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Improving Arctic Sea Ice Thickness Measurements Higher Resolution Data from Airborne Lidar and Radar System Help Validate and Refine US Navy's Arctic Sea Ice Thickness Models By Edward Lundquist Principal Science Writer MCR Federal Arlington, Virginia S cientists from the Naval Research Laboratory (NRL) are dig- ging into a deep problem: How thick is the Arctic sea ice? While satellites can show where the Arctic Ocean is covered with ice, there is no way to directly determine its thickness, which is essential information for building and operating ships to navigate the Arctic. With more open water, thinner sea ice due to retreating ice cover and multiyear ice decline comes an increase in oil and gas exploration, fishing, tourism and commercial vessels in the Arctic. The multiyear ice cover is not only shrinking, it is thinning. As this trend is expected to continue, along with greater activity in the region, it becomes more important to know the extent of ice coverage and thickness. To date, remote sensing capabilities cannot easily nor accu- rately measure sea ice thickness. Still, available observations along with modeling can help provide estimates, which can aid forecasters. Some satellite systems can measure the free- board (the height of ice above the ocean surface) from which total sea ice thickness can be estimated, but they have signifi- cant temporal and spatial coverage limitations. The NRL and its research partners are collecting higher res- olution data with aircraft, in-situ measurements and sub- marines, which can help validate satellite-derived information and ice thickness model output. In 2011, the NRL worked with the U.S. Army Corp of Engineers Cold Regions Research Lab (CRREL), the Navy's Arctic Submarine Lab and NASA. In 2012, the NRL has partnered with the University of Alaska Fairbanks and the Alfred Wegener Institute for Polar and Marine Re- This piece of data was collected using a Riegl LMS-Q560 mounted on a Twin Otter aircraft that was flying ap- proximately 700 feet above the ice at 90 knots. The data shows the topog- raphy of the ice, including ice ridges and a crack in the ice that developed into an opening. www.sea-technology.com AUGUST 2012 / st 15