Upwelling in the Alaskan Beaufort Sea: Atmospheric forcing and local versus non-local response |
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| Authors: | Robert S Pickart Michael A Spall GWK Moore Thomas J Weingartner Rebecca A Woodgate Knut Aagaard Koji Shimada |
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| Institution: | 1. Woods Hole Oceanographic Institution, Woods Hole, MA 02540, USA;2. University of Toronto, Toronto, OT, Canada M5S 1A1;3. University of Alaska, Fairbanks; Fairbanks, AK 99775, USA;4. Applied Physics Laboratory, University of Washington, Seattle, WA 98105-6698, USA;5. Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan;1. ERDC-CRREL, USA;2. Dartmouth College, USA;3. Clark University, USA;4. University of Maryland Center for Environmental Science, USA;5. 424 Russfield Dr Knoxville, TN 37922, USA;6. University of Wellington, New Zealand;7. University of Washington, USA;1. Woods Hole Oceanographic Institution, Woods Hole, MA 02540, USA;2. University of Toronto, Toronto, OT, Canada M5S 1A1;3. Stanford University, Stanford, CA 94305, USA;1. V.I.Il’ichev Pacific Oceanological Institute, Far Eastern Branch, Russian Academy of Sciences (POI FEB RAS), 43 Baltiyskaya Street, Vladivostok 690041, Russia;2. International Arctic Research Center, University of Alaska, 930 Koyukuk Dr., P.O. Box 757340, Fairbanks, AK 99775, USA;3. National Research Tomsk Polytechnic University, Tomsk, Russia;1. Graduate School of Geography, Clark University, Worcester, MA, USA;2. Department of Physics, University of Toronto, Toronto, Ontario, Canada;3. University of Maryland Center for Environmental Science, Solomons, MD, USA |
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| Abstract: | The spin up and relaxation of an autumn upwelling event on the Beaufort slope is investigated using a combination of oceanic and atmospheric data and numerical models. The event occurred in November 2002 and was driven by an Aleutian low storm. The wind field was strongly influenced by the pack-ice distribution, resulting in enhanced winds over the open water of the Chukchi Sea. Flow distortion due to the Brooks mountain range was also evident. Mooring observations east of Barrow Canyon show that the Beaufort shelfbreak jet reversed to the west under strong easterly winds, followed by upwelling of Atlantic Water onto the shelf. After the winds subsided a deep eastward jet of Atlantic Water developed, centered at 250 m depth. An idealized numerical model reproduces these results and suggests that the oceanic response to the local winds is modulated by a propagating signal from the western edge of the storm. The disparity in wave speeds between the sea surface height signal—traveling at the fast barotropic shelf wave speed—versus the interior density signal—traveling at the slow baroclinic wave speed—leads to the deep eastward jet. The broad-scale response to the storm over the Chukchi Sea is investigated using a regional numerical model. The strong gradient in windspeed at the ice edge results in convergence of the offshore Ekman transport, leading to the establishment of an anti-cyclonic gyre in the northern Chukchi Sea. Accordingly, the Chukchi shelfbreak jet accelerates to the east into the wind during the storm, and no upwelling occurs west of Barrow Canyon. Hence the storm response is fundamentally different on the Beaufort slope (upwelling) versus the Chukchi slope (no upwelling). The regional numerical model results are supported by additional mooring data in the Chukchi Sea. |
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