Ancient ice cores begin journey north
More than 100 boxes full of ‘‘white gold’’, unlocked from the icy depths of Antarctica, are destined to provide one of the most significant climate records yet.
A team of scientists from nine nations, led by Dr Nancy Bertler of the Antarctic Research Centre at Victoria University and GNS Science, hit bedrock on Roosevelt Island, in the Ross Sea, at the end of last month.
They had successfully drilled more than 760 metres through an ice sheet.
The ice cores from the Roosevelt Island Climate Evolution project (RICE) will provide the most detailed record of the climate history of the Ross Sea region for the last 30,000 years, during which time the coastal margin of the Antarctic ice sheet retreated after the last great Ice Age.
The data will enable scientists to determine the stability of the Ross Ice Shelf and the West Antarctic Ice Sheet, and establish how they’re likely to respond to global warming.
The cores will be analysed in the purpose-built National Ice Core Research Laboratory at GNS Science in Wellington, but they have to get there first.
A final load of cores and snow samples was delivered to Willy’s Field in McMurdo Sound on a Basler DC3 aircraft last week, and quickly transferred to a refrigerated ‘‘reefer’’, or container.
The 8km journey back to Scott Base took two hours. The reefer was dragged behind a Pisten Bully vehicle, and hooked up to a generator to help keep temperatures down.
Antarctica New Zealand staff were responsible for transporting the cores, and New Zealand Defence Force cargo handler Nicola Lang said it was crucial to keep them from warming or breaking.
Ms Lang said if the cores were damaged in transit, ‘‘you would probably want to run away and hitch a ride to West Antarctica’’.
Dr Bertler said the RICE project, which had seen $7 million in science funding so far, would never have existed without Antarctica NZ’s ‘‘brave’’ support in carrying the burden of logistics for another eight nations.
‘‘Years ago this was seen as an enormous challenge. We’re extremely proud that it was possible, and that we were able to pull it off as a collaboration and as a nation.’’
Dr Bertler said drilling through ice was usually done using a winch system, but the Roosevelt Island team used a ‘‘completely new’’ hydraulic system constructed by Antarctic Research Centre technologists Alex Pyne and Darcy Mandeno, alongside Nelson engineering firm Promachining.
The team expected to encounter brittle ice below 300m, resulting in poor-quality cores, but ‘‘the new technology has been so superior that we got really great core quality all the way to the bottom, which is unheard of’’.
Drilling was completed two weeks ahead of schedule, with ‘‘core like nobody else has recovered from brittle ice. We can break the core much more gently, and far more precisely’’.
The team reached the bottom on December 20, which was an ‘‘amazing moment’’, and it took al- most a tonne of force to break off the last two-metre core.
Dr Bertler said night shift workers brought up a final section of ice, at only 23cm, with ‘‘a clean pluck’’ from the bedrock.
‘‘We sent the drill down again, just to make sure. The next time it came up, it didn’t bring any ice – just sediment. We think there is a possibility that the sediment is from the last inter-glacial period, which is thought to be the last time Roosevelt Island was under water and the most recent time in the past where Earth was slightly warmer than it is now.’’
Average global temperatures were about 1 degree Celsius warmer during the last inter-glacial period, which was ‘‘where we’re heading in the very near future. The increase will depend very much on the path we follow. We have already increased the temperature by 0.7 degrees since 1850’’.
RICE is one of the most logistically significant projects Antarctica NZ has ever supported, at a cost of $4m over four years.
Antarctica NZ programme support supervisor Simon Trotter said supporting the project included setting up the camp at Roosevelt Island, providing staff such as a mechanic and a cook to keep the camp running, transporting the drill rig, fuel and people, as well as getting the cores to Wel- lington intact. Mr Trotter said staff breathed a sigh of relief when the last load made it to Scott Base, because the ice cores were an extremely valuable commodity.
‘‘It’s like gold in terms of the value and in the way it’s treated; gold would be easier to manage.’’
Mr Trotter said the camp would be ‘‘winterised’’ before everyone left Roosevelt Island, and the cargo left behind would be retrieved early next season.
A cargo ship would take the reefer from McMurdo Sound to Lyttelton at the end of February, a nine-day journey, with a backup generator. Trucks would take them on to Wellington in March.
‘‘That’s just the beginning – then the science begins. This core is going to have a climate record that we haven’t seen before. There’s a lot of interest out there.’’
Dr Bertler said temperatures at Roosevelt Island were a lot warmer this season than she had previously experienced, with visible surface melting.
‘‘We’ve been coming to Roosevelt Island for three years now, and this is by far the warmest year we’ve had. The snow pack is very wet. We can’t really say that’s part of global warming, but it has certainly stimulated a lot of discussions around the dinner table about where we’re heading.’’
About 30 top scientists from all nine contributing nations – New Zealand, Australia, Denmark, Germany, Italy, Sweden, the United Kingdom, the United States and China – will descend on Wellington to work on the cores from May to August.
Dr Bertler said the first set of data from the project would be available by August, and the RICE steering committee wanted to have the bulk of its findings available in the next four years – in time for the next Intergovernmental Panel on Climate Change report.
‘‘There will be projects for many, many years to come from the data. No money could come close to describing the value of that core."