Eddy formation in the bays of Kamchatka and fluxes to the open ocean

Abstract

The Eastern Kamchatka Current (EKC) is the western boundary current of the North Pacific subpolar gyre. Southeast of the Kamchatka Peninsula lies a large anticyclonic eddy, the Kamchatka Eddy (KE). This eddy is quasi-stationary. More generally, the oceanic region east of the EKC contains many eddies, several of them large and long lasting. Using surface currents derived from altimetry, particle tracking and a simple two-dimensional numerical model of fluid flow, we investigate the variability of this eddy field, the generation of eddies in the bays of Kamchatka by the EKC and fluxes of water to and from these bays. Firstly, we recover in our analysis of long-lasting eddies, the main eddies of the region. Among strong eddies, the parity bias favors anticyclones. Our numerical simulations give a possible explanation for the process of eddy creation in the bays of the peninsula and show that the northernmost bay produces most anticyclones. Then, we track forward the water particles from these bays and we determine their fate in the open ocean; southeastward and southwestward trajectories are the most frequent. We also track water particles backward from the KE site; they often drift near the Kamchatka coast, but others drift south of this site and remain there, a priori trapped in other eddies. This study confirms the complexity of mesoscale motions and water exchanges in this region.