Date of Award

1-1-2010

Document Type

Campus Access Thesis

Department

Marine Science

First Advisor

Alexander E. Yankovsky

Abstract

Low frequency edge waves with large spatial scales represent an important part of the coastal ocean response to tidal and atmospheric forcing. A semidiurnal tide traveling over the continental shelf and slope can be propagated by a Hybrid Kelvin-Edge Wave (HKEW), which is the fundamental mode propagating only downstream (Kelvin wave direction). A semi-analytical parameter study of the impact of topography on HKEW dispersion characteristics revealed that the group velocity of the HKEW can be very low or even zero over a wide, gently sloping continental shelf. Numerical modeling experiments indicate that when the semidiurnal HKEW traveling over a narrowing shelf encounters such a shelf width that causes a zero group velocity, wave propagation is substantially impaired, leading to wave amplification upstream, strong local dissipation, and offshore radiation. This behaviour is qualitatively consistent with the dynamics of semidiurnal tides on wide shelves narrowing in the direction of tidal wave propagation, including the Patagonia shelf and the South China Sea.

The tropical cyclone's landfall can generate a coastal long-wave response sending a substantial sea surface undulation to hundreds miles away along the coastline. A set of numerical experiments has been performed to study the genesis, category, and propagation of such a long-wave response in a two-dimensional configuration, taking both topographic and atmospheric impact into account. In all experiments tracks of the tropical cyclone are perpendicular to the coastal wall. The results show that fast/slow moving cyclones generate an edge wave (EW)/ continental shelf wave (CSW) response, while intermediate translation speeds lead to mixed wave responses but with relatively low wave heights. The zero mode dominates the EW response. The upstream-propagating EWs are always higher than downstream due to the atmospheric pressure impact, and reach the maximum wave height when wave period is close to the period in the dispersion diagram that is corresponding to the cyclone's spatial scale. Additionally, a broad shelf and/or small size cyclone is favorable for EW generation while a narrow shelf and large-size cyclone is favorable for CSW generation. Increasing the size of the cyclone can also increase the wave height of the CSW.

Share

COinS