Time-series measurements of sea ice draft from the IPS5 sonar ice profiler, collected from three year-long ocean moorings at three sites, C1, C2, C3 in the Chukchi Sea, Alaska, as part of the NOAA OAR and BOEM CHAOZ-X programs by the EcoFOCI group at NOAA, PMEL, 2016-09-03 to 2017-08-20 (NCEI Accession 0316320)

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Ice draft time-series data were collected, 2016-2017, at three stations in the Chukchi Sea (C1, C2, C3) along the Icy Cape mooring line, as part of the 2016 Arctic Long-Term Integrated Mooring Array (ALTIMA) cruise. IPS5 upward-looking sonar ice profiler instruments (ULS, ASL Environmental Sciences) were deployed as year-long moorings in September, 2016 from F/V Aquila (AQ16-01, September 3 to 29, 2016). Moored instruments were out for ~1 year, and recovered the following Fall, 2017. The Chukchi Sea region is a shallow and seasonally ice-covered shelf with depths of ~40-50m. Instruments were mounted above an acoustic release and attached to an anchor constructed from a railroad wheel using 3/8 inch chain. Instrument placement at near-bottom depths was necessary to avoid deep ice-keel interference. These data are part of a 9-year series of ice draft data in the Chukchi Sea, with instruments deployed 2010 to 2018. *** Sonar range pings are measured from the IPS5 transducer to the under-surface of ice or water/waves at 1 Hz. The instrument operates at 420 kHz frequency, with a beam width of 1.8 degrees, a range of 175m (ice) up to 225m(water), and precision of +/- 0.05m. Two pre-programmed data-collection phases (p01 & p02) split the data into estimated times of early open-water/waves and winter-to-spring sea ice. Range, temperature, pressure and a standard speed-of-sound value (1438 m/s) were used to convert ranges to ice draft, and were corrected for atmospheric pressure using NCEP-NARR mean sea-level pressure (ftp://ftp.cdc.noaa.gov/Datasets/NARR/monolevel/; prmsl.2016.nc, prmsl.2017.nc). Tilt magnitude corrections were performed during data processing, and data were filtered for 1-2- and 3-4-point outliers. The speed-of-sound value was not further calibrated. Data methods are attributed to H. Melling of the Institute for Ocean Sciences (IOS), Canada (see reference Melling, 1995). ASL software was used for extracting binary instrument files to ASL Matlab format, and for data processing of range values to ice draft values (https://www.aslenv.com/ice-services.html). Ice draft is the measurement of ice from the ocean surface down to ice depth and excludes above-surface ice; draft is generally accepted as ~90% of ice thickness. *** The cruise was funded by NOAA’s Office of Oceanic and Atmospheric Research (OAR), and the Bureau of Ocean Energy Management (BOEM) Chukchi Acoustics, Oceanography, and Zooplankton (CHAOZ) study, the CHAOZ-Extension (CHAOZ-X) study, and the Arctic Whale Ecology (ARCWEST) study. The work was in collaboration with the NOAA National Marine Mammal Laboratory (NMML), and accomplished by NOAA, Pacific Marine Environmental Laboratory (PMEL) personnel from the EcoFOCI program, which included scientists from both NOAA and the University of Washington, Cooperative Institute for Climate, Ocean, and Ecosystem Studies (UW CICOES). Deployment and recovery operations on this cruise were managed by EcoFOCI personnel from NOAA/PMEL amd UW/CICOES. Ice Profiler time series data were processed at NOAA/PMEL using ASL proprietary Matlab tools, and other standard time-series methods. *** Data contacts: Shaun Bell, Ryan McCabe, Phyllis Stabeno, Peggy Sullivan.

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