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Daily Update Calendar Dispatch 11 - July 25, 2002 By C.A. Linder Weather conditions: snow flurries, mostly cloudy skies, winds 20 knots from the W, calm seas, air temperature 32° F. On the Edge We have passed over the edge of a cliff. The cliff was deep underwater below us, visible only as a series of pixels on our computer screens. This area is known as the “shelfbreak,” the point where the shallow continental shelf slopes away steeply to the deep Beaufort Sea. Using a simple sonar system, we are mapping the changing depth, so that on our way back towards the shelf we can deploy our moorings at precise locations along the “cliff face.” Our mission is to deploy eight WHOI moorings in a line connecting the shallow and deep waters. Since we have learned from historical data that the currents in this region flow along the “isobaths” or lines of constant depth (i.e. along the cliff face, instead of across it), these moorings will provide us with a snapshot every few hours of the waters flowing along the shelfbreak. The variability of this system will offer clues as to how the two sides of the shelfbreak communicate with each other---one of the primary goals of the experiment. The shallowest Beaufort mooring will be in roughly 150 feet of water, and the deepest in 4500 feet of water. Since returning to within sight of Alaska’s coast, we have gained quite a following! A raucous troop of black-legged kittiwakes, glaucous gulls, and parasitic jaegers have been flying along behind us, eating the juvenile arctic cod in the swirling open waters our huge propellers have stirred up. The parasitic jaegers, flying fast just above the ice, harass the smaller kittiwakes and try to get them to drop their fish. It’s fascinating to watch them all wheeling around the stern of the ship, diving and feeding -- an arctic ballet. |
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