Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget

Abstract The Indian Ocean Dipole (IOD) is an interannual climate mode of the tropical Indian Ocean. Although it is known that negative sea surface temperature (SST) anomalies in the eastern pole during the positive IOD are stronger than positive SST anomalies during the negative IOD, no consensus ha...

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Autores principales:	Mai Nakazato, Shoichiro Kido, Tomoki Tozuka
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/904375563c5f432591df6899e7defc66
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spelling	oai:doaj.org-article:904375563c5f432591df6899e7defc662021-11-28T12:21:56ZMechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget10.1038/s41598-021-01619-22045-2322https://doaj.org/article/904375563c5f432591df6899e7defc662021-11-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-01619-2https://doaj.org/toc/2045-2322Abstract The Indian Ocean Dipole (IOD) is an interannual climate mode of the tropical Indian Ocean. Although it is known that negative sea surface temperature (SST) anomalies in the eastern pole during the positive IOD are stronger than positive SST anomalies during the negative IOD, no consensus has been reached on the relative importance of various mechanisms that contribute to this asymmetry. Based on a closed mixed layer heat budget analysis using a regional ocean model, here we show for the first time that the vertical mixing plays an important role in causing such asymmetry in SST anomalies in addition to the contributions from the nonlinear advection and the thermocline feedback proposed by previous studies. A decomposition of the vertical mixing term indicates that nonlinearity in the anomalous vertical temperature gradient associated with subsurface temperature anomalies and anomalous vertical mixing coefficients is the main driver of such asymmetry. Such variations in subsurface temperature are induced by the anomalous southeasterly trade winds along the Indonesian coast that modulate the thermocline depth through coastal upwelling/downwelling. Thus, the thermocline feedback contributes to the SST asymmetry not through the vertical advection as previously suggested, but via the vertical mixing.Mai NakazatoShoichiro KidoTomoki TozukaNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-12 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Mai Nakazato Shoichiro Kido Tomoki Tozuka Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget
description	Abstract The Indian Ocean Dipole (IOD) is an interannual climate mode of the tropical Indian Ocean. Although it is known that negative sea surface temperature (SST) anomalies in the eastern pole during the positive IOD are stronger than positive SST anomalies during the negative IOD, no consensus has been reached on the relative importance of various mechanisms that contribute to this asymmetry. Based on a closed mixed layer heat budget analysis using a regional ocean model, here we show for the first time that the vertical mixing plays an important role in causing such asymmetry in SST anomalies in addition to the contributions from the nonlinear advection and the thermocline feedback proposed by previous studies. A decomposition of the vertical mixing term indicates that nonlinearity in the anomalous vertical temperature gradient associated with subsurface temperature anomalies and anomalous vertical mixing coefficients is the main driver of such asymmetry. Such variations in subsurface temperature are induced by the anomalous southeasterly trade winds along the Indonesian coast that modulate the thermocline depth through coastal upwelling/downwelling. Thus, the thermocline feedback contributes to the SST asymmetry not through the vertical advection as previously suggested, but via the vertical mixing.
format	article
author	Mai Nakazato Shoichiro Kido Tomoki Tozuka
author_facet	Mai Nakazato Shoichiro Kido Tomoki Tozuka
author_sort	Mai Nakazato
title	Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget
title_short	Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget
title_full	Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget
title_fullStr	Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget
title_full_unstemmed	Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget
title_sort	mechanisms of asymmetry in sea surface temperature anomalies associated with the indian ocean dipole revealed by closed heat budget
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/904375563c5f432591df6899e7defc66
work_keys_str_mv	AT mainakazato mechanismsofasymmetryinseasurfacetemperatureanomaliesassociatedwiththeindianoceandipolerevealedbyclosedheatbudget AT shoichirokido mechanismsofasymmetryinseasurfacetemperatureanomaliesassociatedwiththeindianoceandipolerevealedbyclosedheatbudget AT tomokitozuka mechanismsofasymmetryinseasurfacetemperatureanomaliesassociatedwiththeindianoceandipolerevealedbyclosedheatbudget
_version_	1718408028570517504

Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget

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