Current Measurements and Mathematical Modeling in Southern Puget Sound

Abstract

Field observations and mathematical modeling were conducted in order to understand the circulation patterns in Nisqually Reach, Southern Puget Sound. Eight continuously recording current meters at four sites and a two-dimensional finite element model were used. Analysis of the current data showed the currents to consist of a first principal component which was essentially parallel to the channel walls. This component was primarily tidal, although both high and low frequency content was apparent. The high frequency content was attributed to fairly small-scale turbulence. The low frequency currents exhibited fluctuations on the order of several days, with the power spectra showing a secondary peak at 2.5 days. These low frequency fluctuations are probably due to wind effects, occurring both locally and non-locally. Typical circulation patterns predicted by the mathematical model are presented. The model reasonably reproduces the tidal currents but not the high and low frequency content. Other limitations of the model are discussed in light of the analysis of the current meter data.