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Kim Martini's academic career took a turn when she realized she preferred travel and field research to experiments at the laboratory bench. After having earned undergraduate degrees in fine arts and physics, and then a master's degree in physics at the State University of New York at Albany, Kim came to the University of Washington to begin the Ph.D. program in oceanography. "Physical oceanography was the logical choice for me, as I already had a love of the ocean having grown up in a sailing family." Over the past four years she has participated in research cruises all over the world with her advisor, Oceanographer and Affiliate Assistant Professor Matthew Alford.
One field experiment centered on Mamala Bay, Oahu, Hawaii, where the research team observed standing internal waves and enhanced mixing. Internal waves, similar to waves on the surface, occur at the interface between fluids of differing densities, but because the density differences in stratified seawater are much smaller those between water and air, internal waves can have much larger amplitudes, achieving wave heights up to several hundred meters. Like their surface counterparts, internal waves can also shoal onshore, break, and even form standing waves.
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Standing internal waves are caused by the superposition of two free internal waves traveling in opposite directions along the same axis. Kim describes the dynamics observed in Mamala Bay: "An eastbound wave from Kaena Ridge and a westbound wave that originates from Makapuu Point combine to create a standing wave. When averaged over a wave period, standing waves have kinetic and potential energy peaks. These kinetic and potential energy peaks occur at the headlands and the center, respectively, of Mamala Bay. The potential energy peak in the bay center creates vertical displacements over 100 m in water only 500 m deep, which may promote the enhanced mixing measured there." Kim's analysis of the standing internal waves in Mamala Bay was the subject of her master's thesis in oceanography and has also been published as a paper in Geophysical Research Letters.
During a 45-day cruise off the Oregon coast, further questions of internal wave propagation and turbulent mixing were explored. Moorings were placed on the Oregon continental slope to measure whether the semidiurnal internal wave signal detected there is due to the local baroclinic tide, or the onshore shoaling of internal waves generated elsewhere in the Pacific. Alford made Kim an important part of the mooring deployment team, giving her the responsibility of programming, preparing, and recovering the 20+ instruments on each mooring. All were equipped with a profiler that obtains full-depth profiles of velocity, conductivity, temperature, and pressure every three hours using a small motorized wheel to crawl up and down the mooring wire. With the velocities and calculated vertical displacements, the semidiurnal baroclinic internal wave signal was extracted and used to determine the direction and modal content of the internal wave field across the continental slope. "Early analysis suggests that the semidiurnal baroclinic internal waves interact with 'rough' bathymetry on the slope creating near-bottom patches of strong turbulence or 'hotspots', instead of weakly dissipating over a broader area," notes Kim.
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