DETECTION OF RED SEA AND PERSIAN GULF WATERS IN THE NORTHWESTERN PART OF THE INDIAN OCEAN BY ARGO FLOATS DATA

Peculiarities of the spatial distribution of the Red Sea and the Persian Gulf waters in the northwestern part of the Indian Ocean have been investigated based on the Argo float measurement database. 27128 profiles of temperature and salinity were taken into account. To process these data, we used the Argo Model for Investigation of the Global Ocean (AMIGO). This technique allowed us for the first time to obtain a complete set of oceanographic characteristics up to a depth of 2000 m for different time intervals of averaging (month, season, years). Joint analysis of the variability of hydrological characteristics within the depths of 0-500 m during the summer monsoon clearly showed the influence of the Somali Current on the dynamics of the waters of this region: the formation of the largest anticyclone (Great Whirl), coastal upwelling zones, redistribution of water masses in the Gulf of Oman and the Arabian Sea. The main influence on the formation of the temperature and salinity fields is exerted by the Persian Gulf waters. The same analysis of the variability of fields within the depths of 600-1000 m showed the role of the outflow of the Red Sea waters from the Gulf of Aden in the formation of deep waters in this area during the year. And, finally, at depths of 1000-1500 m, a deep anticyclonic eddy is formed, the southern branch of which, moving westward, at 7˚N. reaches Africa and turns to the south with a narrow stream of Red Sea waters, and then, crossing the equator, reaches 15˚S. An original result was obtained for determining the temporal characteristics of the Somali Current: the time of its formation, the values of transports and life expectancy (according to model estimates of the estimated data for 7 years (1960–1996).

Interactions between the Somali Current eddies during the summer monsoon: insights from a numerical study

Three hindcast simulations of the global ocean circulation differing by resolution (1/4 or 1/12°) or parametrization or atmospheric forcing are used to describe the interactions between the large anticyclonic eddies generated by the Somali Current system during the Southwest Monsoon. The present investigation of the Somalian coherent eddy structures allows us to identify the origin and the subsequent development of the cyclones flanked upon the Great Whirl (GW) previously identified by Beal and Donohue (2013) in satellite observations and to establish that similar cyclones are also flanked upon the Southern Gyre (SG). These cyclones are identified as potential actors in mixing water masses within the large eddies and offshore the coast of Somalia. All three simulations bring to light that during the period when the Southwest Monsoon is well established, the SG moves northward along the Somali coast and encounters the GW. The interaction between the SG and the GW is a collision without merging, in a way that has not been described in observations up to now. During the collision the GW is pushed to the east of Socotra Island, sheds several smaller patches of anticyclonic vorticity, and often reforms into the Socotra Eddy, thus proposing a formation mechanism for that eddy. During this process the GW gives up its place to the SG. This process is robust throughout the three simulations.