Alaska Current

Alaska Current. It is a warm, persistent surface current that flows northward along the coast of southeastern Alaska and the Alaska Panhandle, forming the northern branch of the North Pacific Current. This current is a key component of the North Pacific Gyre and significantly influences the climate, marine ecosystems, and coastal conditions of the northeastern Pacific Ocean. Its warm waters moderate the coastal climate and support rich biological productivity from the Gulf of Alaska to the Bering Sea.

Physical characteristics

The Alaska Current is characterized by its relatively warm and saline waters, which are transported from the subtropical Pacific Ocean. It typically flows at speeds of about 0.1 to 0.3 meters per second, with its core located over the continental slope. The current's temperature is several degrees warmer than the surrounding subarctic waters, a contrast clearly visible in satellite sea surface temperature analyses from institutions like the National Oceanic and Atmospheric Administration. Its width varies but generally spans several hundred kilometers, carrying a substantial volume of water from the North Pacific Current into the Gulf of Alaska. The current's properties are monitored by programs such as Argo and the Integrated Ocean Observing System.

Formation and dynamics

The Alaska Current originates as the northward-flowing division of the North Pacific Current after it bifurcates near Vancouver Island. Its formation is driven by the wind-driven Ekman transport associated with the Aleutian Low pressure system and the general circulation of the North Pacific Gyre. As it flows along the complex coastline, influenced by the rugged topography of the Coast Mountains, it interacts with freshwater runoff from major systems like the Copper River and the Stikine River. These dynamics are studied through numerical models at facilities like the Naval Postgraduate School and the University of Alaska Fairbanks. Seasonal variations in strength are linked to shifts in the Aleutian Low and the Pacific Decadal Oscillation.

Ecological significance

This current is ecologically vital, as its warm, nutrient-rich waters foster high primary productivity, forming the base of extensive food webs. It supports major commercial fisheries for species like Pacific salmon, halibut, and pollock, which are critical to the economies of ports like Kodiak and Seward. The current's transport of plankton and larvae influences the distribution of marine life throughout the Gulf of Alaska and into the Bering Sea. It provides crucial foraging grounds for seabird colonies in the Alaska Maritime National Wildlife Refuge and marine mammals including humpback whales and Steller sea lions. Changes in its flow can impact events like harmful algal blooms, monitored by the NOAA Fisheries.

Relationship to other currents

The Alaska Current is intrinsically linked to several other major oceanic flows within the North Pacific Gyre. To the south, it connects with the California Current, with the transition zone studied by the Pacific Gyre project. As it moves westward along the Alaska Peninsula, a portion feeds into the Alaska Stream, which eventually contributes to the formation of the Aleutian Current. Its waters also mix with the colder, fresher Coastal Current that hugs the shoreline. Further west, interactions with the Kamchatka Current and the Oyashio Current influence water mass properties in the North Pacific Ocean. These interactions are a focus of international research collaborations like those during the International Polar Year.

Research and observations

Scientific understanding of this current has advanced through sustained observational programs and international expeditions. Key historical studies were conducted during the HMS ''Challenger'' expedition and the NORPAC project. Modern monitoring employs satellite altimetry from NASA's Jason-3 and in-situ instruments like CTD profilers deployed by the University of Washington and the Woods Hole Oceanographic Institution. Long-term data comes from stations like Ocean Station Papa and repeated hydrographic lines conducted by the Scripps Institution of Oceanography. Research vessels such as the RV Sikuliaq and the NOAA Ship Oscar Dyson regularly sample its properties to understand its role in climate phenomena like El Niño-Southern Oscillation.

Category:Ocean currents of the Pacific Ocean Category:Geography of Alaska Category:Climate of Alaska