David Camuffo, a climate expert who led the study presented Thursday, said that by scrutinizing the paintings and comparing them with the same sites in present-day Venice, scientists found that the city has sunk more than 2 feet since 1727.
"I thought the city's descent might be a relatively recent phenomenon" until Canaletto's works were analyzed, Camuffo said.
But he concluded Venice has been sinking steadily for at least three centuries at a rate of about 8 inches a century.
The scientists turned to Canaletto because precise measurements of the city's sea level only date to 1872, while the artist's works are from the previous century.
Camuffo said Canaletto, whose birth name was Giovanni Antonio Canal (1697-1768), was so true to detail he even painted the dark algae stains on buildings along canal banks, a detail many artists avoided for aesthetic reasons.
"Suddenly I realized we could use this detail to determine the sea level at the time," Camuffo said from his office at the Institute of Atmosphere and Climate Sciences and Climate, in Padua, a day before the study was presented in nearby Venice.
"Nobody knows how high the tide was when Canaletto was working, but we do know the algae on the buildings always occupy the average level reached by high tide where dry and wet spells alternate."
The study analyzed eight paintings by Canaletto and three by his nephew Bernardo Bellotto (1720-1780), who imitated his uncle's style.
Both artists used a "camera obscura," a technique to help them make their work more realistic.
Through the light projected by a lens on a white canvas, Canaletto captured such images as the Bucintoro, the flagship of the Venetian fleet, cruising in front of St. Mark's Square and the gondolas peacefully navigating the Grand Canal.
The experts found one hopeful sign: Venice appears to be sinking more slowly in the last few years, although the reason remains a mystery.
Experts believe both nature and man have caused Venice's descent into the Adriatic. Sea levels are rising worldwide and Venice is sinking because water has been extracted from the subsoil for industrial purposes.