On the variability of density, potential energy, potential temperature, salinity and currents in NW Indian ocean and Gulf of Aden

Abstract EN

The hydrographic data available since 1923 for winter seasons are analyzed to investigate the geographic water property fluctu ation in the NW Indian ocean and Gulf of Aden, Three pronounced changes in the vertical density gradient are determined .

These are the pycnost ad layer which is characterized by low density gradi ent and is found between 40-150 mdepth with den sity ranging between 23.6 and 24,5 (T«: Above the pycnostad, the surface layer is found and below it.

the main pycnocline layer extends to about 1342m (to about 27.65 (T.) .

A strong variability in the density has been detected in the layer between 23.5-26 .0 (T•.

As a result of intrusion of different water masses with different minimum or maximum salinities such as Arabian Sea water (23.92 (T.).Arabian Gulf water (26.23 (T.) and subtropical subsurface water (26.22 (T.) .

Below this layer.

the density gradient is weak except at two patches along 52° and 56°E.

related to flow of subtropical subsurface and Antarctic intermedi ate water.

The meridian time space average potential energy (PE) variat ions show a spot like pattern which may be related to eddies in the area .

Between these spots a strong gradient in PE has been identified .

The water circul ation deduced from meridian distribution of salinity and salinity & temperature anomalies is comprised of many tongues of low and high salinity.

This type of moti on indicates the possibility of eddy formation and the existence of strong front al zones.

One can expect to find double diffusive processes to act.

Ge ostrophic current computations and vertical current calculations indicated the existence of meso scale subsurface eddies.

The thickness of these layers varied between 10 to more than 100 m.