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Krishtalik, Bioelectrochem. Bioenerg. 23, 249 (1990). 55. G. Tian, J. A. Berry, J. P. Klinman, Biochemistry 33, 226 (1994) J. P. Klinman, Chem. Rev. 96, 2541 (1996). 56. R. M. Wachter and B. P. Branchaud, J. Am. Chem. Soc. 118, 2782 (1996). 57. C. F. Yocum, Biochim. Biophys. Acta 1059, 1 (1991) H. Wincencjusz, H. J. van Gorkom, C. F. Yocum, Biochemistry 36, 3663 (1997). 58. B. E. Sturgeon et al., J. Am. Chem. Soc. 118, 7551 (1996). 59. Supported by NIH grant GM-37300 and the USDA Competitive Grants Office. We thank C. F. Yocum, C. Tommos, K. Warncke, N. Lydakis-Simantiris and M. Gardner for useful discussions. 26 October 1996 accepted 28 May 1997 RESEARCH ARTICLE Global Sea Floor Topography from Satellite Altimetry and Ship Depth Soundings Walter H. F. Smith* and David T. Sandwell A digital bathymetric map of the oceans with a horizontal resolution of 1 to 12 kilometers was derived by combining available depth soundings with high-resolution marine gravity information from the Geosat and ERS-1 spacecraft. Previous global bathymetric maps lacked features such as the 1600-kilometer-long Foundation Seamounts chain in the South Pacific. This map shows relations among the distributions of depth, sea floor area, and sea floor age that do not fit the predictions of deterministic models of subsidence due to lithosphere cooling but may be explained by a stochastic model in which randomly distributed reheating events warm the lithosphere and raise the ocean floor. Knowledge of ocean floor topography data is essential for understanding physical oceanography, marine biology, chemistry, and geology. Currents, tides, mixing, and upwelling of nutrient-rich water are all in- fluenced by topography. Seamounts may be particularly important in mixing and tidal dissipation (1), and deep water fisheries on seamount flanks have become economically significant (2). Seamounts, oceanic pla- teaus, and other geologic structures associ- ated with intraplate volcanism, plate boundary processes, and the cooling and subsidence of the oceanic lithosphere should all be manifest in accurate bathy- metric maps. Conventional sea floor mapping is a te- dious process. Ships have measured depth with single-beam echo sounders since the W. H. F. Smith is at the National Oceanic and Atmospher- ic Administration, Code E/OC-2, 1315 East-West High- way, Silver Spring, MD 20910���3282, USA. D. T. Sandwell is at the Scripps Institution of Oceanogra- phy, La Jolla, CA 92093, USA. *To whom correspondence should be addressed. E-mail: walter@amos.grdl.noaa.gov SCIENCE z VOL. 277 z 26 SEPTEMBER 1997 z www.sciencemag.org 1956

60 �� N 30 �� N 30 �� S 60 �� S 0 �� 0 �� 0 �� 30 �� E 60 �� E 90 �� E 120 �� E 150 �� E 180 �� 150 �� W 120 �� W 90 �� W 60 �� W 30 �� W -6 -4 Elevation (km) -2 0 3 Fig. 1. Color shaded-relief image of the modeled topography, illuminated from the northwest. RESEARCH ARTICLE www.sciencemag.org z SCIENCE z VOL. 277 z 26 SEPTEMBER 1997 1957