By Alexander Slavin Posted July 29, 2014
We show modeling evidence, supported by observations, for strong Ekman pumping velocities beneath active leads (Linear Kinematic Features, LFKs) where discontinuity in the sea-ice drifts and the surface ice-ocean stresses momentum transfer are present. The anomalous vertical velocities beneath LKFs extend hundreds of meters below the surface, well into the Atlantic Layer, and bring up large amount of ocean heat (of the order of hundreds of W/m2) into the mixed layer. Results show vertical ocean heat fluxes in winter of approximately 4.2 W/m2 (approximately 40 cm of sea-ice melt) when averaged over the Beaufort Sea, the region where most LKFs are present.
Fig. 1. 7th January 2005. a) - Sea-ice shear strain rate day-1, b) - vertical advective ocean heat flux, W/m2 at 40 m depth, c) - sea-ice stress curl s-1, d) - sea-ice divergence s-1, e) - vertical velocity m/s and f) - difference between the location beneath the mixed layer (where the NTSM is present) and the mixed layer maximum temperatures. The shear strain rate in (a) is capped at 0.2 day-1 to show a wider range of leads.'
We suggest that this process can be important in controlling the Arctic sea-ice mass balance and a potentially important player in the recent sea-ice decline in the Beaufort Sea, one that is not represented in lower-resolution global climate models. In a future climate with thinner and more mobile pack ice, this contribution from the ocean by this mechanism will only amplify.
Alexander Slavin is a CanSISE supported Post-Doctoral Fellow who works with Bruno Tremblay in the Department of Atmospheric and Ocean Sciences at McGill University.