Nasa/JPL

The inevitable rise of global sea levels due to melting glaciers has been 'temporarily' slowed by continents acting as sponges to soak up excess water.

But no, that is not good news.


Nasa said that its Gravity Recovery and Climate Experiment (Grace) satellites had shown for the first time how an increasingly parched Earth has soaked up an additional 3.2 trillion tons of water.

That liquid has been transferred from the sea to soils, lakes and underground stores of water, Nasa said -- temporarily halting the rise in sea levels by up to 20 percent.

In a study published by Nasa and University of California, Irvine, in the journal Science, JT Reager of Nasa's Jet Propulsion Laboratory said that it had previously been assumed that most of the melted ice water from Antarctica and other glaciers would transfer straight to the sea -- and that reliance on groundwater elsewhere would hasten that process.

Instead it appears that the land has absorbed more of that water than expected. "We always assumed that people's increased reliance on groundwater for irrigation and consumption was resulting in a net transfer of water from the land to the ocean," Reager said in a statement.


Nasa/JPL

That process was only made possible by studying more than a decade of data collected by Grace, which was launched in 2002. The satellites measure the distance between each other to an accuracy of one human hair, and so monitor changes in gravitational pull from Earth that results in the amount of water on the surface changing over time. "What we didn't realise until now is that over the past decade, changes in the global water cycle more than offset the losses that occurred from groundwater pumping, causing the land to act like a sponge -- at least temporarily."

Over the longer term, however, there is still very good evidence that sea levels are rising, and will continue to do so for at least the next century. The UN Intergovernmental Panel on Climate Change predicts that sea levels could rise as much as 21 feet over the next 100 years, and that might be accelerated further if melting happens quicker at the core of a glacier than expected. If all the glaciers on Earth were to melt, it would be enough to raise sea levels by about 197 feet worldwide. "These results will lead to a refinement of global sea level budgets, such as those presented in the Intergovernmental Panel on Climate Change reports, which acknowledge the importance of climate-driven changes in hydrology, but have been unable to include any reliable estimate of their contribution to sea level changes," said JPL senior water scientist Jay Famiglietti, in a statement. "We’ll need a much longer data record to fully understand the underlying cause of the patterns and whether they will persist"