U.S. Dept. of Commerce / NOAA / OAR / PMEL / Publications
The Alaskan Coastal Current (ACC) is typically a narrow (<30 km), shallow
(<150 m), and mainly baroclinic flow [Schumacher
and Reed, 1980]. It extends for ~1000 km along the Alaskan coast and
is the dominant circulation feature in Shelikof Strait and on the shelf along
the Alaska Peninsula to Unimak Pass [Reed,
1987]. Shelikof Strait and its associated sea valley are <60 km wide
and extend for ~450 km between the Alaska Peninsula and the Kodiak Island plateau
(Figure 1). The sea valley forms a natural guide
for circulation, connecting the inner shelf to the continental slope. In the
confined areas of Shelikof Strait, current speeds (transport) can be appreciable,
reaching values of ~100 cm s
(3 × 10
m
s) for
brief periods (days) in winter [Schumacher
et al., 1989]. Westward winds generally confine the freshwater discharge
from the mountainous coastal regime to the nearshore. The wind can generate
rapid fluctuations in the transport of the ACC in excess of 106 m
s over the course of a day [Schumacher
et al., 1989].
Figure 1. The study area in the western Gulf of Alaska. The location of the moorings at Wide Bay (21-25, 28, and 29) and Cape Kekurnoi (1-3) are indicated by circles. The inset shows regional circulation. Depths are in meters.
Fisheries Oceanography Coordinated Investigations (FOCI) conducts research on the influence of physical and biological factors on the early life history of walleye pollock (Theragra chalcogramma) in the northeastern Gulf of Alaska. Large concentrations of adult pollock aggregate each March in western Shelikof Strait (Figure 1). They spawn in early April, and by late April patches of larvae can usually be found southwest of the spawning area. Since eggs and larvae are mainly planktonic, transport to this location is largely determined by currents and diffusion. To explore the variability in currents, a three-dimensional, primitive equation, hydrodynamic model driven by winds and freshwater discharge has been tuned to this region [Hermann and Stabeno, this issue].
The purpose of this paper is to compare the simulations from the numerical model with observations. Since the transport of pollock eggs and larvae is most strongly influenced by currents in spring and summer, we focus on this time period. We begin with a comparison between eddies that have been observed in the Shelikof sea valley and those generated by the model. A detailed comparison of model simulations with observations from moored current meters (for 1989 and 1991) follows. Finally, we compare float trajectories generated by the model with those of drifting buoys deployed off Cape Kekurnoi.
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