Acknowledgements The authors gratefully acknowledge financial support from the Office of Naval Research, the National Science Foundation, and the Woods Hole Oceanographic Institution Mellon Awards. In addition, we wish to thank the following those who made valuable suggestions or who have otherwise contributed to the preparation of the manuscript: Larry Armi, Karin Borenäs, Ruth Curry, Claudia Cenedese, Elin Darelius, Heather Deese, Clive Dorman, Ted Durland, Rafaelle Ferrari, Chris Garrett, Frank Gerdes, Melinda Hall, Rob Hetland, Greg Ivey, Ted Johnson, Allan Kuo, Janek Laanearu, Greg Lawrence, Sonya Legg, Susan Lozier, Peter Lundberg, Mike McCartney, Tom McClimans, Terry McKee, Andrew Mosedale, Anna Nikolopoulos, Leaf Thomas, Mary-Louise Timmermans, John Toole, Anna Wåhlin.