Freeze-up / Break-up Study of Arctic Sea Ice on the US Beaufort and Chukchi Seas (2024-2025)

After prior freeze-up studies (2009-10 through 2016-17, then 2019-20 through 2023-24) established long-term warming, delayed freeze-up, and multi-year ice invasion trends in the Alaskan Beaufort and Chukchi Seas, continued monitoring was needed to track whether the accelerating freeze-up delay would persist and to further characterize the ice island and iceberg hazard newly added to the study's scope. This study was designed to document the 2024-25 freeze-up season by describing evolving ice conditions, mapping features including ice island fragments and pile-up events, correlating ice canopy changes with meteorological conditions, and using the full multi-year dataset to characterize present-day freeze-up processes relative to the 1980s. Researchers combined meteorological data, ice charts, drift buoy data, and six RADARSAT-2 satellite images from September 2024 through February 2025 with four aerial reconnaissance flights conducted in late February 2025. The season produced the highest storm count yet recorded in the Beaufort (20, tied with 2013-14) alongside a Chukchi flaw lead frequency (90%) tying the prior record set in 2015-16; the Beaufort's landfast ice underwent a late-season reversal, expanding dramatically in late February and early March to a width of 80 nm at the study area's eastern boundary; and multi-year ice reentered both basins by mid-December, reaching within 22 nm of Point Barrow in the Chukchi by study's end. The fourteen-year dataset shows freeze-up timing trends in the Beaufort and Chukchi diverging in duration growth rate for the first time (2.1 vs. 2.0 days/year, nearly converged) while nearshore freeze-up itself continues trending later in both basins (3.0 and 2.8 days/year, respectively); updated invasion probabilities now stand at about 25% per season for Beaufort multi-year ice, 65% for Chukchi, and a newly split iceberg/ice-island figure of 20% for the Beaufort versus 15% for the Chukchi; and the ice-loads assessment continues to indicate reduced design global ice loads on fixed structures since the 1980s. This abstract was drafted with the assistance of Claude, July 2026.

Following the previous break-up studies, which established that break-up was trending earlier while freeze-up trends later—shortening the overall ice season—alongside a persistent but variable multi-year ice presence, a seventh season of data was needed to continue tracking these trends and to refine the still-unquantified break-up timing trend in the Chukchi Sea. This seventh break-up study, commissioned by BSEE, was designed to describe the 2025 break-up season, map ice features and pile-up/ride-up events, correlate ice canopy changes with meteorological conditions, and compare the 2017 and 2020-2025 seasons with historical break-up patterns. Researchers combined open-source meteorological data, ice charts, drift buoy data, and four RADARSAT-2 satellite images collected from May through July 2025 with four aerial reconnaissance flights—two in the Chukchi in June and two in the Beaufort in July. The Chukchi experienced its fifth-warmest break-up season on record (587 TDD) despite an unusually storm-quiet year in both basins (only two Chukchi storms all season); multi-year ice invaded the region south and west of Point Barrow as early as late April via the Multi-Year Gateway, well ahead of its typical winter entry; and in the Beaufort, the convergence of warm-water plumes from the Mackenzie River and Alaska Coastal Current off Harrison Bay during the last week of July closely echoed the pattern from most prior years, a contrast with 2024's anomalous plume failure. The seven-year dataset confirms that break-up and open water continue trending earlier for Beaufort pack ice specifically, while landfast and lagoon ice show negligible change, compressing the ice season and lengthening the open-water season in both seas; storm frequency during break-up remains roughly 35% above 1980s levels; and multi-year ice's appearance in four of the past seven seasons confirms it remains a relevant, if diminished, consideration for offshore operations despite the broader decline in its probability since the 1980s. This abstract was drafted with the assistance of Claude, July 2026.