Ice, Keels and Changing Seasons in the Chukchi Sea near Icy Cape, Alaska

Margaret E Sullivan, JISAO-NOAA/PMEL, Seattle, WA, United States, Phyllis J Stabeno, NOAA Pacific Marine Environmental Laboratory, Seattle, WA, United States and Carol A Ladd, NOAA/PMEL, Seattle, WA, United States
The Chukchi Sea, a seasonal sea-ice zone, has seen dramatic warming and changes in sea ice in recent years. Ice draft data were collected from upward-looking sonar instruments in the northern Chukchi Sea near 71° N at three stations located along a line west of Icy Cape, Alaska. These instruments provide records of 1-hertz ice draft beginning in the fall of 2010. The records include one station (C2) with eight years of near-continuous data, and 2 stations with more sporadic occupations. Stations were chosen based on locations within the Alaskan Coastal Current, and proximity to Barrow Canyon and Hanna Shoal.

Summers in the Chukchi Sea have predominantly open water and waves with pack ice remnants including >20m keels passing through from June to early July. Open-water conditions persist into fall. Winter seasons vary in length and are mostly ice covered, with short periods of leads, polynya, frazil ice and waves, which are evident in the records and corroborated with other data sources. Spring and fall transition seasons show wide variability in ice and surface conditions. During this record, ice has arrived progressively later in fall. Fall shows a more orderly transition; spring a more chaotic transition. Deep ice keel observations occur late March to July and can be > 25m deep with occurrences of up to 30m in ~45-m water. We investigate the seasonal ice signature, warming trends, and shifts in seasonal transitions. Ice data are compared to co-located current-meter data. Comparisons between in situ ice draft, satellite ice-thickness and model-predicted ice thickness are discussed.