Modeling seasonal to interannual ocean variability of coastal British Columbia

A regional circulation model is used to examine the ocean variability along the Pacific coast of Canada. The model domain extends from the Columbia River to the Alaska Panhandle and is applied to hindcast the period 1995-2008. An extensive model validation indicates that the modeled ocean varies realistically at the seasonal to interannual time scale, including the marked regional response to the 1997-1998 El Nino. The model is used to better understand the ocean response to direct forcing of wind and rivers over the model domain relative to variability outside of the study area. To do so, additional runs are conducted with and without river discharge and seasonal variability in wind stress as well as with and without interannual variability in lateral boundary conditions. It is shown that the seasonal variability of the coastal circulation, such as the reversal of the shelf-break current and summer intensification of the California undercurrent, is of mixed origin, with both remote and local forcing contributing importantly. On the other hand, the modeled strong oceanic anomalies associated with the 1997-1998 El Nino originate from anomalous conditions on the lateral boundaries, except for the locally forced surface warm anomalies.