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Nonlinear processes reinforce extreme Indian Ocean Dipole events

Under global warming, climate models show an almost three-fold increase in extreme positive Indian Ocean Dipole (pIOD) events by 2100. These extreme pIODs are characterised by a westward extension of cold sea surface temperature anomalies (SSTAs) which push the downstream atmospheric convergence fur...

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Detalles Bibliográficos
Autores principales: Ng, Benjamin, Cai, Wenju, Walsh, Kevin, Santoso, Agus
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4481856/
https://www.ncbi.nlm.nih.gov/pubmed/26114441
http://dx.doi.org/10.1038/srep11697
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author Ng, Benjamin
Cai, Wenju
Walsh, Kevin
Santoso, Agus
author_facet Ng, Benjamin
Cai, Wenju
Walsh, Kevin
Santoso, Agus
author_sort Ng, Benjamin
collection PubMed
description Under global warming, climate models show an almost three-fold increase in extreme positive Indian Ocean Dipole (pIOD) events by 2100. These extreme pIODs are characterised by a westward extension of cold sea surface temperature anomalies (SSTAs) which push the downstream atmospheric convergence further west. This induces severe drought and flooding in the surrounding countries, but the processes involved in this projected increase have not been fully examined. Here we conduct a detailed heat budget analysis of 19 models from phase 5 of the Coupled Model Intercomparison Project and show that nonlinear zonal and vertical heat advection are important for reinforcing extreme pIODs. Under greenhouse warming, these nonlinear processes do not change significantly in amplitude, but the frequency of occurrences surpassing a threshold increases. This is due to the projected weakening of the Walker circulation, which leads to the western tropical Indian Ocean warming faster than the east. As such, the magnitude of SSTAs required to shift convection westward is relatively smaller, allowing these convection shifts to occur more frequently in the future. The associated changes in wind and ocean current anomalies support the zonal and vertical advection terms in a positive feedback process and consequently, moderate pIODs become more extreme-like.
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spelling pubmed-44818562015-06-30 Nonlinear processes reinforce extreme Indian Ocean Dipole events Ng, Benjamin Cai, Wenju Walsh, Kevin Santoso, Agus Sci Rep Article Under global warming, climate models show an almost three-fold increase in extreme positive Indian Ocean Dipole (pIOD) events by 2100. These extreme pIODs are characterised by a westward extension of cold sea surface temperature anomalies (SSTAs) which push the downstream atmospheric convergence further west. This induces severe drought and flooding in the surrounding countries, but the processes involved in this projected increase have not been fully examined. Here we conduct a detailed heat budget analysis of 19 models from phase 5 of the Coupled Model Intercomparison Project and show that nonlinear zonal and vertical heat advection are important for reinforcing extreme pIODs. Under greenhouse warming, these nonlinear processes do not change significantly in amplitude, but the frequency of occurrences surpassing a threshold increases. This is due to the projected weakening of the Walker circulation, which leads to the western tropical Indian Ocean warming faster than the east. As such, the magnitude of SSTAs required to shift convection westward is relatively smaller, allowing these convection shifts to occur more frequently in the future. The associated changes in wind and ocean current anomalies support the zonal and vertical advection terms in a positive feedback process and consequently, moderate pIODs become more extreme-like. Nature Publishing Group 2015-06-26 /pmc/articles/PMC4481856/ /pubmed/26114441 http://dx.doi.org/10.1038/srep11697 Text en Copyright © 2015, Macmillan Publishers Limited http://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
spellingShingle Article
Ng, Benjamin
Cai, Wenju
Walsh, Kevin
Santoso, Agus
Nonlinear processes reinforce extreme Indian Ocean Dipole events
title Nonlinear processes reinforce extreme Indian Ocean Dipole events
title_full Nonlinear processes reinforce extreme Indian Ocean Dipole events
title_fullStr Nonlinear processes reinforce extreme Indian Ocean Dipole events
title_full_unstemmed Nonlinear processes reinforce extreme Indian Ocean Dipole events
title_short Nonlinear processes reinforce extreme Indian Ocean Dipole events
title_sort nonlinear processes reinforce extreme indian ocean dipole events
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4481856/
https://www.ncbi.nlm.nih.gov/pubmed/26114441
http://dx.doi.org/10.1038/srep11697
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