Sea Technology

AUG 2012

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search. A primary focus of the NRL and its partners is to collect data for validating and calibrating the higher resolution data sets to optimize instrument suites and the development of pre- dictive sea ice models. Measuring and Calculating Ice Existing sensors can measure the ice freeboard, which often has an overlying snow cover. The freeboard can be isostatically balanced by the buoyancy of the ice below the water line, which is called ice draft. That buoyancy is dependent on the mean density of ice, but if the freeboard can be measured ac- curately and the density relationship calculated, then the av- erage thickness of the sea ice can be determined. Understanding the accuracy and relationships of these meas- urements helps scientists develop new algorithms for regional sea ice models. The Navy's recent research effort is aimed at evaluating, validating and im- proving the existing models. Fieldwork by the Office of Naval Research began in Oc- tober 2011 as a prequel to the NRL's DIS- TANCE (Determining the Impact of Sea Ice Thickness on the Arctic's Naturally Chang- ing Environment) program, which is basic research that will be funded from fiscal years 2012 to 2016. Scientists from the NRL's Remote Sensing, Oceanography and Marine Geosciences divisions are also in- volved in the project. The NRL conducted field research in March 2011 and April 2012 from Barrow, Alaska, using a DHC-6 Twin Otter twin-en- gine turboprop aircraft, which mounted a Riegl USA (Orlando, Florida) LMS-Q560 2D laser topographic lidar, a precision radar altimeter designed and built by NRL Code 7420 engineers, a high-resolution camera and GPS. Twin Otter International (Grand Junction, Colorado) operated the aircraft. Lidar reflects from the top surface of a floating mass, possibly snow sitting on top (Top) Hector Castillo watches daily operations while communicating with the command hut at the Applied Physics Lab Ice Station as the USS Connecticut prepares to submerge during ICEX 2011. (U.S. Navy photo by Kevin S. O'Brien) (Bottom) Sailors and members of the Applied Physics Laboratory Ice Station clear ice from the hatch of the Seawolf-class submarine USS Connecticut (SSN 22) as it surfaces during ICEX 2011. (U.S. Navy photo by Kevin S. O'Brien) 16 st / AUGUST 2012 www.sea-technology.com

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