EGU21-4090, updated on 12 Jan 2022
https://doi.org/10.5194/egusphere-egu21-4090
EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Climatology and process-oriented analysis of the Adriatic sea-level extremes

Jadranka Sepic1, Mira Pasaric2, Iva Medugorac2, Ivica Vilibic3, Maja Karlovic4, and Marko Mlinar4
Jadranka Sepic et al.
  • 1Faculty of Science, University of Split, Split, Croatia (jsepic@pmfst.hr)
  • 2Department of Geophysics, Faculty of Science, University of Zagreb, Zagreb, Croatia
  • 3Institute of Oceanography and Fisheries, Split, Croatia
  • 4Hydrographic Institute of the Republic of Croatia, Split, Croatia

The northern and the eastern coast of the Adriatic Sea are occasionally affected by extreme sea-levels known to cause substantial material damage. These extremes appear due to the superposition of several ocean processes that occur at different periods, have different spatial extents, and are caused by distinct forcing mechanisms.

To better understand the extremes, hourly sea-level time series from six tide-gauge stations located along the northern and the eastern Adriatic coast (Venice, Trieste, Rovinj, Bakar, Split, Dubrovnik) were collected for the period of 1956 to 2015 (1984 to 2015 for Venice) and analysed. The time series have been checked for spurious data, and then decomposed using tidal analysis and filtering procedures. The following time series were thus obtained for each station: (1) trend; (2) seasonal signal; (3) tides; (4-7) sea-level oscillations at periods: (4) longer than 100 days, (5) from 10 to 100 days, (6) from 6 hours to 10 days, and (7) shorter than 6 hours. These bands correspond, respectively, to sea-level fluctuations dominantly forced by (but not restricted to): (1) climate change and land uplift and sinking; (2) seasonal changes; (3) tidal forcing; (4); quasi-stationary atmospheric and ocean circulation and climate variability patterns; (5) planetary atmospheric waves; (6) synoptic atmospheric processes; and (7) mesoscale atmospheric processes.

Positive sea-level extremes surpassing 99.95 and 99.99 percentile values, and negative sea-level extremes lower than 0.05 and 0.01 percentile values were extracted from the original time series for each station. It was shown that positive (negative) extremes are up to 50-100% higher (lower) in the northern than in the south-eastern Adriatic. Then, station-based distributions, return periods, seasonal distributions, event durations, and trends were estimated and assessed. It was shown that the northern Adriatic positive sea-level extremes are dominantly caused by synoptic atmospheric processes superimposed to positive tide (contributing jointly to ~70% of total extreme height), whereas more to the south-east, positive extremes are caused by planetary atmospheric waves, synoptic atmospheric processes, and tides (each contributing with an average of ~25%). As for the negative sea-level extremes, these are due to a combination of planetary atmospheric waves and tides: in the northern Adriatic tide provides the largest contribution (~60%) while in the south-eastern Adriatic the two processes are of similar impact (each contributing with an average of ~30%). The simultaneity of the events along the entire northern and eastern Adriatic coast was studied as well, revealing that positive extremes are strongly regional dependant, i.e. that they usually appear simultaneously only along one part of the coast, whereas negative extremes are more likely to appear along the entire coast at the same time.

Finally, it is suggested that the distribution of sea-level extremes along the south-eastern Adriatic coast can be explained as a superposition of tidal forcing and prevailing atmospheric processes, whereas for the northern Adriatic, strong topographic enhancement of sea-level extremes is also important.

How to cite: Sepic, J., Pasaric, M., Medugorac, I., Vilibic, I., Karlovic, M., and Mlinar, M.: Climatology and process-oriented analysis of the Adriatic sea-level extremes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4090, https://doi.org/10.5194/egusphere-egu21-4090, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.