Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B

Satellite Tracked Drifters in the Bering Sea
John Dunwoody
Physics Dept/Oceanography UAF




The Bering Sea’s inner shelf (<30 m) circulation is poorly known, but it is a critical habitat and migratory corridor for marine organisms and links coastal rivers with mid-shelf waters. The residents of Quinhagak (Kuskokwim Bay) deployed 64 satellite-tracked drifters between June and October in 2008 and 2009, in clusters of 4 drifters at ~2-week intervals, to elucidate the time-varying circulation of the inner shelf. Inner shelf flow variations respond to tides, winds, and coastal freshwater discharge, although the bulk of the non-tidal variability is wind-forced. Summer winds are weak and variable and the inner shelf flow is weakly northward. Winds are strong and northerly in fall, forcing a westward cross-shelf flow. That flow has short (~2 days, 10 km) integral time and decorrelation length scales, which reflect passage of storms. The seasonal partitioning of the flow has important ramifications for this marine ecosystem. Passively drifting organisms move northward along the coast of western Alaska in summer, but offshore through fall. The seasonal flow transitions also affect the salt and nutrient budgets for the Bering shelf, because the fall offshore flow carries dilute, nitrate-poor, inner shelf waters onto the mid-shelf, where the mean flow is sluggish. Hence, coastal waters may remain here through spring and thus affect the mid-shelf nutrient reservoir during the spring bloom. Our results demonstrate that the inner shelf, which is inaccessible to many vessels, can be studied efficiently through collaborations with local communities.


Friday, 4 Feb 2011

Globe Room, Elvey Building

3:45 PM