Before arriving to Petermann glacier, the Boulder Team looked at aerial photos of Washingtonland, located to the west of the glacier, to determine the best camping site for our three-week field study. We wanted to be close to a rich sampling area and somewhere relatively sheltered and flat to make for easy camping. While on the Oden, we inventoried and organized our gear and food in preparation for the helicopter trip to camp. We had just under a ton of supplies for our extended stay, and these were carried in a sling load under the helicopter. This is a particularly dangerous operation for the pilots, and inclement weather pushed our departure a day late.
When we finally arrived with our gear in tow, it took about 6 hours to set up our home for the next couple weeks. Our four sleeping tents were in a sheltered spot, enclosed within a solar-powered electric fence to alert us of a polar bear. Just like camping in any bear-country, the cooking area, gray water, and food storage area need to be kept separate from the sleeping tents. We had an Arctic Oven – a large, insulated, and toasty tent – that we used as our cook tent and social area. We ate very well, and often the cook tent was left smelling like anything from Ethiopian stew to falafel, and for that reason it was particularly vital to keep the food and cooking area separate from where we slept. A large yellow barrel contained all of our food and scented toiletries, we used a small black barrel for our trash and a 35 gal drum for our gray water, which can be a strong bear attractant. All three containers and the Arctic Oven were then encircled by another electric fence. We camped next to a small lake, which served as our water source, and every few days we would go up to the lake to fill our water cooler and chemically treat it for drinking. This lake also served as our refrigerator: our cooler of fresh vegetables, cheese, and fruit lived in the lake, held down by large rocks. The only thing left to consider was where to put our toilet, a Johnson box for which we would need to dig a pit. We placed it out of sight, and it had a perfect view of Petermann glacier. With delicious food, a comfy cook tent, and a great view from the bathroom, it was the ideal camp for a long field season.
(A toilet with an idyllic view)
(Setting up camp)
Safety precautions to limit bear attractants dictate day to day camp life: we kept our gray water and food stuff in separate barrels. The electric fences stayed on while we slept, and the two rifles were in our sleeping tents next to us. Everyday, our safety coordinator/mountaineer, Julia, would wake up and call The Oden on our satellite phone for our diurnal check-in. We usually heard about the weather, and if we would be receiving helicopter support for the day. The best benefit of our extended stay on land was the ability to be flexible; if a helicopter was not available, we could hike closer to camp and still do plenty of sampling. This led to a very productive field excursion, in which we sampled 136 boulders in about two weeks. After our two weeks at our beautiful glacier-side estate, we were flown back to the Oden with all of our gear. From the Oden we are hoping to sample a few islands in Nares Strait in order to save time and fuel for the helicopters.
As opposed to using marine sediments and oceanographic measurements, our group is using a land-based technique to help reconstruct the past history of the Petermann Glacier. Glaciers and ice sheets move forward and backward across a landscape carrying boulders and sediment over long periods of time. When boulders are submerged within the ice, they are shielded from the atmosphere. As the entrained rocks slowly melt out of a glacier, they begin to be bombarded by cosmic rays from the atmosphere, which can change the composition of the rock. Rocks and soil create different forms of elements within their mineral structure once they are exposed to the atmosphere, called cosmogenic isotopes. In this research, we are focusing on an isotope of the element Beryllium. The common form of Beryllium is 9Be, but after being exposed to the atmosphere, 10Be begins accumulating. After our group breaks off a sample of the uppermost surface of a glacially transported boulder, we can measure the amount of 10Be in the rock and figure out how much time has passed since the glacier deposited the boulder on the landscape.
We focused on collecting boulders from lateral moraines, or sinuous ridged hills composed of boulders and glacial material formed during glacier retreat. They represent a time when the glacier was larger or wider. We found a lateral moraine only a short hike from our camp, located just 25m away from the side of the glacier and stretching approximately 5 km in length. We collected pieces of boulders located along the ridge of the moraine that are fairly large, usually ~1 m3, and that are composed of a non-local rock type. Washingtonland and Daugaard-Jensen Land are composed of carbonate bedrock; formations of limestone, dolomite, and other rocks formed in deep marine waters. Since carbonate rocks do not contain the mineral quartz, which is our target for this type of cosmogenic surface exposure dating, we look for granite and sandstone boulders, which contain enough quartz for our analysis. By targeting non-carbonate boulders, we can be sure that the Petermann Glacier transported the rocks from a location in the interior of Greenland before being deposited on the lateral moraine.
(Boulder team hiking along the lateral moraine, along the western shore of Petermann Glacier)
(Grabbing surface samples of the boulder)
Once we return to UW-Madison, we will crush up each rock sample, and isolate all the sand grains to find the quartz minerals. Next we use a strong acid to dissolve the quartz into a clear solution. The final steps require isolating the Be from all the other elements present in the quartz. Finally, we oxidize the Be and send it to an accelerated mass spectrometer to measure the concentration. Once we have all the results, we can calculate the time that a specific boulder was exposed to the atmosphere, interpreting this time as how long ago the glacier left the boulder on the landscape. Combined with results from other boulders, we can begin to date lateral moraines. The age of the moraine might represent a climate event that could be reflected in the sediment cores that the Coring Group are collecting in Petermann FJord, as well as the sediment that the Beach Team is finding on shore.
Written by: Elizabeth Ceperley and Melissa Reusche of University of Wisconsin, Madison.