Hydrographic and transport variability on the Halifax section

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Abstract
Archived data and geostrophic computations are used to examine variability in hydrographic properties and along‐shelf transport on the Scotian Shelf, with focus on the Halifax section and a decadal‐scale hydrographic anomaly during the late 1950s and early/mid 1960s. The long‐term annual cycle shows strong seasonal variations in baroclinic transport on the inner shelf and at the shelf edge, and an associated steric change in adjusted sea level (ASL) at Halifax. Regional wind‐forcing and barotropic currents make smaller contributions to the annual cycle in ASL. In contrast, regional wind‐forcing contributes about 40% of the ASL variability for periods of 6–30 days. Hydrographic sections indicate that the 1950s/1960s anomaly arose from episodic extensions of Labrador Slope Water along the shelf edge followed by on‐shelf intrusions, primarily during the fall‐spring periods of 1958–1959 and 1963–1964. It ended with excursions of Warm Slope Water into the region in 1967–1968. An analysis of monthly temperature anomalies indicates that slope temperatures can account for 50% of the variance of deep shelf temperatures 3–6 months later. Correlations between the hydrographic and baroclinic transport variations indicate increased southwestward flow associated with lower temperatures and salinities, but no evidence was found for large local current events at the onset and termination times of the 1950s/1960s anomaly. Positive correlations between wind‐adjusted ASL and steric anomalies point to the potential for sea level being helpful in monitoring baroclinic transport variability.