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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L16608, doi:10.1029/2006GL026499, 2006

Circumpolar response of Southern Ocean eddy activity to a change in the Southern Annular Mode

Michael P. Meredith

British Antarctic Survey, Cambridge, UK


Andrew M. Hogg

Research School of Earth Sciences, Australian National University, Canberra, Australia


Abstract

Analysis of satellite altimeter data reveals anomalously high Eddy Kinetic Energy (EKE) in the Antarctic Circumpolar Current (ACC) during the period 2000–2002. Around 2–3 years earlier (1998), the circumpolar eastward wind stress (as quantified by the Southern Annular Mode; SAM) showed a significant positive peak, and we have shown previously that the ACC peaked around 1998 in response. An eddy-resolving ocean model is used to investigate the delay between wind forcing and the eddy response, and demonstrates that the lag is due to the time taken to influence the deep circulation of the ACC. Winds over the Southern Ocean have shown a strong climatic increase over the past few decades. If this increase in winds is also reflected as an increase in eddy activity (as our analysis suggests it might), then the increased poleward heat flux may have played a significant role in the observed warming of the Southern Ocean.

Received 4 April 2006; accepted 7 July 2006; published 19 August 2006.

Index Terms: 1616 Global Change: Climate variability (1635, 3305, 3309, 4215, 4513); 4207 Oceanography: General: Arctic and Antarctic oceanography (9310, 9315); 4215 Oceanography: General: Climate and interannual variability (1616, 1635, 3305, 3309, 4513); 4520 Oceanography: Physical: Eddies and mesoscale processes; 3339 Atmospheric Processes: Ocean/atmosphere interactions (0312, 4504).

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Citation: Meredith, M. P., and A. M. Hogg (2006), Circumpolar response of Southern Ocean eddy activity to a change in the Southern Annular Mode, Geophys. Res. Lett., 33, L16608, doi:10.1029/2006GL026499.