Articles | Volume 13, issue 3
Clim. Past, 13, 231–248, 2017

Special issue: Southern perspectives on climate and the environment from...

Clim. Past, 13, 231–248, 2017

Research article 15 Mar 2017

Research article | 15 Mar 2017

Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperature reconstruction

Chris S. M. Turney1,2, Christopher J. Fogwill1,2, Jonathan G. Palmer1,2, Erik van Sebille3,4, Zoë Thomas1,2, Matt McGlone5, Sarah Richardson5, Janet M. Wilmshurst5,6, Pavla Fenwick7, Violette Zunz8,9, Hugues Goosse8, Kerry-Jayne Wilson10, Lionel Carter11, Mathew Lipson1,3, Richard T. Jones12, Melanie Harsch13, Graeme Clark14, Ezequiel Marzinelli14,15, Tracey Rogers14, Eleanor Rainsley16, Laura Ciasto17, Stephanie Waterman1,3,18, Elizabeth R. Thomas19, and Martin Visbeck20 Chris S. M. Turney et al.
  • 1Climate Change Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, New South Wales, Sydney, Australia
  • 2Palaeontology, Geobiology and Earth Archives Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, New South Wales, Sydney, Australia
  • 3ARC Centre of Excellence for Climate System Science, University of New South Wales, New South Wales, Australia
  • 4Grantham Institute and Department of Physics, Imperial College London, London, UK
  • 5Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand
  • 6School of Environment, University of Auckland, Auckland, New Zealand
  • 7Gondwana Tree-Ring Laboratory, P.O. Box 14, Little River 7546, Canterbury, New Zealand
  • 8Université catholique de Louvain, Earth and Life Institute, Georges Lemaître Centre for Earth and Climate Research, Place Pasteur, 3, 1348 Louvain-la-Neuve, Belgium
  • 9Earth System Science and Departement Geografie, Vrije Universiteit Brussels, Brussels, Belgium
  • 10West Coast Penguin Trust, P.O. Box 70, Charleston 7865, West Coast, New Zealand
  • 11Antarctic Research Centre, University of Victoria, Wellington, New Zealand
  • 12Geography, College of Life and Environmental Sciences, Exeter University, Devon, EX4 4RJ, Exeter, UK
  • 13Department of Biology, University of Washington, Seattle, WA, USA
  • 14Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, New South Wales, Sydney, Australia
  • 15Sydney Institute of Marine Science, Chowder Bay Rd, Mosman, NSW 2088, Australia
  • 16Wollongong Isotope Geochronology Laboratory, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW 2522, Australia
  • 17Geophysical Institute, University of Bergen, and Bjerknes Centre for Climate Research, Bergen, Norway
  • 18Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
  • 19British Antarctic Survey, Cambridge, UK
  • 20GEOMAR Helmholtz Centre for Ocean Research Kiel and Kiel University, Kiel, Germany

Abstract. Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine–atmosphere–ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on southwest Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52–54° S). Our annually resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the 1940s, a phenomenon predating the observational record. Climate reanalysis and modelling show a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer. Our results suggest that modern observed high interannual variability was established across the mid-twentieth century, and that the influence of contemporary equatorial Pacific temperatures may now be a permanent feature across the mid- to high latitudes.

Short summary
The Southern Ocean plays a fundamental role in global climate but suffers from a dearth of observational data. As the Australasian Antarctic Expedition 2013–2014 we have developed the first annually resolved temperature record using trees from subantarctic southwest Pacific (52–54˚S) to extend the climate record back to 1870. With modelling we show today's high climate variability became established in the ~1940s and likely driven by a Rossby wave response originating from the tropical Pacific.