Paola Rizzoli will never forget the day the floodwaters submerged the ground-floor apartment of her family’s Venice home. A high school student during the November 1966 flood, Rizzoli, dry but trapped on the third floor, watched from her terrace — and waited for two days — for the salty lagoon water to recede.
The “acqua alta,” or high water, finally did go down. But it has come back time and again, bubbling up through the drains in Piazza San Marco so often that long wooden tables to walk on are now a permanent fixture.
Rizzoli, professor of physical oceanography in the Department of Earth, Atmospheric and Planetary Sciences (EAPS), was inspired by the plight of her hometown to devote her professional life to understanding how and why coastal waters ebb and flow. The knowledge is not only critical for Venice, where Rizzoli is a member of a three-member team consulting on the design and construction of massive gates to hold storm surges at bay, but also for other regions from the Gulf of Maine to Singapore.
Her field is especially important in an age of climate change. “The climate problem is a prediction problem,” Rizzoli says. “We need to predict the different scenarios that may occur in 100 years, particularly the sea level rise in coastal regions. The ocean is critically important to make these predictions, being one of the least understood and observed components of the Earth’s system.”
Rizzoli has developed powerful models that use ocean data such as current, temperature and salinity — gathered from instruments mounted on moorings extending from the surface to the depths — plus weather and tide data. The models simulate, predict and verify the complex circulation patterns of the waters around bays and gulfs. In the case of Singapore bay, an artificial bay with a series of channels that interact with the open ocean and the South China Sea, these can be extremely complex, as well as extremely important for fishing fleets, port managers and others.
Rizzoli, recognized recently by the Italian government for her work on the latest report of the Intergovernmental Panel on Climate Change (IPCC) — which shared the 2007 Nobel Peace Prize with Al Gore — also studies ocean systems in the tropical and equatorial oceans controlled by the Intertropical Convergence Zone (ITCZ), where trade winds from the northern and southern hemispheres meet. Modes of variability in these ocean systems are strongly coupled with the atmosphere and can cause intense droughts or excessive rainfall on the surrounding land masses, such as Africa and Brazil. The climate of these regions can contribute to debilitating tropical diseases such as malaria and meningitis, which are very sensitive to the rhythms of variability in rainfall, temperature and humidity.
In collaboration with Changseng Chen at the University of Massachusetts at Dartmouth, Rizzoli has adapted her data assimilation packages, which insert data into modeling software, to the Finite Volume Coastal Ocean Model (FVCOM). These packages combine predicted fields of velocity, temperature, salinity — among others — with observations available from the region being studied, thus providing patterns of ocean circulation consistent with the model’s dynamics and the data. The researchers use the models to evaluate the effects of local conditions on sediment transport and nutrient dispersal.
As part of the Singapore-MIT Alliance, Rizzoli will be the only School of Science member of an interdisciplinary team. She will spend a semester in residence in spring 2009, helping with modeling simulations to determine the placement of future data-collection instruments and the trajectories of autonomous underwater vehicles designed by MIT ocean engineers that will collect more fine-tuned data than ever before possible.
After earning a degree in physics, Rizzoli was drawn to oceanography when Italy’s National Research Council created a laboratory to explore the flooding and sinking in Venice. At the time, no one knew why the floods kept occurring, destroying priceless pieces stored in museum basements, shutting down schools and businesses and adversely affecting tourism. For the last five years, Venice has been under water 120 days a year. “People are sick and tired of it,” she said.
Rizzoli said researchers now know that Venice is the victim of storm surges. An elaborate, $5 billion system of gates to be built in the three inlets connecting the lagoon with the open sea are expected to safeguard Venice from high waters. Expected to be operational by 2012, the system consists of mobile barriers that temporarily separate the lagoon from the Adriatic Sea. Gates are being constructed at the lagoon inlets of Lido, Malamocco and Chioggia, the three openings in the barrier island through which tides propagate. In normal tidal conditions, the gates’ caissons (a type of pontoon) are completely invisible. During high waters, the caissons fill with air and are raised up like fans to prevent the tide from entering.
Rizzoli is looking forward to a time when Venice is no longer threatened by acqua alta. But, taking no chances, Rizzoli’s Venice apartment, which she visits periodically, is not in the low-lying neighborhood where she grew up. Her apartment, with its spectacular views of the lagoon, is near the Arsenal, one of the highest points in the city.