What lies half a kilometre deep beneath the ice is hoped to tell us about climate change of the past — and how we might shape our future.
An international team of researchers co-led by GNS Science, Victoria University of Wellington and Antarctica New Zealand have used a hot water drill to melt through 580m of ice to obtain the longest sediment core retrieved from the remote Siple Coast.
The 1.92m sediment core – with a geological record potentially dating back millennia hidden within its layers – is expected to provide crucial insight into the West Antarctic Ice Sheet's past response to climate warming, GNS Science, Victoria University of Wellington and Antarctica New Zealand said today in a joint press release.
The core was retrieved by a 27-person strong contingent of scientists, drillers and other crew members who set up camp at the KIS-3 drilling site, the "grounding zone" of the West Antarctic Ice Sheet where the vast ice mass begins to float as the Ross Ice Shelf.
Located 860km from Scott Base, the team lived and worked in tents on the ice from late November through to January as part of the Sensitivity of the West Antarctic Ice Sheet to 2°C (SWAIS2C) project, with logistical support from Antarctica New Zealand and the United States Antarctic Program (USAP).
To retrieve the core deep in the Antarctic seafloor, the crew used a hot water drill to melt through nearly 580m of ice, breaking through the base of the ice shelf into the 55m-thick ocean cavity lying between the ice and the ancient layers of mud and rock below. A simple weight-driven coring system that hangs from a rope and winch was then used to punch into the sea floor and bring the sediment back to the ice shelf surface.
The team’s ultimate goal was hugely ambitious – to obtain a geological record contained in sediment layers hidden under the ice shelf, at depths of up to 200 metres below the ocean floor. To retrieve a sediment core this deep into an Antarctic seafloor requires a custom-designed drilling system (known as the AIDD – Antarctic Intermediate Depth Drill).
The drill had never been used so far from a base and so close to the centre of the West Antarctic Ice Sheet.
SWAIS2C's co-chief scientist from GNS Science and Victoria University of Wellington, Richard Levy, said the crewwere attempting "to acquire sediment samples that no one has previously been able to obtain".
"It’s cutting-edge science and incredibly challenging work," Levy said.
However, technical challenges meant operations were halted, and the decision was made to retrieve the equipment and end deep-drilling operations for the season.
"This year we got tantalisingly close. With the knowledge we’ve gained from the samples collected and the technological experiments conducted we have an excellent chance next year to recover the long sediment cores to provide the climate insights we’re chasing," Levy said.
The 200 m core they’re seeking is expected to reach back hundreds of thousands of years – potentially even millions of years. The record would include the last interglacial period 125,000 years ago, when Earth was around 1.5C warmer than pre-industrial temperatures – similar to the temperatures we are approaching this year due to climate change.
Fellow SWAIS2C co-chief scientist Tina van de Flierdt, from Imperial College London, said it will hold valuable information into Antarctic ice and its response to global warning.
"The West Antarctic Ice Sheet is currently losing mass at an unprecedented rate," van de Flierdt said.
"It is one of the most vulnerable components in the Earth system to increasing warming. But we fundamentally do not know when and how fast it will disintegrate and raise global sea level by several metres."
Levy said the "sequence of rocks in the sediment" will give researchers a picture of "how the West Antarctic Ice Sheet behaved when it was a bit warmer than today – if we find marine algae it’s likely the ice sheet retreated".
"This information will allow us to build a much better picture of how Antarctic ice will respond to future warming, which parts will melt first, and which parts will remain," he said.
The samples the team collected from the sea floor will also be studied for their microbiological content to reveal more about the microorganisms living in the environment. Important data was also collected on the ocean currents and properties at the grounding zone.
"These samples offer a huge increase in the amount of material we have to help us understand the present-day environment beneath the ice shelf, and the history those sediments represent. They also give us insight into the types of rock we will need to drill through to get those deeper records we’re seeking," Levy said.
Preparations are underway for SWAIS2C to return to the site next season
"We are thrilled with what we’ve achieved. It’s a massive step forward towards our ultimate goal to recover the sediment we need to answer the big questions that are crucial for humanity as we adapt and plan for sea-level rise," van de Flierdt said.
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