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On the Variability of Arabian Sea Mixing and its Energetics
Author(s) -
Singh Shikha,
Valsala Vinu,
Prajeesh A. G.,
Balasubramanian Sridhar
Publication year - 2019
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2019jc015334
Subject(s) - climatology , mixed layer , forcing (mathematics) , energetics , buoyancy , empirical orthogonal functions , precipitation , wind stress , structural basin , environmental science , geology , atmospheric sciences , geography , meteorology , physics , paleontology , quantum mechanics , thermodynamics
The mechanism of interannual variability of Arabian Sea (AS) mixing is studied by examining its energetics from 60 years of model output (1950–2009) generated using an ocean general circulation model. The model results are compared with ocean reanalysis data for the same period. Both model and reanalysis data show consistent patterns of interannual variability of AS mixing. It is observed that the dominant mode of interannual variability has a basin‐wide structure with monotonic sign throughout the basin, albeit with a higher intensity in the central and southeast regions of the AS. The variability is primarily controlled by El Ni n ˜ o‐Southern Oscillation with shallower (deeper) mixed layer during El Ni n ˜ o (La Ni n ˜ a). During a typical La Ni n ˜ a year, the wind stress forcing, heat fluxes, and evaporation minus precipitation together cause deepening of mixed layer depth (MLD) in AS. This MLD variability has the strongest signal in winter months (i.e., December to February [DJF]). Further, the resolved mixing energetics suggest that the dominant forcing of MLD variability changes with seasons and has a regional preference. Buoyancy production of turbulent kinetic energy (TKE) governs the mixing and associated MLD variability in central AS during September to November (SON) and in northeast AS during DJF. Both buoyancy and mechanical production of TKE govern MLD variability in southwest to central AS from June to August and southeast AS in SON. Thus, the study highlights basin‐wide structure of interannual variability of AS mixing along with its controlling mechanisms with strong regional dependency owing to the contrasting nature of forcing prevailing over various parts of the AS.