Ocean circulation within the North Water Polynya of Baffin Bay

The North Water Polynya is a recurrent polynya at the northern end of Baffi n Bay. As part of the International North Water Project, recording current meters were moored within this polynya during 1997-98 to study the physical reasons for its existence. The data demonstrate that the North Water Polyn ya is dominated by a strong southward flow of cold water and ice from the A rctic Ocean. Although the West Greenland Current directs a modest flow of w armer water towards the polynya from the south-east, this flow loses much o f its heat south of the polynya through re-circulation into and isopycnal m ixing with the Arctic outflow. If an ice jam stops the inflow of ice from t he north, the continued drift of ice southward below the blockage is suffic ient to create a large polynya without oceanic heating. However, upwelling near the Greenland coast can bring relatively warm water to the base of the turbulent surface layer where it is entrained via convection driven by bri ne growing from ice. The resulting flux of sensible heat supplies about one -third of the heat loss at the surface and slows ice growth. Because the se nsible heat flux is dependent upon freezing, it decreases as ice growth slo ws in spring and cannot, itself, generate ice-free waters early in the year .