Larsen Ice Shelf Has Progressively Thinned

during each event are also indicated. June 1982 to June 1983 (intense event, 1 transect); August 1986 to July 1987 (medium, 7 transects); October 1991 to May 1992 (marginal intensity, 2 transects); October 1992 to October 1993 (marginal, 3 transects); April 1994 to June 1995 (marginal, 8 transects); and April 1997 to April 1998 (intense, 15 transects). 12. To test biases caused by undersampling, we computed time trends of SST using the regularly spaced monthly mean values extracted from the compilation of Reynolds et al. (13) for the non–El Niño periods (11) in the Niño 3.4 area. The SST trends thus computed are compared with those computed using our limited SST values measured concurrently with PCO2. They are found to be in agreement within 1 SD, indicating that the time trends computed with our limited number and irregular spacing of measurements are consistent with those obtained with the full set of the SST data. For example, for the post1990 trend, the full data yield –0.14° 0.02°C year 1 (n 87), which compares with –0.12° 0.06°C year 1 (n 32) for the most consistent case; and for the post-1992 trend, the full data yield –0.11° 0.11°C year 1 (n 66), which compares with 0.01° 0.09°C year 1 (n 26) for one of the least consistent cases. 13. R. W. Reynolds, N. A. Rayner, T. M. Smith, D. C. Stokes, W. Wang, “NOAA optimum interpolation (OI) sea surface temperature (SST) V2” (2003) (available at ftp://ftpprd.ncep.noaa.gov/pub/cmd/sst/papers/ oiv2pap/). 14. C. Marzban, J. T. Schaefer, Mon. Weather Rev. 129, 884 (2001). 15. W. H. Press, B. P. Flannery, S. A. Teukolsky, W. T. Vetterling, Numerical Recipes (Cambridge Univ. Press, Cambridge, 1986), pp. 491–494. 16. Z values greater than 2.575 indicate sufficient evidence for claiming that the test is valid with a greater than 99% probability. 17. T. Takahashi, J. Olafsson, J. Goddard, D. W. Chipman, S. C. Sutherland, Global Biogeochem. Cycles 7, 843 (1993). 18. GLOBALVIEW-CO2: Cooperative Atmospheric Data Integration Project—Carbon Dioxide. (CD-ROM, NOAA Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado, 2001) (also available on Internet via anonymous FTP to ftp.cmdl.noaa.gov. Path: ccg/ co2/GLOBALVIEW ). 19. R. L. Borgne, R. A. Feely, D. J. Mackey, Deep-Sea Res. II 49, 2425 (2002). 20. T. P. Guilderson, D. P. Schrag, Science 281, 240 (1998). 21. D. Gu, S. G. H. Philander, Science 275, 805 (1997). 22. M. J. McPhaden, D.-X. Zhang, Nature 415, 603 (2002). 23. N. Schneider, A. J. Miller, M. A. Alexander, C. Deser, J. Phys. Oceanogr. 29, 1056 (1999). 24. J. E. Dore, R. Lukas, D. W. Sadler, D. M. Karl, Nature 424, 764 (2003). 25. D. E. Archer et al., Deep-Sea Res. II 43, 779 (1996). 26. R. Wanninkhof, K. Thoning, Mar. Chem. 44, 189 (1993). 27. N. R. Bates, T. Takahashi, D. W. Chipman, A. H. Knapp, J. Geophys. Res. 103, 15567 (1998). 28. D. W. Chipman, J. Marra, T. Takahashi, Deep-Sea Res. 40, 151 (1993). 29. Supported by grants from NOAA, NASA, and Ford Motor Company (T.T.), and from NOAA (R.A.F.) for field operations. We thank R. Wanninkhof of NOAA and H. Y. Inoue of the Japan Meteorological Research Institute for providing data; D. Martinson of LDEO and C. Marzban of the Department of Statistics, University of Washington, Seattle, for advice on statistics; and B. Linsley of the State University of New York at Albany for critical reading of the manuscript. This is LDEO contribution no. 6500, PMEL contribution no. 2579, and University of Washington and Joint Institute for the Study of the Atmosphere and Ocean contribution no. 1021.