Seasonal and Interannual Variability of Current, Temperature and Salinity off Southwest Nova Scotia

Strong annual signals are found in temperature, salinity, and current measurements at two sites off Cape Sable, Nova Scotia. Differences in means and annual cycles indicate that the along-isobath current is not controlled by wind stress at these time scales. The phase of the primary peak of freshwater runoff into the Gulf of St. Lawrence (RIVSUM) is consistent with the advection of a salinity minimum to Cape Sable at an average speed of 6 km∙d−1, but the secondary peak is not observed and may be masked by the seasonal inflow of slope water into the Gulf of Maine via Northeast Channel. A diffusive model, forced by air–sea interaction, provides a reasonable fit to the annual temperature cycles with vertical diffusivities of 15–50 × 10−4 m2∙s−1. Correlations between residual longshore wind stress and along-isobath current, deep salinity, and temperature are consistent with wind-driven upwelling. Furthermore, warm-core rings in the slope water sometimes enhance onshore heat and salt fluxes to create positive temperature and salinity anomalies off Cape Sable, especially in late summer. February ocean temperature anomalies to 50 m are related to winter-average cross-shore wind (and related heat flux residuals), but do not persist on seasonal time scales.