Arctic | Climate and Oceanography
Examining a multi-year seasonal ice record along the Icy Cape line in the Chukchi Sea Presenter: Margaret (Peggy) Sullivan , peggy.sullivan@noaa.gov, University of Washington, CICOES Phyllis Stabeno , phyllis.stabeno@noaa.gov, NOAA Pacific Marine Environmental Laboratory Stephanie Grassia , Stephanie.Grassia@noaa.gov, Cooperative Institute for Climate, Ocean & Ecosystem Studies, University of Washington Rapid sea-ice changes in the Pacific Arctic are occurring in the Chukchi Sea. Sea ice provides a medium for ice algae, which supports benthic communities. It influences water-column temperature, which determines the range and habitat for fish and shellfish; it provides a platform or a barrier for various marine mammals; and it serves as erosion protection for coastal areas. Sonar ice draft data were collected from fall 2010 to fall 2019 at three sites along the Icy Cape mooring line, extending offshore ~250 km from Icy Cape, Alaska. Deployment locations were located within the seasonal ice zone between 163° to 166° W longitude and 70° to 72° N latitude, in water depths shallower than 50 m. The area is influenced by the Alaskan Coastal Current flowing from Bering Strait, which advects water from the Bering Sea northward to the Arctic Basin. In addition, a coastal polynya often occurs near the easternmost mooring. Ice freeze-up typically occurred from November to early December, with ice keels as deep as 20 m being advected past the mooring sites. Extensive winter ice cover persisted from January to March or early April, and ice melt or breakup often began in May and extended as late as late July. The underside of seasonal ice is extremely irregular ranging from slush to deep keels, which can exceed 30 m. Using satellite ice concentration, we calculated the window of transition from summer open water to fall-winter ice as defined by Johnson and Eicken (2016), and obtained results similar to the moored observations. During winter months, with maximum ice cover (>90%), median ice thickness increased from 0.6 m to 1.1 m, with keel depths sometimes exceeding 20 m. Finally, we delineated trends in the annual cycle of ice formation (e.g., the timing of ice formation is becoming later), persistence (e.g., winter ice cover is steady), and the character of the sea ice during the melt season. Long-term in-situ sea-ice observations are sparse in this region. Future investigations will include comparison to model results and to satellite estimates of ice thickness.
Alaska Marine Science Symposium 2023 64
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