Analysis Of Interannual Variation Of Sae Surface Salinity In Equatorial Central Indian Ocean And Preliminary Assessment Of Global Warming Basedon CMIP Models

The upper marine environment in the tropical Indian Ocean has its unique characteristics affected by the Asian monsoon.Studying the changes and influencing mechanismofsae surface temperature and salinity on different time scales in the equatorial central Indian Ocean is of great significance for understanding the evolution of the upper ocean environment in the Indian Ocean,especially in the context of global warming,andthe salinity exchange between the eastern and western Indian Oceans and their great impact on local marine ecosystems.The basic assessment of Indian Ocean warming based on the current major international coupling models is of great significance for accurately grasping the current models' ability to simulate the climate of Indo-pacific ocean,and in-depth understanding of the impact of global warming.Based on the observation data and model simulation results,this paper conducted a preliminary analysis on the two issues of the interannual time scale equatorial Indian Ocean sea surface salinity changes and the global sea surface temperature warming assessment based on the CMIP models.The main results are as follows:(1)An interannual time scale analysisof the changesofsea surface salinity in the central equatorial Indian Ocean in autumn was carried out,studying the effects of two types of El Ni?o events(eastern and central El Ni?o)on the sea surface salinity in the central equatorial Indian Ocean in autumn.The results show that during the Eastern El Ni?o events,a positive anomalous center of sea surface salinity appears in the waters near Sumatra-Java Island,and a negative anomalous center appears in the central equatorial Indian Ocean.The central El Ni?o event is the opposite.(2)During the east/central El Ni?o events,the salinity anomalies in the central equatorial Indian Ocean were negative/positive.Quantitative salinity budget analysis shows that during the Eastern and Central El Ni?o events,horizontal advection is the main factor in sea surface salinity changes in the equatorial Central Indian Ocean.During the eastern El Ni?o events,anomalous latitudinal advection plays a dominant role in the advection of the meridional gradient of climatic salinity;while during the central El Ni?o events,advection term is dominated by advection effect of anomalous zonal flow on the meridional gradient of climatic salinity and anomalous meridional flow on the zonal gradient of climatic salinity.(3)The analysis of CMIP models' results under historical scenarios shows that different models have a large difference in the ability to simulate the SST warming trend of the tropical Indian Oceanin the late 20 th century.The average CMIP models' simulation results underestimate the warming intensity of the Indian Ocean.The analysis results of SST warming trend variability indicate that the average of CMIP models can roughly reflect its spatial distribution characteristics,but the intensity is weak compared with the observation.Also,the ability to simulate Indian Ocean SST warming of CMIP5 is superior to CMIP6.