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Modeling Decadal Changes on the Indian Ocean Section 15 at 32S


Murray, RJ and Bindoff, NL and Reason, CJC, Modeling Decadal Changes on the Indian Ocean Section 15 at 32 S, Journal of Climate, 20, (13) pp. 3106-3130. ISSN 0894-8755 (2007) [Refereed Article]

DOI: doi:10.1175/JCLI4160.1


A near-global ocean model with resolution enhanced in the southern Indian Ocean has been spun up to seasonal equilibrium and then driven by NCEPNCAR reanalysis 1 monthly mean forcings and Hadley SSTs over the period 19482002. The aim was to simulate changes in the subsurface properties observed in hydrographic surveys at 32S in the Indian Ocean in 1965, 1987, and 2002. These surveys showed a zonally averaged cooling on isopycnals of 0.5 and 0.3C in mode and intermediate waters between 1965 and 1987 and a warming of the mode water coupled with a continued cooling of the intermediate water between 1987 and 2002. The major changes in isopycnal depth and temperature modeled in this study were confined to the mode water and were qualitatively similar to those observed but concentrated in a lower density class and in the eastern half of the section. The dominant changes here were multidecadal, with maximum temperatures on the σθ = 26.7 kg m−3 isopycnal being reached in 1968 and minimum temperatures in 1990. The simulations showed a propagation of interannual anomalies toward the section from a region of deep late winter mixed layers in the southeast Indian Ocean within a period of several years. Surface temperatures in this region were lowest in the 1960s and highest in the late 1980s. Temperatures on isopycnals showed the opposite variation, consistent with SST having the controlling effect on mixed layer density and depth. Isopycnal depths within the mode water were strongly correlated with temperature, implying a redistribution of mode water density classes, the greatest volume of mode water being produced in a higher density class (σθ = 26.827.0 kg m3) during the period of cooler surface forcing in the 1960s and 1970s than during the warmer period following (σθ = 26.626.8 kg m3).

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical oceanography
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Understanding climate change
Objective Field:Climate variability (excl. social impacts)
UTAS Author:Murray, RJ (Mr Ross Murray)
UTAS Author:Bindoff, NL (Professor Nathan Bindoff)
ID Code:50281
Year Published:2007
Web of Science® Times Cited:4
Deposited By:IASOS
Deposited On:2007-08-01
Last Modified:2009-04-03

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