Collaborative Research: The Dynamics of Near-Surface Velocity Structure in the Coastal Ocean from Observations and Models

University Of Maine, Orono ME

Investigators

Abstract

This study will concentrate on elucidating the processes that influence the top part of the water column, from about 10 m depth to the air-water interface. This layer is unresolved by different techniques that are used to measure ocean’s near-surface currents. For example, high-frequency radars resolve the skin of the water column but provides no information underneath. On the other hand, current velocity profilers tend to miss the portion of the water column right underneath the surface. This study will attempt to fill in the gap with the help of a numerical model that resolves the hydrodynamics of the upper-ocean layer and that considers the effects of surface waves. The study will also investigate the influence on surface currents of different water densities within the surface layer. The initial proposition is that wave action will tend to homogenize the vertical distribution of near-surface currents. The project will support one graduate student and undergraduate research opportunities at University of Maine, and will develop outreach activities with US Coast Guard Academy cadets. The proposal will study the dynamics of flows in the upper meters of the coastal ocean, including the influence of surface gravity waves and the modification to the dynamics by stratification and buoyancy fluxes. This portion of the water column is rarely observed and limited to short periods, which makes it difficult to distinguish the effects of winds and waves on water velocity profiles. The approach of the study will be to pair existing HF-radar measurements with upward-looking current profilers, and compare the velocity profiles to 1D numerical model (GOTM) results with distinct turbulence parametrizations and vertical stratification. The PIs propose that wave breaking and Langmuir turbulence will tend to homogenize vertical gradients in the velocity profile, together with an Eulerian flow related to the Stokes-Coriolis mechanism. In terms of BI, beyond the scientific merit, the proposal would provide parametrizations of near-surface processes driven by waves in models and for particle trajectory studies. The study would support a graduate student and undergraduate research opportunities at University of Maine, and will develop outreach activities with USCG Academy cadets. 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.