Community-scale changes to landfast ice along the coast of Alaska over 2000-2022

Abstract

Landfast sea ice that forms along the Arctic coastline is of great importance to coastal Alaskan communities. It provides a stable platform for transportation and traditional activities, protects the coastline from erosion, and serves as a critical habitat for marine mammals. Here we present a full assessment of landfast ice conditions across a continuous 7,885 km length of the Alaska coastline over 2000-2022 using satellite imagery. We find that the maximum landfast ice extent, usually occurring in March, averaged 67,002 km2 during our study period: equivalent to 4% of the state’s terrestrial land area. The maximum extent of landfast ice, however, exhibits considerable interannual variability, from a minimum of 29,871 km2 in 2019 to a maximum of 87,571 km2 in 2010. Likewise, the landfast ice edge position averages 22.9 km from the coastline but, at the community-scale, can range from 2.8 km (in Gambell) to 71.1 km (in Deering). Landfast ice breakup date averages June 2nd but also varies considerably both between communities (May 3rd in Quinhagak to July 24th in Nuiqsut) and interannually. We identify a strong control of air temperature on breakup timing and use this relationship to project future losses of ice associated with Paris Climate Agreement targets. Under 2°C of global air temperature warming, we estimate the average Alaskan coastal community will lose 19 days of ice, with the northernmost communities projected to lose 50 days or more. Overall, our results emphasize the highly localized nature of landfast ice processes and the vulnerability of coastal Arctic communities in a warming climate.