engleski

Precise Determination of Relative Mean Sea Level Trends at Tide Gauges in Adriatic

Relative mean sea level trends for nine tide gauges in Adriatic have been determined with high precision using common mean sea level variability. Respective tide gauges are Venezia – Punta Della Salute and Trieste in Italy ; Koper in Slovenia ; Rovinj, Bakar, Split – Rt Marjana, Split – Harbour and Dubrovnik in Croatia and Bar in Montenegro. Annual and inter-annual sea level changes, which are driven by climate variations, make it difficult to calculate precisely the sea level trends. Averaging over a year removes seasonal changes. However, systematic effects from changes of meteorological parameters and associated ocean circulation that last for longer than a year are maintained, as well as long-periodic tidal effects. One can assume that such inter-annual changes are very similar for close sites, especially in closed seas such as Adriatic. Accordingly, common interannual variation of sea level can be determined for all nine tide gauges in question from annual means, under assumption that residual variations for each site are close to random. Such approach makes it possible to separate before mentioned systematic effects from eustatic rise of global sea level and effects of regional and local vertical land movements. However, to separate two latter effects reliable vertical land movement from several decades of GPS measurements are needed. Through common adjustment of nine tide gauge time series of annual means from PSMSL, common mean sea level variability as well as relative mean sea level trends and mean sea level for each tide gauge have been determined. For 50-year period relative trends have been determined with standard deviations from 0.1 to 0.3 mm/yr (later is for datagauges with shorter records). Values of annual common mean sea level variability are determined with standard deviations of less than 4 mm. Once when GPS record reach required length for precise determination of vertical land movement with respect to the ellipsoid, from such precise relative trends, reliable absolute mean sea level trends could be determined.

relative MSL trends; sea level variation; tide gauges

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