Tuesday, June 25, 2013

A walk across a drained thaw lake basin...

Participants in the NGEE Arctic project are interested in better understanding feedbacks between ecosystems and climate. These feedbacks, both negative and positive, can arise through changes in the flux of CO2  and methane to and from the atmosphere. One of the factors that drive carbon cycle processes in the Arctic is the distribution of water across the landscape. Our team began exploring this dynamic last year across a series of inter-connected low- and high-centered polygons on the BEO. Those studies are going well and we have made significant progress in gathering the process knowledge required to inform a range of models from the individual polygon to climate grid cells.

Another important feature of Arctic landscapes that drives carbon, water, and energy-related dynamics is the presence of drained thaw lake basins (DTLBs) across the coastal plain. These occupy a large portion of the land surface and are known to be of various ages (e.g., young to ancient), each with unique soil and vegetation characteristics. The NGEE Arctic project will begin to study these this year in an area just south of the BEO. We laid out transects using LiDAR data, courtesy of Craig Tweedie, and a site visit in April. However, we had not seen this area in a snow-free condition. That was our goal today.

Rich, Victoria, Bryan, Gus, and I drove along the west edge of the BEO before turning east and then south again on a road that goes to the gravel pit. We stopped just before the entrance to the gravel pit and headed across the tundra to our west. Our map, an original product of Ken Hinkel at the University of Cincinnati and his colleagues, showed that we would walk first across an old DTLB and then up and over a slight ridge to a DTLB that was considerably younger. The old DTLB was wetter, polygons were filled with water, and in some areas were beginning to coalesce into larger bodies of water. Gus confirmed that this was a feature of the admittedly poorly understood life cycle of DTLBs. By comparison, the younger DTLB had a quite different composition of vegetation and lacked any well-define polygonal structure or ponding water.

Our team will lay out a sampling transect across this area and begin a series of measurement campaigns in early July. Our goal is to assess CO2 and methane exchange, and energy budgets, across the various DTLBs and relate those potential differences to soil water content, degree of inundation, soil temperature, and vegetation. All this information will be useful as we add new insights about landscape feedbacks to climate models.