Collaborative Research: Lee Waves and Turbulence Forced by the Kuroshio

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Roughly 1 TW is input into the ocean circulation by wind-work. How this balanced energy is dissipated to maintain steady state remains uncertain but is important for correctly modeling balanced energy pathways in ocean general circulation models. Loss to lee-wave generation followed by turbulence production has been hypothesized to account for 20-75 percent. The research will clarify lee-wave generation and the waves' role in dissipating vs. redistributing balanced energy. Results from this project will be presented at conferences and published in peer-reviewed journals to make them available to the wider scientific community. Data will be archived at public sites at University of Washington (UW) Applied Physics Laboratory (APL) and Northwest Research Associates. An improved model parameterization for the dissipation and redistribution of balanced flows and induced mixing by lee-wave generation is an expected outcome. The project will support a postdoctoral researcher in data analysis and internal-wave physics. Seattle K-12 classroom visits and active engagement with UW and local science centers is planned. The project will also contribute to the summer program for UW undergraduate students and the annual Pacific Science Center Polar Science Weekend.Lee-wave generation (0.2-0.75 TW) and bottom drag (~0.25 TW) are two hypothesized sinks. The passage of the Kuroshio through Tokara Strait affords an accessible case to evaluate lee-wave generation and dissipation that impact a major western boundary current. It has been assumed that lee-wave generation is lost to turbulence. However, measurements in Antarctic Circumpolar Current jets find that turbulent dissipation rates fall short of predictions by as much as an order of magnitude. Measurements will be made to study internal lee-wave generation and evolution, hydraulic jumps, turbulence and water-mass transformation where the Kuroshio crosses a seamount chain in Tokara Strait. Line-arrays of chi-augmented EMAPEX profiling floats will be deployed at across-stream locations upstream of the seamount chain to be swept across by the Kuroshio, obtaining along-stream/depth sections from the surface to the bottom ( 600 m depth), and from up- to downstream of the shoal topography with a focus on the flow structure and turbulence in the lee. These measurements will address whether lee-wave generation and bottom drag represent major sinks for balanced flows. These measurements will offer a more complete assessment of lee-wave generation and the fate of lee waves than has hitherto been performed.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.