Earth Science

Out of our original top 3 favourite glaciers to check for ice cores there was still one left to go. This was the Baker Glacier, visible clearly from our previous site on Mount Hutton, almost directly across on the other side of the Murchison Glacier Valley. Baker Glacier is relatively low altitude at 2360 metres. None the less, because it is also east of the Main Divide, it will have relatively low accumulation rates and, with a depth of about 70m, potential for a longer core than we got on Mount Hutton. However the radar images showed a very strong reflector at about 30 – 40 metres, possibly due to the presence of water or rock debris about half way down, a potential indicator of trouble ahead. By now we had our gear preparation down to a tee, and were set for another blitz approach to get in and out before impending bad weather trapped us in. We flew in to the upper part of the Baker Glacier, directly opposite the imposing cliffs of the East Face of Malte Brun. Almost immediately an ice avalanche rumbled down the face, I guess as some sort of greeting to us.Within a couple of hours the drill was set to go and the tents were in place. After getting past the initial surface snow, we were soon pulling up nice quality ice cores, full of air bubbles trapped within a matrix of ice. As usual, Uwe helped Xinsheng at the drill control box and I worked with Dan bagging, labelling and packing the cores. Evening fell whilst we continued working, expecting to go on until the early hours, all being well with the ice. However at about 8.30pm, with 30 metres of core recovered, we suddenly started getting wet ice again. The strong reflector layer in the radar images was explained. One further drill section confirmed that the ice was getting wetter and Xinsheng again called a halt to the drilling. We were to get some sleep after all. In the photo, Dan is holding the final section of ice core that we drilled. We decided to pack up as much as possible in order to make a swift departure in the morning. Once the net load was more or less organised, we got out the dice and played a game of Zilch, sitting on ice core boxes with our head torched on. During the night occasional avalanches roared down the cliffs in the dark. A beautiful sunrise lit up the scene as we got ready for our final helicopter ride down to the valley floor.

After yet another day of sorting out and preparing our gear, the weather forecast looked quite promising for a few days. We decided to fly back up to Mount Hutton and drill non stop until we either came to bedrock of had to stop for other reasons, such as water in the ice. The four of us -Xinsheng, Dan, Uwe and myself, again flew up to the peak. It is a spectacular location with steep drop offs falling hundreds of metres down on all sides. Once up there you are committed! A sky of whispy clouds stretched above Mount Cook . Our heli put us safely on the landing spot, with our emergency survival gear (tents, food and extra warm clothing). This is standard procedure just in case something prevents the second load from being delivered – a sudden change in the weather or problems with the heli. Whilst the other three went up to the drill site (the same place that we had drilled our 10 metres core already), I walked across to a beautiful horizontal scoop in the snow that we had chosen for a campsite. Although the weather was sunny and calm, I made sure that the tents were well attached to the ground with snow stakes and shovel loads of snow on their snow flaps. We wanted to be able to go to bed very late without worrying about a change in the weather. By about lunchtime I could hear the humming of the generator at the site about 200 metres away telling me that the drilling had started. Once finished with the campsite I walked up to the others, feeling the effort more than usual due to the altitude. The drill site was now top notch. We had an upgraded snow wall to keep the wind off us, the drill pit was enlarged and the hot plate was on, melting snow for hot drinks and food. Uwe had decided to start a new core right next to the previous one to see if we could get a better quality first 10 metres that was less broken into sections than the first had been. Progress was very good, with no technical problems. The ice was mostly very bubbly glacier ice, immediately below this year’s winter snow. At the top there was a distinct layer of small pebbles and grit, but below that we saw little evidence of summer dirt layers. Sometimes there were clear areas in the ice, suggesting melting and re-freezing, but we found it difficult to interpret the age of the ice or what its features were telling us. Is it a remnant of old ice or all quite recent? Only the later analysis will tell. Uwe was measuring the ice temperature in the cores, which stayed consistently below freezing at about – 3 deg C. This was very promising! We had never drilled ice below 0 deg before. At last we had found some accessible cold ice in the Southern Alps! Once the routine of drilling and bagging the cores was established, there was time to look around, take pictures and chat. As the drill gets deeper, it takes longer and longer to winch up the core each time.  I took advantage of the opportunity to take an ice axe and climb the short distance up to the summit for a view from the top.Taking care not to slip I peered down the East face – a very long way down! After a few minutes I carefully cut steps back down off the summit to rejoin the others. The photo shows my tracks from near the top and you can see the drill site and our tents in the distance Just around 9pm we started to find bits of gravel in the ice cores at about 33 metres depth. Then suddenly Xinsheng said “Is finished!” – We could hear the drill clunking against rock down below in the hole. The first ever New Zealand ice core drilled to bedrock had just been drilled, a humble 35 metres from the surface.

