Chipping Away at the Footprints of the Past Thursday, Oct. 11 On the day after my reconnaissance on the glacier with Mike Roberts, David Putnam and I set forth to begin reconstructing the history of Drukso Gangri ('Dragon Tooth Glacier') from the footprints it has left behind on the landscape. We awoke early to a spectacularly clear morning. The sun first illuminated the high peaks surrounding our campsite, and a dense layer of morning frost crunched underfoot. David and I drank hot naja as rays of sunlight slowly illuminated our campsite, adding welcome warmth to the frigid morning air. Humans, mules and horses were soon warming their cold backs in the strong morning sun. Soon all members of our team had arisen and were preparing for the first day of real work. Professor Summer Rupper was rejuvenated and ready to spring into action on Drukso Gangri. After organizing their gear, Summer, Mike, Josh, Tshewang and Pashupati left to conduct work on the ice that I described in detail in my most recent post. David and I set out to begin our reconstruction of the past behavior of Drukso Gangri. To reconstruct past glacier fluctuations, we map ridges of rock debris that form at glacier edges called moraines. Moraine ridges define the margins of a formerly robust glacier at periods when climate was colder than today. To discern the age of these moraines, we collect rock samples from large moraine boulders and apply a relatively new isotopic method called beryllium-10 surface-exposure dating. This technique relies on the fact that once a boulder emerges from the melting tongue of ice and is deposited on a moraine ridge, it is also beginning its exposure to the incoming particle flux associated with cosmic rays from outer space. These cosmic particles bombard and destroy oxygen and silicon in quartz, creating a unique "cosmogenic" byproduct called beryllium-10. Once exposed, atoms of beryllium-10 gradually accumulate in the rock surface at a known rate. Thus, by sampling an exposed rock surface and by measuring the number of beryllium-10 atoms contained within that rock sample, we can calculate how long ago a rock fell from the glacier. After collecting rock samples in the field, we will ship them back to the Cosmogenic Nuclide Laboratory at the Lamont-Doherty Earth Observatory of Columbia University, where the samples will undergo chemical processing under the guidance of Professor Joerg Schaefer, who is a lead investigator on this Bhutan project. Altogether, with these methods we can reconstruct glacier behavior from the "ground up," to draw inferences about how Bhutan's climate and ice have changed in the past. As we began our sampling, our first priority was to target the youngest moraine ridges that dam Tachanggay Tso, which is the lake that now occupies the recent footprint of Drukso Gangri. The ages of these most recently constructed moraines will tell us when Drukso Gangri last maintained a robust, healthy profile. The fresh, sparsely vegetated character of these large moraine ridges implies that they were probably formed within the past 150 years or so, but because of the lack of historical records, we can't say for sure. Our beryllium dates will help to answer this question. To collect rock samples for beryllium analyses from hard granite moraine boulders, we drill three or four holes into a portion of the top surface of the boulder. Into each of these holes we place two tapered shims and a wedge. We gently tap the wedges with a hammer until the pressure of the shims cracks the rock. If this is done properly, we can dislodge a perfect sample from a rock surface that would be nearly impossible to collect with just a hammer and chisel. We venture from boulder to boulder on moraine ridge crests applying this method. At each sample site we measure boulder dimensions, collect high-resolution GPS coordinates, employ a compass and clinometer to map the heights of surrounding mountains that impede cosmic radiation, draw detailed diagrams of the sample and its surroundings, and take photographs from all angles. Beginning with the youngest moraines at the mouth of Tachanggay Tso, we progressively worked our way away from the glacier and toward the oldest moraines at the edge of the field area. Sample collection took us a total of three days to complete. Although we had planned for several more days, a mix-up with the food supplies cut our time short. In this regard, we were very thankful we had the help of Paul Krusic (University of Stockholm), Tshewang Rigzin and Pashupati Ssarma, as well as our young and energetic guide Sangay. Sangay, in particular, turned out to be an essential part of our team. He learned the sampling method faster than most I have ever worked with, including graduate students. As I learned from our head guide, Karma Tshering, Sangay was orphaned at a young age, after which time he became a yak herder in the mountains with his uncle. He received no formal education, but eventually came to work in the tourism and trekking industry based on his level of fitness and knowledge of the mountains. Sangay's proficiency and accuracy with the drill and wedge system quickly surpassed my abilities. His work ethic, boundless enthusiasm and energy were astonishing, and proved to be essential for accomplishing a week of work in three days without sacrificing quality. Thanks to the help of Sangay and the others, we were able to make a full, thorough collection of samples from across the entire moraine sequence in the time we had. At the end of the three days, almost all scientific objectives were met. Summer and her team had successfully established an array of ablation stakes on the glacier and erected a weather station. They then set off on the trail back toward civilization. By the third day of work, David, Tshewang, Pashupati and I were the remaining scientists. We had collected 56 samples across the moraine belt, and only one goal remained. Because our high-resolution "differential" GPS device system had limited battery capacity, I reserved the last full day for obtaining a complete collection of GPS coordinates from all samples. As had been the case in previous days, we were greeted with early morning sunshine that rid the ground of frost. However, unlike those days, a layer of eerie gray cloud quickly shrouded the early morning sun. Chencho Wangdi, our horseman, became uneasy, and humbly requested that we pack up camp and leave. He sensed that the clouds presaged a storm and stated that the Rinchen Zoe region would be under heavy snows by 3 p.m. Chencho's predictions would turn out to be eerily precise. Some of our Micmac friends back in northern Maine have a saying: "If you want to tell the creator a joke, tell him your plans." Indeed, my plans for a final day of data collection faced a serious challenge and required revision or possibly even abandonment. Would it still be possible to collect the final remaining GPS data without putting the safety of humans or horses at risk? Yet again, it seemed that the possibility of complete scientific success, although tantalizingly close, had become as murky as the sky.