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Title: Pacific Walker Circulation variability in coupled and uncoupled climate models

Journal Article · · Climate Dynamics
 [1];  [2];  [3];  [3]
  1. Univ. of Oslo (Norway); New York Univ., Abu Dhabi (United Arab Emirates)
  2. Univ. of Oslo (Norway)
  3. Univ. of Colorado, Boulder, CO (United States); National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)
+ Show Author Affiliations

There is still significant uncertainty concerning twentieth century trends in the Pacific Walker Circulation (PWC). In this paper, observational datasets, coupled (CMIP5) and uncoupled (AGCM) model simulations, and additional numerical sensitivity experiments are analyzed to investigate twentieth century changes in the PWC and their physical mechanisms. The PWC weakens over the century in the CMIP5 simulations, but strengthens in the AGCM simulations and also in the observational twentieth century reanalysis (20CR) dataset. It is argued that the weakening in the CMIP5 simulations is not a consequence of a reduced global convective mass flux expected from simple considerations of the global hydrological response to global warming, but is rather due to a weakening of the zonal equatorial Pacific sea surface temperature (SST) gradient. Additional clarification is provided by additional uncoupled atmospheric general circulation model simulations in which the ENSO-unrelated and ENSO-related portions of the observed SST changes are prescribed as lower boundary conditions. Both sets of SST forcing fields have a global warming trend, and both sets of simulations produce a weakening of the global convective mass flux. Yet, consistent with the strong role of the zonal SST gradient, the PWC strengthens in the simulations with the ENSO-unrelated SST forcing, which has a strengthening zonal SST gradient, despite the weakening of the global convective mass flux. Overall, our results suggest that the PWC strengthened during twentieth century global warming, but also that this strengthening was partly masked by a weakening trend associated with ENSO-related PWC variability.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER); Research Council of Norway
Grant/Contract Number:
AC02-05CH11231; AC05-00OR22725
OSTI ID:
1565115
Journal Information:
Climate Dynamics, Vol. 43, Issue 1-2; ISSN 0930-7575
Publisher:
Springer-VerlagCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 104 works
Citation information provided by
Web of Science

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Cited By (25)

Investigating the Uncertainty in Global SST Trends Due to Internal Variations Using an Improved Trend Estimator journal March 2018
Tropical Pacific climate variability over the last 6000 years as recorded in Bainbridge Crater Lake, Galápagos: A 6000 year Record of ENSO Variability journal August 2017
Pacific sea surface temperature linkages with Tanzania's multi‐season drying trends journal February 2019
Observational and modelling evidence of a zonal circulation over the North Pacific journal December 2019
Interannual Weakening of the Tropical Pacific Walker Circulation Due to Strong Tropical Volcanism journal April 2018
Interaction of the recent 50 year SST trend and La Niña 2010: amplification of the Southern Annular Mode and Australian springtime rainfall journal January 2016
Long‐Term Trend of the Tropical Pacific Trade Winds Under Global Warming and Its Causes journal April 2019
On the Delayed Coupling Between Ocean and Atmosphere in Recent Weak El Niño Episodes journal October 2019
Atmospheric circulation as a source of uncertainty in climate change projections journal September 2014
Uncertainty in near-term global surface warming linked to tropical Pacific climate variability journal April 2019
Reconciling opposing Walker circulation trends in observations and model projections journal April 2019
Decadal Western Pacific Warm Pool Variability: A Centroid and Heat Content Study journal October 2017
A dichotomy between model responses of tropical ascent and descent to surface warming journal March 2019
Altimeter-era emergence of the patterns of forced sea-level rise in climate models and implications for the future journal December 2018
Will surface winds weaken in response to global warming? journal November 2016
Strengthening of the Walker Circulation in recent decades and the role of natural sea surface temperature variability journal March 2019
Weakening and eastward shift of the tropical Pacific Walker circulation during the Last Glacial Maximum journal July 2019
Past and future rainfall in the Horn of Africa journal October 2015
Oxygen minimum zones in the tropical Pacific across CMIP5 models: mean state differences and climate change trends journal January 2015
ESD Reviews: Climate feedbacks in the Earth system and prospects for their evaluation journal January 2019
Predicting East African spring droughts using Pacific and Indian Ocean sea surface temperature indices journal January 2014
Oxygen minimum zones in the tropical Pacific across CMIP5 models: mean state differences and climate change trends journal January 2015
Past and future rainfall in the Horn of Africa text January 2015
ESD Reviews: Climate feedbacks in the Earth system and prospects for their evaluation text January 2019
Predicting East African spring droughts using Pacific and Indian Ocean sea surface temperature indices journal March 2014

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54 ENVIRONMENTAL SCIENCES
Pacific Walker Circulation
Hydrological cycle
ENSO