In winter 2013, a sea ice breakout in the Beaufort Sea produced extensive fracturing and contributed to record ice export. Rheinlænder et al. (2022, https://doi.org/10.1029/2022GL099024) simulated this event using the neXtSIM sea ice model, reproducing a realistic progression of lead opening and ice drift following the track of an anticyclone. Their simulations indicate strong winds and thin ice are key factors in breakouts. We discuss observational records giving additional insight into the mechanisms controlling breakout events, including the role of wind direction. Breakouts are common and have occurred under weaker winds than in 2013 and in thicker ice of previous decades. During 2013 and other events, patterns of lead opening during breakout followed changes in wind direction relative to the coast with anticyclone position. For skillful predictions of future breakouts, models must reproduce this behavior, and their performance should be assessed across a range of wind and ice conditions.

Abstract. Throughout winter, sea ice leads open episodically from headlands along the Alaskan coast under the winds of passing weather systems. As leads extend offshore into the Beaufort Sea, they produce ice velocity discontinuities that are challenging to represent in models. Here, we investigate how synoptic wind patterns form large-scale leads originating from Point Barrow, Alaska and influence Pacific Arctic sea ice circulation. We identify 135 leads from January–April 2000–2020 and generate an ensemble of lead opening sequences by averaging atmospheric conditions, ice velocity, and lead position across events. On average, leads open as the winds of migrating high-pressure systems drive differing ice-coast interactions across Point Barrow. Southward winds compress the Beaufort ice pack against the coast east of Point Barrow over several days, slowing sea ice drift. As offshore winds develop in the west, a lead opens and separates the western ice pack from the coast. The eastern ice pack remains in contact with the coast, drifting at half the rate of western ice despite similar wind speeds. As a result, sea ice drifts asymmetrically along the Alaskan coast during these events. Most events occur under north or east-northeast winds, and wind direction relative to the coast controls patterns of opening and ice drift. These findings highlight how coastal boundaries modify the response of the consolidated ice pack to wind forcing in winter. Observed connections between winds, ice drift, and lead opening provide effective test cases for sea ice models aiming to capture realistic ice transport during these recurrent events.

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Abstract. Throughout winter, the winds of migrating weather systems drive the recurrent opening of sea ice leads from Alaska's northernmost headland, Point Barrow. As leads extend offshore into the Beaufort and Chukchi seas, they produce sea ice velocity discontinuities that are challenging to represent in models. We investigate how synoptic wind patterns form leads originating from Point Barrow and influence patterns of sea ice drift across the Pacific Arctic. We identify 135 leads from satellite thermal infrared imagery between January–April 2000–2020 and generate an ensemble of lead-opening sequences by averaging atmospheric conditions and ice velocity across events. On average, leads open as migrating atmospheric highs drive differing ice–coast interactions across Point Barrow. Northerly winds compress the Beaufort ice pack against the coast over several days, slowing ice drift. As winds west of Point Barrow shift offshore, the ice cover fractures and a lead extends from the headland into the pack interior. Ice west of the lead accelerates as it separates from the coast, drifting twice as fast (relative to winds) as ice east of the lead, which remains coastally bound. Consequently, sea ice drift and its contribution to climatological ice circulation becomes zonally asymmetric across Point Barrow. These findings highlight how coastal boundaries modify the response of the consolidated ice pack to wind forcing in winter, producing spatially varying regimes of ice stress and kinematics. Observed connections between winds, ice drift, and lead opening provide test cases for sea ice models aiming to capture realistic ice transport during these recurrent deformation events.