Abstract. Three hindcast simulations of the global ocean circulation differing by resolution (1/4 or 1/12°) or parameterization or atmospheric forcing are used to study the fast 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 major actors in mixing water masses within the large eddies and offshore the coast of Somali. 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 encounter the GW. The interaction between the SG and the GW is a collision without merging, collision during which 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 the Socotra Eddy. During this process, the GW gives up its place to the SG which in turn becomes a new Great Whirl. This process is robust throughout the three simulations.
Interactions between the Somali Current eddies during the summer monsoon: insights from a numerical study
