Management and Scientific Services in Support of the U.S. JGOFS Arabian Sea Process Study

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Smith 9310577 Management and Scientific Services in Support of the U.S. JGOFS Arabian Sea Process Study Some of the strongest atmospheric forcing of oceanic properties anywhere on our planet is observed in the Arabian Sea where seasonally reversing monsoon winds drive fast-flowing, vertically extensive currents, complex eddy fields, broad-scale, open ocean upwelling, coastal upwelling and pronounced mixed-layer deepening. Cycles of production in this region are driven by the ocean's response to monsoon winds and therefore exhibit large and regular seasonal oscillations, During the southwest monsoon season (June-September inclusive), primary productivity is maximal owing to strong winds which not only cause the uplift of deep water rich in nutrients, but also deliver aeolian dust to the surface layer of this tropical ocean. During the northeast monsoon (October-November inclusive) and intermonsoon periods, primary productivity is markedly reduced. A major rationale for the choice of the Arabian Sea as a process study site is the strong and seasonally reversing physical forcing of the region. It is safe to say no investigator working in this program will be able to properly interpret her/his data without understanding the physical regime. For an expedition of the scale of the U.S. JGOFS Arabian Sea Process Study, 9 cruises spread over an annual monsoon cycle, it is necessary to provide a consistent set of measurements of the background density, tracer and nutrient fields. These data are crucial for the interpretation and resolution of the seasonally changing, background mean flows which are the setting for the more specialized pelagic and benthic studies of the expedition. These measurements are also needed to estimate the transport of nutrients into the euphotic zone and to provide insight into the chemical constraints placed upon physiological processes. This project will provide the basic, background observational program which will include ship- based measurement of depth-resolved temperature, salinity, nutrients, oxygen, and currents. The methods to be employed will be standardized and consistent throughout the expedition, using protocols already established either by U.S. JGOFS or U.S. WOCE or protocols agreed upon by all investigators prior to the beginning of the expedition. ***