Breaking Internal Waves and Turbulence on Shelf Slopes

Jeffrey Koseff, Perry L. McCarty Director and Senior Fellow - Stanford Woods Institute for the Environment; William Alden Campbell and Martha Campbell Professor of Civil and Environmental Engineering, Stanford University

Internal waves, the subsurface equivalent to the more widely-known surface waves, are ubiquitous in the world’s oceans. These waves are known to be responsible for a large part of the vertical mass and momentum redistribution in the world’s stratified oceans and lakes. Internal waves are primarily generated by the winds and the tides, and are known to propagate thousands of kilometers from their generation site before they break, usually on the continental shelf or at ocean ridges. Internal waves affect numerous ocean processes including the transfer of nutrients, sediment, and larvae between deep waters and the continental shelf environment, and can cause dramatic changes in temperature, salinity, and chlorophyll levels in coral reefs. Moreover, mixing generated by internal waves is thought to play an essential role in the transport of deep, cool nutrient-rich waters into the shallower waters of critical coastal ecosystems such as Monterey Bay and Georges Bank.

In this talk I will discuss a series of laboratory and field experiments we performed in order to understand what happens when internal waves break on shelf slopes such as found in mid-ocean (seamounts) and on the continental shelf. I will look at the energetics of the breaking events as well as the characteristics of the bolus structures which often form as a result of the breaking. Because fluid mechanics is at its essence a visual science emphasis, in this talk, will be placed on visualization and imagery.