Topic Area
 
 

Project Team Member:

LCDR David O. Neander, NOAA

Major Findings

The general circulation of the Gulf of Alaska (GoA) is dominated by the cyclonic Pacific subpolar gyre. The eastern boundary current associated with this gyre forms the Alaska Coastal Current (ACC), a weak, broad current which flows northward along the coasts of British Columbia and Alaska. Along this eastern margin the ACC flow is highly variable due to variations in wind stress and freshwater influx. Baroclinic instabilities resulting from wind and buoyancy forcing can lead to the formation of mesoscale eddies along the coast, which slowly propagate westward into the GoA.

Recent analysis of temperature and sea level data has shown that Kelvin waves generated during extremes of the El Nin?o Southern Oscillation (ENSO) can propagate from the tropical Pacific up the west coast of North America to the Aleutian Island chain. The ENSO events leading to the coastal-trapped Kelvin waves, in conjunction with the aforementioned baroclinic instabilities have been shown to destabilize the ACC by enhancement of the vertical velocity shear. The instability ultimately results in the formation of multiple strong anticyclonic eddies, which can last for 1-3 years. These mesoscale eddies significantly increase cross shelf mixing and enhance transport of nutrients, zooplankton, larvae and fish across the front formed by the ACC.

References:

Brink, K.H. and A.R. Robinson, 1998. Coastal Processes in the Northern North Pacific, The Sea, Volume 11, 395-414

Melsom, A., S.D. Meyers, H.E. Hurlburt, E.J. Metzger and J.J. O’Brien, 1999: ENSO Effects on Gulf of Alaska Eddies, Earth Interactions, 3.

Royer, T.C., 1982. Coastal freshwater discharge in the northeast pacific. Journal of Geophysical Research, 87, 2017-2021.

Tabata, S., 1982. The anticyclonic, baroclinic eddy off Sitka, Alaska, in the Northeast Pacific Ocean. Journal of Geophysical Research, 103C, 3033-3040.

Website: http://www.ios.bc.ca/ios/osap/projects/eddy.htm

Website: http://earthobservatory.nasa.gov/Study/Eddies/eddies_3.html