Unexpected "Swarm" Of Marine Life In Newly Explored Antarctic River Deep Beneath The Ice

A team of scientists from Te Herenga Waka - Victoria University of Wellington, NIWA, and GNS have made an astonishing discovery 500m under the Antarctic ice.

The Antarctica New Zealand-supported researchers were studying a suspected under-ice estuary, hundreds of kilometres from the edge of the Ross Ice Shelf, to see what role it plays in climate-induced ice shelf melt. When they drilled down into the river, their camera was inundated by dozens of small amphipods - a type of animal from the same family that includes lobsters, crabs, and mites.

Professor Craig Stevens is a NIWA Physical Oceanographer and was part of the team. He said that while there was a climate change motivation for the work, there was a huge element of discovery on the expedition.

"We’ve done experiments in other parts of the ice shelf and thought we had a handle on things, but this time big surprises were thrown up. For a while, we thought something was wrong with the camera but when the focus improved, we noticed a swarm of arthropods around 5mm in size," Professor Stevens said.

"We were jumping up and down because having all those animals swimming around our equipment means that there’s clearly an important ecosystem there. We’ve taken some water samples back to the lab to look at the DNA and other properties of the water to see what makes it unique, as we were observing something not seen in other systems close by," he said.

The estuary was initially spotted by Huw Horgan, Associate Professor of geophysical glaciology at the Antarctic Research Centre at Te Herenga Waka, and the project’s lead.

He was studying satellite imagery of the Ross Ice Shelf from his office computer when something caught his eye. He spotted a groove in the ice and suspected something interesting was going on there - probably an under-ice estuary.

Researchers have known there’s a network of hidden freshwater lakes and rivers flowing underneath the Antarctic ice sheets. Dr Horgan says that these hidden rivers had yet to be directly surveyed.

"Getting to observe and sample this river was like being the first to enter a hidden world. On the ice shelf surface there is a little valley snaking down to the coast. Beneath this, there is a cathedral-like cavern, hundreds of meters high, teeming with life. All this hidden under the vast ice shelf," Dr Horgan said.

"It was an incredibly exciting expedition because of the rare opportunity it offered to study this type of environment. We’ve left instruments there that should provide observations for years to come. This will tell us about the water flow, temperature and pressure at two-minute intervals so we can get a good picture of how the river behaves and how it interacts with the ocean and ice sheet," he said.

The findings didn’t end there - the team had deployed their mooring just a few days before the dramatic eruption of the Tonga volcano, Hunga Tonga- Hunga Ha’apai. While studying the estuary, their instruments detected a significant pressure change as the tsunami made its way through the cavity.

Craig Stevens said that seeing the effect of the Tongan volcano, which erupted thousands of kilometres away, reminded him just how connected our whole planet is.

"Here we are, in a forgotten corner of the world, seeing real-time influences from events that felt worlds away. It was quite remarkable," he said.

Dr Richard Levy from GNS Science and Te Herenga Waka - Victoria University of Wellington leads the programme that supported the discovery.

"It’s discoveries like these that emphasise how much there is to learn about the Antarctic system," Dr Levy said.

"The ice sheets have a massive influence on sea level. Not only are we working to better determine what they will do in the future, but we get to make these startling and unexpected discoveries along the way."

Supported by Antarctica New Zealand, this field work was undertaken by a multidisciplinary team from Te Herenga Waka-Victoria University of Wellington’s Antarctic Research Centre, NIWA, GNS Science, and the Universities of Otago and Auckland. It was funded by the Antarctic Science Platform, Te Herenga Waka and Royal Society of New Zealand, as part of strategic Antarctic science investment improving our understanding of climate change and ecosystems resilience.

Read more about the story and other Antarctic research in the latest issue of Water & Atsmosphere: https://niwa.co.nz/news/the-search-for-answers-in-the-ice

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