EFFECT OF OCEAN CHLOROPHYLL ON TROPICAL PACIFIC SST AND ITS MECHANISM—A ROMS-BASED OCEAN PHYSICAL-ECOLOGICAL INTERACTIVE SIMULATION
The impacts of ocean chlorophyll on annual mean and interannual variability of sea surface temperature(SST)in the tropical Pacific Ocean are still controversial,exhibiting model dependence;and the attention paid to seasonal variation is insufficient.To investigate how chlorophyll affects the annual mean and seasonal SST in the tropical Pacific Ocean,a coupled ocean physical-ecological model based on the regional ocean modelling system(ROMS)is employed to compare an interactive ocean physical-ecological experiment with a reference experiment without chlorophyll.Results indicate that chlorophyll can increase the annual mean SST in most areas of the tropical Pacific,but decrease the SST in the eastern equatorial Pacific.The former is attributed to a direct heating effect:Chlorophyll absorbs more shortwave radiation within the surface layer,retaining more heat and warming the SST.The latter is dominated by a dynamic cooling effect:Chlorophyll absorbs more shortwave radiation in the mixed layer,resulting in a significant reduction in the shortwave radiation penetrating below the mixed layer,which enhances the stratification,shallows the mixed layer,strengthens upper ocean divergence,intensifies upwelling in the eastern equatorial Pacific Ocean,and cools the SST.However,this cooling effect does not persist throughout the year;it exhibits clear seasonal dependence in the eastern equatorial Pacific Ocean:The direct heating effect dominates during January-April;after that,the indirect dynamic cooling effect dominates.As a result,chlorophyll reduces SST in the eastern equatorial Pacific by about 0.5 ℃ and enhances its seasonal variability.This study obtained both cooling and warming impacts on eastern equatorial Pacific SST by using the ROMS,which will help explore why cooling or heating effects dominate in different models.
万方数据
维普
