Anomalous mid-twentieth century atmospheric circulation change over the South Atlantic compared to the last 6000 years

Chris S M Turney, Richard T Jones, David Lister, Philip Jones, Alan N Williams, Alan Hogg, Zoë A Thomas, Gilbert P Compo, Xungang Yin, Christopher J Fogwill, Jonathan Palmer, Steve Colwell, Rob Allan, Martin Visbeck

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Abstract

Determining the timing and impact of anthropogenic climate change in data-sparse regions is a considerable challenge. Arguably, nowhere is this more difficult than the Antarctic Peninsula and the subantarctic South Atlantic where observational records are relatively short but where high rates of warming have been experienced since records began. Here we interrogate recently developed monthly-resolved observational datasets from the Falkland Islands and South Georgia, and extend the records back using climate-sensitive peat growth over the past 6000 years. Investigating the subantarctic climate data with ERA-Interim and Twentieth Century Reanalysis, we find that a stepped increase in precipitation across the 1940s is related to a change in synoptic atmospheric circulation: a westward migration of quasi-permanent positive pressure anomalies in the South Atlantic has brought the subantarctic islands under the increased influence of meridional airflow associated with the Amundsen Sea Low. Analysis of three comprehensively multi-dated (using 14C and 137Cs) peat sequences across the two islands demonstrates unprecedented growth rates since the mid-twentieth century relative to the last 6000 years. Comparison to observational and reconstructed sea surface temperatures suggests this change is linked to a warming tropical Pacific Ocean. Our results imply ‘modern’ South Atlantic atmospheric circulation has not been under this configuration for millennia.
Original languageEnglish
Article number064009
Number of pages14
JournalEnvironmental Research Letters
Volume11
Issue number6
Early online date9 Jun 2016
DOIs
Publication statusPublished - 9 Jun 2016

Keywords

  • southern annular mode (SAM)
  • Southern Hemisphere westerlies
  • subantarctic climate extremes
  • temperature
  • climate reanalysis
  • anthropogenic climate change
  • El Niño-Southern Oscillation (ENSO)

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