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

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. Lastly, our results imply 'modern' South Atlantic atmospheric circulation has not been undermore » this configuration for millennia.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [1] ;  [7] ;  [8] ;  [1] ;  [1] ;  [9] ;  [10] ;  [11]
  1. Univ. of New South Wales, Sydney, New South Wales (Australia). Climate Change Research Centre, School of Biological, Earth and Environmental Sciences
  2. Exeter Univ., Devon (United Kingdom). Dept. of Geography
  3. Univ. of East Anglia, Norwich (United Kingdom). Climatic Research Unit, School of Environmental Sciences
  4. Univ. of East Anglia, Norwich (United Kingdom). Climatic Research Unit, School of Environmental Sciences; King Abdulaziz Univ., Jeddah (Saudi Arabia). Center of Excellence for Climate Change Research, Dept. of Meteorology
  5. Univ. of New South Wales, Sydney, New South Wales (Australia). Climate Change Research Centre, School of Biological, Earth and Environmental Sciences; Extent Heritage, Waterloo (Australia)
  6. Univ. of Waikato, Hamilton (New Zealand). Waikato Radiocarbon Laboratory
  7. Univ. of Colorado, Boulder, CO (United States). Cooperative Institute for Research in Environmental Sciences; NOAA, Boulder, CO (United States). Physical Sciences Division, Earth System Research Laboratory
  8. ERT, Inc., Asheville, NC (United States)
  9. British Antarctic Survey, Cambridge, (United Kingdom)
  10. Met Office Hadley Centre, Exeter (United Kingdom)
  11. Kiel and Kiel Univ., Kiel (Germany). GEOMARHelmholtz Centre for Ocean Research
Publication Date:
OSTI Identifier:
1287270
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Environmental Research Letters
Additional Journal Information:
Journal Volume: 11; Journal Issue: 6; Journal ID: ISSN 1748-9326
Publisher:
IOP Publishing
Research Org:
University of California
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES southern annular mode (SAM); Southern Hemisphere westerlies; subantarctic climate extremes; temperature; climate reanalysis; anthropogenic climate change; El Nino-Southern Oscillation (ENSO); hemisphere westerly winds; climate-change; annular mode; sea-ice; antarctic peninsula; holocene climate; carbon accumulation; regional climate; slowing-down; trends