Seals and robots study Antarctic currents | Polarjournal
Elephant seals have been used as “assistants” in research projects for years. The data loggers used do not affect the animals and fall off the head again after a while. The devices are partially lost, but can also be collected again. Data is transmitted via satellite. Photograph: C. Guinet, CEBC/Chize, Fance)

The study of the currents conditions in the Southern Ocean requires a great deal of technical effort and a lot of time to find out more about the driving forces of sea ice formation. Sea ice in Antarctica plays an important role in the global climate. But how and by whom should data be collected throughout the year, even in winter? Quite simply: elephant seals equipped with data loggers, who spend their non-reproductive time in Antarctic waters, and Autonomous above- and underwater vehicles equipped with the most modern measurement tools. An international research project has now discovered the major role of the smallest ocean currents along the ice edge of Antarctica.

The two studies, recently published in the journals of the American Geophysical Union, have shown that upper ocean currents, which are between 0.1 and 10 kilometers in size, have a major influence on the physical processes under sea ice, especially in winter. For this purpose, data from the Weddell Sea were collected by elephant seals equipped with so-called data loggers and evaluated by the researchers. “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 the lead author of the seal study, Dr. Louise Biddle. “It’s a really valuable insight into what was previously completely unknown in the Southern Ocean.” The animals spend their non-reproductive time along the ice edges of the Southern Ocean and hunt there for squid.

“It’s a really valuable insight into what was previously completely unknown in the Southern Ocean.”

Dr Louise Biddle

The data collected showed that more energy is accumulated under sea ice in the Antarctic winter than previously thought. One advantage that the elephant seals have over technical equipment (UAV) is the temporal and spatial resolution of the data volume. While UAVs only carry out repetitive measurements about every 10 days, elephant seals are more consistent to their diving site. This allows for the measurement of the small currents and fluxes that occur within a few hours and only in the range of 100 meters – 10 kilometers.

The data gathered by elephant seals were supplemented by the two autonomously operating robotic devices SB Kringla (left) and the Seaglider (right). The two devices independently collected oceanographic data at the sea ice edge for three months. The devices are only 2 meters long and weigh between 52 and 60 kilos, but can operate independently for more than 6 months. Photo: SCOOTECH

The significance of the data gathered by the elephant seals in 2008 has become apparent just now. A second research group led by assistant professor Sebastian Swart from the University of Gothenburg used the latest robotic technology in the shape of two devices: the Kringla sail buoy working on the surface and the seaglider, an underwater glider. The head of the Swedish Centre for Ocean Observing Technology (SCOOT) says: “These new ocean robots, which we can control via satellite, have allowed us to measure the ocean at unprecedented high resolution.” In their work, the scientists were able to further refine the data of the elephant seals and show that during times, when no storms whip up the Southern Ocean, ocean currents become much more energetic. This energy enhances the mixing of water layers and the transport of heat, carbon and nutrients into the depths. “The measurements have revealed strong physical linkages between the atmosphere and the ocean,” explains Professor Swart.

“It’s pretty amazing we can “remotely” control these robots in the most far-flung parts of the world while collecting new science data.”

Sebastian Swart

Particularly noteworthy is the fact that the two devices are just 2 meters long and weigh only 52 and 60 kilograms respectively. Nevertheless, they were able to collect a kind of data in the Ocean for three months, which otherwise cannot be collected by satellites or ships. “It’s pretty amazing we can “remotely” control these robots in the most far-flung parts of the world while collecting new science data,” Swart continues.

The South African icebreaker S.A. Agulhas II served as a platform for the research team for their work. From South Africa, the researchers were able to take the ship to the edge of the sea ice zone and launch their robots there. Photo: Environment ZA, Youtube

Source: Michael Wenger, PolarJournal

Link to the studies:

Swart et al (2020) Geophys Res Let 47 (6) Submesoscale Fronts in the Antarctic Marginal Ice Zone and Their Response to Wind Forcing

Biddle et Swart (2020) J Geophys Res Oceans 125 (6) The Observed Seasonal Cycle of Submesoscale Processes in the Antarctic Marginal Ice Zone

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