Sea Level Variations in Shelf Waters off the Coast of British Columbia: From Subsynoptic to Interannual Time Scales

Abstract Sea level variations beyond monthly time scales in the northeast Pacific are analyzed using simulation results of a high-resolution regional model, tide gauge and altimeter observations, and surface winds. Along a zonal section extending westward from the Tofino tide gauge on Vancouver Island, sea level variations are mostly accounted for by steric height. On the shelf, the sea level variations are dominated by salinity in the lower half of the water column, with the seasonal maxima occurring in winter caused by the wind-driven downwelling. In the deep ocean, the variations are dominated by temperature in the upper layer up to 50–60-m depth, with a maximum in the summer. In between, the sea levels show a minimum seasonal amplitude over the continental slope because this is the inflection point between the out-of-the-phase variations on the shelf and in the deep ocean. The deseasonalized anomalies of the halosteric and thermosteric heights at Tofino are coherent at time scales of less than 20 months. At time scales less than 5 months, both are correlated with winds over a midlatitude zone extending from the coast to offshore, and at time scale of 5–20 months, both are correlated with the winds in the same midlatitude band and with winds in the equatorial Pacific Ocean.