Transport of surface waters from the Juan de Fuca eddy region to the Washington coast

A seasonal cold eddy located off the mouth of the Strait of Juan de Fuca has been implicated as an initiation site for toxic HABs affecting the Washington coast. To investigate the fate of eddy waters, a diagnostic finite element circulation model was developed for this region and the northern Washington shelf. The model was based on hydrographic data from several cruises in the summer of 1998, a year in which record levels of toxin were measured in razor clams at Washington beaches. Additional model forcing included tides and surface wind stress typical of fair weather/upwelling conditions or fall storms.The model showed strong retention in the eddy and a preferred southeastward trajectory for model drifters leaving the eddy. ARGOS-tracked drifters released in the vicinity of the eddy in the summers of 2001 through 2003 were consistent with model results generated with 1998 data demonstrating the robust nature of the large-scale currents in this region. Model and true drifter results show that the Juan de Fuca eddy is an important source region for PNW shelf waters. Furthermore, both model and true drifters moved onshore during storms suggesting that surface waters of the Juan de Fuca eddy can impact the Washington coast.