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Marine Robot Finds ‘Hidden’ Water Between Arctic and Atlantic Oceans

David Paul

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Marine Robots

These previously hidden patches of water could dramatically change our understanding of how the ocean’s food web forms.

A group of scientists working with an autonomous marine robot glider have discovered what they believe to be previously ‘hidden’ patches of water that could change our knowledge of how food webs form in the ocean.

The patches were formed in the northern part of the Barents Sea, as cooler and fresher water from the Arctic moves south and becomes trapped within the warmer and saltier water from the Atlantic.

Known as ‘eddies’ – circular movements of water that have broken off from an ocean current – they measure around 30 kilometres across.

Despite their size, the eddies are invisible to satellites and had gone unnoticed until oceanographers from the Scottish Association for Marine Science (SAMS), in Oban, picked up unusual readings during a trial mission of an underwater glider.

The autonomous glider moves across the ocean to depths of 200 metres collecting data, including heat and salinity, every kilometre. This allowed the SAMS team to measure one of these eddies in detail.

While this eddy’s surface temperature was like the surrounding water, masking it from satellites, its lower salt content made it stand out in the glider readings.

Dr Marie Porter, a SAMS oceanographer and lead author on a report about the discovery, published in Geophysical Research Letters, said her findings had implications for understanding the distribution of nutrients that fuel the entire Arctic ecosystem.

She said: “We get a pretty good idea about what’s happening on the very surface of our ocean through satellites, but eddies like this one have been hidden from view because they have warmed at the surface since leaving the Arctic.

“This temperature masking means we have previously underestimated how much water moves within these patches in the Arctic Seas. It begs the question: how many more of these hidden eddies are occurring in the ocean today?”

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Arctic oceanographer Prof Finlo Cottier of SAMS, a co-author on the paper, commented: “SAMS has been working with ocean gliders for over a decade and we know that they are the ideal tool for measuring the detailed properties of the ocean.

“This work gives us precise measurements of important structures in the Arctic that we couldn’t previously obtain.”

The discovery was made during a two-week trial of the glider ‘Zephyr’ in July 2017, ahead of a longer mission as part of the Arctic PRIZE project. The project is funded by the Natural Environment Research Council’s Changing Arctic Ocean programme.

David Paul

Staff Writer, DIGIT

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