FY 1987

Meteorology of the northern Gulf of Alaska

Wilson, J.G., and J.E. Overland

In The Gulf of Alaska: Physical Environment and Biological Resources, D.W. Hood and S.T. Zimmerman (eds.), DOC/NOAA, DOI, 31–54 (1986)

The Gulf of Alaska is one of the most active meteorological regions on earth. The types of weather found there are primarily caused by the passage of storm systems along the Aleutian storm track. Many of these storms are stalled by the high coastal mountains that ring the Gulf and are subsequently dissipated. Variability in the weather of the Gulf of Alaska is largely determined by planetary-scale motions, in particular by the presence of a high-pressure system that blocks the normal passage of storms. Large interannual variations are the norm. Throughout the year, offshore winds are predominantly from the south in the eastern Gulf, from the east in the northcentral region, and from the west, but highly variable, near the Aleutian Islands. Wind intensity is the greatest in the winter months of October through April. The nearshore wind field can be quite variable due to the presence of the high mountain barrier to onshore flow. Examples of nearshore wind phenomena include coastal wind jets, gap winds, and katabatic winds. Winter air temperatures over the ocean are generally warmer than at continental stations at the same latitude due to relatively warm ocean-water temperatures. Frequently during the winter cold, continental air will stream over the region, bringing a dramatic drop in air temperature. The Gulf of Alaska is almost always cloud covered and the precipitation away from the coast is on the order of 100 cm/y. Storms that cross the Gulf drop as much as 800 cm/y of precipitation in the form of rain and snow in the high coastal mountains. These mountains provide substantial storage for runoff. The weather in the Gulf of Alaska affects the regional oceanography by means of both wind-induced currents and coastal currents driven by differences in water density from the large runoff of fresh water along the coast of southeast Alaska. Because the weather influences the Gulf current systems and ocean stability, it has a major impact on the variability of the oceanic biological community.