Changes In Pacific Ocean Water Cycle And Salinity Under Global Warmin

Global warming caused by CO₂ emissions has caused significant climate change.Based on observational,reanalysis and model simulation data,the quantitative changes and relationships between the water cycle and salinity at different spatial scales,and the influence of the ocean water cycle on the ocean stratification through the influence of the ocean salinity changes was further studied by systematically analyzed the spatio-temporal variation characteristics of the Pacific water cycle under the background of global warming and the influence of the water cycle on the ocean salinity changes,The effect of water cycle changes on salinity under global warming with increased CO₂ emissions were were further determined by model simulation.Under global warming,water cycle and salinity show obvious increasing trend,with precipitation dominating the spatial-temporal variations of water cycle and salinity,especially in the subtropical and tropical Pacific Ocean,resulting in an enhanced trend of both water cycle and salinity changes.Through quantitative analysis of the relative contribution of temperature and salinity to the long-term trend of density change,it is found that the salinity of the sea surface promoted the density of the upper layer of the tropical western Pacific to decrease,which made the ocean stratification strengthen.Salinity changes resulting from enhanced water cycling stabilize the upper ocean stratification in the tropical Pacific.In terms of quantitative changes under global warm,it is found that the enhancement rate of water cycle in the Pacific is similar to the global and other ocean basin scale results.The difference in the contribution of the water cycle and related ocean physical processes to salinity changes makes the salinity enhancement rate of the Pacific basin scale only 3.5%,which is weaker than that of the global and other ocean basins.The surface forcing caused by the water cycle dominates the salinity changes in the equatorial western Pacific,ITCZ and SPCZ.At the same time,the salinity enhancement rate（6%）in the Pacific Ocean under different global warming scenario of CMIP6 are still weaker than that of the global ocean（9%）.and there is a1:2 quantitative relationship between the global water cycle and salinity under the multi-model constraint,and the Pacific Ocean is up to 1:1.The results of the faf-water experiment in CMIP6 Flux-Anomaly-Forced Model Intercomparison Project further reveal the importance of the influence of water cycle on Marine physical field and climate change.The freshwater flux closely related to the water cycle increases the salinity changes in the tropical Pacific under the background of global warming with increasing CO₂,and the increase in the western Pacific is larger than that in the eastern Pacific.Not only the climatological state and the long-term trend change of salinity become fresher in the central-western Pacific,especially in the warm pool and the temperature increases in the central-eastern Pacific.Both temperature and salinity changes presents ENSO-like spatial modes.Moreover,the ENSO interannual variability amplitude and asymmetry increase by 10%and 40%respectively.It not only verifies the feedback effect and mechanism of salinity changes,which are closely related to freshwater flux,on SST,further illustrates that under global warming,the changes of water cycle in the Pacific Ocean are strengthened,which leads to obvious changes in its corresponding freshwater flux,and further affects the stability of ocean stratification by affecting ocean salinity changes,thus promoting the occurrence and development of El Nino.On the contrary,it promotes the occurrence and development of La Nina.