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Science Briefing |
Jim Moore and Lia Pennington (JOSS) have been on board the Des Grosseilliers this month setting up SHEBA's on-line data catalog, developed by JOSS's Nimal Gamage and colleagues. The catalog will be run both on the ship and at a mirror site in Boulder, with satellite communications linking the two.
An international project coordinated by the University of Washington's Applied Physics Laboratory, SHEBA will track the transfer of energy between the ocean, sea ice, and atmosphere during a full year of freezing and melting. Project goals include better interpretation of satellite remote-sensing data from the Arctic and a better understanding of how sea ice interacts with the rest of the global climate system.
The four Flux-PAMs stations needed some repackaging to withstand a year of high winds (up to 30 meters per second--67 miles per hour--in storms) and low temperatures (down to -50 degrees Celsius, or -58 degrees Fahrenheit), along with three months of darkness. Flux-PAMs (portable automated mesonet) surface meteorological stations record standard surface variables: winds, temperature, humidity, and pressure. In addition, they measure vertical transport fluxes of long- and short-wave radiation, sensible heat, and momentum.
For SHEBA, the stations' solar-charged batteries were replaced with propane-powered thermoelectric generators. The generators, their fuel bottles, and storage batteries go into an insulated box with the station's electronics so the generator can keep the electronics warm enough to operate. The whole unit is mounted on a rugged sled (the kind used for towing behind snowmobiles). With their towers folded and loaded on top, the sled-mounted stations can be moved to different surfaces (such as new ice, multiyear ice, and melt ponds). John Militzer headed the project that made the stations iceworthy.
SHEBA also marks the debut of ATD's new GPS-Loran Atmospheric Sounding System (GLASS). There's no loran coverage near the Beaufort sea, and the available Omega radio navigation system, less accurate than GPS, is being phased out. This gave ATD the boost to develop a rawindsonde capable of using GPS (Global Positioning System) as well as loran. "GPS will work virtually anywhere," explains Ned Chamberlain, who wrote the new software for GLASS.
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| Shown here is the original projected location (top diamond) and possible 15-month drift path (arrow and second diamond) for the SHEBA research camp. The shaded region encloses 90% of the spread of possible final positions, based on a statistical model of randomly varying ice motion. The bold line depicts the average southward extent of 50% ice coverage in September. (Illustration from SHEBA Science Plan, courtesy SHEBA Project Office.) |
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You can follow SHEBA's progress on the web. Recent news from the Web site: The Canadian Coast Guard icebreaker Des Grosseilliers reached the SHEBA "home ice floe" at latitude 75 degrees 17 minutes north, longitude 142 degrees 42 minutes west at 14:35 ADT on 2 October. The prevailing ice thickness at the site was about two meters under hummocks, and varied down to under one meter under the (frozen) melt ponds.
At 19:00 on 5 October, the air temperature was -22 degrees Celsius and winds were from the northwest at 10 knots. The four Flux-PAMs were brought out on the ice to be prepped for setup that day, looking "like four boxy versions of R2D2."
