Southern Ocean wind stress in CMIP5 models: Role of wind fluctuations

Xia Lin, Xiaoming Zhai, Zhaomin Wang, David Munday

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Abstract

The Southern Ocean (SO) surface wind stress is a major atmospheric forcing for driving the Antarctic Circumpolar Current and the global overturning circulation. Here the effects of wind fluctuations at different time scales on SO wind stress in 18 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are investigated. It is found that including wind fluctuations, especially on time scales associated with synoptic storms, in the stress calculation strongly enhances the mean strength, modulates the seasonal cycle, and significantly amplifies the trends of SO wind stress. In 11 out of the 18 CMIP5 models, the SO wind stress has strengthened significantly over the period of 1960-2005. Among them, the strengthening trend of SO wind stress in one CMIP5 model is due to the increase in the intensity of wind fluctuations, while in all the other 10 models the strengthening trend is due to the increasing strength of the mean westerly wind. These discrepancies in SO wind stress trend in CMIP5 models may explain some of the diverging behaviors in the model-simulated SO circulation. Our results suggest that to reduce the uncertainty in SO responses to wind stress changes in the coupled models, both the mean wind and wind fluctuations need to be better simulated.

Original languageEnglish
Pages (from-to)1209-1226
Number of pages18
JournalJournal of Climate
Volume33
Issue number4
Early online date31 Oct 2019
DOIs
Publication statusPublished - 15 Feb 2020

Keywords

  • ANNULAR MODE
  • CLIMATE
  • Climate models
  • HISTORICAL BIAS
  • MERIDIONAL OVERTURNING CIRCULATION
  • POWER INPUT
  • REANALYSIS
  • Reanalysis data
  • SEA
  • STORM TRACKS
  • Southern Ocean
  • TRENDS
  • VARIABILITY
  • Wind
  • Wind stress

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