Phys. Oreonogr. 24, 233 (1994). 14. Matenals and methods are available as supporting material on Science Online. 15. G. T. Mitchum, W. Sturges, I. Plot Deettooge. 12,1310 (1982). 16. 5. 1. LenD, L Phys. &mow. 24, 2061 (1994). 17. 5.1. LenD, L Phys. Greasy,. 31, 2749 (2001). 1B. J. M. Mart Phys. Ocean*. 32