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Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework

Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework
Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework
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%-30% over the period analysed, 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.
Precipitation, Evaporation, Global Ocean, Temperature-Salinity, Atmospheric Reanalysis
0148-0227
8787-8806
Grist, Jeremy P.
ffea99af-f811-436f-9bac-5b02ba6dc00f
Josey, Simon A.
2252ab7f-5cd2-49fd-a951-aece44553d93
Zika, Jan D.
16ede49c-f859-4351-ad8d-33412e574dec
Evans, Dafydd G.
4e1ed170-9119-4b35-a45f-55f8d07fa24e
Skliris, Nikolaos
07af7484-2e14-49aa-9cd3-1979ea9b064e
Grist, Jeremy P.
ffea99af-f811-436f-9bac-5b02ba6dc00f
Josey, Simon A.
2252ab7f-5cd2-49fd-a951-aece44553d93
Zika, Jan D.
16ede49c-f859-4351-ad8d-33412e574dec
Evans, Dafydd G.
4e1ed170-9119-4b35-a45f-55f8d07fa24e
Skliris, Nikolaos
07af7484-2e14-49aa-9cd3-1979ea9b064e

Grist, Jeremy P., Josey, Simon A., Zika, Jan D., Evans, Dafydd G. and Skliris, Nikolaos (2016) Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework. Journal of Geophysical Research, 121 (12), 8787-8806. (doi:10.1002/2016JC012091).

Record type: Article

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%-30% over the period analysed, 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.

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Submitted date: September 2016
Accepted/In Press date: 4 November 2016
e-pub ahead of print date: 19 December 2016
Keywords: Precipitation, Evaporation, Global Ocean, Temperature-Salinity, Atmospheric Reanalysis
Organisations: Marine Systems Modelling, Physical Oceanography, National Oceanography Centre

Identifiers

Local EPrints ID: 400488
URI: http://eprints.soton.ac.uk/id/eprint/400488
ISSN: 0148-0227
PURE UUID: 498992ed-f123-48d1-8fae-6620f2797eb9

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Date deposited: 10 Nov 2016 17:18
Last modified: 07 Jan 2022 21:55

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Contributors

Author: Jeremy P. Grist
Author: Simon A. Josey
Author: Jan D. Zika
Author: Dafydd G. Evans

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