Low‐frequency sea level and current fluctuations along the coast of northwest Italy

Abstract

Two‐month long records of current, sea level, and wind stress, collected during April and May of 1977, are analyzed for locations in the shallow waters off the coast of northwest Italy. The mean current was directed along the coast towards the northwest with a strength of 5.0–6.0 cm s−1; this flow continued past the island of Elba, progressing from the Tyrrhenian Sea into the Ligurian Sea. Sea level fluctuations were coherent along the Ligurian coast of Italy and were mainly due to a wind‐induced setup caused by the semienclosed nature of the basin; only a fraction of the sea level disturbances in the Tyrrhenian Sea propagated into the Ligurian basin. There was low coherence between the nearshore current and sea level, suggesting that shelf waves may play only a minor role in the dynamics of the region. Instead, the relation between the wind stress, current, and the slope of the sea level suggested that the region displays characteristics similar to those of a semienclosed area. The alongshore currents were coherent with the wind at the 5‐day time scale; this agrees with the period of cyclone activity in the area and suggests that the shelf waters respond coherently when the wind field is spatially well organized during cyclogenesis. Consequently, an adequate hydrodynamic model of the region would need to couple both the atmospheric and the coastal responses.