST areas because the net heat flux accumulates enough energy to support the development of SST in warm pools. Furthermore analyses of upper ocean heat budget between heat advection and heat diffusion suggest that heat diffusion processes may be a mechanism for transporting excessive amount of heat that the warm pool through enhancing the SST gradient around the edge of the warm pool. In the Pacific and the Atlantic, the warm pools have a maximum increase rate of 60% of their original area. The area increase rate between 29 °C and 30 °C in the global oceans is as high as 51% of area. An ensemble empirical mode decomposition analysis shows that the interannual component has strong influence on the variability of the warm pool in the Pacific, presumably because of the presence of El Nino-Southern Oscillation, while the annual cycle dominates the variability in the Atlantic and the Indian Ocean.

Research highlights
► The warm pools have larger area increase rates than that at lower SST areas.
► The net heat flux accumulates energy to support the development of SST in warm pools.
► Heat diffusion processes enhance the SST gradient around the edge of the warm pool.