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

• Published in: Climate of the past Vol. 13; no. 3; pp. 231 - 248
• Main Authors: Turney, Chris S. M, Fogwill, Christopher J, Palmer, Jonathan G, van Sebille, Erik, Thomas, Zoel, McGlone, Matt, Richardson, Sarah, Wilmshurst, Janet M, Fenwick, Pavla, Zunz, Violette, Goosse, Hugues, Wilson, Kerry-Jayne, Carter, Lionel, Lipson, Mathew, Jones, Richard T, Harsch, Melanie, Clark, Graeme, Marzinelli, Ezequiel, Rogers, Tracey, Rainsley, Eleanor, Ciasto, Laura, Waterman, Stephanie, Thomas, Elizabeth R, Visbeck, Martin
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 15-03-2017; Copernicus Publications
• Subjects: 20th century; Analysis; Antarctic circulation; Antarctic ice sheet; Anthropogenic factors; Archives & records; Atmosphere; Atmospheric circulation; Atmospheric models; Atmospheric pressure; Carbon cycle; Climate; Climate models; Climate variability; Environmental science; Geobiology; Heat; Human influences; Interannual variability; Islands; Ocean temperature; Ocean-atmosphere interaction; Ocean-atmosphere system; Oceans; Planetary waves; Polar climates; Research centers; Rossby waves; Sea surface; Sea surface temperature; Southern Hemisphere; Subtropical climates; Surface temperature; Surface water; Temperature; Time series; Tree growth; Trends; Tropical climate; Variability; Wave packets; Wave trains; Wind; Southern Ocean; New Zealand; Southern Hemisphere; United Kingdom > UK; Belgium; Sydney New South Wales Australia; Australia; New South Wales Australia; South Pacific; Macquarie Island
• ISSN: 1814-9332; 1814-9324; 1814-9332
• DOI: 10.5194/cp-13-231-2017

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.