Ocean Science www.ocean-sci.net 1812-0784 1812-0792 3 1 2007 10.5194/os-3-55-2007 http://www.ocean-sci.net/3/55/2007/ http://www.ocean-sci.net/3/55/2007/os-3-55-2007.html http://www.ocean-sci.net/3/55/2007/os-3-55-2007.pdf 55 57 2007-02-06 Inferring the zonal distribution of measured changes in the meridional overturning circulation A. M. de Boer a.deboer@uea.ac.uk H. L. Johnson University of East Anglia, Norwich, UK University of Reading, Reading, UK Recently, hydrographic measurements have been used to argue that the meridional overturning circulation at 25° N has decreased by 30% over the last 50 years. Here we show that the most likely interpretation consistent with this approach (i.e., with the dynamic method together with a level-of-no-motion assumption and Ekman dynamics) is that any decrease in strength of the deep western boundary current must have been compensated, not by a basin-wide increase in upper layer southward flow, but by changes in the nonlinear region immediately outside of the Florida Straits. Bryden, H. L., Longworth, H. R., and Cunningham, S. A.: Slowing of the Atlantic meridional overturning circulation at 25 degrees N, Nature, 438, 655–657, 2005. Cushman-Roisin, B.: Introduction to Geophysical Fluid Dynamics, Prentice Hall, 1994. Ducet, N., Le Traon, P. Y., and Reverdin, G.: Global high-resolution mapping of ocean circulation from the combination of T/P and ERS-1/2, J. Geophys. Res., 105, 19 477–19 498, 2000. Ekman, V. W.: On the influence of the earth's rotation on ocean currents, Ark. Mat. Astron. Fys., 2, 1–53, 1905. Lee, T. L., Johns, W. E., Zantopp, R. J., and Fillenbaum, E. R.: Moored Observations of Western Boundary Current Variability and Thermohaline Circulation at 26.5° in the Subtropical North Atlantic, J. Phys. Oceanogr., 26, 962–983, 1996. Pedlosky, J.: Geophysical Fluid Dynamics, Springer, 710 pp, 1987. Stewart, R. H.: Introduction to Physical Oceanography, http://oceanworld.tamu.edu/resources/ocng_textbook/contents.html, 2005. Sverdrup, H. U.: Wind-Driven Currents in a Baroclinic Ocean – with Application to the Equatorial Currents of the Eastern Pacific, Proceedings of the National Academy of Sciences of the United States of America, 33, 318–326, 1947. Wunsch, C.: The Ocean Circulation Inverse Problem, Cambridge University Press, 443 pp, 1996.