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The rivers are not only on the surface. There are underground currents, such as the stunning “river” Hamza, an aquifer of thousands of kilometres long that discharges its water to the ocean, four kilometers below the Amazon river. And under the ice of Greenland and Antarctica, there is a veritable lost world of rivers, lakes and canyons that do not appear on maps, but whose currents are home to forms of life is barely known. But our ignorance goes even further.

A study published this week in “Scientific Reports” has reported the surprising finding that appears to be the system of underwater river more huge all over the planet . Scientists from the University of Western Australia have identified the existence of significant currents flowing on the bottom of the sea, on the continental shelf off the coast of australia. This phenomenon had already been studied, but only now has seen its continental dimension, extending around the whole of Australia. His name is “Dense Shelf Water Cascades” (DSWC), something as well as waterfalls platform of dense water.

According to have concluded the researchers, led by Charitaha Pattiaratchi, these rivers form in winter and are a result of the cooling of the water surface, in front of the australian coast. When this cooling occurs, the water becomes more dense and tends to sink to flow out to sea on the continental shelf thanks to the action of gravity on the tilted platform. According to the data collected, these flows extend up to distances of 10,000 kilometers of the coast.

Around the coast of Australia form a gigantic system of ocean currents in winter, which connects the coast with the interior of the ocean – Mahjabin et al., Scientific Reports, 2020

Besides, this process does not occur in areas isolated, but around the perimeter of Australia. In fact, as has been said in a press release, Yasha Hetzel, co-author of the work, the cooling simultaneous coastal waters around Australia it had not been documented until now .

Transportation from the coast to the sea inside

As expected, these currents have a large influence on the transport of nutrients, animal matter and vegetable and pollution out to sea, what makes you think that the rivers submarines are of great importance globally.

“The ocean close to the coast receive all of the suspended matter, and dissolved, that includes nutrients , plants, animals and pollution,” said Hetzel. “Represents an important component of the ocean environment, connecting the earth with the deep ocean”.

In the opinion of Pattiaratchi, this makes the finding is very relevant: “This is the most important discovery in coastal oceanography in decades, and not just in Australia, but globally.”

Given that these underwater river flowing under the surface, could not be observed by means of satellites. His study was only possible thanks to robots, autonomous underwater that allowed us to obtain a huge amount of information. In particular, the robots carried out 126 missions between the years 2008 and 2019.

As has been said Tanziha Mahjabin, first author of the paper, “the data have been collected for more than a decade and are spending more than 2,500 days at sea”. The only way they have been able to examine what happened in different areas of the giant Australia at different times of the year.

Soon, the researchers will try to study the contribution of these currents, DSWC to the flow of nutrients and biogeochemical fluxes, by uniting the coasts and the interior of the ocean.