The effect of explosive tropical volcanism on ENSO

Shayne McGregor, Axel Timmermann

Research output: Contribution to journalArticleResearchpeer-review

61 Citations (Scopus)

Abstract

This study examines the response of El Nino-Southern Oscillation (ENSO) to massive volcanic eruptions in a suite of coupled general circulation model (CGCM) simulations utilizing the Community Climate System Model, version 3 (CCSM3). The authors find that the radiative forcing due to volcanic aerosols injected into the stratosphere induces a model climatic response that projects onto the ENSO mode and initially creates a La Nina event that peaks around the time the volcanic forcing peaks. The curl of the wind stress changes accompanying this volcanically forced equatorial region cooling acts to recharge the equatorial region heat. For weaker volcanic eruptions, this recharging results in an El Nino event about two seasons after the peak of the volcanic forcing. The results of the CCSM3 volcanic forcing experiments lead the authors to propose that the initial tropical Pacific Ocean response to volcanic forcing is determined by four different mechanisms one process is the dynamical thermostat mechanism (the mean upwelling of anomalous temperature) and the other processes are related to the zonal equatorial gradients of the mean cloud albedo, Newtonian cooling, and mixed layer depth. The zonal gradient in CCSM3 set by bothmixed layer depth and Newtonian cooling terms oppose the zonal sea surface temperature anomaly (SSTA) gradient produced by the dynamical thermostat and initially dominate the mixed layer zonal equatorial heat budget response. Applying this knowledge to a simple volcanically forced mixed layer equation using observed estimates of the spatially varying variables, the authors again find that the mixed layer depth and Newtonian cooling terms oppose and dominate the zonal SSTA gradient produced by the dynamical thermostat. This implies that the observed initial response to volcanic forcing should be La Nin alike not El Nin o, as suggested by paleo-climate records. (c) 2011 American Meteorological Society.
Original languageEnglish
Pages (from-to)2178 - 2191
Number of pages14
JournalJournal of Climate
Volume24
Issue number8
DOIs
Publication statusPublished - 2011
Externally publishedYes

Cite this

McGregor, Shayne ; Timmermann, Axel. / The effect of explosive tropical volcanism on ENSO. In: Journal of Climate. 2011 ; Vol. 24, No. 8. pp. 2178 - 2191.
@article{4f8a868479a2426ab27e1f6c6bc1ec1b,
title = "The effect of explosive tropical volcanism on ENSO",
abstract = "This study examines the response of El Nino-Southern Oscillation (ENSO) to massive volcanic eruptions in a suite of coupled general circulation model (CGCM) simulations utilizing the Community Climate System Model, version 3 (CCSM3). The authors find that the radiative forcing due to volcanic aerosols injected into the stratosphere induces a model climatic response that projects onto the ENSO mode and initially creates a La Nina event that peaks around the time the volcanic forcing peaks. The curl of the wind stress changes accompanying this volcanically forced equatorial region cooling acts to recharge the equatorial region heat. For weaker volcanic eruptions, this recharging results in an El Nino event about two seasons after the peak of the volcanic forcing. The results of the CCSM3 volcanic forcing experiments lead the authors to propose that the initial tropical Pacific Ocean response to volcanic forcing is determined by four different mechanisms one process is the dynamical thermostat mechanism (the mean upwelling of anomalous temperature) and the other processes are related to the zonal equatorial gradients of the mean cloud albedo, Newtonian cooling, and mixed layer depth. The zonal gradient in CCSM3 set by bothmixed layer depth and Newtonian cooling terms oppose the zonal sea surface temperature anomaly (SSTA) gradient produced by the dynamical thermostat and initially dominate the mixed layer zonal equatorial heat budget response. Applying this knowledge to a simple volcanically forced mixed layer equation using observed estimates of the spatially varying variables, the authors again find that the mixed layer depth and Newtonian cooling terms oppose and dominate the zonal SSTA gradient produced by the dynamical thermostat. This implies that the observed initial response to volcanic forcing should be La Nin alike not El Nin o, as suggested by paleo-climate records. (c) 2011 American Meteorological Society.",
author = "Shayne McGregor and Axel Timmermann",
year = "2011",
doi = "10.1175/2010JCLI3990.1",
language = "English",
volume = "24",
pages = "2178 -- 2191",
journal = "Journal of Climate",
issn = "0894-8755",
publisher = "American Meteorological Society",
number = "8",

}

The effect of explosive tropical volcanism on ENSO. / McGregor, Shayne; Timmermann, Axel.

