Expert on rogue waves and ocean tides
"Kids who are good at math often think of physics as something that’s unconnected with problems facing society. But studying the 'environmental physics' of the ocean, atmosphere, and renewable energy is one way of combining intellectual challenge with societal relevance. You really can combine your love of mathematics with doing something useful in the world."
Chris Garrett’s first university degree was in mathematics, which he now uses to study the dynamics of the ocean. He specializes in small-scale processes that stir and mix the ocean. These mixing processes have crucial effects on ocean circulation and climate. But like clouds in the atmosphere, they are too small to be treated directly in global computer models. Instead, small-scale processes have to be represented with formulae that come only from understanding their physics.
“Many motions are driven by buoyancy forces, subtly complicated by the competing influences of heat and salt,” wrote Garrett in chapter 10 of Perspectives in Fluid Dynamics, a Cambridge University Press monograph. “This competition manifests itself in powerful ways on the large scale of the global ocean circulation and may be associated with climate variability. On the small scale it gives rise to surprising ‘double-diffusive’ effects associated with the different diffusion rates of heat and salt.”
The ocean and atmosphere form a coupled system, fluid and dynamic. Each profoundly influences the other as they exchange momentum, heat, and water. Garrett has studied these exchanges in the context of various semi-enclosed seas, such as the Mediterranean, which are subject to rapid change and can be used as test basins for physical oceanographic questions that are relevant to the entire globe.
He also studies the dynamics and statistics of “rogue” waves that are often blamed for loss of ships at sea, or for people being swept off the shore. His examination of iceberg trajectories provided valuable information on ocean eddies as well as a predictive scheme for the offshore oil industry.
Garrett's work on the basic physics of ocean tides led to the examination of power generation potential from both tidal elevation and tidal currents. In both situations, extracting more than a small amount of power can have significant effects on the tides themselves and hence on local ecology. When giving talks on tidal power, Garrett ends his presentations with a picture of the Candu nuclear reactor at Point Lepreau on the Bay of Fundy and suggests that “maybe the best use of cold, strong tidal currents in power generation is to provide cooling water for nuclear reactors.” Garrett is also cautious about using ocean waves for large amounts of power. Generating one gigawatt – enough power for a city of a million or so – would require the energy of the waves along about 100 kilometres of coastline, with major requirements for infrastructure and significant environmental impacts. “Things that sound really promising at first are often less ‘green’ if large scale use is contemplated,” he says, “though small-scale use of tidal and wave power in remote communities, for example, could be valuable.”
Garrett has been a member of many working groups of scientists and advisory boards at the local, national, or international level. One of his concerns is the use of the ocean for waste disposal. He has served as a member and chair of the Marine Monitoring Advisory Group for the Capital Regional District in Victoria, BC. Along with many other professional marine scientists, he has concluded that the environmental impact of the discharge of finely screened wastewater into the deep, vigorously mixed, waters of Juan de Fuca Strait is very small. Local businesses are regulated so that many pollutants no longer enter the wastewater. “Land-based secondary sewage treatment here is a low priority for marine environmental protection,” he says. “We would much rather have the money spent on things that really would benefit the environment.”
Throughout his career, Garrett has maintained contact and friendship with many of his former advisors, collaborators and students. To celebrate his 65th birthday in 2008, more than forty of his colleagues assembled near Victoria to present papers in a relaxed setting and discuss common scientific interests. Garrett retired in 2010 from the position of Lansdowne Professor of Ocean Physics (jointly with Physics & Astronomy departments at the University of Victoria) which he held since 1991. He is still involved in various projects and voluntary scientific advisory committees.
Profile written by Paula Johanson.