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Researchers believe that water exchange between the Gulf of Alaska and PWS is the primary physical process influencing the abundance and distribution of microscopic plants and animals, called plankton, that form the base of the marine food chain. Plankton provide food for schools of herring and other small fishes as well as juvenile salmon. Yet oceanographers have only a vague understanding of how much water is actually exchanged, at what frequency, and at what times during the year.
Since this single process has such an effect on life within the Sound, scientists have created a program within the PWSOS to monitor and understand the process more completely. This program will couple hydrography (periodically surveying properties of the ocean water column at many places) with a series of moorings (that continuously monitor water properties at fixed locations) across the Sound. The goal of this observational program is to improve our understanding of the magnitude and frequency of the exchange of water between the Gulf of Alaska and PWS and the forces driving these exchanges.
To provide this information, five ADCPs (see description under Buoyed Weather Stations) will be deployed in each PWS entrance to obtain measurements of water transport. Subsurface moorings will be instrumented with one upward looking and one downward looking ADCP mounted on hydrodynamically streamlined buoys. Additional downward looking ADCPs will be mounted on the NOAA weather buoys. An ADCP will also be temporarily moored in each of the four relatively narrow and shallow passages west of Montague Strait.
Each of the subsurface moorings will also have three conductivity-temperature recorders (CTDs) mounted at three different depths. These instruments will periodically sample temperature and salinity and thus track changes in water properties over time. Used in conjunction with the ADCP current measurements, they will help identify periods of deepwater exchange (which tends to be colder and saltier) between PWS and the Gulf of Alaska. They will also be able to determine the amount of freshwater coming into the Sound from the Copper River Delta or any of the many glaciers around the Sound.
The information gathered from the moorings will be coupled with data collected through the hydrography program. CTD (conductivity, temperature and depth) sensors will be attached to boats that will run four transects across Hinchinbrook Entrance and Montague Strait twice each year (spring and fall). The results of these surveys will track changes in the physical characteristics of the surface waters in PWS through the year's seasons.
Information from this program will be housed in the PWSOS long-term oceanographic database and will give scientists extensive information on the movement of water between the Gulf of Alaska and Prince William Sound. Data collected by the oceanographic moorings will be accessible through the AOOS and PWSOS web pages and archived at the University of Alaska Fairbanks.
Data Access
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