Physical Diagnosis of the 2016 Great Barrier Reef Bleaching Event.

Widespread coral bleaching across the Great Barrier Reef (GBR) in 2016 is often reportedly caused by El Niño and/or global warming. However, the GBR is not in a region where it is straightforward to anticipate sea surface temperature (SST) warming during El Niño, and the role of climate change is unclear. This study uses a diverse range of observations to investigate the physical causes of SST anomalies that developed on the GBR in 2016. Warm SST anomalies developed in two stages. Initial warming was caused by El Niño shifting the global‐scale pattern of convection, increasing solar radiation in the Coral Sea. The warm anomaly was extended and amplified near the coast by a terrestrial heat wave propagating across eastern Australia, further warming the GBR through turbulent heat flux. It is concluded that El Niño caused the SST anomaly, and global warming increased its amplitude and extended it by several months. Key Points: A quantitative heat budget analysis of the 2016 marine heat wave in the Great Barrier Reef lights a path to large‐scale climate processesThe waning El Niño of 2015/2016 warmed regional seas with solar radiation; a terrestrial heat wave in Australia intensified coastal warmingLong‐term trends in marine and terrestrial records clarify role of global warming, widespread coral mortality in 2016 unlikely without it [ABSTRACT FROM AUTHOR]