Shorefast Sea Ice Breakup

The formation and breakup of shorefast ice along Arctic coastlines and within fjords is one fo the most dramatic seasonal environmental changes on Earth. Unlike drift ice, which forms and moves in the open ocean, shorefast sea ice is frozen to the coast and therefore provides a perennial platform integral to the ecology, socioeconomics and culture of the pan-Arctic region. Coastal Arctic communities depend on shorefast ice for traditional subsistence activities and transportation as the ice provides a vital link between otherwise isolated villages. The ice is also a critical habitat for Arctic mammals and protects Arctic coastlines from erosion.

Shorefast sea ice occurs along coastlines and in narrow fjords and therefore cannot be resolved by the coarse passive microwave sensors typically used to monitor changes in sea ice from space. Consequently, less is known about changes in shorefast ice breakup and the processes which drive it. Using MODIS imagery, I mapped decadal changes in the timing of shorefast ice breakup in and around 28 coastal communities in Greenland and northern Canada. These satellite-derived estimates of breakup timing revealed that breakup timing is strongly correlated with springtime air temperature, but the sensitivity of the relationship varies substantially between communities. We combine these observations with future climate scenarios to estimate an annual reduction of 5–44 days in the length of the springtime shorefast ice season by 2100. Paradoxically, we find that the coldest communities are projected to experience the largest reductions in springtime ice season duration. Our results emphasize the local nature of climate change and its varied impacts on Arctic communities.

This research is part of a larger three-year project involving co-production of knowledge about shorefast ice in Uummannaq, North Greenland. The goal of this work, led by Jonathan Ryan at Brown and Brigt Dale at the Nordland Institute in Norway, is to combine our satellite-derived research on ice breakup with local knowledge about the sea ice and how it is changing. We conducted our first fieldwork for this project in Uummannaq in spring 2019.

Relevant Publications

Cooley, S.W., J.C. Ryan, L.C. Smith, C. Horvat, B. Pearson, B. Dale and A. Lynch (2020), Coldest Canadian Arctic communities face greatest reductions in shorefast sea ice, Nature Climate Change.