A surprising lesson from Antarctica: Life flourishes even under 500 feet of ice
Scientists found "a beautiful, thriving ecosystem" in a dark and isolated location: The former shadow of a glacier.
When an iceberg the size of Chicago broke off from one of Antarctica's massive floating glaciers in January, a team of scientists working nearby quickly pivoted, steering their ship to explore the newly revealed seafloor.
What they found surprised and amazed them.
“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," said Patricia Esquete of the Centre for Environmental and Marine Studies and the Department of Biology at the University of Aveiro, Portugal.
She was part of an international team of scientists from the Schmidt Ocean Institute working in the Bellingshausen Sea. When they got word that a new iceberg, named A-84, had broken off, they shifted their work to see what was revealed on a seabed that had been covered by almost 500 feet of ice for centuries.
Less than two weeks later, they were in place and began using autonomous underwater vehicles called gliders to quickly inventory what proved to be a thriving ecosystem that had lived for hundreds of years with no light and few nutrients.
“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,” Esquete said.
Douglas McCauley, a professor of ocean science at the University of California, Santa Barbara, was impressed the research team was flexible enough to divert course to take those observations.
"Some of the best discoveries come when disciplined scientists that have spent years planning every minute of a cruise years in advance are brave enough to go: 'OMG a gigantic iceberg just calved off – let go see what was under that!'" he said.
It proved to be a fortuitous diversion of their ship, R/V Falkor (Too). In water as much as 4,200 feet deep the team from the Schmidt Ocean Institute found a surprisingly flourishing ecosystem that included icefish, giant sea spiders, octopus, corals and sponges.
They suspect they've found several new species, but determining that will take time.
Such opportunities to see what lives in these areas are rare, said Andrew Thurber, a professor of Ecology, Evolution, and Marine Biology at UC Santa Barbara who specializes in Antarctic research.
With the advent of remote submersible robots it shouldn't be hard to work under significant ice, he said, but it remains a serious technological challenge for marine science.
It's not just "Send a robot under the ice and it comes back with cool data," he said. "In reality, they often have issues and with hundreds of meters of ice over their head – the odds of getting home become bleak."
What are these sea creatures eating under the ice?
One of the mysteries of the discovery is what these sea creatures have been eating. Close to a mile down, with a 500-foot layer of ice between them and the sun for centuries, there's not a lot of choice when it comes to dinner.
"These communities are very far removed from the sun and this source of energy," Thurber said.
In the deepest depths of the ocean, sea inhabitants rely on a constant rain of nutrients that slowly sinks down from the surface.
Called "marine snow," it's composed of dead animals, plants, feces and other organic materials. The name comes from the fact that it looks like "little white fluffy bits" slowly falling through the water column, according to the National Oceanographic and Atmospheric Administration.
But the newly uncovered area has been covered by ice for centuries, cut off from surface nutrients. The discovery of so much life – and such big life – was unanticipated, Thurber said.
"We would expect there to be an animal community that is more like what is in the deep-deep sea, which is smaller animals and incredible diversity but not large animals except in unique cases," he said.
Instead there were large invertebrates. "That is why this is such a surprising discovery," he said.
The scientists hypothesize that ocean currents are moving nutrients around and that the currents are possibly the mechanism that sustains life beneath the ice sheet, though how that works precisely isn't yet known.
Where did this iceberg come from?
The iceberg, named A-84, broke away from the George VI Ice Shelf, one of the massive floating glaciers attached to the Antarctic Peninsula. Ice shelves are permanent floating sheets of ice that connect to a landmass, according to the National Snow and Ice Data Center. Such ice shelves are an important part of the earth's cryosphere.
The breaking off of this huge iceberg is an example of the ongoing shrinkage happening at the earth's poles over the past few decades as part of climate change.
This raises a question of what to do with the newly opened areas.
"Open seafloor can either be an area to expand industry but also opens up pristine habitats with unknown biodiversity, potential for drug discovery, and often long lived species that are susceptible to human activities," Thurber said.
Should the areas be turned into marine conservation areas or exploited, most likely for fishing?
"I think that is something that we, as a global collaborative community charged with management of the Antarctic, are faced with in light of our rapidly changing globe," he said.
Can these mysterious creatures survive in open ocean?
One of the biggest questions for the scientists is whether the sea creatures that had been happily living in an ecosystem covered by ice will fare now that the ice is gone.
"Some of them can move. Some of them, though, are embedded in that seabed. So they're anchored in place and they of course, will not be able to move," said Jyotika Virmani, executive director of Schmidt Ocean Institute.
"Until we go back or until scientists go back in a few months or a year, it's really difficult to say how this ecosystem is going to evolve," she said. "But the the fact that we have this baseline information is phenomenal."