A “serendipitous” discovery offers new insights into how ecosystems can thrive beneath floating sections of the Antarctic ice sheet.
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Giant sea spiders, ice fish and octopuses are among the surprisingly abundant creatures scientists have found in a stretch of sea that used to be covered by ice.
An international team onboard the Schmidt Ocean Institute’s Falkor (too) research vessel were on a trip around Antarctica earlier this year, studying “the interface between ice and sea” when a rare opportunity suddenly opened up.
On 13 January, an iceberg the size of Chicago named A-84 broke away from the George VI Ice Shelf, one of the massive floating glaciers attached to the Antarctic Peninsula ice sheet.
“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,” says expedition co-chief scientist Dr Patricia Esquete from 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.”
What did the scientists find under the iceberg space?
Pausing their work in the Bellingshausen Sea, the team reached the site of the vacated iceberg on 25 January, becoming the first to investigate an area never before accessible to humans.
They carried out the first detailed study of the geology, physical oceanography and biology beneath such a large area once covered by a floating ice shelf. The ice that calved off of the sheet was approximately 510 square kilometres - exposing an equivalent area of seafloor.
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 of 1,300 metres.
Large corals and sponges were discovered supporting an array of animal life, including what the team suspect to be several new species - though it will take years to determine this.
How does life survive beneath a floating ice sheet?
Little is known about what dwells beneath Antarctica’s floating ice shelves. This expedition is the first to use an ROV to explore this remote environment. It offers new insights into how ecosystems can function in such submerged depths.
Deep-sea ecosystems typically rely on nutrients from the surface slowly raining down to the seafloor, the Schmidt Ocean Institute explains.
However, these Antarctic ecosystems have been covered by 150-metre-thick ice for centuries, completely cut off from surface nutrients.
Ocean currents also move nutrients, and the team says that currents are a possible mechanism for sustaining life beneath the ice sheet. The precise process is still a mystery, however.
What else does the Antarctic ice shelf expedition teach us?
“Serendipitous moments are part of the excitement of research at sea - they offer the chance to be the first to witness the untouched beauty of our world,” says Schmidt Ocean Institute executive director, Dr Jyotika Virmani.
Although the stuff of marine researchers’ dreams, the circumstances around the iceberg’s breakaway are concerning.
Iceberg calving is a normal occurrence for ice shelves. But climate change is accelerating the process, causing the ice sheet to shrink over the last few decades.
“The ice loss from the Antarctic Ice Sheet is a major contributor to sea level rise worldwide,” says expedition co-chief scientist Sasha Montelli of the UK’s University College London (UCL).
The international team - comprising scientists from Chile, Germany, Norway, New Zealand, and the US - also used the opportunity to gather data on the ice sheet’s past behaviour.
And they deployed autonomous underwater vehicles called gliders to study the impacts of glacial meltwater on the region. Preliminary data suggest “high biological productivity” and a strong meltwater flow from the George IV ice shelf.
“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,” says Montelli.
“We will undoubtedly make new discoveries as we continue to analyse this vital data,” she adds - so watch this space.
