Close interactions between two pairs of vertically stacked counterrotating eddies under sea ice were investigated in numerical experiments. The numerical model contains a stratified ocean capped by an ice layer. Under the ice layer a shallow brine source produces a top cyclone and a submerged anticyclone, while a shallow freshening source generates a top anticyclone and a submerged cyclone. Ice-exerted friction dissipates the top eddies in time, leaving submerged ones in lone existence. In this work, winning vortices are sought from a brine-brine pair, a freshening-brine pair, and a freshening-freshening pair. Brine and freshening sources are made equal in strength to level the playing field. When closely paired, fission, an increase in the number of subsurface vortices, occurs from a brine-brine pair and a freshening-brine pair but not from a freshening-freshening pair. Consequences of fission invariably increase the number of submerged anticyclones. A heuristic argument is given to explain this polarity. The strong interaction among closely packed eddies operates in timescales of tens of days, helping to explain the predominance of submerged anticyclones under the Arctic sea ice. ¿ 1999 American Geophysical Union