CAREER: Lagrangian investigation of upper ocean turbulence

University Of Delaware, Newark DE

Investigators

Abstract

Turbulent processes in the upper ocean play a key role in weather and climate systems by coupling the ocean and atmosphere. Upper ocean turbulence also distributes nutrients, pollutants, plankton, and bubbles in the ocean mixed layer. The fate of chemical and biological substances in the mixed layer depends on the history of advective turbulent fluid paths. Besides being dispersive, ocean turbulence also aggregates substances to increase encounter rates between them. Upper ocean turbulence is driven by surface waves: Wave-current interactions lead to wind-aligned vortices, called Langmuir circulation (LC), and breaking waves are a source of near surface turbulent kinetic energy. Together, LC and the stochastically breaking wave field lead to complicated nonlocal and intermittent transport. To better understand the dynamics of the complex oceanic boundary layer and to educate students about upper ocean processes, the PI will carry out an interwoven research and education program. This project is a systematic Lagrangian investigation following trajectories of fluid parcels with the Research Objectives to: 1) Develop a Lagrangian analysis framework of the upper ocean with realistic surface wave effects to investigate fundamental mechanisms of fluid exchange in the presence of surface waves, 2) Examine the role of LC and breaking waves in upper ocean transport to assess systematically the accuracy of common upper ocean boundary layer parameterizations, 3) Apply the Lagrangian analysis to quantify plastic marine debris that has emerged as a major ocean pollutant and to revisit related classic ideas of particle trapping in the upper ocean. Tracks of particles will be computed from state-of-the art upper ocean large eddy simulation models with LC and breaking wave effects. As part of the Lagrangian analysis, this project will apply a new and integrative dynamic systems approach to the wave-driven upper ocean boundary layer. To directly utilize knowledge gained from this study, the PI will examine observed distributions of plastic marine debris. The project involves two related education activities that are linked to the research activities on upper ocean dynamics with the Education Objectives to: 1) Educate students about ocean physics and its role in climate change and global pollution, 2) Inspire students to pursue STEM education and careers by engaging students in problem-based learning and implementing Next Generation Science Standards, 3) Involve underrepresented students. The first educational activity will involve the PI's participation in the active education programs on marine debris at the Sea Education Association, reaching out to undergraduate students and the general public. The second education activity is centered on developing a hands-on laboratory educational unit, which will be incorporated into regular curricula of high schools with a large number of underrepresented students and also into the University of Delaware's Forum to Advance Minorities in Engineering Program, which is aimed at increasing the effective participation of minority students in engineering and other science professions. Both activities incorporate the PI's expertise in geophysical fluids dynamics, upper ocean physics, and ongoing research collaborations. Intellectual Merit: By revealing regions of attraction, repulsion, and intense mixing, the Lagrangian framework provides a natural approach to investigating turbulence that has yet to be systematically explored in the context of wave-driven upper ocean dynamics. Thus, the study bears high potential to uncover a novel, highly physical description of upper ocean turbulence that will ultimately enhance the parameterizations of turbulent transport in larger scale ocean models. Broader Impacts: The PI will advance coupled ocean-atmosphere models of weather and climate by improving the ability to parameterize air-sea fluxes and ocean turbulence. The research will facilitate communication between the ocean physics and marine debris research communities, a necessary step in effectively quantifying and ultimately managing ocean pollution. Because the topic of marine pollution is accessible to a broad audience, the project activities present a unique opportunity to educate the general public, high school minority students, undergraduate students, and graduate students about ocean turbulence and fluid dynamics in a collaborative environment with experts in upper ocean dynamics, numerical modeling, dynamic systems theory, and sea-going oceanography.