Freeze-up and Break-up of Arctic Sea Ice in the U.S. Beaufort and Chukchi Seas (2023-2024)

After prior freeze-up studies (2009-10 through 2016-17, then 2019-20 through 2022-23) 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 delay in freeze-up timing and the recent pattern of multi-year ice invasions would persist into a thirteenth season. This thirteenth study in the series, commissioned by BSEE, was designed to document the 2023-24 freeze-up season by describing evolving ice conditions, mapping features 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 RADARSAT-2 satellite imagery collected from September 2023 through February 2024 with four aerial reconnaissance flights conducted in late February 2024. The season produced the second-longest Beaufort freeze-up duration on record (69 days) alongside the highest total storm-day count yet observed there (46), driven by unusually long-lived easterly storms in both basins; a 7.1-km ice pile-up near the Canning River mouth far exceeded any prior measurement in the series; and while Chukchi pile-up activity hit record lows in count, height, and encroachment, multi-year ice still pushed to within 7 nm of Point Barrow in December. The thirteen-year dataset confirms accelerating freeze-up delay, now trending later at a converged rate of 3.4 days/year in both basins, and updated invasion probabilities—about 25% per season for Beaufort multi-year ice and 65% for Chukchi—while an ice-loads assessment continues to indicate that reduced invasion frequency and floe thickness have lowered design global ice loads on fixed structures since the 1980s, a conclusion now reinforced by iceberg/ice island invasion tracking extended to a 13-year baseline. 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 declining multi-year ice presence, a sixth season of data was needed to continue tracking these trends and to follow up on a pair of grounded ice island fragments first discovered northwest of Point Barrow during the preceding freeze-up study. This sixth break-up study, commissioned by BSEE, was designed to describe the 2024 break-up season, map ice features and pile-up/ride-up events, correlate ice canopy changes with meteorological conditions, and compare the 2017 and 2020-2024 seasons with historical patterns. Researchers combined open-source meteorological data, ice charts, drift buoy data, and RADARSAT-2, RCM, MODIS, and VIIRS satellite imagery from May through July 2024 with four aerial reconnaissance flights—two in the Chukchi in June and two in the Beaufort in July. The 2024 season was unremarkable by recent standards across nearly every metric—air temperatures, wind frequencies, and storm counts all fell close to the six-year average in both basins—while multi-year ice remained absent from both nearshore regions for the third time in six years; the two ice island fragments located in February were revisited and found still grounded but reduced in plan-view dimensions, consistent with mechanical abrasion from surrounding pack ice; and the expected convergence of warm-water plumes from the Alaska Coastal Current and Mackenzie River in the central Beaufort failed to materialize due to anomalously low Mackenzie discharge, a break from the recent pattern. The six-year dataset reinforces that break-up and open water are trending earlier while freeze-up trends later, shortening the ice season at a rapid rate in both seas; storm frequency during break-up remains more than 40% above 1980s levels; and while multi-year ice presence during break-up has declined markedly since the 1980s, its appearance in three of the past six seasons confirms it remains a relevant, if now less frequent, consideration for offshore operations. This abstract was drafted with the assistance of Claude, July 2026.