Rights: The University of Waikato Published 21 June 2007 Download

Dr Katja Riedel of NIWA explains how the air that was trapped in the ice is being extracted. The scientist uses a device she nicknames “the cheese grater”.


Once we have ice cores back here in Wellington, we try to extract this air out of the ice core, and we do this by grating the ice, and we have a device called a cheese grater, but it’s official name is probably the gas extraction device. That is a very big glass container with a metal grater inside. And we put this 1 kg ice piece inside, and then take all the air out, and we call that we’re putting a vacuum on it and we shake the hell out of it.

So it’s really vigorously shaking, and the whole block of ice becomes small ice flakes and fluffy snow back again, and that means that all the little bubbles are now destroyed.
Once we have the air out of the ice, we need to get the air into something else, and we do this by using a cryo cooler, and that is an instrument that makes very cold temperatures, and we use here liquid helium to do that. And it cools down to 15 kelven, which is really, really cold. And you really don’t want to stick your finger in that, because your finger would fall off immediately. So we use this cold plate there to freeze over all the air, so the air is actually not gas any more, but it’s really liquid or kind of even solid. So that is how we freeze it over into what we call a trap, but this container then we can take to our different instruments, and chuck it on there and measure it.