Abstract. The City of Venice and the surrounding lagoonal ecosystem are highly vulnerable to variations in relative sea level. In the past ~150 years, this was characterized by a secular linear trend of about 2.5 mm/year resulting from the combined contributions of vertical land movement and sea-level rise. This literature review reassesses and synthesizes the progress achieved in understanding, estimating and predicting the individual contributions to local relative sea level, with focus on the most recent publications. The current best estimate of historical sea-level rise in Venice, based on tide-gauge data after removal of subsidence effects, is 1.23 ± 0.13 mm/year (period from 1872 to 2019). Subsidence thus contributed to about half of the observed relative sea-level rise over the same period. A higher – yet more uncertain – rate of sea-level rise is observed during recent decades, estimated from tide-gauge data to be about 2.76 ± 1.75 mm/year in the period 1993–2019 for the climatic component alone. An unresolved issue is the contrast between the observational capacity of tide gauges and satellite altimetry, with the latter tool not covering the Venice Lagoon. Water mass exchanges through the Gibraltar Strait currently constitute a source of substantial uncertainty for estimating future deviations of the Mediterranean mean sea-level trend from the global-mean value. Subsidence and regional atmospheric and oceanic circulation mechanisms can deviate Venetian relative sea-level trends from the global mean values for several decades. Regional processes will likely continue to determine significant interannual and interdecadal variability of Venetian sea level with magnitude comparable to that observed in the past, as well as non-negligible differential trends. Our estimate of the likely range of mean sea-level rise in Venice by 2100 due to climate change is presently estimated between 11 and 110 centimetres. An improbable yet possible high-end scenario linked to strong ice-sheet melting yields about 170 centimetres of mean sea-level rise in Venice by 2100. Projections of natural and human induced vertical land motions are currently not available, but historical evidence demonstrates that they can produce a significant contribution to the relative sea-level rise in Venice, further increasing the hazard posed by climatically-induced sea-level changes.
Empirical Modeling and Impact of Transient Effects on the Mean Sea Level Trend Estimates from the Global Tide Gauge Data