The upper ocean response to the monsoon in the Arabian Sea
Fischer, Albert S.
MetadataShow full item record
Estimation of the upper ocean heat budget from one year of observations at a moored array in the north central Arabian Sea shows a rough balance between the horizontal advection and time change in heat when the one-dimensional balance between the surface heat flux and oceanic heat content breaks down. The two major episodes of horizontal advection, during the early northeast (NE) and late southwest (SW) monsoon seasons, are both associated with the propagation of mesoscale eddies. During the NE monsoon, the heat fluxes within the mixed layer are not significantly different from zero, and the large heat flux comes from advected changes in the thermocline depth. During the SW monsoon a coastal filament exports recently upwelled water from the Omani coast to the site of the array, 600 km offshore. Altimetry shows mildly elevated levels of surface eddy kinetic energy along the Arabian coast during the SW monsoon, suggesting that such offshore transport may be an important component of the Arabian Sea heat budget. The sea surface temperature (SST) and mixed layer depth are observed to respond to high frequency (HF, diurnal to atmospheric synoptic time scales) variability in the surface heat flux and wind stress. The rectified effect of this HF forcing is investigated in a three-dimensional reduced gravity thermodynamic model of the Arabian Sea and Indian Ocean. Both the HF heat and wind forcing act locally to increase vertical mixing in the model, reducing the SST. Interactions between the local response to the surface forcing, Ekman divergences, and remotely propagated signals in the model can reverse this, generating greater SSTs under HF forcing, particularly at low latitudes. The annual mean SST, however, is lowered under HF forcing, changing the balance between the net surface heat flux (which is dependent on the SST) and the meridional heat flux in the model. A suite of experiments with one-dimensional upper ocean models with different representations of vertical mixing processes suggests that the rectified effect of the diurnal heating cycle is dependent on the model, and overstated in the formulation used in the three-dimensional model.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2000
Suggested CitationThesis: Fischer, Albert S., "The upper ocean response to the monsoon in the Arabian Sea", 2000-09, DOI:10.1575/1912/4012, https://hdl.handle.net/1912/4012
Showing items related by title, author, creator and subject.
Intraseasonal rainfall variability in the Bay of Bengal during the Summer Monsoon : coupling with the ocean and modulation by the Indian Ocean Dipole Jongaramrungruang, Siraput; Seo, Hyodae; Ummenhofer, Caroline C. (John Wiley & Sons, 2017-01-24)The Indian Summer Monsoon rainfall exhibits pronounced intraseasonal variability in the Bay of Bengal (BoB). This study examines the intraseasonal rainfall variability with foci on the coupling with sea surface temperatures ...
Liu, Lingling; Huang, Rui Xin; Wang, Fan (John Wiley & Sons, 2018-07-02)Based on the characteristics of oceanic circulation in a monsoon‐dominated ocean, a new framework of annual ventilation, including subduction and obduction, is postulated and applied to the North Indian Ocean based on both ...
Fischer, Albert S. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-09)The unusual twice-yearly cycle of mixed layer deepening and cooling driven by the monsoon is analyzed using a recently collected (1994-95) dataset of concurrent local air-sea fluxes and upper ocean dynamics from the ...