Open AccessMechanisms controlling seasonal‐to‐interannual mixed layer temperature variability in the southeastern tropical Indian Ocean
Author(s) -
Halkides D. J.,
Lee Tong
Publication year - 2009
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008jc004949
Subject(s) - thermocline , advection , climatology , upwelling , mixed layer , environmental science , forcing (mathematics) , sea surface temperature , ocean general circulation model , flux (metallurgy) , ocean current , climate model , geology , atmospheric sciences , oceanography , climate change , general circulation model , physics , materials science , metallurgy , thermodynamics
We use an Estimating the Circulation and Climate of the Ocean assimilation product to investigate seasonal‐interannual mixed layer temperature (MLT) budgets in the southeastern tropical Indian Ocean (SETIO) during 1993–2006. We examine spatial inhomogeneity of the SETIO MLT budget, contrasting three subregions with different forcing/circulation characteristics to better understand the area mean budget over the full SETIO. The subregions are the equatorial zone (box 1), the Sumatra‐Java upwelling zone (box 2), and east of the thermocline ridge (box 3). Seasonally, surface heat flux dominates MLT in all regions; advection and subsurface processes generally play secondary roles. On interannual scales, surface heat flux makes major contributions in all three boxes to termination of SETIO cooling associated with the Indian Ocean Zonal/Dipole Mode. Ocean dynamics show vital differences between regions: Subsurface processes cool box 1 and 2 but warm box 3. Horizontal advection warms box 1 but cools box 2 and 3. Averaging the MLT budget over the SETIO obscures regional physics. We explain spatial variations of the SETIO MLT budget in terms of differences in forcing, circulation, MLT distribution, and mixed layer and barrier layer thicknesses. We also examine SETIO MLT budget differences during 1994, 1997, and 2006, years exhibiting notable SETIO cooling events. In box 1, horizontal advection dominates warming after the 1994 and 2006 coolings, while in 1997, surface heat flux dominates warming. In box 2, cooling peaks earlier in 1994 than in 1997 and 2006 because of subsurface processes. Last, we show that the MLT budget is very different from heat budgets for fixed depth layers (e.g., the top 50–60 m).