P. N. Golovin
State Research Center, Arctic and Antarctic Research Institute, St. Petersburg, Russia
Received January 10, 2001; in final form, May 22, 2001
Abstract—In the winter–spring period, each opening of a coastal ice polynya results in the intensification of
3D turbulent convection. Reaching the seasonal pycnocline, at the Richardson numbers of the pycnocline
Ri>10, the convective layer weakly interacts with it and spreads beyond the polynya under fast ice in the form
of a 3D gravity current. The initial local pattern of the gravity currents in the vicinity of the fast ice edge is
formed when a compensation countercurrent toward the polynya is generated in the upper quasi-homogenous
layer (UQL). Due to the baroclinic instability and under the action of the Coriolis force, the initial gravity cur-
rent further transforms into a quasi-2D mesoscale gravity current, the direction of which in the quasi-steady
state is the same as that of the edge of the fast ice. It becomes large-scale in extent since it develops over the
entire polynya. Outside of the zone of the compensation current in the upper quasi-homogeneous layer both in
the polynya and under fast ice after the dynamical fitting, the direction of the current in all the layers is the same
as that of the quasi-2D mesoscale gravity current. This scheme of formation and evolution of gravity currents
in the region of the polynya is based on the results of laboratory modeling and in many respects is supported by
field observations in the region of the coastal polynyas in the Laptev Sea.
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