Contribution of high-frequency (T < 2 h) sea level oscillations to the Adriatic sea level maxima
Krešimir Ruić, Jadranka Šepić, Marko Mlinar, Iva Međugorac
Abstract
Abstract Sea level time series of up to 17.5 years length, recorded with a 1 min sampling interval at 18 tide gauges, evenly distributed along the eastern and western coast of the Adriatic Sea (Mediterranean), were analysed in order to quantify contribution of high-frequency sea level oscillations to the positive sea level extremes of the Adriatic Sea. Two types of sea level extremes were defined and identified: (1) residual extremes which are mostly related to storm surges and (2) high-frequency ( T < 2 h) extremes, strongest of which are meteotsunamis. The detailed analysis of extremes led to the following conclusions: (1) high-frequency sea level oscillations can dominate positive sea level extremes; (2) even when not dominating them, high-frequency oscillations can considerably contribute to extreme sea levels; (3) contribution of high-frequency oscillations to total signal is governed by a combination of bathymetry and atmospheric forcing, resulting in the strongest high-frequency oscillations over the middle Adriatic; (4) residual extremes mostly happen from October to January when they are also the strongest, while high-frequency extremes spread more evenly throughout the year, with the strongest events peaking during May to September; (5) tide gauge stations can be divided into three distinct groups depending on the characteristics of high-frequency oscillations which they record. Conclusively, both low-frequency and high-frequency sea level components must be considered when assessing hazards related to sea level extremes, implying that availability and analysis of 1 min sea level data are a must.