A combination of weather patterns over the Indian and Pacific oceans funneled so much rain over Australia that the world’s sea levels fell in 2011, scientists said. 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.
According to a U.S. study, the effect caused by the La Niña weather pattern around Australia meant global sea levels fell for 18 months during 2010 and 2011, bucking the long-term trend of rising sea levels caused by higher temperatures and melting ice sheets.
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.
Dr John Fasullo, a scientist at the National Centre for Atmospheric Research (NCAR) in the U.S. said: ‘It’s a beautiful illustration of how complicated our climate system is.’ ‘The smallest continent in the world can affect sea level worldwide. 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 via 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 0.3 inches for around 18 months. In a bid to explain the phenomenon, the scientists found La Niña coincided with two other weather patterns that effectively funneled 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.
Dr Fasullo told NBC News: ‘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.’
