Wind Forcing and Warm Water Upwelling in a Recurring Beaufort Shelf Polynya

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Abstract The Beaufort Shelf has historically been reported to exhibit limited polynya activity in winter. Yet, recent satellite observations show episodic recurrence of a large polynya west of Mackenzie Canyon, a site of significant shelf‐basin exchange. Here, we investigate satellite‐detected occurrences of this polynya over winters 2003–2025, including their relation to regional winds, ice drift, and ocean conditions. The polynya is observed to open when easterly winds drive rapid ice drift over the shelf, mechanically opening the ice near Qikiqtaruk (Herschel Island). Under strong and persistent forcing, open water extends northwestward, sometimes occupying large portions of the shelf. Its comparison to a 1‐D coastal polynya model suggests that this observed polynya growth could reflect contributions from ocean heating. Fluxes of interior ocean heat to the shelf are confirmed across two winters of mooring observations, which revealed coincident upwelling along the western flank of Mackenzie Canyon as polynyas formed. Warm upwelled waters were advected by a strong shelf current directed along the axis of polynya extension. Transported heat could suppress an estimated of daily ice growth over the shelf, comparable to that otherwise expected from the estimated surface heat losses. Recent years have featured several extreme polynyas, some exceeding 400 km in length. These events are rare and occur under exceptional wind forcing. However, increased ice drift speeds in the last decade coincide with more frequent and extensive openings, suggesting that large polynyas may be becoming a more prominent feature over the shelf as the mobility of the winter ice cover increases.

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