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

Chris S.M. Turney*, Christopher J. Fogwill, Jonathan G. Palmer, Erik Van Sebille, Zoë Thomas, Matt McGlone, Sarah Richardson, Janet M. Wilmshurst, Pavla Fenwick, Violette Zunz, Hugues Goosse, Kerry Jayne Wilson, Lionel Carter, Mathew Lipson, Richard T. Jones, Melanie Harsch, Graeme Clark, Ezequiel Marzinelli, Tracey Rogers, Eleanor RainsleyLaura Ciasto, Stephanie Waterman, Elizabeth R. Thomas, Martin Visbeck

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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.

Original languageEnglish
Pages (from-to)231-248
Number of pages18
JournalClimate of the Past
Volume13
Issue number3
DOIs
Publication statusPublished - 15 Mar 2017

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