Advective heat transports here appear to be an important component in the regional heat budget, accounting for about half the seasonal variation in oceanic heat storage.
Climate models attempting to describe and predict the coupled ocean-atmosphere heat budget are now quantitatively testable on scales exceeding 1000km at the equivalent accuracies of 2cm rms in sea level. These values place stringent demands on the models for accurate calculation of barotropic and baroclinic components. They require great care in dealing with the exchange of fresh water across the air-sea interface and raise serious questions about the accuracy of conventional meteorological estimates.
REFERENCES AND NOTES
1. W. Munk and C. Wunsch, Philos. Trans. R. Soc. London Ser. A, 307, 439 (1982).
2. A demonstration of this system, on a much smaller scale in the western Mediterranean, was described by D. Menemenlis, A. T. Webb, C. Wunsch, U. Send, and C. Hill, Nature, 385, 618 (1996).
3. J. G. Patullo, W. H. Munk, R. Revelle, and E. Strong, J. Mar. Res., 14, 88 (1955); C. Wunsch, Rev. Geophys., 10, 1 (1972); A. E. Gill and P. P. Niiler, Deep Sea Res., 20, 141 (1973).
4. M. F. Meier, Science, 226, 1418 (1984); R. S. Nerem et al., Geophys. Res. Lett., 24, 1331 (1997).
5. I. Fukumori, R. Raghunath, and L.-L. Fu, Geophys. Res., 103, 5493 (1998).
6. Current meter data indicate that the surface kinetic energy in this region is about 5% barotropic[C. Wunsch, J. Phys. Oceanogr. ,27, 1770 (1997)]. Direct quantitative estimates of the barotropic contribution to η (the sea level anomaly) cannot, however, be made easily from these data because of lack of knowledge about the wavenumber characteristics of the barotropicmode.
7. W. Munk, P. F. Worcester, and C. Wunsch, Ocean Acoustic Tomography (Cambridge Univ. Press, New York, 1995).
8. B. M. Howe, Technical Memorandum 3-96, Applied Physics Laboratory, University of Washington, 1996; ATOC Instrumentation Group, Oceans'95, 3, 1483 (1995).
9. The transmission schedule is determined by the sampling requirements of the associated ATOC Marine Mammal Research Project. The biological elements of ATOC have been the source of controversy (A. S. Frankel and C. W. Clark, Canadian J. Zoology, in press; see also http://atoc.ucsd.edu).
10. The transmitted signal is phase modulated and encoded using a linear maximal shift register sequence containing 1023 digits. The transmission parameters of the signal are as follows: center frequency 75Hz, bandwidth 37.5Hz (quality factor, Q=2), power 260W (195dB re 1 μPa at 1m), sequence period 27.28s, digit length 26.667ms, and total duration 44 periods, or 1200.32s. A coded signal is necessary to overcome transducer peak power limitations; although the noise level of the source blends with oceanic background levels within a few hundred kilometers, the signal processing makes it possible to hear the source at great distances, ＞ 10,000km, as if all the transmitted energy were contained in a single 26.667-ms digit pulse.
