The role of large‐scale under‐ice topography in separating estuary and ocean on an arctic shelf

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Abstract
The Mackenzie Shelf in the Canadian Beaufort Sea receives large amounts of freshwater runoff in winter and, yet, it also produces ventilating water masses by brine rejection from growing ice. We examine physical and chemical data to see how these contradictory processes can occur juxtaposed on the shelf. Measurements of salinity and δ18O both from ice cores and the water column are used to infer the separation into two convective regimes due to the under‐ice topography of the system of large pressure ridges that forms at the boundary between landfast ice and pack ice. Outside this ridge system the ice cover is subject to frequent openings due to offshore ice motion. The inner regime is thus dominated by the impoundment of Mackenzie River water, whereas the outer regime is subject to brine enhancement. This paper compares freezing processes and system evolution for these two regimes in winter.