A team of scientists drilling through the edge of the Antarctic ice sheet to study whether its underside may be melting were stunned when they discovered fish more than 700 metres below the surface – and more than 800 kilometres from open ocean.
The researchers are the first to reach and sample the grounding zone of the Antarctic ice sheet - the place where the ice, the land and the ocean all converge. This work builds on earlier seasons of the National Science Foundation’s WISSARD project, during which the team explored the subglacial Whillans Ice Stream, which drains into the Ross Ice Shelf.
Science leader and glacial geologist Ross Powell says one of the primary objectives was to sample sediment in the grounding zone to learn about the mechanics of ice sheets and their potential melting from below. He says scientists are keen to understand the ocean circulation underneath the ice and how the ocean interacts with the underside of the ice where it begins to lift off the land.
'The rate of melting of the ice by the ocean is one of the important factors that governs how fast the ice sheet actually flows into the ocean because the faster it loses ice the faster it will flow into the ocean to replace what is lost.'_Ross Powell
In scientific terms, this is called positive feedback – an increase in melting that in turn leads to more ice loss, continually speeding up the melting process. “One of the big concerns that scientists have in terms of global warming is that, potentially, warm ocean waters can penetrate deep underneath the ice shelf and start melting the bottom of the ice shelf and also right at the grounding line where the major ice sheet comes in contact with the ocean.”
The West Antarctic Ice Sheet, the smaller of two ice sheets that cover the continent, is grounded partly below sea level and is therefore thought more sensitive to melting by a warming ocean.
The team used a hot-water drill to melt a 740m-deep hole through the ice to a thing wedge of ocean water, measuring only 10 metres deep and separating the ice from the seafloor. When they lowered a small robot festooned with cameras through the hole, they could see a muddy sea floor strewn with boulders that had been melting out from the underside of the ice.
“That was the first indication that the bottom of the ice was melting,” says Ross Powell, an expat Kiwi based at Northern Illinois University. “When we put the cameras down we could see material raining out from the bottom of the ice.”
But then, a fish swam into view - leaving him “gobsmacked”.
Ross Powell says the team included microbiologists because everybody expected to find microbial life, but there were no biologists specialising in any creatures of a higher taxonomic order.
'I’ve worked in these environments for close to 40 years now and they are never that hospitable to any life. They certainly don’t have what you’d think of as a supportable food web for organisms to live on. The fact of a higher order of biology there was just totally flooring to me.'
While the images of the fish and invertebrates the team discovered are now being identified by experts, Ross Powell and his team members will focus on analysing the sediment and ice samples they brought back from the perpetually dark and supercooled world under Antarctica’s ice.
“On a small scale it was a bit like what they did at NASA with the moon landing,” says Ross Powell. “I draw analogies to exploring other planets when we do this stuff because these are environments that are totally new to science. Nobody has seen these places before.”