A Climatology of Ocean-Atmosphere Heat Flux Estimates over the Great Barrier Reef and Coral Sea: Implications for Recent Mass Coral Bleaching Events

A regional-scale estimate of the surface heat budget of the Great Barrier Reef and Coral Sea (10degree-26degree S, 142degree-155degree E) has been developed for the period 1995-2005 in the hope of understanding the trends of sea surface temperatures and the surface heat balance. This report describes the methodology to acquire input parameters from satellite observations, the resultant individual components of the surface heat budget, and their validation with existing datasets and surface measurements. The accuracy of individual flux components of the heat budget were analyzed with an array of surface measurements. Derived monthly averaged latent and sensible heat flux estimates show RMS errors of approximately 25.2 and 3.4 W m2, respectively. Monthly averaged longwave and shortwave radiation flux estimates show RMS errors of approximately 6.7 and 13.3 W m2, respectively. These improved estimates allow a higher confidence in studies that examine recent sea surface temperature (SST) trends and observed mass coral bleaching for the region. It is proposed that the greatest uptake of heat occurs over the spring/summer period in the central and southern regions of the Great Barrier Reef, agreeing well with areas where anomalously high sea surface temperatures are observed and where the most significant coral bleaching has occurred, and not in the most northern, more tropical region, as might be expected. The surface heat budget climatology was used to examine the mass bleaching episode that occurred in 2002. Results show that areas of maximum and minimum bleaching are better discriminated by the anomaly from mean seasonal values in the net surface heat flux (QNET), with accuracy of 86% and 79%, respectively, than by absolute QNET, absolute SST, or SST anomaly. Possible reasons for this are discussed.