Assessing recent air‐sea freshwater flux changes using a surface temperature‐salinity space framework. Issue 12 (19th December 2016)

• Record Type: Journal Article
• Authors: Grist, Jeremy P.; Josey, Simon A.; Zika, Jan D.; Evans, Dafydd Gwyn; Skliris, Nikolaos
• Is Part Of: Journal of geophysical research. Volume 121:Issue 12(2016:Dec.)
• Page Start: 8787
• Page End: 8806
• Publication Date: 2016-12-19
• Subjects: precipitation -- evaporation -- Global Ocean -- temperature‐salinity -- atmospheric reanalysis; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2016JC012091
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: A novel assessment of recent changes in air‐sea freshwater fluxes has been conducted using a surface temperature‐salinity framework applied to four atmospheric reanalyses. Viewed in the T‐S space of the ocean surface, the complex pattern of the longitude‐latitude space mean global Precipitation minus Evaporation (PME) reduces to three distinct regions. The analysis is conducted for the period 1979–2007 for which there is most evidence for a broadening of the (atmospheric) tropical belt. All four of the reanalyses display an increase in strength of the water cycle. The range of increase is between 2% and 30% over the period analyzed, with an average of 14%. Considering the average across the reanalyses, the water cycle changes are dominated by changes in tropical as opposed to mid‐high latitude precipitation. The increases in the water cycle strength, are consistent in sign, but larger than in a 1% greenhouse gas run of the HadGEM3 climate model. In the model a shift of the precipitation/evaporation cells to higher temperatures is more evident, due to the much stronger global warming signal. The observed changes in freshwater fluxes appear to be reflected in changes in the T‐S distribution of the Global Ocean. Specifically, across the diverse range of atmospheric reanalyses considered here, there was an acceleration of the hydrological cycle during 1979–2007 which led to a broadening of the ocean's salinity distribution. Finally, although the reanalyses indicate that the warm temperature tropical precipitation dominated water cycle change, ocean observations suggest that ocean processes redistributed the freshening to lower ocean temperatures. Key Points: PME in T‐S framework shows three distinctive cells of tropical (warm) P, subtropical E, mid‐high latitude (cold) P All four atmospheric reanalyses show a strengthening of the water cycle between 1979 and 2007 T‐S framework shows that most of the increase in precipitation occurs in warm sector