Relation between daily variations in sea level and meteorological forcing in Sancti Petri Channel (SW Spain)

Abstract

Sea level series were recorded from October 2006 to January 2007 at two different sites in a shallow-water estuary of SW Spain. Results showed a very significant temporal variability in daily sea level. Moreover, 85% of the variance was explained by atmospheric pressure variability, obtaining a relation between sea level and atmospheric pressure of around –2 cm hPa–1. A more detailed study showed the existence of two different types of oscillations in daily sea level: the first, with periods of 10 days, was related to the inverted barometer (IB) effect associated with synoptic-scale atmospheric pressure oscillations (IB factor of around 1.4 ± 0.1 cm hPa–1), and the second, with periods of more than 10 days, was related to pressure changes in the planetaryscale atmospheric waves. Even though the high barometric behaviour of the 10-day period was partially related to the local winds, the shallowness of the study area invalidated the assumption of a static IB effect (–1 cm hPa–1). Rather, it was the dynamic IB effect that explained the displacement of the IB factor relative to the static assumption.

Keywords

• inverted barometer effect
• long-period sea level oscillations
• shallow waters