Jennifer MacKinnon Jennifer MacKinnon has always loved physics because of its ability to explain how the world works in a basic way. As an undergraduate at Swarthmore College near Philadelphia, however, she felt that many fields of physics were getting too esoteric and unconnected to the real world. When she graduated in 1995, she was ready to switch to something more practical. Oceanography seemed like an exciting way to combine basic research with practical applications. She checked out the University of Washington, where she met Professor Michael Gregg of APL-UW. "He seemed really excited about the work he was doing," she recalls, "more so than a lot of other people." She asked him to be her advisor. He agreed. It was an auspicious match. "Jennifer proved to be a quick and eager student," Gregg notes, "doing very well in all her classes. She is stimulating and fun to work with." On her part, MacKinnon is finding oceanography even more exciting than she thought it would be. Now, when she sees different kinds of waves go by, she thinks, "Oh, I understand how that works." MacKinnon's first research cruise was in 1996, when she participated in the Coastal Mixing and Optics project, a large, interdisciplinary research program on the continental shelf off Martha's Vineyard in New England. The fall of 1997 found her on the other side of the continent, on a cruise to study mixing in Monterey Canyon, on the continental shelf south of San Francisco. In the fall of 1998, she traveled south of the equator to the shallow Banda Sea, an area of the Indonesian through-flow thought to be a region where water from the Pacific might be mixing with water from the Indian Ocean. MacKinnon's research, which is funded under a National Defense Science and Engineering Graduate fellowship, focuses on the small-scale processes that control mixing on continental shelves. Energy is pumped into the ocean by the winds and tides. In order to balance the energy budget, the energy that is added to the ocean must be offset by energy that is subtracted from the ocean. Much of this energy is dissipated through turbulent mixing. Turbulent mixing in the open ocean has been studied for many years. Now, research is turning to shallower areas such as the continental shelves, where mixing is complicated by tides, fronts, nonlinear waves (solibores), and strong boundary layers at the surface and bottom. Understanding mixing on the continental shelves is important not only because of its role in balancing the energy budget but also because of its effect on properties such as sediment transport, sound propagation, and biological productivity. Nutrients on the shelves are limited and must be replenished from deeper water. The rate at which nutrients are transported onto the shelves by turbulent mixing controls the rate at which phytoplankton can grow, which, in turn, controls how fast zooplankton can grow, which controls how many fish that feed on zooplankton the area can support, and so on up the food chain. After obtaining her M.S. in May 1999, MacKinnon was a participant in a special summer fellowship program at the Woods Hole Oceanographic Institution on mixing and stirring in fluids.