Coastal fresh water discharge in the northeast Pacific

Abstract

Very high annual rates of precipitation in the coastal mountains that border the northeast PacificOcean produce large fresh water discharges (23000 m 3 s-i). This discharge has been ignored previously since it does not enter the ocean in the form of large rivers, but, instead, the water enters by way of numerous small rivers and streams. Thus, it acts as a line source instead of a point source. This coastal discharge contributes at least 40% of the fresh water that enters the northeast Pacific from the atmosphere. The discharge is comparable to the mean annual discharge of the Mississippi River system. The fresh water creates a cross-shelf density gradient that drives an alongshore baroclinic jet.The width of this jet is less than 25 km with speeds in excess of 100 cm s -•. It extends along the coast from southeast Alaska to at least Kodiak Island. Apparently, the flow is maintained as a narrow current adjacent to the coast by wind stress that causes downwelling conditions here throughout most of the year.

A hydrological digital elevation model for freshwater discharge into the Gulf of Alaska

“…However, these stations are sparse in Alaska and are not evenly located. Because of complicated terrain, it is difficult to determine the spatial scale that atmospheric forcing at a station can represent [Royer, 1982]. Thus it is necessary to use the gridded reanalysis data to cover all the grids in the model domain.…”

“…Royer [1979Royer [ , 1981 also applied a box model discharge model to the region and discussed the sources of the discharge and the effects on the salinity of the coastal current, because freshwater discharge into coastal seas plays a more important role in the subpolar ocean than in the subtropical and tropical oceans. Royer [1982] estimated that freshwater discharge from this 600 km  150 km area in northeast Pacific Ocean is about 23,000 m 3 s…”

“…Nevertheless, in the Gulf of Alaska, meteorological data at one station are not representative of other stations due to the nonuniform distribution of synoptic weather system in space. Thus Royer [1982] used two divisionally averaged data (southeast and southern coast) from coastal stations to drive his model. As shown in section 3.1, even in Valdez, data collected from several stations around this small city have quite pronounced differences because of orographic effects and complicated terrain distribution.…”

“…Tully and Barber [1960] treated the freshwater runoff as an estuary. Royer [1982] discussed the effect of precipitation and runoff on the coastal circulation in the Gulf of Alaska (GOA) using a simple hydrological model driven by air temperature and precipitation data from the National Weather Service. The model forcing data were divisionally averaged into two regions: southeastern and southern coast divisions.…”

Seismic and non-seismic influences on coastal change in Alaska--Fieldtrip guide and conference abstracts, 5th International Conference of IGCP 588

“…Bagley Ice Field, Bering Glacier, Seward-Malaspina Glacier). The southern flanks of the St. Elias Mountains receive high precipitation with rates of >3 m/yr, mostly as snow that feeds the large glacial systems (Royer, 1982). Fletcher and Freymueller (2003 …”