Alaska Coastal Current
The Alaska Coastal Current is a narrow, high-speed, westward flow which extends for more than 1000 kilometer along the coast of Alaska. This is a separate feature from the offshore, deepwater Alaskan Stream; however, it was not recognized as such up until the mid-1970s when a series of hydrocast surveys in the area was begun which led to its identification as a distinct circulation feature. The ACC is driven by freshwater discharge from the mountainous and coastal regions around the Gulf of Alaska and the consequent nearshore confinement of this low-salinity water by westward winds. It is typically narrow (< 50 kilometers), shallow (< 150 meters) and partially baroclinic. It flows most intensely between 145 and 155 degrees W through the Shelikov Strait between the Alaskan Peninsula and Kodiak and Afognak Islands, but extends recognizably along the Peninsula as far as 165 degrees W.
The baroclinic speed and transport have been estimated as typically <30 cm/sec and 0.4 Sverdrup (Sv), respectively, in the winter, spring and summer. In the fall, when the freshwater influx leads to the spin-up of the ACC, the speeds and transports have been estimated as 89-133 cm/sec and 1.0-1.2 Sv, respectively.
Current mooring measurements have yielded estimates of six-month mean total transports ranging from 0.85 Sv at 151 degrees W to 0.64 Sv at 155 degrees in the Shelikof Strait, with daily means as high as 2.5 Sv and marked variability from day to day. This variability is thought to be chiefly due to variations in windforcing caused by the passage of large-scale storms along the coast. The mean baroclinic transport as estimated from the same measurements was found to be about 75% of the total.
Further Reading
- Peter Saundry. 2011. Seas of the world. Topic ed. C. Michael Hogan. Ed-in-chief Cutler J.Cleveland. Encyclopedia of Earth
- P. J. Stabeno, R. K. Reed, and J. D. Schumacher. The Alaska Coastal Current: Continuity of transport and forcing. J. Geophys. Res., 100:2477–2485, 1995.
