Collaborative Research: Study of Convectively-Breaking Internal Solitary Waves of Depression: High Accuracy/Resolution Modeling and Observational Data Analysis

GSTDTAP

项目编号	1634182
	Collaborative Research: Study of Convectively-Breaking Internal Solitary Waves of Depression: High Accuracy/Resolution Modeling and Observational Data Analysis
	Ren-Chieh Lien
主持机构	University of Washington
项目开始年	2016
	2016-09-01
项目结束日期	2019-08-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	229684(USD)
国家	美国
语种	英语
英文摘要	Internal solitary waves (ISWs) are ubiquitous oceanic phenomena found on continental slopes and shelves, in submarine canyons, and over oceanic topographic features. They can carry energy over long distances while maintaining their shapes, are efficient suppliers of nutrients into the upper ocean, and can impact primary production and marine ecology through the exchange of heat, salt, nutrient, and water masses between the open ocean and coastal waters. For example, recent measurements of internal solitary waves shoaling on the continental shelf of New Jersey indicate that waves linked to shear instability in their interior are responsible for 50% of the total heat flux across the pycnocline and drive horizontal particle transport over a few kilometers, thereby exerting a critically important role for the shelf energetics and ecology. On account of the massive overturns in their interior, the turbulent diffusivities and particulate transport in convectively-breaking ISWs are expected to be as much as a hundred times larger than those in shear-unstable ISWs. Existing in-situ observations of convectively unstable ISWs are limited in their resolution of the associated turbulence due to the transient nature of these instabilities and instrument limitations. This project will enable the robust determination of the mechanisms and preferred locations of convective (and shear) instability of shoaling ISWs. The implications of convective breaking will be addressed through quantifying the associated turbulent fluxes and particle transport as a function of parameter space. A more reliable assessment of whether convectively-breaking ISWs are a critically important feature of most environments rich in high-amplitude waves will be possible. The improved understanding and quantification of the convective breaking process in shoaling ISWs, in terms of preferred locations of occurrence, underlying physics, turbulent fluxes and onshore particulate transport, will facilitate the reliable parameterization of such processes in larger-scale models. The parameterizations of ISW breaking and resulting turbulence, phenomena focused on the continental slope and shelf, might be fundamentally different from those typically used for internal tides, internal lee waves and stratified turbulence in the open ocean. One Ph.D. student, a native of Puerto Rico and member of a under-represented minority, will be trained in stratified ocean physics and high performance computing. The findings of this study will be integrated in relevant coursework in Environmental Fluid Mechanics at Cornell and in on-going outreach efforts at Ithaca High School and the Applied Physics Laboratory at the University of Washington's Space Grant Summer Undergraduate Research Program. Analysis codes, post-processed results and select raw data will be made available to the broader community through a dedicated online database. This project will investigate the breaking, due to primarily convective (but also shear) instability, of internal solitary waves (ISWs) shoaling over gently sloping realistic (and idealized) bathymetries. High-accuracy/resolution Large Eddy Simulations (LES) will be integrated with analysis of an extensive dataset of convectively breaking ISWs over the continental slope in the South China Sea. Previous analysis of these observations has revealed convectively unstable, large-amplitude ISWs with recirculating turbulent cores in their interior associated with order 100 meter overturns and intensified dissipation and mixing, roughly a thousand times greater than in the open ocean. The mechanisms leading to the convective instability and the associated turbulence mixing remain unknown. Two-dimensional simulations will first investigate the mechanisms and preferred locations of ISW breaking due to convective instability as a function of bottom slope, initial wave steepness and background baroclinic tidal current. Focusing on convective breaking, a range of computation/data intensive parallel three-dimensional LES, equipped with Lagrangian particle tracking, will then provide enhanced spatiotemporal resolution of the breaking process and will quantify the dependence of the resulting turbulent fluxes and wave-scale horizontal energy fluxes on the above parameters. Beyond providing bathymetric and stratification/current forcing to the LES, the existing SCS observations, and further analysis thereof, will serve as a basis for consistency checks and exploration of common trends in parameter space between LES and field data. Analysis of data from, actual and model, Lagrangian floats will examine and quantify particle entrainment, transport and detrainment by convectively-breaking ISWs, namely waves with recirculating cores. Alternative Lagrangian estimates of turbulent fluxes and dissipation rates will enable the computation of associated eddy diffusivities. These results will determine how ISW-driven turbulence relates to the regimes of weak wave-wave interaction and stratified turbulence and the transition between them.
来源学科分类	Geosciences - Ocean Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/70195
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Ren-Chieh Lien.Collaborative Research: Study of Convectively-Breaking Internal Solitary Waves of Depression: High Accuracy/Resolution Modeling and Observational Data Analysis.2016.