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

• Published in: Climate of the Past
• Main Authors: Turney, CSM, Fogwill, CJ, Palmer, JG, Van Sebille, E, Thomas, Z, McGlone, M, Richardson, S, Wilmshurst, JM, Fenwick, P, Zunz, V, Goosse, H, Wilson, K-J, Carter, L, Lipson, M, Jones, RT, Harsch, M, Clark, G, Marzinelli, E, Rogers, T, Rainsley, E, Ciasto, L, Waterman, S, Thomas, ER, Visbeck, M
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2017
• Subjects: Science & Technology; Physical Sciences; Geosciences; Multidisciplinary; Meteorology & Atmospheric Sciences; Geology; HEMISPHERE SURFACE CLIMATE; SEALS MIROUNGA-LEONINA; ANNULAR MODE; CAMPBELL-ISLAND; NEW-ZEALAND; POPULATION-DYNAMICS; ROCKHOPPER PENGUINS; MACQUARIE ISLAND; WEST ANTARCTICA; PAST MILLENNIUM; Paleontology; 0406 Physical Geography And Environmental Geoscience; Antarctic; Austral; Campbell Island; New Zealand; Pacific; Southern Ocean; West Antarctica; Antarc*; Antarctica; Ice Sheet; Macquarie Island; Mirounga leonina
• Online Access: http://hdl.handle.net/10044/1/46007; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000396734600001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202; https://doi.org/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.