Volume 11, Number 4, 2003
Ever since Fabrice Veron was a young boy growing up near the ocean in Bordeaux, France, he has been following a course that has ultimately led him to Delaware.
He first earned bachelor's and master's degrees in applied mathematics and mechanical engineering from the University of Bordeaux. With this background, he returned to his fascination with the ocean and completed a doctorate in oceanography from Scripps Institution of Oceanography at the University of California, San Diego.
Currently, as an assistant professor in the Physical Ocean Science and Engineering Program at the College of Marine Studies, he is dedicated to understanding the interactions that occur between the ocean and the atmosphere and their effect on global climate change.
Even on a calm day, there's a lot happening between the top few feet of the ocean and the bottom few feet of the atmosphere, Veron says. Mass is transferred from the ocean to the air in the form of salt, water droplets and gases; energy is transferred from the wind to the water in the form of waves and currents; and heat is exchanged through radiation and other processes.
Variations in the wind, waves and currents over time--even in just a few minutes--make it difficult to understand the dynamics of these interactions. Yet, at the Air-Sea Interaction Laboratory at UD, Veron is able to generate wind, waves and currents in a repeatable, controllable manner. By having the ability to control these conditions, he is able to evaluate the importance of individual variables.
The laboratory consists of a large flume or wave tank, approximately 140 feet long, 3 feet wide and 4 feet high, which holds 8,000 gallons of water. The tank is equipped with a programmable wave maker and a wind tunnel capable of generating winds with speeds of up to 56 feet per second. The temperature of the water and air also can be independently controlled and set from 41 to 104 degrees Fahrenheit.
One end of the tank is equipped with an artificial beach to dissipate wave energy and eliminate wave reflection. In addition, the wave tank is able to tilt, making it one of the most technologically advanced of its kind in the world. Tilting the tank enables Veron to create a flat water surface when currents or wind are generated and to determine the amount of drag that the wind creates.
"Even though air-sea interactions generally occur as small disturbances relative to the size of the ocean, they can have far-reaching effects," Veron says. "For example, over half the particles in the air are salt particles, with an even higher percentage in coastal areas.
"These particles have been suspended in the air from surface-breaking waves and bursting bubbles. Salt particles provide favorable locations for atmospheric water vapor to condense, thereby forming clouds in the lower atmosphere which have a large impact on global climate."
Veron studies the suspension of salt particles by creating waves of varying speeds and heights in the wave tank. He then uses multiple techniques to measure and count the number of particles that are ejected as water droplets into the atmosphere. By comparing the size and number of droplets that are ejected with the types of waves that are generated, he can determine which factors are important in the suspension process.
In related climate research, Veron is analyzing the effect that turbulence has on the exchange of carbon dioxide and other gases between the atmosphere and the water. The presence of carbon dioxide and other gases in the atmosphere is associated with global warming through what is known as the "greenhouse effect." When waves break at the surface and trap bubbles, there is the potential for more carbon dioxide to be dissolved in the water.
"This is exactly why you stir your coffee in the morning as opposed to letting the sugar that falls to the bottom dissolve on its own. The stirring action helps dissolve sugar faster in your cup of coffee," he notes. "If the water is not turbulent, there is no mixing taking place, and the surface water becomes saturated with carbon dioxide.
"The sea surface also plays an important role in the global heat budget; the upper few feet of the ocean contain as much heat as the entire atmosphere. If the water and air are calm, the heat exchange is very slow. Once the water becomes turbulent, however, heat can be rapidly released from the water into the atmosphere and vice versa."
By measuring the turbulence of the water and the air above the water, Veron can obtain data critical to understanding how heat is exchanged between the atmosphere and the ocean.
Veron also notes that water droplets can transfer large amounts of heat from the ocean to the air when sea spray is generated. This is thought to be an important mechanism through which storms and hurricanes get a significant amount of energy. The wave tank can also be used to study how turbulence and waves interact. Veron can control wind speed, and even before waves can be seen by the naked eye, an instrument can detect very small oscillations of the water surface, indicating that waves are being formed.
In addition to global effects, small-scale interactions between the air and sea can have a significant impact at the local level. In coastal areas, wind and breaking waves generate surface currents. According to Veron, these currents can directly affect the dispersion of floating pollutants, such as oil or industrial surfactants.
Surface currents also are important to sediment transport, which is partly responsible for changes in the coastline. Currently, in a project funded by Sea Grant, Veron is studying how breaking waves affect sediment transport in the surf zone. By adding sediment to the beach in the wave tank, Veron can create a physical model of the seafloor. He can then observe how particles are suspended and transported by waves.
In addition to conducting such cutting-edge research, Veron applies his fascination with waves to the medium of sound. Having studied classical piano since the age of 5, he recorded and produced his second CD last year. And, several years ago, he wrote and recorded the music to a documentary that aired on the Discovery Channel.
--Kari Gulbrandsen