首页|Responses of the Southern Ocean mixed layer depth to the east-ern and central Pacific El Ni?o events during austral winter
Responses of the Southern Ocean mixed layer depth to the east-ern and central Pacific El Ni?o events during austral winter
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Based on the Ocean Reanalysis System version 5(ORAS5)and the fifth-generation reanalysis datasets derived from European Centre for Medium-Range Weather Forecasts(ERA5),we investigate the different impacts of the central Pacific(CP)El Niño and the eastern Pacific(EP)El Niño on the Southern Ocean(SO)mixed layer depth(MLD)during austral winter.The MLD response to the EP El Niño shows a dipole pattern in the South Pacific,namely the MLD dipole,which is the leading El Niño-induced MLD variability in the SO.The tropical Pacific warm sea surface temperature anomaly(SSTA)signal associated with the EP El Niño excites a Rossby wave train propagating southeastward and then enhances the Amundsen Sea low(ASL).This results in an anomalous cyclone over the Amundsen Sea.As a result,the anomalous southerly wind to the west of this anomalous cyclone advects colder and drier air into the southeast of New Zealand,leading to surface cooling through less total surface heat flux,especially surface sensible heat(SH)flux and latent heat(LH)flux,and thus contributing to the mix layer(ML)deepening.The east of the anomalous cyclone brings warmer and wetter air to the southwest of Chile,but the total heat flux anomaly shows no significant change.The warm air promotes the sea ice melting and maintains fresh water,which strengthens stratification.This results in a shallower MLD.During the CP El Niño,the response of MLD shows a separate negative MLD anomaly center in the central South Pacific.The Rossby wave train triggered by the warm SSTA in the central Pacific Ocean spreads to the Amundsen Sea,which weakens the ASL.Therefore,the anomalous anticyclone dominates the Amundsen Sea.Consequently,the anomalous northerly wind to the west of anomalous anticyclone advects warmer and wetter air into the central and southern Pacific,causing surface warming through increased SH,LH,and longwave radiation flux,and thus contributing to the ML shoaling.However,to the east of the anomalous anticyclone,there is no statistically significant impact on the MLD.
Southern Oceanmixed layer depthCentral Pacific El NiñoEastern Pacific El NiñoRossby wave train
Yuxin Shi、Hailong Liu、Xidong Wang、Quanan Zheng
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School of Oceanography, Shanghai Jiao Tong University, Shanghai 200240, China
Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Greater Mekong Subregion,Yunnan University,Kunming 600650,China
College of Oceanography,Hohai University,Nanjing 210098,China
Department of Atmospheric and Oceanic Science,University of Maryland at College Park,College Park 20742,USA
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Oceanic Interdisciplinary Program of Shanghai Jiao Tong UniversitySino-German Mobility ProgramShanghai Frontiers Science Center of Polar Science(SCOPS)
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