Seasonal and interannual variability in the circulation of puget sound. Washington: a box model study

Abstract

ABSTRACT A prognostic, time-dependent box model of circulation in Puget Sound, Washington is used to study seasonal and interannual variations in residence times and interbasin transports. The model is capable of repro-ducing salinity variability in the Sound at seasonal timescales, and is shown to have hindcast skill at interannu-al timescales. Modelled transports vary as much between years as between seasons. The largest seasonal feature is a sharp transport drop in late autumn into the deep Main Basin of the Sound, which is shown to be caused by increased river flow into Whidbey Basin. The high degree of transport variability leads to large interannual dif-ferences in residence times; for instance, for Whidbey Basin the residence time varies from 33 to 44 days in the period between 1992 and 2001 and for southern Hood Canal it varies from 64 to 121 days. This indicates that residence time estimates based on a year or less of data may not yield representative values. A forcing sensitivi-ty study shows that in all basins except the South Sound, salinity variability in the Strait of Juan de Fuca accounts for more of the seasonal variability than river variability does. However, year-to-year variability in river dis-charge affects interannual variability in transports as much as the Strait of Juan de Fuca salinity does. The model demonstrates poorest skill in the basins most affected by the Strait of Juan de Fuca salinity, indicating that the sparse data available for the Strait may not provide adequate boundary conditions for the model. RÉSUMÉ [Traduit par la rédaction] Nous utilisons un modèle de prévision à boîte, fonction du temps, de l