Cool water brought by upwelling in the Sanya Bay benefits corals in the background of global warming

It has been reported that global warming has negative effects on coral ecosystems in the past 50 years and the effects vary in different ocean environment. In order to make clear the coral reef status in the background of global warming along the south coast of Hainan Island of China, satellite and in situ data are used to retrieve the information of the coral reef status and surrounding environmental factors. The results show that cool water induced by upwelling along the south coast of Hainan Island is found in the area every summer month, especially in the relatively strong El Niño years (2002–2003 and 2005). From the NOAA satellite data, degree heating week (DHW) index does not exceed 3 in Sanya Bay even in the relatively strong El Niño years. By comparison of a coral reef growth rate in the Sanya Bay with respect to El Niño events from 1957 to 2000, coral’s growth rate is relatively greater during 1972, 1991–1994 and 1998 El Niño event. By analyzing the environmental factors, it is found that the cool water induced by upwelling may be the main reason for protecting corals from global warming effects.