Gulf of Alaska | Mammals DOCTORATE POSTER PRESENTATION Evaluating changes in ice habitats at Alaskan tidewater glaciers using spectral reflectance techniques for digital image analysis
Presenter: Courtney Pegus , ccpegus@alaska.edu, University of Alaska Fairbanks Shannon Atkinson , shannon.atkinson@alaska.edu, University of Alaska Fairbanks John Jansen , john.jansen@noaa.gov, Alaska Fisheries Science Center | NOAA Fisheries
Tidewater glaciers release ice pieces into the marine environment as part of a seasonal calving cycle that generates areas of floating ice persisting near the terminus of the glacier from spring to early summer. This calved ice forms a floating structure that is used as haul-out substrate by harbor seals. A warming climate impacts the persistence and complexity of ice habitats (and associated ecosystems) for arctic and sub-arctic marine mammals that occupy ice-dominated ecosystems. Aerial imagery from fixed-wing aircraft is one of the most efficient tools to evaluate these remote, expansive, and dynamic habitats. Our study will use spectral reflectance of floating ice in images over a 9-year span (2006 and 2015) to estimate the relative area of open water versus ice-covered water in the fjords adjacent to the Alaskan glaciers of Columbia, Harvard, and Yale. The objectives for this study were to: 1) estimate the ratio of open water: ice- covered areas (OWIR) for all floating ice, 2) estimate the ratio of open water: to ice-covered areas for ice that is usable as seal habitat ( ≥ 2.0 m at longest dimension) (OWI2R), 3) estimate the proportion of suitable ice habitat actually occupied by seals and 4) examine spatial and temporal variability by statistically comparing these metrics between glaciers and time periods. Our study is unique in focusing on changes within and among tidewater glaciers as it pertains to variation in habitat used by harbor seals over a period of rapid glacial degradation. Ultimately, regular and frequent surveys of these glacial habitats will improve the resolution to better understand the mechanisms whereby rapid climate change and loss of habitat will necessarily limit these harbor seal populations that are some of the most abundant and critically important to the species in Alaska.
Alaska Marine Science Symposium 2023 254
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