  In an effort to understand the dynamics of the Arctic sea-ice edge, we
present a simple model of heat and mass transfer in the Fram Strait that
reveals some fundamental mechanisms controlling sea-ice extent in the marginal
seas and the depth and properties of the Arctic mixed layer. We identify and
study key mechanisms relating to the sea-ice wedge described by Untersteiner, a
boundary-layer structure near the ice edge, demonstrating how ice thickness and
extent depend on ice-export rates, atmospheric forcing and the properties of
incoming warm and salty Atlantic water in the West Spitsbergen Current. Our
time-dependent results demonstrate a seasonal asymmetry between the rates of
ice advance and retreat and explain the significant variations in the Southerly
extent of sea ice across the Fram Strait, with a long ice tongue corresponding
with the East Greenland Current. Our simple model indicates that thinning of
the Arctic sea-ice cover will lead to warming and freshening of the North
Atlantic, which would give a de-stabilizing feedback to the Arctic ice cover,
leading to a slowdown of the Atlantic Meridional Overturning Circulation.
