Collaborative Research: Alongshelf Currents Driven by Obliquely Incident Shoaling Internal Bores

University Of Washington, Seattle WA

Investigators

Abstract

Internal bores generated by shoaling internal waves are known to be significant mechanisms of energy dissipation, cross-shelf exchange, and vertical mixing. Recent observational work has revealed that obliquely incident internal bores drive strong cross-shelf and along-shelf gradients in energy flux and water properties on the inner shelf. Robust theory suggests this energy flux divergence should drive a mean along-shelf current. However, mean along-shelf flows driven by dissipating internal waves have only been studied in the case of internal wave reflection on the continental margin, not for shoaling internal bores on the inner shelf. The project will examine the wave-mean flow interaction of dissipating shoaling internal bores for along-shelf currents on the inner shelf, including how the dissipation of shoaling internal bores can drive a time-averaged along-shelf current. Physical insights gained from idealized modeling will permit identification of the along-shelf flow in a detailed observational and high-resolution realistic modeling dataset. Along-shelf transport is relevant for biologically and physically important processes such as population connectivity and scalar transport. As such, this work may lead to reinterpretation or re-analysis of existing inner-shelf field observations and guide new experiments. The project will investigate internal bore-driven along-shelf currents, using idealized modeling, analyses of field observations, and realistic circulation model output. A process-motivated numerical experiment will be employed to characterize the along-shelf flow under simplified conditions and systematically varied forcing, while analyses of field observations and realistic model output will verify the presence, structure, and variability of the flow in nature. The relationship of internal bore dissipation to the magnitude and cross-shelf location of the along-shelf current is of particular interest. The numerical model will be used to determine how bore dissipation and the along-shelf current depend on ambient stratification, topographic slope, and planetary rotation. Field data and realistic modeling results will be used to quantify the time-averaged along-shelf circulation and its dynamics. A comparison between idealized modeling results and both observational and realistic modeling data will be vital in confidently attributing the measured along-shelf flow signal to internal bore dissipation. 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.