Document Type



Sea-ice cover across the Arctic has declined rapidly over the past several decades owing to amplified climate warming. The Pacific walrus (Odobenus rosmarus divergens) relies on sea-ice floes in the St. Lawrence Island (SLI) and Wainwright regions of the Bering and Chukchi seas surrounding Alaska as a platform for rest, feeding and reproduction. Lower concentrations of thick ice floes are generally associated with earlier seasonal fragmentation and shorter annual persistence of sea-ice cover, potentially affecting the life history of the Pacific walrus. In this study, 24 Landsat satellite images were classified into thick ice, thin ice or open water to assess sea-ice fragmentation over the spring-summer breakup period. Geospatial fragmentation analyses traditionally used in terrestrial landscapes were newly implemented in this study to characterize the ices-cape environment. Fragmentation of sea ice was assessed based on the Percent of Landscape, Number of Patches, Mean Area, Shape Index, Euclidean Nearest Neighbor and Edge Density. Results show that lower sea-ice concentrations in both the SLI and Wainwright regions were associated with smaller sea-ice floes. In the Bering Sea, lower sea-ice concentrations were also associated with increases in the number of ice floes, floe isolation and edge density. By contrast, lower sea-ice concentrations in the Chukchi Sea were associated with ice floes that were more circular in shape. The continuation of sea-ice decline with shift-ing icescape characteristics may result in walruses having to swim longer dis-tances in the northern Bering Sea and adapt to use less-preferred, rounder ice floes in the Chukchi Sea.

Publication Title

Polar Research

Publication Date









climate change, Cryosphere, Landsat, remote sensing, sea ice, sea ice-obligate species

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

Included in

Geography Commons



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.