Recent evolution of sea-level extremes at Trieste (Northern Adriatic)

The evolution of sea-level extremes at Trieste (Northern Adriatic) is analysed for the 1939–2001 period by studying the occurrence of positive and negative surges and positive and negative anomalies of observed sea level. Marked interannual and multiannual fluctuations are recognized, which can be related to the observed changes in the atmospheric pressure and wind regimes that affected the Adriatic region in the period of interest. Over the period under study, weak and moderate surges of both signs do not exhibit a clear trend, while the frequency of both strong positive and negative surges tends to decrease. Weak and moderate positive sea-level anomalies become more frequent, while all negative anomalies tend to exhibit a negative trend, because of the superposition of the general mean sea-level rise on the surge evolution. One consequence is that the frequency of strong positive anomalies, among which flood events, appears to be almost stable. The role of the anomalous behaviour of sea-level extremes observed in the winters 1989–1993, as a consequence of persisting atmospheric pressure anomalies, is also investigated.