“We are interested in studying what happens to this material as it makes its way to the ocean… The transformations that it undergoes.”
Jason Dobkowski, lab manager in the Department of Ecology and Evolutionary Biology at the University of Michigan, explained his work as he crouched on treacherous muddy ground to collect water at a sampling site on Wolverine Lake. Water colored like chocolate milk plumed into the lake from the collapsing permafrost on the bank and mixed with clearer water flowing in from a more established stream. The color represented “Silt and material coming out of the permafrost and flowing into the lake. That can have drastic effects on the lake itself, and on all the organisms living in the lake.” Dobkowski said the material “Can change the chemistry and the biology of the water and can have a huge effect on what happens to the carbon that was once frozen in the permafrost here as it thaws and gets reintroduced to the global carbon cycle.”
Dobkowski was careful to also collect water from a different inlet where the water ran clearer. “We’re really interested in what’s happening to the lake as this giant thaw slump continues to grow and deposit material into the lake. To understand that we’ve got to know everything that is coming into the lake, and what’s happening while it’s in the lake, and what happens when it leaves the lake. And how it may affect the lakes that are downstream.” The water flowing into Wolverine Lake will flow through the aquatic system and eventually reach the Arctic Ocean.
Why they’re testing
Dr. Rose Cory, professor of aquatic geochemistry at the University of Michigan, described the situation: “There is a large amount of carbon that has been locked away frozen for thousands of years in permafrost soils. You can basically think about this carbon as having been in a freezer– not participating in the carbon cycle. Now that the Arctic is warming faster than the rest of the earth,” Cory said, “The carbon that the permafrost soils contain thaws out; it becomes unfrozen.”
The flow of water from snow melt or rain transports the newly thawed ancient carbon into Arctic waterways. Carbon in water has the potential to become airborne carbon dioxide, an important greenhouse gas with global impacts. “Once it is in those lakes and streams and rivers it can be turned into carbon dioxide and we’re looking at how and how fast that soil is turned into carbon dioxide.”
Understanding the chemical characteristics of the water through field sampling and further lab testing helps the research team decode newly thawed Arctic carbon, its journey, and its impact on our climate.
Sampling in the field
Members of the team sample water from sites all along the length of two rivers in northern Alaska: the Sagavanirktok River and the Kuparuk River. Their testing, conducted when thaw begins in spring, after snow melt is complete in July, and as late as possible in August, provides a ‘snapshot’ of each rivers’ conditions on the testing day.
At sampling sites the researchers collect water samples in sealable containers that they’ll take back to the lab for more specific measurements. While they’re in the field, though, they observe and record the river activity and conditions. They also measure temperature, pH levels and alkalinity by submerging the ends of devices that look like small batons connected to wires.
“We are just capturing a sample of the river water. I was measuring pH, alkalinity, writing down temperature and estimating discharge,” Collin Ward, PhD Candidate in the Department of Earth and Environmental Sciences at the University of Michigan, explained for FrontierScientists. He labeled some of his work as observational. “[I] compare the daily changes in the river: how’s it flowing, is it a wider channel, is it a deeper channel, and is the speed faster or is it slower? What’s the color of the water?” Ward added, “I’m also taking some quantitative measurements, like I said: temperature, connectivity and pH.”
While water alone has a pH of 7, water in nature usually contains additives. For example, carbon dioxide (CO2) dissolves in water (H2O) to form an acid called carbonic acid (H2CO3). If the river water pH measures greater than 7 it is described as basic; if its pH is less than 7 it is described as acidic.
A related measurement the scientists record is the water’s alkalinity: the amount of bases in the water which can neutralize acidic pollution from i.e. rainwater. Rainwater is slightly acidic because it has combined with carbon dioxide (CO2), nitric oxide (NO), and sulfur dioxide (SO2) naturally present in our atmosphere. When human-caused combustion and emissions add heightened levels of gasses to Earth’s atmosphere, it can result in rain that is more acidic than normal– acid rain. The acidity of water impacts habitat conditions for local organisms including fish and even tiny micro-organisms.
Methane and CO2
Besides collecting water and taking measurements, the team also collects samples of the dissolved gasses present in the river water. Dobkowski described the process. They begin by filling a syringe fully with river water. Dobkowski explained “We can then pull in ambient air from the atmosphere, close the syringe and equilibrate it by shaking it in the water at the temperature it was collected; that will cause the fraction of gas in the water and in the air to equilibrate, so gas will come out of the water or gas will go into the water depending on how saturated that water was to begin with.” He used another syringe to collect the gas that had gathered in the shaken syringe.
Once analyzed in the lab, the gas sample will show the scientists the state of dissolved gasses in the river water where it was collected. Dobkowski expects to find two potent greenhouse gasses “A lot of Arctic rivers are supersaturated in carbon dioxide and sometimes in methane. It depends on processes happening upstream.” Methane in the atmosphere is over 20 times more effective at trapping heat than carbon dioxide is, but it does not remain airborne in the atmosphere for nearly as long as carbon dioxide does.
All this fieldwork isn’t a walk in a park. After all, the scientists are working in Alaska’s North Slope. Luckily parts of the Sagavanirktok River are accessible from the Dalton highway, the famous haul road traveled in the winter by Ice Road Truckers. Other testing sites are harder to reach, requiring long treks through bear country. Wolverine Lake, one of the myriad (usually un-named) lakes along the North Slope rivers, was named by the scientists for the wolverine they encountered on the way there. Sometimes the scientists can catch a ride to remote testing spots with a helicopter serving Toolik Field Station, a center for scientific research on the North Slope.
Though the Arctic is remote the results of its rapid warming can have widespread impact. Science like this will help us understand what happens as Arctic permafrost carbon is reintroduced to the global carbon cycle.
Laura Nielsen 2015
Frontier Scientists: presenting scientific discovery in the Arctic and beyond
- ‘Sunlight controls water column processing of carbon in arctic fresh waters’ Cory, R.M., C.P. Ward, B.C Crump, G. W. Kling (2014) Science, 10.1126/science.1253119