Yesterday (Nov, 13) was of course full moon, but there are 12 or 13 of them every year. It was nowhere near perigee (Nov. 23), in fact a bit closer to apogee (Nov. 7). So why were the tides so high in Venice? And why only Venice or was this a world wide phenomenon?
Perfect storm, so to speak, is what I read. Basically, high spring tide as you indicated, plus a storm surge caused by a north-east storm in the Adriatic and high winds. Just bad luck. Plus global sea levels are rising, but this was mainly just a combination of factors due to weather and tide. Oh, and Venice is sinking as well, which probably contributed some…
It appears that the core issue is storm surge, exacerbated by the high tide:
(bolding mine)
…Curses! Ninja’d again!
Sea height is influenced by a lot of things. The tidal influence of the moon and sun are clearly important, but so are things like wind direction and speed, and resonance effects / sloshing modes of nearby water bodies.
Extreme weather (e.g., a hurricane) can increase sea height on the US coast by 15+ feet, so a few extra inches isn’t a stretch under more normal conditions.
Here’s a list of the highest tides in Venice since 1923. So not quite a hundred years ago. 3 of those occured before 1966 (the previous record holder and close-ish to the midpoint of the time span). 16 afterwards with 11 since 2000. (I guess the 1968 one is closer to the midpoint. So like a 5-15 split.)
The banning of artesian wells in the 60s helped slow down subsidence. But still a lot more recent peaks than before. Sea level rise in general isn’t helping.
Note that some years appear more than once. Like 2019 and 1979. That suggests overall persistent weather patterns play a role. A high or low gets stuck somewhere and winds start to push water for a long period of time. Sort of like El Nino.
A look at a map shows you part of the problem. Venice is located near the end of the Adriatic Sea, which is a long narrow inlet of the Mediterranean aligned roughly SE-NW. If you get strong winds from the southeast, they push a load of extra water up the Adriatic right towards Venice. The same effect, but with winds from the opposite quarter, can lead to disastrous storm surges on the North Sea coasts of the UK and Netherlands, as in 1953.
Low pressure exacerbates the problem, as lower atmospheric pressure raises the local sea level slightly too.
The news reports (NPR has one) relate that the houses were shaking and shutters slamming, so this was an excessively high wind - so as mentioned above, the “perfect” storm. the Adriatic is long and narrow, so it magnifies the effect of a wind from the south. Another point was that the wooden bench walkways they usually put out so people could walk above the tide in St Mark’s Square - most washed away.
To restate - the problem was that starting around 1900, mainland Mestre began sucking a lot of groundwater out of wells near Venice. This had the effect of causing the ground to subside and Venice to sink. The problem is not so much climate change, as poor control of groundwater use. Since they stopped this practice (170’s) Venice has stopped sinking - but not necessarily rebounding.