When the Lagoon was frozen over in Venice from A.D. 604 to 2012: evidence from written documentary sources, visual arts and instrumental readings

The paper reconstructs when the Lagoon of Venice, Italy, was frozen over in the last 1400 years. The paper combines various proxies and instrumental readings, i.e.: written documentary sources since the origin of Venice; evidence from visual arts referring to 1709, 1789 and 1791 as well as some pictures taken in 1929 and 2012; finally, instrumental observations since 1716. A critical revision has been made of all sources in order to reject duplications or exaggerations introduced by late compilations. To this aim the various dating styles, the social and historical context of the city of Venice over time and the combined historical, statistical and climatological criteria necessary to validate data have been considered. The physics of ice formation, the influence of tides, the ice bearing capacity have been useful to interpret data. The passage from proxies to index and temperature in modern units is also discussed. The written sources provide basic information before the instrumental period and made possible a classification of winter severity. The visual arts provide a general view of what happened when the Lagoon was frozen over in the 18th century; in addition, they allow an estimate of the ice slab thickness. Visual arts, however, cannot be used for dating purposes. Finally, the instrumental readings are compared with the proxies in order to improve the interpretation of the above proxies. The result is a comprehensive, critically revised list of the harsh winters in Northern Italy and the meteorological situation responsible for their occurrence.