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

• DOI: 10.5194/cp-13-231-2017
• Publication Date: 2017-03-15T12:38:10Z
• Authors: Chris S. M. Turney; Christopher J. Fo...; 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 Rainsley; Laura Ciasto; Stephanie Waterman; Elizabeth R. Thomas; Martin Visbeck
• Keywords: POPULATION-DYNAMICS; 550; Stratigraphy; anzsrc-for: 0406 Physical Geography and Environmental Geoscience; NEW-ZEALAND; WEST ANTARCTICA; SEALS MIROUNGA-LEONINA; Social and Behavioral Sciences; 551; Environmental protection; 01 natural sciences; Environmental pollution; CECI [CISM]; ROCKHOPPER PENGUINS; PAST MILLENNIUM; Medicine and Health Sciences; Meteorology & Atmospheric Sciences; GE1-350; Geosciences, Multidisciplinary; Global and Planetary Change; GB; Multidisciplinary; anzsrc-for: 3709 Physical Geography and Environmental Geoscience; Palaeontology; anzsrc-for: 37 Earth Sciences; Geology; HEMISPHERE SURFACE CLIMATE; 16. Peace & justice; TD172-193.5; Physical Sciences; 3701 Atmospheric Sciences; Geosciences; 0406 Physical Geography And Environmental Geoscience; 3702 Climate Change Science; CAMPBELL-ISLAND; TD169-171.8; G1; 3708 Oceanography; 14. Life underwater; anzsrc-for: 3701 Atmospheric Sciences; MACQUARIE ISLAND; 0105 earth and related environmental sciences; 13 Climate Action; Science & Technology; anzsrc-for: 3702 Climate Change Science; Paleontology; 37 Earth Sciences; 3709 Physical Geography and Environmental Geoscience; 14 Life Below Water; anzsrc-for: 3708 Oceanography; Environmental sciences; 13. Climate action; ANNULAR MODE

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.