Between 2010 and 2011, the smallest continent caused the biggest drop in sea levels. How was Australia responsible?

Between 2010 and 2011, the global sea levels dropped by a quarter of an inch (half a millimeter) because of extreme rainfall over Australia during that time. This was observed by scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, and the University of Colorado at Boulder. How could the smallest continent have such a large effect on sea levels all over the world?

A unique and unusual set of circumstances made it all happen. Data from the NASA/German Aerospace Center's Gravity Recovery and Climate Experiment (GRACE) spacecraft showed that the drop was the result of a very strong La Nina that began in late 2010. It changed rainfall patterns all over our planet, moving huge amounts of Earth's water from the ocean to the continents.

On average, Australia received almost one foot (300 millimeters) of rain more than normal! The continent experienced wide spread flooding. The excess water was prevented from running back into the ocean by dry soils and the mountain-ringed topography of the country's vast interior, called the Outback. The water not being able to return to the oceans is what made global sea levels drop.

Since 2011, when the atmospheric patterns shifted out of their unusual combination, sea levels have been rising at a faster pace than usual of about 0.4 inches (10 millimeters) per year.

(Source)