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Gulf of Alaska

The Gulf of Alaska is really blooming brightly right now in this SeaWiFS image. (Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE).

The Gulf of Alaska is part of the northeastern Pacific Ocean off the Alaskan coast. The broad shelf steeply slopes towards the deep-sea plain in the east and towards the Kuril Trench in the west. The seafloor is partly structured by submarine channels, rises and guyots. The Alaska gulf coast is deeply cut by the Cook Inlet and the Prince William Sound.


The counter clockwise rotating Alaska gyre, originating from the Kuroshio Drift to the east, dominates the oceanography of the Gulf of Alaska.


The Gulf of Alaska is characterized by a rather maritime and wet climate. Mean annual precipitation rates regionally exceed 5 meters. Temperatures are relatively mild in winter and mostly cool in summer. The climate of the widely treeless Aleutian Islands is rather harsh and foggy, damp, and cold in the winter and subject to violent winds.


The Gulf of Alaska shelf hosts a diverse ecosystem, which includes many different commercially used species such as crab, shrimp, pollock, salmon, halibut and mackerel. In the past years, the National Marine Fisheries Service prohibited fishing for pollock in certain areas of the gulf. The salmon shark and the blue shark are the major sharks in the Gulf of Alaska. Salmon sharks are year-round residents, while blue sharks are summer visitors, which migrate northward from transition zone waters located south.


Thirteen different species of marine mammals feed in the Gulf of Alaska gyre year round. Pinnipeds, killer whales and sperm whales are found in the Alaskan gyre in summer; additionally baleen species like blue, fin and sei whales are abundant. Minke and humpback whales are primarily coastal species and are not considered to occur in significant numbers in the outer gyre.


Many different sea birds like petrels, albatrosses and gulls are abundant year round in the Gulf of Alaska.



Massive Oil Spill in the Prince William Sound


The Gulf of Alaska was faced to one of the most catastrophic marine oil spills in younger history. One of the largest marine oil spills in history happened in March 1989 when the giant Exxon Valdez tanker ran aground in Prince William Sound in the Gulf of Alaska. The crashed tanker spilled more than 42.000 tons of crude oil into the sea causing slick coverage on a 1,600 kilometer long coastal band. The environment damage was estimated to as much as 3 to 15 billion US$ and the oil spill killed hundreds of thousands of fish and seabirds as well as thousands of sea otters.


Few months after the accident - in summer of that year - the Alaska Department of Environmental Conservation estimated that still a 149 kilometer long shoreline in Prince William Sound was heavily oiled and 459 kilometers were at least lightly or moderate polluted.


A year later a monitoring revealed that oiling had decreased by around 73 per cent. Two years later - in 1991 - another monitoring estimated that only 1.4 kilometer of heavily polluted shoreline remained. In 1992 the estimate of heavily oiled shoreline in the sound was only 0.2 kilometer.


Smaller-scale studies dealing with continued clean-up efforts and restoration of oiled mussel beds conducted between 1995 and 1999 showed that the oil was surprisingly persistent and often in a relatively unweathered state, containing high concentrations of toxic and biologically available polycyclic aromatic hydrocarbons. Long-term monitoring in the oiled areas also revealed that populations of mammal and bird species like sea otters and ducks still have not recovered from the oil attack ten years ago. According to recent investigations it seems that remaining small-scale subsurface oil deposits may become a permanent source of low-level oil pollution within the spill-affected area significantly influencing the regional ecosystem.



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