Satellite-tagged seals and underwater robots uncover new ocean currents

Two new studies from the University of Gothenburg, utilizing novel research techniques involving tagged elephant seals and robotic gliders, have uncovered new small-scale ocean currents in the Southern Ocean and highlighted their big importance.

satellite tagged seal
A Weddell seal collects data in the ocean while swimming. This information doesn’t only help marine sciences researchers, but also biologist, to understand the seals’ habitat better (Photo from University of Gothenburg)

As the technology available to researchers has improved over time, the only limiting factor to what can be uncovered about our oceans is the imagination of those involved. Nowhere is that more evident than the Department of Marine Sciences at the University of Gothenburg in Sweden, where two new studies involving different yet equally innovative research methods have uncovered new secrets about the Southern Ocean. Using both satellite-tagged elephant seals and remotely-controlled underwater gliders the researchers there have discovered new small-scale ocean currents, which they have also shown play an important role in controlling the amount of heat and carbon absorbed by the oceans.

Submesoscale flows

Both new studies out of the University of Gothenburg focus on what are known as submesoscale flows, which are small-scale ocean currents that are between 0.1-10km in size and occur over hours and days rather than being permanent ocean fixtures. Very little is known about these types of currents compared to larger ones because they are much harder to find and study, because they are not visible from satellites or easily identified using ship-based data. As a result not a lot is known about submesoscale activity in the Antarctic region, especially in an around the sea ice.

Novel research techniques

The first study released by the Department of Marine Sciences at Gothenburg was led by Associate Professor Sebastiaan Swart whose team located and studied the submesoscale flows in the region using highly-advanced ocean gliders. In a press release he said that these underwater robots “allowed us to measure the ocean at unprecedented high resolution” going on to explain that “we can remotely ‘steer’ these robots in the most far-flung parts of the world… while collecting new science data”. His team looked closely at the rate of ocean mixing and transport of properties, such as heat, carbon and nutrients, into the deep ocean. They found that there was strong seasonal variability in submesoscale activity and also greater energy levels when there was low surface winds.

deploying glider
A deep diving ocean robot is deployed in the Southern Ocean by the research team. This “glider” spent five months in the ocean to collect data and transfer them to the researchers via satellite (Photo from University of Gothenburg)

The next study released by the university, led by Dr Lousie Biddle (also part of the first study) and Sebastiaan Swart,  focused on the submesoscale activity in and around sea ice. This was a much more ambitious research aim because of how hard it is to survey under the sea ice, even with advanced robots. So instead they turned to research assistants that were much more at home in this environment – elephant seals. By attaching special satellite tags to the pinnipeds they were able to use them as natural drones recording data under the ice. “Using the data collected by the seals, we’re able to look at the impact these upper ocean currents have underneath the sea ice for the first time” explains Dr Biddle, who went on to say “It’s a really valuable insight into what was previously completely unknown in the Southern Ocean”.

What have we learned?

The second study by Biddle and Swart confirmed what the first found regarding a strong seasonal variation in the strength of these newly uncovered currents. However, counter to previous assumptions that an increase in sea ice over winter reduces their strength, they found that even when ice coverage is high these currents still have a significant effect on the ocean and how it is mixed. Together the two studies have greatly improved our understanding of small-scale ocean and climate processes in the region, which could have implications on a global scale.

'selma' glider
Dr Louise Biddle with “Semla”, a glider from the University of Gothenburg. The glider can dive to 1000 metres and send back information via satellite to the researchers working close to the ice edge (Photo from University of Gothenburg)

These kinds of observations, which are only possible thanks to technology advancements and the ingenuity of the researchers, have helped to start filling a ‘critical knowledge gap’ in the ocean that has important implications for things like climate change. Swart and colleagues are therefore ‘very excited’ for what comes next.

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