Arabian Sea mixed layer deepening during the monsoon : observations and dynamics
Fischer, Albert S.
MetadataShow full item record
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 Arabian Sea. The winter northeast monsoon has moderate wind forcing and a strongly destabilizing surface buoyancy flux, driven by large radiative and latent heat losses at the sea surface. Convective entrainment is the primary local mechanism driving the observed mixed layer cooling and deepening, although horizontal advection of thermocline depth variations affect the depth which the mixed layer attains. Modifications of a one-dimensional mixed layer model and heat balance show that the primary nonlocal forcing of the upper ocean is the horizontal advection of temperature gradients below the mixed layer base. The summer southwest monsoon has strong wind stresses and a neutral to stabilizing surface buoyancy flux, limited by the extreme humidity of the atmosphere, which suppresses both the radiative and latent heat losses at the surface. Wind-driven shear instabilities at the base of the mixed layer, which entrain cooler and fresher water primarily produces the observed mixed layer cooling and deepening. Horizontal advection of cooler water within the mixed layer influences the local heat balance at the mooring site. Ekman pumping velocities play only a small role in the upper ocean evolution during both monsoon seasons.
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1997
Showing items related by title, author, creator and subject.
Fischer, Albert S. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2000-09)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 ...
Deciphering isotopic signals of monsoon-induced upwelling in foraminifera from the Western Arabian sea sediment trap Stuart, Dana R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-03)Isotopic analyses have been made on four species of foraminifera collected with a PARFLUX Mark VI sediment trap in the Arabian Sea during the 1986 and 1987 monsoons. Two of the species are non-spinose thermocline dwellers ...
Naqvi, S. W. A.; Moffett, James W.; Gauns, M. U.; Narvekar, P. V.; Pratihary, A. K.; Naik, H.; Shenoy, D. M.; Jayakumar, D. A.; Goepfert, Tyler J.; Patra, Prabir K.; Al-Azri, Adnan; Ahmed, S. I. (Copernicus Publications on behalf of the European Geosciences Union, 2010-07-05)Extensive observations were made during the late Southwest Monsoon of 2004 over the Indian and Omani shelves, and along a transect that extended from the southern coast of Oman to the central west coast of India, tracking ...