Nature Geoscience 2, 13–14 (2009); published online: 23 December 2008; corrected after print: 23 December 2008.

In the print version of this News & Views the reference list should have included the following:

8. Longuett-Higgins, M. S. Phil. Trans. R. Soc. London A 266, 511–607 (1968).

9. Rossby, C. G. J. Marine Res. 2, 38–55 (1939).

10. Haurwitz, B. J. Marine Res. 3, 254–267 (1940).

11. Munk, W. H. Prog. Oceanog. 40, 7–37 (1997).

These references are included in the HTML and PDF versions.