The 228-metre core of ancient mud and rock was drilled from under 523m of ice, at Crary Ice Rise, on the edge of the West Antarctic Ice Sheet, more than 700km from Scott Base, and is believed to be the longest ever drilled from under an ice sheet.
The core is now in more manageable 1m sections at the University of Otago Repository for Core Analysis (ORCA) facility, in Dunedin, and is being examined by scientists from around the world over the next two weeks.
The core was recovered as part of the Sensitivity of the West Antarctic Ice Sheet to 2°C project (SWAIS2C), which was led by Earth Sciences New Zealand, Victoria University of Wellington and Antarctica New Zealand.
More than 120 scientists from about 50 international research organisations are collaborating on the project.
Now many of them are examining the core sediment for telltale indications of the environmental conditions under which it was deposited.
Victoria University of Wellington Antarctic Research Centre director Rob McKay said the core aimed to capture a history of whether or not the West Antarctic Ice Sheet had always been there, or whether it had melted in the past when there were warmer climates.
‘‘We’re only 10 metres down into that sediment at the moment, but we’re already seeing a change from when there are lots of glaciers, to when there’s almost none.
‘‘A core that’s just been cut open a minute ago is full of little microscopic algae that live in open waters.
‘‘So to have open water algae, fossils, in the sediment means there was no ice sheet cover over that site.’’
He said experts from around the world were studying the cores, and could tell how old the sediment was by the type of fossils of marine organisms that were found in it.
‘‘So if those species went extinct five million years ago, we know that those sediments are older than five million years ago.
‘‘It’s still a work in progress, but we think we’re heading into those climates that are slightly older than five million years ago at the moment.’’
Prof McKay said scientists were worried about ice shelves breaking up, because if the vast West Antarctic Ice Sheet melted, it held enough ice to raise global sea level by 4m-5m.
Satellite observations over recent decades showed the ice sheet was losing mass at an accelerating rate, but there was uncertainty around the temperature increase that could trigger rapid loss of ice.
In addition to pinning down the time when the ice would fully melt and the corresponding global temperature, analysis would help scientists quantify the environmental factors that drove the ice sheet retreat, such as determining what the ocean temperatures were at that time.
‘‘Sea level is rising, on average, about 3mm a year, but it’s actually increased quite rapidly in the last few years, largely because of the extreme warming.
‘‘It’s very hard to get rates of retreat from these sediments, but what these sediments do is allow us to plug numbers into computer models, and we’ll see if we can recreate that amount of ice change in the past.
‘‘Those are the tools that we use to project how rapid sea level rise could occur in the future.’’
It would provide vital information for climate scientists to help the world prepare for the impacts of climate change.