Today we flew up to our highest planned drill site on Mount Hutton. Yulan stayed behind, and with us instead were Tom McRae and Ron Madden from TV1. Because of the prospect of poor weather forecasted for tomorrow, we had decided to do a rapid reconnaissance drill only. If the results proved to be good we would come back with a better weather window to drill deeper. Mount Hutton is relatively remote – on the eastern side of the Park in the Liebig Range. We hoped that with the higher elevation and the location some distance away from the main divide, we would get a better preserved and longer climate record. Our radar survey showed a depth of only 50 metres of ice, but perhaps 50 metres of thinner layers would be as good as 100 metres of thicker ice further to the West (such as on Annette Plateau). The flight up was spectacular the icy clouds producing a nice sundog spectrum . Mount Hutton has a small glacier on top. It has a ridge running straight up the middle, and our drill site was about 3/4 of the way up the ridge from our landing site at the bottom. I went a head with Uwe to find our spot and start digging in. The winter snow was only 1.5 metres deep here (as opposed to 4 metres on Annette Plateau)Tom and Ron were interested in what we were attempting, asked lots of questions and interviewed us for their news programme. When they left at about 1pm, Dan went down with them, leaving Uwe, Xinsheng and myself. By 4pm we finished drilling having got down to 10 metres, with very nice, bubbly glacier ice immediately below the top surface snow. The heli arrived and flew away with the net load of gear, then returned half an hour later to pick us up. The evening light was beautiful across the big peaks of the Southern Alps.

Dan and I got up early and each went of for a walk around the glacier. I climbed up Mount Annette and then returned through the wind scoop. The plane arrived and by the time it was fully packed there was no room to fit both of us in! I decided I would be happy to walk down to the village. I set out with a pair of bamboo poles and snow shoes. The way down involved crossing some steep slopes, with wonderful views across the Mueller glacier and I was happy when I reached the valley floor where Uwe had come to pick me up. The photo shows the tracks I followed across the mountainside.

Yesterday we dragged the drill and equipment across the glacier, set it up in a newly dug pit and made a protective wall of snow blocks. After 10 metres we came to wet ice and decided there was no point to continue. Back to the drawing board.After having further close looks at the radar images, we decided to have a third attempt higher up the glacier. Today we again moved all the gear to a new drill site. This time we hit wet ice only 4 metres down. Our first 45 metre core was starting to look like a lucky strike compared to this! We decided to strike camp. Within a few hours most of the gear was packed and stacked in heaps. Later in the afternoon 3 helicopter loads got most of the gear away, as well as Uwe, Xinsheng and Yulan. Dan and I stayed on, doing some final sorting and planning to fly out by plane at 11 in the morning.

After yesterdays progress, today’s was disappointing. During the night, water had seeped into the drill hole and other technical issues slowed down the drilling. Then from about 45 metres below the surface we pulled up an ice core that was dripping with water. We must have drilled into a water conduit in the glacier. We lowered a weighted cord down the borehole and when we pulled it back up about 13 metres of it was wet. The water had flooded our drill hole. This was very disappointing. We discussed what to do and decided that the next day we would set the drill up for another attempt about 300 metres away, near to an interesting wind scoop on the side of the glacier. This feature is about 70 metres deep and several hundred metres long, where the strong winds have scooped out the snow and ice all around the side of the peak of Mount Annette.

