Observations of surface waves and wave-driven transport on the inner shelf
Abstract
Observations of surface waves and wavedriven transport on the inner shelf Project Summary The inner shelf region is an important gateway between the surfzone (coast) and the midshelf for the transport of heat, sediment, nutrients, pollutants, and larvae. Due to the vicinity to the shoreline, and the limited depth in this region, across-shelf transport on the inner is severely constrained and depends critically on the vertical and/or lateral (along-shelf) variability of the (Lagrangian) flow field. The principal drivers of cross-shelf transport on the inner shelf are surface waves and wind, which drive vertically sheared flow and Eulerian return flows (‘undertow’), and provide a direct driver of cross-shelf circulation. The breaking of surface waves in the surf zone drives coastal circulation cells (rips) that can extend into the inner shelf, contributing to both vertical and lateral exchange. Furthermore, refraction over the shelf and coastal features can cause spatial inhomogeneity in the wave and wind field, which can contribute to two-dimensional circulation and transport across the inner shelf. Despite recent progress in understanding cross-shelf circulation on the inner shelf, the wave-driven contribution is still poorly understood. In this project we propose to make detailed measurements of the variable wave forcing and wavedriven Lagrangian mean flow response across the inner shelf using a combination of free-drifting and fixed instruments. We will develop and deploy a fleet of surface and subsurface drifting instruments equipped with IMU/GPU sensor packages. We will estimate the mean flow field sampled with an IMU drifter with irregularly-sampled GPS locations. To understand the observed dynamics, and use the observations to further our understanding of the physical processes in the inner shelf, we will develop a wave-current theory with the aim to incorporate effects of wave nonlinearity, inhomogeneity, and the modulation of the mean flow by infragravity wave motion. Through the development and application of the new instruments and optimization methods, combined with the analysis of the new dataset and theory development, this project will provide a first direct observation of the wave-driven Lagrangian mean flow and Stokes drift, and contribute to our understanding of the wave-driven dynamics on the inner shelf.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512568
Entities
People
- T. T. Janssen
Organizations
- Northwest Research Associates
- Office of Naval Research
- United States Navy