Effect of surface restoring on subsurface variability in a climate model during 1949–2005
Initializing the ocean for decadal predictability studies is a challenge, as it requires reconstructing the little observed subsurface trajectory of ocean variability. In this study we explore to what extent surface nudging using well-observed sea surface temperature (SST) can reconstruct the deeper...
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ftdatacite:10.7892/boris.70464 2023-05-15T17:35:30+02:00 Effect of surface restoring on subsurface variability in a climate model during 1949–2005 Swingedouw, Didier Guilyardi, Eric Mignot, Juliette Ray, Sulagna 2015 application/pdf https://dx.doi.org/10.7892/boris.70464 http://boris.unibe.ch/70464/ en eng Springer info:eu-repo/semantics/restrictedAccess 530 Physics CreativeWork article 2015 ftdatacite https://doi.org/10.7892/boris.70464 2021-11-05T12:55:41Z Initializing the ocean for decadal predictability studies is a challenge, as it requires reconstructing the little observed subsurface trajectory of ocean variability. In this study we explore to what extent surface nudging using well-observed sea surface temperature (SST) can reconstruct the deeper ocean variations for the 1949–2005 period. An ensemble made with a nudged version of the IPSLCM5A model and compared to ocean reanalyses and reconstructed datasets. The SST is restored to observations using a physically-based relaxation coefficient, in contrast to earlier studies, which use a much larger value. The assessment is restricted to the regions where the ocean reanalyses agree, i.e. in the upper 500 m of the ocean, although this can be latitude and basin dependent. Significant reconstruction of the subsurface is achieved in specific regions, namely region of subduction in the subtropical Atlantic, below the thermocline in the equatorial Pacific and, in some cases, in the North Atlantic deep convection regions. Beyond the mean correlations, ocean integrals are used to explore the time evolution of the correlation over 20-year windows. Classical fixed depth heat content diagnostics do not exhibit any significant reconstruction between the different existing bservation-based references and can therefore not be used to assess global average time-varying correlations in the nudged simulations. Using the physically based average temperature above an isotherm (14°C) alleviates this issue in the tropics and subtropics and shows significant reconstruction of these quantities in the nudged simulations for several decades. This skill is attributed to the wind stress reconstruction in the tropics, as already demonstrated in a perfect model study using the same model. Thus, we also show here the robustness of this result in an historical and observational context. Article in Journal/Newspaper North Atlantic DataCite Metadata Store (German National Library of Science and Technology) Pacific |
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English |
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530 Physics |
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530 Physics Swingedouw, Didier Guilyardi, Eric Mignot, Juliette Ray, Sulagna Effect of surface restoring on subsurface variability in a climate model during 1949–2005 |
topic_facet |
530 Physics |
description |
Initializing the ocean for decadal predictability studies is a challenge, as it requires reconstructing the little observed subsurface trajectory of ocean variability. In this study we explore to what extent surface nudging using well-observed sea surface temperature (SST) can reconstruct the deeper ocean variations for the 1949–2005 period. An ensemble made with a nudged version of the IPSLCM5A model and compared to ocean reanalyses and reconstructed datasets. The SST is restored to observations using a physically-based relaxation coefficient, in contrast to earlier studies, which use a much larger value. The assessment is restricted to the regions where the ocean reanalyses agree, i.e. in the upper 500 m of the ocean, although this can be latitude and basin dependent. Significant reconstruction of the subsurface is achieved in specific regions, namely region of subduction in the subtropical Atlantic, below the thermocline in the equatorial Pacific and, in some cases, in the North Atlantic deep convection regions. Beyond the mean correlations, ocean integrals are used to explore the time evolution of the correlation over 20-year windows. Classical fixed depth heat content diagnostics do not exhibit any significant reconstruction between the different existing bservation-based references and can therefore not be used to assess global average time-varying correlations in the nudged simulations. Using the physically based average temperature above an isotherm (14°C) alleviates this issue in the tropics and subtropics and shows significant reconstruction of these quantities in the nudged simulations for several decades. This skill is attributed to the wind stress reconstruction in the tropics, as already demonstrated in a perfect model study using the same model. Thus, we also show here the robustness of this result in an historical and observational context. |
format |
Article in Journal/Newspaper |
author |
Swingedouw, Didier Guilyardi, Eric Mignot, Juliette Ray, Sulagna |
author_facet |
Swingedouw, Didier Guilyardi, Eric Mignot, Juliette Ray, Sulagna |
author_sort |
Swingedouw, Didier |
title |
Effect of surface restoring on subsurface variability in a climate model during 1949–2005 |
title_short |
Effect of surface restoring on subsurface variability in a climate model during 1949–2005 |
title_full |
Effect of surface restoring on subsurface variability in a climate model during 1949–2005 |
title_fullStr |
Effect of surface restoring on subsurface variability in a climate model during 1949–2005 |
title_full_unstemmed |
Effect of surface restoring on subsurface variability in a climate model during 1949–2005 |
title_sort |
effect of surface restoring on subsurface variability in a climate model during 1949–2005 |
publisher |
Springer |
publishDate |
2015 |
url |
https://dx.doi.org/10.7892/boris.70464 http://boris.unibe.ch/70464/ |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.7892/boris.70464 |
_version_ |
1766134674013290496 |