Geophys. Res. Lett. http://doi.org/ngx (2013)

A significant drop in global sea level, up to a maximum of −7 mm, occurred in 2011. This decline was the greatest seen since satellite measurements began and it coincided with an exceptionally strong La Niña event — to which it has been attributed.

John Fasullo, of the National Center for Atmospheric Research, USA, and co-workers use observations — satellite and in situ and reanalysis data to explore the physical reason for the large fall in sea level. They find water storage in Australia contributed substantially to the decrease, with South America contributing to a lesser degree.

Australia has unique surface hydrology, which limits surface runoff to rivers and oceans. The continent received anomalously high precipitation from late 2010 to late 2011 due to the influence of the atmospheric circulation (Southern Annular Mode) and variability in sea surface temperature (Indian Ocean Dipole) on La Niña. The increased precipitation and water storage were the cause of the decline, highlighting the role that natural cycles have in global mean sea-level changes.