My research focuses on decomposition of organic carbon in soils, including particulate and dissolved organic carbon. Specifically, I’m interested in how decomposition rates are influenced by environmental conditions (temperature, moisture, and hydrology) and the chemical structure of carbon, and what the relative importance of these factors are in the face of a changing climate. One aspect of my research is to understand the chemistry of carbon frozen in permafrost soils, and how fast it may be decomposed when it thaws. It is important for us to know how quickly this protected carbon may be decomposed and released to the atmosphere as carbon dioxide and methane, because of the potential impacts it has on global climate.
Over the past few years, I’ve learned that collecting frozen soils can go very smoothly…or not so smoothly. The best equipment for getting at those soils is a permafrost auger. This consists of a steel coring barrel, two blades that attach to the end of the barrel, and a gas-powered motor. As you can guess, this equipment is not easy to carry around in remote areas, especially in boggy black spruce forests. However, in the subarctic, these places are some of the best areas to find permafrost. Thus, the adventures begin!
The first time I went permafrost coring, I mostly observed. It was early May in Fairbanks, Alaska, and the weather was quite pleasant. I was with my advisor from the University of Colorado, Dr. Jason Neff, and Dr. Jennifer Harden of the USGS. Also accompanying us were Jon Carrasco (Univ. Colorado), Dr. Dave McGuire (USGS and University of Alaska-Fairbanks), and Dr. Merritt Turetsky (then at USGS).
It looked like hard work, but simple enough. Basically, you need two to three reasonably strong people to stand on opposite sides of the core barrel, start the motor, and push the barrel into the frozen ground as the blades do the cutting. After awhile, you pull the core barrel up and extract the frozen soil. I was cautioned that you NEVER want to get the barrel stuck, because then you’re through. Remember to never stop drilling while the barrel is in the permafrost, have several sets of sharp blades, and if it feels like you’re striking something hard (like a rock) immediately pull the barrel up. On that day, everything went fine and the barrel didn’t get stuck.
The second time I went permafrost coring, it was a cold March day in Fairbanks, Alaska. I was with Paul Schuster of the USGS. There were a couple feet of snow on the ground, but we were fortunate enough to have the help of Jamie Hollingsworth and Brian Charlton (Bonanza Creek Long Term Ecological Research site), and their snowmobiles. We piled the coring equipment on a sled, and hauled it into the site with snowmobiles. While I was a little nervous about getting the core barrel stuck, I knew that Jamie and Brian were experienced permafrost corers. By the end of the day, we successfully extracted several soil cores and were headed back home to warm up.
By the third time I went permafrost coring, I was pretty confident. I figured that I knew enough now to be able to avoid getting the core barrel stuck, and that overall the chances of doing that were relatively low anyway. It was a warm August day in Fairbanks, Alaska, and the mosquitoes were past their peak. I was with Paul Schuster again, as well as Dr. Mary Jo Baedecker (Scientist Emeritus, USGS), and Dr. Bob Eganhouse (USGS). We were setting out to collect permafrost soils for microbial population analyses. After sampling the active layer (the seasonally unfrozen soil above the permafrost) and digging a pit big enough for the core barrel to fit into, we cut our first core. The blades were sharp, and it was like cutting through butter (well, frozen butter). While Mary Jo began sub-sampling that core for microbial analyses, Paul and I began collecting a second core. About 20 seconds into drilling, everything can to a sudden stop. We were through.
We later found out that we had struck a chunk of wood. Once the core barrel stopped turning, it immediately became frozen in the permafrost itself. We tried running the motor forward and then running it in reverse and it wouldn’t budge. Paul said no problem, he knew what to do. This happened to him last summer, and he was able to use a “cheater bar” and a wrench to muscle it out.
We tried it….and ended up bending the stem of the barrel! It was frozen solid.
After thinking about our various options, we decided that our best bet was to bring out a jackhammer. We drove back to Fairbanks and found a place where we could rent one. Unfortunately, they only had jackhammers that ran on electricity, so we also had to rent a 200+ lb generator. We weren’t sure how we’d get that out to the field site, but we’d cross that bridge the next day. Fortunately our site was only about 100 yards from a dirt road.
The next morning, we drove to the field site and assessed the situation. The power cord on the jackhammer wasn’t long enough to reach the road, so we would have to haul the generator into the forest (remember, this was a boggy place with soft ground). It had wheels on one end, and we had two plastic tables that we could lay on the ground to wheel it on. By leap-frogging the tables, we were able to bring the generator within reach of the jackhammer and the stuck core barrel. After an hour or more of jackhammer-ing, we liberated the core barrel!
Through these experiences I have become a well-rounded permafrost corer. I know what to do to minimize the chances of getting a core barrel stuck, and I also have experienced the ordeal of extracting a stuck barrel. I’ll be going back to Alaska in April for another round of permafrost coring, and although each situation is different, I am confident that I’ll be able to handle whatever happens….. (to be continued?).
Story by: Dr. Kim Wickland, USGS - Boulder, CO