ANTARCTICA: Scientists have discovered vibrant communities of ancient sponges and corals on the newly exposed seafloor following the calving of the giant A-84 iceberg. This offers new insights into how ecosystems function beneath ice shelves
An international team on board Schmidt Ocean Institute's R/V Falkor (too) working in the Bellingshausen Sea rapidly changed their research plans to study an area that was, until recently, covered by ice. On 13 January, an iceberg named A-84, which is the size of Chicago, broke away from the George VI Ice Shelf, one of the massive floating ice shelves attached to the Antarctic Peninsula.
The team reached the newly exposed seafloor on 25 January and became the first to investigate an area that had never before been accessible to humans. The expedition was the first detailed, comprehensive, and interdisciplinary study of the geology, physical oceanography, and biology beneath such a large area once covered by a floating ice shelf. The ice that calved was 510 square kilometres (209 square miles), revealing an equivalent area of seafloor.
"We seized upon the moment, changed our expedition plan, and went for it so we could look at what was happening in the depths below," said expedition co-chief scientist Dr Patricia Esquete of the Centre for Environmental and Marine Studies (CESAM) and the Department of Biology (DBio) at the University of Aveiro, Portugal. "We didn't expect to find such a beautiful, thriving ecosystem. Based on the size of the animals, the communities we observed have been there for decades, maybe even hundreds of years."
Using Schmidt Ocean Institute's remotely operated vehicle, ROV SuBastian, the team observed the deep seafloor for eight days and found flourishing ecosystems at depths as great as 1300 metres. Their observations include large corals and sponges supporting an array of animal life, including icefish, giant sea spiders, and octopus.
Little is known about what dwells beneath Antarctica's floating ice shelves. In 2021, British Antarctic Survey (BAS) researchers first reported signs of bottom-dwelling life beneath the Filchner-Ronne ice shelf in the Southern Weddell Sea. The expedition on R/V Falkor (too) was the first to use an ROV to explore sweeping landscapes containing abundant life in this remote environment.
The team was surprised by the significant biomass and biodiversity of the ecosystems and suspect they have discovered several new species.
Deep-sea ecosystems typically rely on nutrients from the surface slowly raining down to the seafloor. However, these Antarctic ecosystems have been covered by 150-meter-thick (almost 500 feet) ice for centuries, completely cut off from surface nutrients. Ocean currents also move nutrients, and the team hypothesizes that currents are a possible mechanism for sustaining life beneath the ice sheet. The precise mechanism fueling these ecosystems is not yet understood.
In addition to collecting biological and geological samples, a team of oceanographers, led by the University of Cambridge, the University of East Anglia and the British Antarctic Survey, deployed autonomous underwater vehicles to characterise the ocean circulation of the region, and study the impacts of glacial meltwater on the physical and chemical seawater properties. Preliminary data suggests that the meltwater flow could be the source of the nutrients sustaining the thriving life found under the newly exposed ice shelf.
The newly exposed Antarctic seafloor also allowed the international team, with scientists from Portugal, the United Kingdom, Chile, Germany, Norway, New Zealand, and the United States, to gather critical data on the past behaviour of the larger Antarctic ice sheet. The ice sheet has been shrinking and losing mass over the last few decades due to climate change.
"The ice loss from the Antarctic Ice Sheet is a major contributor to sea level rise worldwide," said expedition co-chief scientist Sasha Montelli of University College London (UCL), United Kingdom, also a 2019 Schmidt Science Fellow. "Our work is critical for providing longer-term context of these recent changes, improving our ability to make projections of future change - projections that can inform actionable policies. We will undoubtedly make new discoveries as we continue to analyse this vital data."
The expedition was part of Challenger 150, a global cooperative focused on deep-sea biological research and endorsed by the Intergovernmental Oceanographic Commission of UNESCO (IOC/UNESCO) as an Ocean Decade Action.
Dr Svetlana Radionovskaya, a paleoceanographer and marine geologist from BAS was onboard. She says:
"We were thrilled by the incredible opportunity to move into the area and explore the newly exposed seafloor. These samples and research will provide key insights into ice sheet dynamics, oceanography and sub-ice shelf ecosystems. At a time when the West Antarctic Ice Sheet is melting at an alarming rate, understanding these dynamics and their impacts is particularly crucial."
