Sounds, Sites and Sediment from the RV Polarstern

Outside, the temperature is below zero, and there are spectacular, ever-changing views of ocean, sky, and ice, but Dr Mardi McNeil is ensconced in The Batcave.

This lab at the base of the RV Polarstern is mostly closed off to the outside world except for its equipment, which interacts with its surroundings similarly to a bat, hence the nickname. Here, Dr McNeil spent weeks working odd hours of the day and night interpreting data streams about the seabed beneath them.

“Days at sea are a mix of excitement and the mundane,” Dr McNeil explains. “There is always the excitement and anticipation of what the next sample or mapping of the seabed might reveal. As the multibeam sonar sweeps across the seabed creating a map of the topography it feels like we are modern Antarctic explorers, seeing an area for the first time.”

Between February and April this year, Dr. McNeil, a SAEF investigator based at Geoscience Australia, has been onboard the RV Polarstern. Operated by the German Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), it is one of the world’s most advanced polar research vessels.

She has been participating in EASI-3, a voyage to investigate the East Antarctic Ice Sheet and record how it interacts with the adjacent Southern Ocean. Led by Professor Sebastian Krastel from the Christian Albrechts University of Kiel, the voyage included over 50 scientists from Germany, France, Spain, Greece and Argentina, as well as six Australians.

Using a multidisciplinary approach, the team has conducted marine and land-based fieldwork, which will enable them to build a window into the past 50,000 years of the region’s history and understand what happened as climate conditions fluctuated.

“Studies on the variability of ice sheets on different time scales have so far concentrated on the West Antarctic Ice Sheet,” Dr McNeil explains. “In contrast, little is known about the response of the East Antarctic Ice Sheet to climate change, especially at the continent-ocean boundary.”

With six research voyages already under her belt, Dr McNeil brought expertise in marine sedimentology, geomorphology, and seabed mapping to the multidisciplinary team of scientists and technicians.

The ship operates 24 hours a day, which helps maximise the time available for data collection and means working in shifts. Dr McNeil was on the midnight to 4 am and midday to 4 pm shift, catching sleep in two blocks in between.

Her role within “The Batcave” was to interpret acoustic data from the sub-bottom profiler, one of the ship’s survey tools that uses sound waves to map beneath the seabed. It shows the seabed surface’s top 10 to 50 metres of sediment.

“This acoustic data allows us to interpret whether part of the seabed was previously covered by the ice-sheet, whether the seabed is hard or soft, and whether the layers of sediment are disturbed or undisturbed,” Dr McNeil explains.

This information was then provided to the geology team, who would use it to decide where to collect the sediment cores and how deep to core them. “These sediment cores will help us reconstruct the palaeoenvironment over time and hopefully provide ages for ice sheet advance and retreat,” Dr McNeil says.

Dr McNeil certainly wasn’t stuck in The Batcave for the entire voyage. She got to take a helicopter flight over the Vanderford Glacier to observe the structure of the ice surface, as well as land on the continent to help construct a global navigation satellite system (GNSS) station that will help measure ice sheet movement and relative sea level. She also saw the Aurora Australis for the first time and a bevy of wildlife, “we saw many whales, mostly Humpback and Minke, Emperor and Adelie penguins, Weddell, Crabeater and Leopard seals, plus lots of birds including albatross and snow petrels.”

She also qualifies that from The Batcave, “There were portholes to look out of but often they were covered with heavy steel shutters in case of storm waves.”

Dr McNeil says that the weather was highly variable, with everything from clear blue skies to blizzards to days of “pea soup fog.” As with any voyage to the Southern Ocean, the weather was a constant challenge making the daily weather forecasts a critical part of planning, especially when flying helicopters and deploying scientific instruments from the ship’s deck. This meant they always had to have a Plan B (and often a C and D) and accept that sometimes they couldn’t complete everything they’d planned.

However, the team has returned having mapped an incredible ~134,350 m2 of the seabed and collected ~18,000 km of sub-surface profiles and 39 sediment cores across three locations between Wilhelm II Land and Wilkes Land, near Australia’s Casey Station. They also set up four GNSS stations, tagged 15 seals, deployed 7 Argo floats, and collected continuous atmospheric methane measurements.

Now back out in the light and on land, the work begins to process and analyse all these samples and their data for insights into the East Antarctic Ice Sheets history to help us predict our future.

Dr McNeil thanks Professor Andrew Mackintosh, Geoscience Australia, and the Alfred Wegener Institute for supporting her participation in the voyage. She also thanks all the scientists and crew onboard, especially the voyage Chief Scientist Sebastian Krastel from Christian Albrecht University Kiel for his leadership and support.

About the author

Anna Quinn is SAEF’s Senior Communications Adviser