Gulf of Alaska | Mammals
Reduction in iceberg habitat during tidewater glacier advance Presenter: Jason Amundson , jmamundson@alaska.edu, University of Alaska Southeast Lynn Kaluzienski , lmkaluzienski@alaska.edu, University of Alaska Southeast
Jamie Womble , jamie_womble@nps.gov, National Park Service Andrew Bliss , andrew_bliss@nps.gov, National Park Service Linnea Pearson , linnea_pearson@nps.gov, National Park Service
Icebergs in proglacial fjords serve as pupping, resting, and molting habitat for aggregations of harbor seals ( Phoca vitulina richardii ). One of the largest aggregations in Southeast Alaska is found in Johns Hopkins Inlet in Glacier Bay*, where seals utilize icebergs produced by Johns Hopkins Glacier. The tidewater glacier has advanced about 2 km over the last half century and has been a reliable source of icebergs throughout this time. As with other tidewater glaciers, the advance of Johns Hopkins Glacier has been enabled by the growth and continual redistribution of a submarine moraine at the glacier terminus, which has (1) limited mass losses due to iceberg calving and submarine melting and (2) enabled the glacier to thicken by providing flow resistance. In recent years the moraine has started to reach sea level and is visible at low tides, and consequently there has been a steady decline in iceberg concentrations in the fjord as revealed by a 15- year record of aerial photographic surveys. We find that the iceberg size distributions can be approximated by power-law distributions, with relatively little variability and no clear trends in the power-law exponent, despite large changes in ice fluxes over seasonal and interannual timescales. Thus, our observations suggest that sustained tidewater glacier advance should typically be associated with reductions in the number of habitable icebergs, which may have implications for seal distribution and behavior. *Tlingit placenames for the study site: Johns Hopkins Inlet: Tsalx̱aan Niyaadé Woolʼéexʼi Yé Johns Hopkins Glacier: Tsalx̱aan Niyaadé Sítʼ Glacier Bay: Sit’ Eeti Geeyi
Alaska Marine Science Symposium 2023 249
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