P6.4 Wind-forced upwelling on the continental slope of the Alaskan Beaufort Sea

Monday, 2 May 2011
Kennedy Room (1st Floor) (Omni Parker House )
Lena M. Schulze, WHOI, Woods Hole, MA; and R. S. Pickart

Easterly winds along the north slope of Alaska, driven by remote Aleutian low storms, drive upwelling of subsurface waters onto the Beaufort Sea shelf. This results in a net flux of salt, nutrients, and zooplankton that impact the ecosystem on the shelf. The storms are most frequent in autumn and winter, but can occur in any season. Using data from a two-year (August 2002--September 2004) oceanic mooring array across the shelfbreak at 152W in the Beaufort Sea, and wind data from a weather station 150km to the west, the upwelling response of the ocean is characterized. Over the course of the two-year record, 45 events were identified. In the absence of wind a shelfbreak current advects Pacific-origin water to the east, emanating from the Chukchi Sea. During a storm event the current reverses to the west, and isopycnals are displaced upwards towards the shelf. Seasonal composite averages of the events reveal pronounced differences. During the winter season (November - July) cold, weakly-stratified Pacific winter water in the interior basin is drawn onto the shelf, and the reversed shelfbreak jet is strongest near the shelfbreak. During the summer (August - October) Pacific summer water is advected onto the shelf and the reversed jet is strongest over the continental slope. In both seasons offshore Ekman flow and onshore return flow is observed at the shelfbreak. The individual events are characterized in terms of strength (hydrographic and flow response), wind-forcing, and the impact of ice concentration and ice velocity, in order to identify trends and relationships.
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