See below for more details on the February ice realignments at the SHEBA base camp.
|ATD's Kurt Knudson braves the rime to work on one of the Flux-PAMs.|
|Boreal beauty: A sundog adds some light to the wan Arctic sky.|
|Home away from home for the SHEBA team, the Des Groseilliers shimmers in this nighttime view from base camp. (Photo courtesy of Marty Mulhern, NOAA.)|
|The SHEBA base camp--separated into three floes by ice breakups in February--is pictured here in October as seen from the nearby Des Grosseilliers . (Photo by Lia Pennington.)|
Surprises from the initial SHEBA data gathered in October are outlined in a paper recently published on the Web. Salinity measurements in the upper 100 meters (330 feet) of the water column imply a net summertime influx of about 2 meters of fresh water. In contrast, only 0.8 meters of freshwater input were deduced in the same region in a 1975 sea-ice project.
"We were struck [in October] by the lack of thick ice," write the authors, led by Miles McPhee (McPhee Research Company). "Where we expected the mean thickness to be between 2 and 3 meters, we were hard-pressed to find floes more than 1.5 meters thick." Changes in local precipitation, river runoff, and even warming elsewhere in the Arctic between 1975 and 1997 appear unlikely to have triggered these changes. Scientists are thus exploring the idea that changes in atmospheric circulation might have stepped up a positive feedback between ice melt and albedo to accelerate the usual seasonal melting.
With the Des Grosseilliers in position through the fall of 1998, "the SHEBA project is well poised to investigate if and how the ice pack will reestablish equilibrium. The possibility that the ice is thinning rapidly lends a sense of urgency to our measurements over the next melt season."
A more tangible urgency reached the camp this past month. On 29 January, a crack formed through the central camp area. Initially a few inches wide, by 4 February it was more than four feet across and growing. All but one of the power lines from ship to camp were severed by the movements, and the camp buildings were dispersed on three separate floes. Power has since been restored to most buildings, and the camp is being reconfigured.
Meanwhile, a shifting ice ridge put the crunch on one of the four Flux-PAM stations on 12 February. The PAM's tripod and radiometers were damaged by the moving mass of ice, but the data system and most of the sensors were unharmed, notes Flux-PAM manager Tom Horst (ATD). The hapless station had already incurred some cable damage earlier in the project, thanks to a visit from a local polar bear. On the bright side, the sun came back in February for the first time since early November. BH
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