Sunday, December 29, 2013
Saturday 28 December
The misty conditions quickly lifted and it has become a warm, bright sunny Saturday. Just after breakfast it was almost like a Saturday morning in suburbia, but the âœlawnmowerâ sound was doctor Malcolm using the snow-blower to excavate a trench to take our ice core boxes: very timely given the warm conditions, as we need to get them out of the sun.
One of the Hobart scientists, Andrew, has got a laser spectrometer up and running and is measuring our first ice samples (for those interested, this device measures isotopes of oxygen and hydrogen in the water/ice, which can be interpreted as past temperatures). We are interested to see seasonal variations in the ice, especially in the shallow sections near the surface, as these will tell us more about the annual snowfall rate here.
The main core drilling continues, at 114 metres, and the team have been working hard to solve some technical problems with the drill. The firn air coring has now reached 102 metres and we are in the special zone called the â˜lock-inâ™ zone, where the ice is still porous enough to allow us to pump trapped air out, but the air itself is now isolated from the modern atmosphere. The point of this is that we can get very large samples of air that is decades old: much larger that can be obtained from bubbles in a relatively small ice core. Such large samples can be used to measure exotic gases like carbon-14 methane.
Others have been busy making use of the good weather to drill a shallow core. This is important because the setup of the big drills makes it difficult to get a nice undisturbed ice core from the surface, which gets trampled and cut away. The shallow core will be about 20-30m deep and the measurements on this core will overlap the other ice cores and allow the continuous record to be assembled.
The changeover of staff between the two half seasons is getting closer. We could be flying out as early as Tuesday, so we are working hard to complete the firn core and air extractions and leaving time to pack up. The actual pumping takes a couple of hours, filling flasks as well as making online measurements. We are looking at the depth remaining (which is sort of unknown, but we estimate to be another 10 metres or so) and figuring out how many extractions we can fit in the time left; the more the better!
How quickly things change â" the firn air coring has hit a nasty snag. The drill stopped feeding near 103 m and after a lot of diagnosis we think the problem is the buildup of fine snowy dust in the bottom of the hole â" accumulated from the drill runs abrading the hole, and probably from the insertion and removal of the long bladder that is used to seal the hole during air extraction. Whatever the exact cause, the drill is not successfully getting a bite on the ice and so our progress is halted. We have a few ideas to try tomorrow, and Trevor, one of the drilling experts in camp says he has seen this problem before and that a solution can generally be found. While this turn of events makes for some suspense/intrigue for readers, I must say Iâ™d prefer a more boring blog at this point!