Sea Technology

SEP 2012

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Taking the Temperature Of the Arctic With UMVs Arctic Wave Gliders Gather 900,000 Measurements During a Two-Month Mission in the Beaufort Sea By Christian Meinig Director of Engineering NOAA Pacific Marine Environmental Laboratory Seattle, Washington Dr. Michael Steele Senior Principal Oceanographer Applied Physics Laboratory University of Washington Seattle, Washington and Dr. Kevin Wood Research Scientist Joint Institute for the Study of the Atmosphere and Ocean University of Washington Seattle, Washington O ver the past five years, the loss of Arctic sea ice has been dramatic, especially in the Pacific sector. Satellite data indicate that the summertime ice-free area in the Beau- fort Sea has increased by roughly 80 percent since 2007, in comparison to climatology (1981 to 2010). This has caused a tremendous increase in the air-sea exchange of heat in the upper ocean, a classic example of ice-albedo feedback, in which the dark ocean surface absorbs far more radiation than highly reflective sea ice. The result is an unprecedented warming of the upper ocean during the summer and early autumn. Quantitative impacts of this heat transfer on ocean and atmosphere are not well known. Previous scien- tific studies have relied on numerical model output, satellite remote sens- ing or sparse in-situ (surface) observa- tions. The major limitation has been the ability to economically carry out sustained observation in the surface layer of the seasonal ice zone, a tech- nically and operationally challenging domain. Ship time is expensive in the Arctic and ranges between $25,000 to $80,000 per day, depending on capa- bility. To overcome these issues, NOAA Pacific Marine Environmental Labora- www.sea-technology.com SEPTEMBER 2012 / st 23 tory (PMEL) and Liquid Robotics Inc. (Sunnyvale, California) deployed two Wave Glider unmanned maritime vehicles (UMVs), energy-self-sufficient surface vehicles that can be configured for extended research missions in challenging environments, such as the Beaufort Sea. Mission Objectives Beginning in early summer, sea ice melts and ocean heat content increases from intensifying solar radiation. Buoy- ant freshwater from the melting sea ice and from significant amounts of river runoff result in an increasingly stratified ocean surface layer. This effectively traps more heat at the surface, accelerating further melting and heating. Some of this heat is stored in the ocean until autumn, when it can delay the onset of freeze-up, and may, as it is released back to the atmosphere, warm and destabilize the marine atmospheric boundary layer and possibly the regional at- mospheric circulation. Heat absorbed in summer also de- scends into the deepening winter mixed layer, which can continue to melt sea ice throughout the winter. The mission objectives were to collect critical tempera- ture data in the upper 6 meters, following a prescribed track with one vehicle leading the other by 12 hours to study di- urnal heating effects and to take surface images from an aft- mounted camera at prescribed times for situational aware- Arctic Wave Glider system components.

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