全球变化下中国南海诸岛珊瑚礁热压力临时避难所研究

Thermal Stress Temporary Refugia Under Global Change for Coral Reefs in the South China Sea Islands

选取第五次耦合模式比较计划(CMIP5)模式中较适宜于南海海表面温度(SST)模拟的加拿大地球系统模式(CanESM2),并获取其在IPCC RCP2.6、RCP4.5和RCP8.5温室气体排放情景下模拟的2006-2100年南海SST数据。基于南海诸岛珊瑚礁和线性回归方法分析了RCPs情景下的珊瑚礁区夏季SST上升趋势,并基于热周指数(DHW, Degree Heating Weeks)及年白化时间指数分析了RCPs情景下的南海诸岛珊瑚礁热压力临时避难所,主要得出以下结论:①RCPs情景下,明显变暖的珊瑚礁海域均为南沙群岛;②年白化时间不晚于全球珊瑚礁平均年白化时间的珊瑚礁像元占南海诸岛总珊瑚礁像元的比例,在RCP2.6、RCP4.5和RCP8.5情景下分别为17%、29%和42%,均分布在南沙群岛;③RCPs情景下,较高纬度的西沙群岛、中沙群岛和南沙群岛北部为未来南海诸岛珊瑚礁热压力临时避难所。

The SST data for IPCC RCP2.6, RCP4.5 and RCP8.5 are selected from the Canadian Earth System Model of the CCCma(CanESM2) of CMIP5(Coupled Model Intercomparison Project Phase 5), which is more suitable for the area of South China Sea. Based on the coral reef pixels of Nansha archipelagoes and the linear regression method, the summer SST rising trend in each RCP scenario was analyzed for the South China Sea Islands. Moreover, the temporary refugia in the RCP scenarios were investigated based on two thermal stress indexes of Degree Heating Weeks(DHW) and the onset of annual bleaching conditions. The main results are as following: 1) In three RCP scenarios, the apparently warming reef areas are the Nansha Islands;2) The proportion of coral reefs projected to experience annual bleaching conditions not later than the global median year is 17%, 29% and 42% in RCP2.6, RCP4.5 and RCP8.5 scenarios respectively. These reefs are located in the Nansha Islands;3) Reefs of Xisha Islands, Zhongsha Islands, Dongsha Islands and the northern Nansha Islands in the higher latitudes are the future temporary refuges. This article supplements the global temporary refugia in a warming world and proves the important role of the South China Sea Islands in the future global coral reef sustainability, which is also of great significance for mitigating greenhouse gas emissions and coping with climate change.