Temperature and salinity variability on the eastern Newfoundland shelf: The annual harmonic

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Abstract A 36‐year time series from an oceanographic station, Sta. 27, located off St John's, Newfoundland, has been used to derive the amplitudes and phases of the annual harmonics of temperature and salinity at fixed depths from 0 to 175 m. The analysis has been also carried out for the Newfoundland and Labrador Shelf, divided into about 40 areas, using monthly mean values from the available literature. At the surface, temperature (salinity) amplitudes are about 5°C (0.5–1.0) decreasing to <1°C (0.1) at 150 m. The surface temperature (salinity) amplitude is generally lower (higher) in the north. The phase of the annual harmonic increases almost linearly with depth at least for the upper 75 m in most regions and to the bottom at Sta. 27. Surface temperature amplitudes are nearly in phase (±6 d) throughout the region. On the other hand, the surface salinities in the north generally lead those in the south. Simple kinematic models that incorporate vertical diffusion and horizontal advection are developed in order to interpret the observations. The results indicate that vertical mixing in the region could be parametrized by a diffusion coefficient of about 10−4 m2 s−1 and that horizontal currents of about 0.2 m s−1 (0.1 m s−1) are representative of the upper 50 m (50–100 m). Other processes such as the annual ice cycle and runoff from the land are identified as important.