Relationship between sea surface salinity and ocean circulation and climate change
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Based on Argo sea surface salinity (SSS) and the related precipitation (P), evaporation (E), and sea surface height data sets, the climatological annual mean and low-frequency variability in SSS in the global ocean and their relationship with ocean circulation and climate change were analyzed. Meanwhile, together with previous studies, a brief retrospect and prospect of seawater salinity were given in this work. Freshwater flux (E-P) dominated the mean pattern of SSS, while the dynamics of ocean circulation modulated the spatial structure and low-frequency variability in SSS in most regions. Under global warming, the trend in SSS indicated the intensification of the global hydrological cycle, and featured a decreasing trend at low and high latitudes and an increasing trend in subtropical regions. In the most recent two decades, global warming has slowed down, which is called the “global warming hiatus”. The trend in SSS during this phase, which was different to that under global warming, mainly indicated the response of the ocean surface to the decadal and multi-decadal variability in the climate system, referring to the intensification of the Walker Circulation. The significant contrast of SSS trends between the western Pacific and the southeastern Indian Ocean suggested the importance of oceanic dynamics in the cross-basin interaction in recent decades. Ocean Rossby waves and the Indonesian Throughflow contributed to the freshening trend in SSS in the southeastern Indian Ocean, while the increasing trend in the southeastern Pacific and the decreasing trend in the northern Atlantic implied a long-term linear trend under global warming. In the future, higher resolution SSS data observed by satellites, together with Argo observations, will help to extend our knowledge on the dynamics of mesoscale eddies, regional oceanography, and climate change.
KeywordsSea surface salinity Ocean circulation Climate change Multi-scale interaction
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We thank Water Cycle Observation Mission (WCOM) group and PhD Student Qiwei SUN for their helps. Argo salinity data is available at (http://www.argo.ucsd.edu), EN4salinity data is obtained from (http://hadobs.metoffice.com/en4/index.html), CCMP wind data is provided by RSS (http://www.remss.com), sea surface height data is provided by AVISO (https://www.aviso.altimetry.fr), GPCP precipitation data is obtained from NASA/GSFC, evaporation data is provided by OAFlux (http://oaflux.whoi.edu), and ERA Interim sea level pressure data is provided by ECMWF (http://apps.ecmwf.int/datasets). This work was supported by the Chinese Academy of Sciences (Grant No. XDA19060501), the State Oceanic Administration of China (Grant No. GASI-IPOV AI-02), and the National Natural Science Foundation of China (Grant Nos. 41525019, 41506019 & 41830538).
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