Stochastic Modeling of Short Term Variations of Sea Level in Eastern Canada
Hourly sea level records from three stations in eastern Canada (Québec-Lauzon, Harrington-Harbour and Halifax) are analyzed both in frequency domain from 1970 to 1979 and in time domain during 1973. At the three stations, the deterministic model explains 90 to 96% of the total variability of sea level. The semidiurnal and diurnal tides contribute largely to its variations. The residual series, less than 10% of the initial variations of sea level, contain irregular values including extreme values of seiches and storm surges. Such random variations are analyzed and modeled following the method described by Box and Jenkins (1976). The long period variations (2 to 30 days) can be attributed to meteorological forcing (atmospheric pressure and winds). The short period variations (some hours to one day) can be attributed to longitudinal seiches, semidiurnal and diurnal atmospheric tides, and inertial oscillations. The water discharge from the St. Lawrence River contributes 29% of the monthly residual sea level at Québec-Lauzon. The atmospheric pressure and winds contribute respectively 8.1% and 8.9% at this station. They contribute 52.1% and 7.7% at Harrington-Harbour and 41.8% and 14.3% at Halifax. The regression coefficients of residual sea level on atmospheric pressure are respectively estimated to be -1.507 cm (hPa)-¹ (± 0.345 cm (hPa)-¹), 0.776 cm (hPa)-¹ (± 0.112 cm (hPa)-¹) and 0.825 cm (hPa)-¹ (± 0.008 cm (hPa) -¹) at the three stations. Compared to the coefficient of the inverted barometer, estimated to be -1 cm (hPa)-¹, the effect of the atmospheric pressure on sea level variations seems to be amplified at Québec-Lauzon by the wind effects (and water discharge) while it is reduced at Harrington-Harbour and Halifax.
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Document Type: Research Article
Affiliations: 1: Département d'Océanographie et d'Aquaculture, Institut National de Recherche Halieutique, Casablanca, Maroc 2: Baird and Associates, Ottawa, Ontario, Canada
Publication date: July 1, 2000