Freeze-up of Arctic Sea Ice in the U.S. Beaufort and Chukchi Seas (2015-2016)

Previous freeze-up studies (2009-10 through 2014-15) established long-term warming and delayed freeze-up trends in the Alaskan Beaufort and Chukchi Seas, but continued year-over-year monitoring remained necessary to track how landfast ice, the coastal flaw lead, and multi-year ice behavior were evolving relative to the 1980s baseline. This study was designed to document the 2015-16 freeze-up season by locating and mapping ice features of interest and correlating ice movement with meteorological conditions and historical patterns. The study combined remote sensing, meteorological data, and aerial reconnaissance to describe ice conditions and quantify changes relative to the 1980s dataset. The 2015-16 winter was exceptionally warm, ranking as the second warmest on record at Barrow and the warmest in seven years at Deadhorse, and produced first-year ice thickness (148 cm in the Beaufort, 145 cm in the Chukchi) that tied or nearly matched the lowest values recorded in the seven-year study series. Freezing-degree days at Barrow continue to decline at roughly 46 per year, and freeze-up now occurs about three to four weeks later than in the 1980s in the Beaufort and about one month later than in the 1970s in the Chukchi, substantially lengthening the open-water season; first-year ice thickness has fallen by over 11% since the early 1980s; storm frequency during freeze-up has risen by about 50% since the early 1980s, while mid-winter storm frequency has increased only modestly; and while landfast ice patterns west of Prudhoe Bay and the Chukchi flaw lead's frequency remain comparable to historical norms, the probability of large multi-year ice invasions into the Beaufort has fallen substantially, reflecting a shrinking permanent polar pack and a more northerly summer ice edge. This abstract was drafted with the assistance of Claude, July 2026.