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Antarctic voyage will explore ocean hidden under ice for 100,000 years

February 15, 2019 This article courtesy of Nature News.

Scientists on board German research icebreaker Polarstern hope to observe underwater ecosystem changing in real-time.

Scientists are setting out to explore a marine realm that was hidden from the Sun for more than 100,000 years.

In July 2017, a giant iceberg broke off from the Larsen C ice shelf east of the Antarctic Peninsula, revealing a large swathe of ocean that had lain in darkness beneath the ice.

The newly exposed seabed might hold clues to the evolution and mobility of marine life and its response to climate change.

A team led by Boris Dorschel, chief scientist of a 45-strong international team on board the German research icebreaker Polarstern, is planning to set off from Chile this week to explore for the first time the sea that the ice had concealed. The ship is currently docked in Puntas Arena in Chile, where it is being loaded for the nine-week expedition.

But the remote area is hard to reach, and severe weather could make it challenging to conduct research there.

“It’s thrilling to explore one of the last white spots on Earth,” says Dorschel, who is based at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany. “But it’s a nerve-racking affair, too. Local weather and ice conditions might interfere any time.”

The 5,800-square-kilometre chunk of ice chunk of ice that calved from Larsen C in 2017 has since drifted some 200 kilometres northwards.

What lies beneath

Scientists are keen to explore what species might have thrived under the ice, and how the ecosystem has coped with the sudden change. The first attempt to do so failed last year, when sea ice up to 5 metres thick forced the James Clark Ross vessel, operated by the British Antarctic Survey (BAS), to turn back in February 2018.

“We were close,” says Katrin Linse, a BAS marine biologist in Cambridge, UK, who led the foiled expedition. “And it was a devastating day when the captain decided to turn round.”

Linse is unable to take part in this year’s cruise, but members of her team are on board. In her Cambridge office — 13,000 kilometres from Puntas Arena — she nervously studies maps of sea ice every day, hoping that the route will be clear.

Conditions currently look favourable: the ice that stopped the BAS expedition is now drifting out of the Weddell Sea, a Southern Ocean region between the Antarctic Peninsula and mainland Antarctica farther to the east.

In January, a team on board the South African research vessel Agulhas II anchored at a site 200 kilometres north of where the iceberg broke off. It took ocean and sea-floor samples there, but sea-ice conditions and other research priorities meant it didn’t go further south. The Polarstern will now attempt to advance farther south, to the site where the iceberg calved.

The Polarstern, operated by the Alfred Wegener Institute, is Germany’s flagship polar explorer vessel and one of the best-equipped research icebreakers in the world. Satellite imagery and renaissance flights by its two helicopters will guide the ship through the pack ice — ice floating in the sea, formed by smaller pieces freezing together — which can be abundant even in southern summer months, when the extent of sea ice is close to its annual minimum.

Under a southern Sun

If ice and weather conditions allow, the team could reach the site from Chile within just a few days. The scientists would then have several weeks of southern summer to extensively sample ocean fauna and chemistry, and to map the uncharted seabed.

“We’ll work around the clock to collect as much data as possible,” says Dorschel. “We’ve tools on board which should provide a perfect view of the ocean and the sea floor.”

In addition to standard water-sampling tools, the scientists will use a small, remotely operated vehicle for underwater exploration, and a towed ocean-floor observation system for optical and acoustic surveys of deep-sea topography and habitats.

The team suspects that a deep-sea ecosystem such as in the Weddell Sea evolved in the darkness beneath the ice.

That ecosystem may change significantly within a few years if new species colonize the area. Isotopic analysis of tissue from species such as gastropods and bivalves could reveal whether the food web has changed already since the iceberg broke off, as chemical signatures in animals’ tissues hold clue to their diets.

Untouched by human hands

Samples collected in the pristine area, completely unaffected by commercial fishing or other human activities, would be an invaluable resource for biodiversity researchers. The data could help scientists to address questions relating to how marine communities develop, and how quickly new species colonize previously ice-covered areas, says Linse.

Rapidly rising temperatures in the air and ocean around the Antarctic peninsula, a hotspot of global climate change, add urgency to such research: any changes in species composition and food-web structure following the disappearance of ice might shed light on the fate of polar ecosystems in a warming world.

“Here’s a unique opportunity to find out how vulnerable or resilient marine life is to rapid environmental change,” Linse says. “This is exciting science for us all — I hope very much that it can be done.”


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