Changing water cycle and freshwater transports in the Atlantic Ocean in observations and CMIP5 models
Changing water cycle and freshwater transports in the Atlantic Ocean in observations and CMIP5 models
Observations over the last 40 years show that the Atlantic Ocean salinity pattern has amplified, likely in response to changes in the atmospheric branch of the global water cycle. Observational estimates of oceanic meridional freshwater transport (FWT) at 26.5° N indicate a large increase over the last few decades, during an apparent decrease in the Atlantic Meridional Overturning Circulation (AMOC). However, there is limited observation based information at other latitudes. The relative importance of changing FWT divergence in these trends remains uncertain. Ten models from the Coupled Model Intercomparison Project Phase 5 are analysed for AMOC, FWT, water cycle, and salinity changes over 1950–2100. Over this timescale, strong trends in the water cycle and oceanic freshwater transports emerge, a part of anthropogenic climate change. Results show that as the water cycle amplifies with warming, FWT strengthens (more southward freshwater transport) throughout the Atlantic sector over the 21st century. FWT strengthens in the North Atlantic subtropical region in spite of declining AMOC, as the long-term trend is dominated by salinity change. The AMOC decline also induces a southward shift of the Inter-Tropical Convergence Zone and a dipole pattern of precipitation change over the tropical region. The consequent decrease in freshwater input north of the equator together with increasing net evaporation lead to strong salinification of the North Atlantic sub-tropical region, enhancing net northward salt transport. This opposes the influence of further AMOC weakening and results in intensifying southward freshwater transports across the entire Atlantic.
Ocean freshwater transports · Freshwater budget · Water cycle · Salinity · Atlantic Ocean
4971-4989
Skliris, Nikolaos
07af7484-2e14-49aa-9cd3-1979ea9b064e
Marsh, Robert
702c2e7e-ac19-4019-abd9-a8614ab27717
Mecking, Jennifer
9b090069-5061-4340-b736-9690894ce203
Zika, Jan D
1843cce7-77ce-4ef6-9f79-bcf4f9db30e5
1 June 2020
Skliris, Nikolaos
07af7484-2e14-49aa-9cd3-1979ea9b064e
Marsh, Robert
702c2e7e-ac19-4019-abd9-a8614ab27717
Mecking, Jennifer
9b090069-5061-4340-b736-9690894ce203
Zika, Jan D
1843cce7-77ce-4ef6-9f79-bcf4f9db30e5
Skliris, Nikolaos, Marsh, Robert, Mecking, Jennifer and Zika, Jan D
(2020)
Changing water cycle and freshwater transports in the Atlantic Ocean in observations and CMIP5 models.
Climate Dynamics, 54 (11-12), .
(doi:10.1007/s00382-020-05261-y).
Abstract
Observations over the last 40 years show that the Atlantic Ocean salinity pattern has amplified, likely in response to changes in the atmospheric branch of the global water cycle. Observational estimates of oceanic meridional freshwater transport (FWT) at 26.5° N indicate a large increase over the last few decades, during an apparent decrease in the Atlantic Meridional Overturning Circulation (AMOC). However, there is limited observation based information at other latitudes. The relative importance of changing FWT divergence in these trends remains uncertain. Ten models from the Coupled Model Intercomparison Project Phase 5 are analysed for AMOC, FWT, water cycle, and salinity changes over 1950–2100. Over this timescale, strong trends in the water cycle and oceanic freshwater transports emerge, a part of anthropogenic climate change. Results show that as the water cycle amplifies with warming, FWT strengthens (more southward freshwater transport) throughout the Atlantic sector over the 21st century. FWT strengthens in the North Atlantic subtropical region in spite of declining AMOC, as the long-term trend is dominated by salinity change. The AMOC decline also induces a southward shift of the Inter-Tropical Convergence Zone and a dipole pattern of precipitation change over the tropical region. The consequent decrease in freshwater input north of the equator together with increasing net evaporation lead to strong salinification of the North Atlantic sub-tropical region, enhancing net northward salt transport. This opposes the influence of further AMOC weakening and results in intensifying southward freshwater transports across the entire Atlantic.
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Changing water cycle
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Accepted/In Press date: 23 April 2020
e-pub ahead of print date: 5 May 2020
Published date: 1 June 2020
Additional Information:
Funding Information:
This work is part of the UK Natural Environment Research Council funded project CLimate scale analysis of Air and Water masses (CLAW). We acknowledge the World Climate Research Program’s Working Group on Coupled Modeling, which is responsible for CMIP5, and we thank the climate modelling groups for producing and making available their model output. We acknowledge the Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory, for making available the freshwater flux datasets.
Publisher Copyright:
© 2020, The Author(s).
Keywords:
Ocean freshwater transports · Freshwater budget · Water cycle · Salinity · Atlantic Ocean
Identifiers
Local EPrints ID: 440806
URI: http://eprints.soton.ac.uk/id/eprint/440806
ISSN: 0930-7575
PURE UUID: 5697f757-8cd7-42ed-bff2-3e2cc65c4881
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Date deposited: 19 May 2020 16:31
Last modified: 17 Mar 2024 03:25
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Author:
Jennifer Mecking
Author:
Jan D Zika
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