Monday, June 29, 2015

A Change in Scenery...

The NGEE Arctic team has spent the majority of their time and energy over the last three years conducting research on the Barrow Environmental Observatory (BEO). The microtopographic features scattered across the tundra including centers, rims, and troughs of low- and high-centered polygons have made for fascinating research relevant to biogeochemistry, vegetation dynamics, and hydrology. However, there are other interesting geomorphological features in the area, most notably drained thaw lake basins (DTLBs). These basins range in age from young (50 years) to old (300 to 2000 years) to ancient (2000 to 5500 years). Fortunately, scientists like Ken Hinkle from the University of Cincinnati and his colleagues have identified, delineated, and aged many of the DTLBs across the Barrow Peninsula. It is now possible to conduct research that can then be related to age and other characteristics of DTLBs.

Our team recognized the opportunity to extend research to DTLBs several years ago and established a transect from young to ancient DTLBs along which we can conduct studies. We have collected a number of datasets from these areas south of the BEO in the previous two years and today we returned to measure CO2 and CH4 flux and energy balance for the third, and perhaps final, year.

Bryan, Ori, and Ian (LBNL) packed everything we needed into the truck and picked me up at the BEO. We assembled the necessary equipment, calibrated instruments, and then began the long walk to our initial sampling location. Ori has become quite experienced at measuring CO2 and CH4 flux using static chambers so once her field notebook was in order she launched into that task. It would involve pulling a sled loaded with gas analysis instruments several kilometers across the DTLBs, stopping at each of 35 to 40 locations where PVC collars have been previously placed into the ground. Ori used a combination of transparent and opaque chambers to determined rates of uptake and release of these two greenhouse gases. Each location that Ori measured has also been characterized for vegetation composition and thaw depth. Active layer soils sampled previously are taken back to the laboratory for analysis. Getting accurate and reliable measurements is a challenging and time-consuming task, but one that Ori enjoys.

While Ori was busy with flux measurements, I joined Bryan and Ian to determine surface energy balance for rough 90 locations along the transect. Bryan devised the sensor package for the NGEE Arctic tram on the BEO so that the suit of sensors can easily be detached and secured to a hand-held system known affectionately as the portable energy pole (PEP). It has an automated data capture routine that can be activated from a small on-board computer. Bryan and Ian shared responsibilities for the PEP and for measurements of thaw depth and soil temperature. I measured soil water content using a time-domain instrument.

It took 8 to 9 hours to complete all measurements across the transect.  Once we finished measuring energy balance with the PEP, we walked back and helped Ori with the sled. It was a long day walking through inundated areas, although we were fortunate that the mosquitoes were not bad. Bryan and I made a late-day trip out to the BEO and transferred the PEP sensors back onto the tram.

Given the data we collected today, we now have a three-year dataset on processes of interest to biogeochemistry, vegetation dynamics, and hydrology for DTLBs of different ages. The plan is to evaluate these data over the coming year and publish results soon. Those results will also be evaluated for what they tell us about carbon and energy balance processes of interest to climate models.