By 9am all was set for drilling to start Having dug a pit about 2 metres deep into the snow to find a hard layer for the drill to stand on securely, we were still another 2 metres from the previous summer surface of the glacier that was now under a total of 4 metres of this winter’s snow.This is how we drill the ice cores: It is fascinating to watch the way Xinsheng operates his drill. First he makes sure it is aiming exactly straight down by holding onto the motor while the drill barrel cuts its way down into the ice. Initially the rotating core barrel is at the surface, but soon he will hold onto the wire line to feel how the drill is cutting down deep in the drill hole. After a certain distance has been drilled – usually just less than 1 metre, the power gauge on the control box shows that the motor is starting to struggle. Xinsheng then tells Yulan to stop the motor, gives the wire a few sharp tugs to break off the core from the ice below, and then Yulan switches on the winch motor to haul the drill up to the surface. The drill barrel is then detached from the motor, and the ice core, along with a mass of ‘chips’ is pushed out of the barrel onto a core tray. One of us measures the core, matches it with the previous section and cuts it to fit it into the 1 metre ‘layflat’ polythene bag that is already prepared and labelled. The core then goes into an ice core box, with all necessary details noted into the field notebook. There are quite a few technical issues that can slow down the drilling process. The quality of the ice can change, and sometimes faults develop with the drill itself. Xinsheng has an amazing ability to remedy these pitfalls – I was impressed watching his resourcefulness as we progressedSo here on Annette Plateau, our first drilling was going well. There were several dust layers in the core at intervals, most likely suggesting summer layers where melting at the surface had concentrated wind blown dust into a distinct deposit. Progress was good. Apart from a short wet layer at 29 metres, the ice was looking cold and bubbly – good quality glacier ice. We continued drilling until 11 pm by which time we had reached about 40 metres below the surface.

By 8am we were all at the airport loading a huge pile of supplies into a sling net for the helicopter to take up to the Annette Plateau. I went up with the first flight with the job of pointing out our chosen drilling location to our pilot Brendan. Unfortunately the GPS co-ordinates were wrong (!) so I had to make a best guess using the footprints of the radar traverses which were still visible. After landing and unloading the net, the heli flew away leaving me with the mountains, the glacier, the sun and the silence – for a short time at least. I started to sort out the gear and soon two planes landed beside me, with the rest of the team and more gear on board. After we had unloaded, a short walk around the area showed that my judgement of the drill location was about 80 metres out so we had to drag the gear pile to the correct position.   The day was spent putting up the drill shelter and digging a snow pit under it’s protective cover. We also put up the tents and organised the equipment to start drilling the next day. It was a beautiful clear night when we turned in, with a bracing minus 12 degrees C discouraging prolonged stargazing….

 Today I jumped into a helicopter with Lawrence Kees and Alice Doughty from Victoria University Wellington. We flew up to the Annette Plateau to do some further radar work. I took the opportunity to test the snow conditions for securing tents and see if there were any possible snow caving sites nearby as a back-up. I dug a snow pit about two metres deep and then used my avalanche probe to feel deeper down. It was mainly soft snow with a few slightly denser layers. At about 4 metres deep I could feel the hard ice of the last summer surface. This means that in order to secure our tents against very strong winds we will have to use lots of ‘deadmen’ – large sacks filled with snow and buried to act as anchors. Tent pegs – even snow stakes would be no good in these conditions. This Photo shows Lawrence and Alice setting of to traverse up and down to complete the radar survey, I took a walk around the edge of the glacier to see if there were any suitable sites for snow caving. I was looking for steep angled snow slopes of drifted snow at least 2.5 – 3m deep. By probing around I found a good spot that was within about 2 – 300 metres of our intended drill location. This was great – it was a reassuring safety back up for our accommodation on the mountain. The helicopter returned to collect us at about 1 o’clock. It was carrying a sling load off ice core boxes. Uwe had obviously decided that the weather forecast was good enough to go ahead with the drilling from tomorrow. The short flight back to the airport gave us a spectacular view of Mount Cook seen up the Hooker Valley. When I got back to the Lodge, the team told me about the improved weather forecast for the next week. Action Stations for tomorrow! Paul left as planned to go back home to the US, leaving five of us: Yulan, Xinsheng Dan, Uwe and myself to make up the drill team. If all goes according to plan, we will be up on the Annette Plateau for several days and I will tell you how we get on when we are back down in civilisation again.