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W33
Atlas Pg. 17,18

Somali Current, Arabian Sea
Upwelling, eddies, temperature discontinuities, current shears, phytoplankton

Significance:  For the next two years, the Joint Global Ocean Flux program (JGOFS)-an international program studying the exchange between the hydrosphere, atmosphere and biosphere, is targeting a multi-pronged study in the Arabian Sea. Seasonal phytoplankton blooms and upwelling dominate the Somali coast.  Because the Somali Current moves away from the coast during the summer (southwest) monsoons, the upwelling of cold, nutrient-rich water produces a biologically active region.  Chlorophyll in the marine algae changes the water color near the coast.  Coastal upwelling is apparent from the beginning of seasonal transition in May.  The strongest cold water features are related to points of land and islands such as Masirah and Socotra.  Phytoplankton, rich waters and cold plumes from these regions are drawn hundreds of kilometers out into the Arabian Sea by the Somali Current, forming oceanographic fronts and eddies.  The color changes, frontal discontinuities and current shears have been documented off Ras al Hadd, Oman, into the Gult of Oman, and Ras Asir, Somalia, into the western Arabian Sea.

The high productivity waters are an important marine resource.  The location, size, and intensity of these features will help us understand their formative processes, as well as assist in answering questions about the general physical oceanography of the basin.

During the JGOFS Arabian Sea Campaign, several oceanographic research vessels will be collecting data, in conjunction with ocean color data from the soon-to-be launched SEAWIFS satellite.  Also, an instrumented buoy will be moored at 15°30'N and 60°30'E (see map).

Physical Characteristics:  The physical oceanography of the Northern Arabian Sea is dominated by the wind-driven currents of the seasonal monsoons.  From May to October, the summer monsoon brings persistent southwest winds.  These winds blow over a long fetch from south of the equator, producing large swells and heavy seas, and creating the Somali Current, a western boundary current.  The atmosphere is a continual haze of blowing spray, sand and dust.  However, due to offshore winds the near coastal area is frequently cloud free.

Observation Techniques:  Use two cameras, if possible, with 100 mm and 250 mm lenses.  Use different viewing angles and CIR to photograph phytoplankton-rich waters off the eastern coast of Oman (18-22°N).  Upwelled water appears darker than the surrounding ocean when photographed in sun glint.  Also photograph frontal discontinuities and eddies in the sun's glint.

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Center Point 11°N, 114°E

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