This story is Part II of a three part series investigating methane emissions (click here for Part I).
In the expansive tundra surrounding Barrow, Alaska, where, at times, the population density of caribou exceeds that of people, annual precipitation is less than 5 inches (127 mm). Cloudy days are frequent and any month can bring snowfall. It is a frigid desert. Throughout the short summers, methane gas moves imperceptibly through the spongy soil where it forms, to the atmosphere, where it traps radiated energy.
In spite of the low precipitation, water is a prominent landscape feature on Alaska’s north slope. In spring, meltwater flows to sea through braided streams, leaving the tundra clear for a short burst of vigorous biological activity. Thaw lakes – stationary bodies of water that freeze every winter and thaw every summer – provide wet conditions perfect for anaerobic decomposition. As a result, summer on the North Slope leads to the release of methane gas.
Even with summertime methane emissions, the Arctic Coastal Plain is a net sink for carbon, which is sequestered through the growth of plants and lichens. This organic matter is then frozen during the long cold winter and often incorporated into the permafrost by repeated cycles of freezing and thawing. In spring, most organic matter from prior years remains inundated by the surface waters of the uppermost “active layer,” and it never fully decomposes.
Although many scientists agree that the current warming trend is likely to continue, it is unknown whether a warmer climate will turn the Arctic Coastal Plain from a sink to a source of greenhouse gases. Furthermore, it remains unknown how climate change will affect rates of aerobic decomposition (which results in the release of CO2) and anaerobic decomposition (which results in the release of CH4).
Cove Sturtevant and Dr. Walt Oechel from San Diego State University in California are addressing some of these questions in a manipulative experiment near Barrow. They are investigating the responses of CO2 and CH4 fluxes to different water levels in a thaw lake. The purpose of their research is to establish baseline methane flux levels, explore the response of methane emissions to different water levels, and examine how emissions of these greenhouse gases may change in future climate scenarios.
To accomplish this, they used an LI-7700 Open Path CH4 Analyzer. According to Sturtevant, “the LI-7700 allows you to measure methane flux at the landscape scale, which can be really important in the arctic, where you can have very high variation in fluxes over just a meter.”
Not only does the LI-7700 enable landscape level measurements of methane flux, it is designed with environments like the arctic in mind. In contrast with other technologies, the LI-7700 features a wide operating temperature range, which makes it suitable for use in extreme environments. Many field research sites are not conveniently located near the power grid, but this is no barrier for the LI-7700. It operates with as little as 8 watts of power, which makes it possible to power the analyzer with a simple solar/battery power supply system. Since it is designed with field research in mind, the LI-7700 is well suited for measuring flux at the ecosystem level.
In the Arctic Coastal Plain, where only the most robust life forms endure, the analysis of carbon flux will provide useful insight into the consequences and risks of climate change. Important research, like that being carried out by Sturtevant and Oechel, is possible thanks to innovative devices like the LI-7700.
Cove Sturtevant studies with Dr. Walt Oechel at San Diego State University: http://gcrg.sdsu.edu/
Photos courtesy of Cove Sturtevant.