SPEM Modeling of Shelikof Strait

Viewing the Animations:

  • Click on a YEAR in the left panel to animate of the salinity and velocity fields at 40m.
  • Use the "STOP" button in the browser menu to halt.
  • Click the YEAR again to repeat from the beginning.
  • To replace an animated image with this informational text click the Information item in the menu to the left.

Background

The Shelikof Strait region of the northern Gulf of Alaska is an important spawning ground for Walleye Pollock. The role of the physical environment in determining the productivity has been studied there since the early 1980s by FOCI (Fisheries-Oceanography Coordinated Investigations).

The circulation in the vicinity of Shelikof Strait was modeled using SPEM. This Sigma-coordinate Primitive Equation Model solves the equations of motion, driven by the winds and coastal runoff. Realistic wind forcing fields are derived from FNOC surface pressure analyses with ageostrophic adjustment in the region of the Strait (Stabeno et al., 1995). Coastal runoff time series were provided by Thomas C. Royer. The results presented here show the evolution of circulation (the scale arrow in the lower left is in units of m/s) and salinity (in psu) at 40 meters from March to September in each year from 1978 to 1999.

References

Hermann, A.J. and P.J. Stabeno 1996 J. Geophys. Res. 101(C1): 1129-1149. An eddy-resolving model of circulation on the western Gulf of Alaska Shelf: 1. Model development and sensitivity analyses.
Hermann, A.J., S. Hinckley, B.A. Megrey, and P.J. Stabeno 1996 Fisheries Oceanogr., 5(Suppl. 1), 39-57. Interannual variability of the early life history of walleye pollock near Shelikof Strait as inferred from a spatially explicit, individual-based model.
Stabeno, P.J. and A.J. Hermann 1996 J. Geophys. Res. 101(C1): 1151-1161. An eddy-resolving model of circulation on the western Gulf of Alaska Shelf: 2. Comparison of results to oceanographic observations.
Stabeno, P.J., A.J. Hermann, N.A. Bond, and S.J. Bograd 1995 Modeling the impact of climate variability on the advection of larval walleye pollock (Theragra chalcogramma) in the Gulf of Alaska. In Climate Change and Northern Fish Populations, R.J. Beamish (ed.), Can. Spec. Publ. Fish. Aquat. Sci., 121, 719-727.

Acknowledgements

This research was supported by NOAA's Fisheries Oceanography Coordinated Investigations. Al Hermann and Mick Spillane are both supported by the Joint Institute for the Study of the Atmosphere and Oceans (JISAO), under cooperative agreement NA67RJ0155.

Disclaimer

The model has been calibrated for several years in which current meter and drogued drifter data were available. As in weather hindcasts, we trust the model to be "statistically correct", that is, a fair representation of mean conditions, the degree of variability, and the overall frequency and strength of eddies, but not their exact position or strength on a given day. This version of the model does not include large-scale interannual changes in the strength of the Alaska Gyre system; hence it can only reasonably account for changes in circulation due to local wind forcing and upstream runoff.

Larger-scale models, which include the larger-scale interannual dynamics, are currently in development by our group with GLOBEC support.

The animations are series of images created from the model output using Ferret and combined into an animated GIF using Whirlgif.

Updated 9/13/2002 by Mick Spillane.