within 200 km of the coastline over an area of approximately 30,000 km2. Data are fed to the National HF Radar Network12 and are also available from UAF.13 Current vectors are calculated at 6-km spatial resolution and represent velocity in the upper 1 to 2 m of the water column. The systems can only operate during the open water season (approximately July to October), and waves must be present to measure currents. There can be spatial data gaps close to shore, due to the geometry of the coastline. Fully automated solar–wind energy hybrid power modules have been developed to provide power to the HFRs, meteorological sensors, and satellite-based communications. In the case of an oil spill, additional HFR systems could be installed in about three days at remote sites, with plans to create a more portable system that could be deployed in one day. An expansion of the HFR array is being considered, where additional systems could be maintained by local communities (Thomas Weingartner, UAF, personal communication).

Three UAF autonomous underwater vehicles (AUVs) are operating over most of the northeast Chukchi Sea14 and can sample an area for up to four months (see Weingartner et al., 2013b). These gliders presently cannot operate under sea ice cover, as developments are needed for under-ice navigation and through-ice communications. Pilot missions under sea ice will be made in 2014, as well as research missions as part of the Office of Naval Research Emerging Dynamics of the Marginal Ice Zone initiative and the European Union Arctic Climate Change, Economy and Society project. In addition to standard temperature and salinity measurements, AUVs can be equipped with sensors to measure colored dissolved organic matter and chlorophyll, to map ice topography by multibeam sonar, and to compute water velocity.

Instrument systems towed from ships are also used to measure temperature, salinity, and bio-optical properties at high horizontal resolution in the water column and can be used when conditions do not permit the use of AUVs—during strong ocean currents, for example. Additional applications of AUVs and towed vehicles include autonomous mapping of plumes (e.g., sediment, oil) and ice features (e.g., draft, keel depths, bottom scouring), mapping and imagery of hydrographic and bottom features, and incorporating water sampling with biochemical optical measurements for chemical laboratory analysis (e.g., Wadhams et al., 2006; Wilkinson et al., 2007). To supplement these data, moorings anchored to the seafloor can collect water-column measurements, as well as information on overlying sea ice drift and thickness, in one location over seasonal or longer timescales.15

Ice-tethered profilers are automated, drifting ocean profiling instruments that are deployed in drifting sea ice or in open water conditions to sample physical and some biological parameters in the upper water column (to 750 m depth) during all seasons, providing essential data on vertical ocean stratification for assimilation into numerical forecast models (Krishfield et al., 2008; Toole et al., 2010). They transmit ocean data in near real-time from surface buoys, with horizontal resolution on the order of 1 km and vertical resolution on the order of 25 cm. At present, they are deployed in central Arctic Ocean basins, but future ice-tethered profilers designed for shallower profiling depths could provide these data for the shallower Chukchi Sea and boundaries of the Beaufort Sea.

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12 See http://cordc.ucsd.edu/projects/mapping/.

13 See http://dm.sfos.uaf.edu/chukchi-beaufort/index.php.

14 See http://www.ims.uaf.edu/artlab/instruments/gliders.php.

15 See, for example, https://www.whoi.edu/beaufortgyre/.



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