NavList:

John, you wrote:
"As a physicist, I can attest that this is 100% true. In fact, it's usually a sign that the professor decided to "punt" (Americanism) on a topic he couldn't prepare in time for lecture. "

Heh. Yes. Also used jokingly, as in: "these few equations, which I have written on a 3x5 card, are the fundamental equations of atmospheric dynamics. Everything from a summer breeze to a giant hurricane follows from these equations. Next week's weather forecast...? We leave that as an exercise for the reader." :-)

And you wrote:
"I'm beginning to think that the only way currents can affect waves is through some gradient effect - where the current velocity changes rapidly as a function of depth or position. As a sea kayaker, I've seen this effect in tidal races, but here there are changes in current velocity with respect to shallow bottoms and edges."

Yes, what I was getting at is that the waves are clearly going to be changed as they traverse that boundary region where the velocity ramps up. Just picture a nice, clean, nearly-sinusoidal train of ocean swells approaching a simple straight section of the Gulf Stream. The wave front will bend. It's a type of refraction. You mentioned "tidal races". There's one just off the western end of Fishers Island in Long Island Sound known as "The Race", and there the water is very deep, so it's not an interaction with the bottom. But you can see the chop there from half a mile away easily when conditions are right.

Here's an article that explores the refraction idea a little further:
http://fer3.com/x.aspx/waves
(links to the page at Ocean Navigator). This author also adds something that I didn't know which is that the NOAA offshore forecast -routinely- refers to higher waves in the Gulf Stream when the wind is out of the north. This author makes a pretty good case that waves travelling opposed to a current are focused by the gradient in velocity along the current boundary. I would love to see some calculational confirmation nevertheless.

-FER