In: Journal of Climate, Vol. 24, No. 8, 2011, p. 2178 - 2191.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - The effect of explosive tropical volcanism on ENSO

AU - McGregor, Shayne

AU - Timmermann, Axel

PY - 2011

Y1 - 2011

N2 - This study examines the response of El Nino-Southern Oscillation (ENSO) to massive volcanic eruptions in a suite of coupled general circulation model (CGCM) simulations utilizing the Community Climate System Model, version 3 (CCSM3). The authors find that the radiative forcing due to volcanic aerosols injected into the stratosphere induces a model climatic response that projects onto the ENSO mode and initially creates a La Nina event that peaks around the time the volcanic forcing peaks. The curl of the wind stress changes accompanying this volcanically forced equatorial region cooling acts to recharge the equatorial region heat. For weaker volcanic eruptions, this recharging results in an El Nino event about two seasons after the peak of the volcanic forcing. The results of the CCSM3 volcanic forcing experiments lead the authors to propose that the initial tropical Pacific Ocean response to volcanic forcing is determined by four different mechanisms one process is the dynamical thermostat mechanism (the mean upwelling of anomalous temperature) and the other processes are related to the zonal equatorial gradients of the mean cloud albedo, Newtonian cooling, and mixed layer depth. The zonal gradient in CCSM3 set by bothmixed layer depth and Newtonian cooling terms oppose the zonal sea surface temperature anomaly (SSTA) gradient produced by the dynamical thermostat and initially dominate the mixed layer zonal equatorial heat budget response. Applying this knowledge to a simple volcanically forced mixed layer equation using observed estimates of the spatially varying variables, the authors again find that the mixed layer depth and Newtonian cooling terms oppose and dominate the zonal SSTA gradient produced by the dynamical thermostat. This implies that the observed initial response to volcanic forcing should be La Nin alike not El Nin o, as suggested by paleo-climate records. (c) 2011 American Meteorological Society.

AB - This study examines the response of El Nino-Southern Oscillation (ENSO) to massive volcanic eruptions in a suite of coupled general circulation model (CGCM) simulations utilizing the Community Climate System Model, version 3 (CCSM3). The authors find that the radiative forcing due to volcanic aerosols injected into the stratosphere induces a model climatic response that projects onto the ENSO mode and initially creates a La Nina event that peaks around the time the volcanic forcing peaks. The curl of the wind stress changes accompanying this volcanically forced equatorial region cooling acts to recharge the equatorial region heat. For weaker volcanic eruptions, this recharging results in an El Nino event about two seasons after the peak of the volcanic forcing. The results of the CCSM3 volcanic forcing experiments lead the authors to propose that the initial tropical Pacific Ocean response to volcanic forcing is determined by four different mechanisms one process is the dynamical thermostat mechanism (the mean upwelling of anomalous temperature) and the other processes are related to the zonal equatorial gradients of the mean cloud albedo, Newtonian cooling, and mixed layer depth. The zonal gradient in CCSM3 set by bothmixed layer depth and Newtonian cooling terms oppose the zonal sea surface temperature anomaly (SSTA) gradient produced by the dynamical thermostat and initially dominate the mixed layer zonal equatorial heat budget response. Applying this knowledge to a simple volcanically forced mixed layer equation using observed estimates of the spatially varying variables, the authors again find that the mixed layer depth and Newtonian cooling terms oppose and dominate the zonal SSTA gradient produced by the dynamical thermostat. This implies that the observed initial response to volcanic forcing should be La Nin alike not El Nin o, as suggested by paleo-climate records. (c) 2011 American Meteorological Society.

UR - http://journals.ametsoc.org/doi/pdf/10.1175/2010JCLI3990.1

U2 - 10.1175/2010JCLI3990.1

DO - 10.1175/2010JCLI3990.1

M3 - Article

VL - 24

SP - 2178

EP - 2191

JO - Journal of Climate

JF - Journal of Climate

SN - 0894-8755

IS - 8

ER -