Scientists have worked out that a combination of weather patterns over the Indian and Pacific oceans funnelled so much rain over Australia that the world’s sea levels fell in 2011.
Unlike other continents, the soils and topography of Australia prevent almost all of its rain from running off into the ocean, causing dry areas of Australia to act like an enormous sponge.
This went against the long-term trend of rising sea levels caused by higher temperatures and melting ice sheets, initially confusing scientists.
The scientists said that as the atmospheric patterns have returned to normal, more rain is falling over the tropical oceans once more and the seas are rising again.
The research, published in Geophysical Research Letters, links the fall in sea levels to more water storage on land, which occurred at the same time as La Niña.
Dr John Fasullo, a scientist at the National Centre for Atmospheric Research (NCAR) in the US said: ‘It’s a beautiful illustration of how complicated our climate system is.’
“Its influence is so strong that it can temporarily overcome the background trend of rising sea levels that we see with climate change.”
Dr Fasullo said most of the rain that normally falls over land usually travels back to the sea through streams and rivers over months so when there is torrential rain over the land, the effect on the world’s sea levels is almost invisible.
However, during the La Niña of 2010-11, which saw the temperature of the eastern Pacific Ocean drop and more rainfall over land then normal, global sea levels dropped by 7.6mm for around 18 months.
The fall goes against the larger trend of sea levels rising by around 2.54mm a year since 1993, which is believed to be caused by melting glaciers and ice sheets as well as water temperatures warming up, which are linked to global warming.
In a bid to explain the phenomenon, the scientists found La Niña coincided with two other weather patterns that effectively funnelled the water over Australia’s land mass, where it seldom rains.
The Indian Ocean Dipole weather pattern, which carried atmospheric moisture across the ocean from the west, met the easterly moving moisture from La Niña.
A third pattern called the Southern Annular Mode then caused the rain to fall on the huge continent.
“You have this collision of transports in the Pacific and then southward into Australia, so a big funnel of tropical moisture into Australia, and that led to one of the wettest years on record in Australia, if not the wettest,” Dr Fasullo said.
Almost 305mm of rain fell over Australia during the period and the rain was effectively trapped in the Outback with nowhere to go.
“No other continent has this combination of atmospheric set-up and topography,” Dr Fasullo said.
“Only in Australia could the atmosphere carry such heavy tropical rains to such a large area, only to have those rains fail to make their way to the ocean.”
Much of the water collected in the Lake Eyre basin, likened to a massive inland sea in the east of the country, while most of the rest of the water was absorbed by the dry soil of the Western Plateau.