The Alaskan Coastal The Alaskan Coastal CurrentCurrent

Presented by: Gerry ButricoPresented by: Gerry Butrico

The Alaskan Coastal CurrentThe Alaskan Coastal Current

• Formed by storm systems associated with Formed by storm systems associated with the Aleution Lowthe Aleution Low

• Results in persistent cyclonic winds that Results in persistent cyclonic winds that impel onshore surface Ekman Transport impel onshore surface Ekman Transport and costal downwelling and costal downwelling

• Year round current, trapped near the coastYear round current, trapped near the coast• Forced by wind and buoyancyForced by wind and buoyancy• Most prominent circulation of the Gulf of Most prominent circulation of the Gulf of

Alaska’s continental shelfAlaska’s continental shelf

The Alaskan Coastal CurrentThe Alaskan Coastal Current

• Precipitation is a result of winds Precipitation is a result of winds blowing over the mountains near the blowing over the mountains near the coastcoast

• The coast is on the windward side of The coast is on the windward side of the Mountainsthe Mountains

• Rainfall between 2-6 m/yrRainfall between 2-6 m/yr• Wind stress and runoff have seasonal Wind stress and runoff have seasonal

variabilityvariability– Wind is strong in winter, weak in summerWind is strong in winter, weak in summer

The Alaskan Coastal CurrentThe Alaskan Coastal Current

• Runoff is weak in the winter because Runoff is weak in the winter because most of the precipitation is stored as most of the precipitation is stored as snow along the coast.snow along the coast.

• Strongest during summer thaw and Strongest during summer thaw and rainrain

• Runoff causes lower salinity near the Runoff causes lower salinity near the surfacesurface– Controls horizontal and vertical density Controls horizontal and vertical density

gradients.gradients.

The Alaskan Coastal CurrentThe Alaskan Coastal Current

• Freshwater runoff flows on top of the Freshwater runoff flows on top of the denser salt water. denser salt water.

• The coriolis force, along with the The coriolis force, along with the coastal down welling caused by coastal down welling caused by Ekman Transport causes the buoyant Ekman Transport causes the buoyant water to flow as a currentwater to flow as a current

The EndThe End

Source:Source: Weingarther, Thomas J., Seth L. Weingarther, Thomas J., Seth L. Dainelson, Thomas C. Royer, 2005: Freshwater Dainelson, Thomas C. Royer, 2005: Freshwater variability and predictability in the Alaska Costal variability and predictability in the Alaska Costal Current, Current, Deep Sea Research IIDeep Sea Research II, , 5252, 169-191., 169-191.