Decadal changes in the South Indian Ocean thermocline

McDonagh, Elaine L., Bryden, Harry L., King, Brian A., Sanders, Richard J., Cunningham, Stuart A. and Marsh, Robert (2005) Decadal changes in the South Indian Ocean thermocline. Journal of Climate, 18 (10), 1575-1590. (doi:10.1175/JCLI3350.1).

Abstract

A significant change in properties of the thermocline is observed across the whole Indian Ocean 32°S section between 1987 and 2002. This change represents a reversal of the pre-1987 freshening and decreasing oxygen concentrations of the upper thermocline that had been interpreted as a fingerprint of anthropogenic climate change. The thermocline at the western end of the section (40°–70°E) is occupied by a single variety of mode water with a potential temperature of around 13°C. The thermocline at the eastern end of the 32°S section is occupied by mode waters with a range of properties cooling from ~11°C at 80°E to ~9°C near the Australian coast. The change in θ–S properties between 1987 and 2002 is zonally coherent east of 80°E, with a maximum change on isopycnals at 11.6°C. Ages derived from helium–tritium data imply that the mode waters at all longitudes take about the same time to reach 32°S from their respective ventilation sites. Dissolved oxygen concentration changes imply that all of the mode water reached the section ~20% faster in 2002 than in 1987.

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Contributors

Author: Harry L. Bryden

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