Dr Katja Riedel of NIWA explains how ice cores are collected and that drilling in the ice has to be conducted in a careful manner.
DR KATJA RIEDEL
We collect ice cores by drilling for the ice. So the first thing is we travel to Antarctica and then we build up a big drilling rig. And there are 2 ways of drilling. One is that you either use heat, and that is melting, you simply melt the ice, or the other way is you just drill like your dentist will drill into your teeth with a little diamond drill. But our little diamond drill would have 20 centimetres in diameter and would weigh several tonnes.
We want an ice core as long as possible. And one thing here is that the ice is a kind of liquid and very slowly it flows. And at some stage all the ice pressure around your drill hole will actually close your drill hole. So you bring down your drill, drill 1 or 2 metres, bring the drill up, take out the ice core, and then feed the drill back down again. So you do it piece by piece.