Another Season Nearly Complete for NGEE Arctic Tram…

Bryan Curtis (LBNL) told me earlier this week that, according to plan, the NGEE Arctic tram has performed admirably since it went operational in May, 2015. The automated cart has made hundreds of trips down the 65 meter track, once every 3 hours in fact, around the clock. During that time a suite of sensors have monitored albedo, NDVI, and multiple components of the surface energy balance as snow melted in the spring, low-lying area became inundated with water, vegetation grew throughout the summer and senesced in autumn, and then the onset of snow this winter. Throughout this time additional measurements of soil temperature and moisture, chamber-based and eddy covariance CO₂ and CH₄ flux, active layer thickness, geophysics, and phenology were made either along the tram or within the tram footprint. The co-location of so many high-resolution measurements, once analyzed together, should yield an unprecedented dataset to inform scaling and modeling. The NGEE Arctic team anticipates letting the tram operate for another few weeks and then disassembling the system in early November.

NEON in the Neighborhood…

The Barrow Environmental Observatory (BEO) is home to many research projects. In 2012, NGEE Arctic joined a distinguished list of projects being funded by multiple state and federal agencies. Now that list expands to include the National Ecological Observatory Network (NEON). NEON is sponsored by the National Science Foundation and is a continental-scale initiative that provides long-term infrastructure for examining ecological change over time. We have known for several years that NEON would deploy a monitoring site in Barrow (and elsewhere in Alaska) and we are finally beginning to see evidence of that deployment. Monitoring plots have been established, equipment and supplies have arrived and are being assembled in Barrow, and trail mat is being strategically placed to support scientists who will be coming and going from the field site throughout the season.

Having laid several kilometers of trail mat over the last 4 years, I was intrigued by the sled-based system that NEON personnel have devised to minimize the physical requirements of laying meter after meter of walk way. Although I have not seen it in operation, I am told that staff can connect the trail mat sections while standing up rather than bending or kneeling down to place and secure cable ties that will hold the sections together. Pretty creative…

Raising Temperatures on the Tundra…

The NGEE Arctic project is interested in the fate of active layer soils and permafrost as it potentially warms in the coming century. So far, however, few manipulative studies have experimentally controlled in situ temperatures in the tundra. Intended to address specific hypotheses, scientists working on the NGEE Arctic project from Lawrence Berkeley National Laboratory (LBNL) have developed a small linear heater that once inserted into the active layer can be monitored and controlled to warm soils and permafrost to 4-5 ^oC above ambient. The approach was deployed at our Barrow field sites in early 2015 and evaluated throughout the season. Ori Chaffe and Bryan Curtis are busy this week monitoring system performance and conducting flux measurements. The team has a lot of data to analyze, but preliminary results look encouraging both in terms of magnitude of warming, temperature profiles with depth, and the monitored consequences of warming for CO₂ and CH₄ flux.

Margaret Torn, soil ecologist at LBNL will be talking about the technique and its impact of greenhouse gas emissions at the fall meeting of the American Geophysical Union (AGU) in San Francisco, CA.

 

New Techniques on the Tundra…

Earlier this summer we featured a short blog on a new approach to ecosystem warming that was being developed by Keith Lewin and Alistair Rogers from Brookhaven National Laboratory. Keith and Alistair recognized the challenges of ecosystem warming experiments in the Arctic given lack of electrical power and requirements for remote operation. They designed a zero-power warming (ZPW) chamber that can, using a pair of passively activated louvers, warm air to 4 ^oC above ambient. One ZPW chamber and a corresponding control chamber were deployed on the Barrow Environmental Observatory (BEO) earlier this summer and have successfully operated throughout the summer, fall, and now into the winter. I have not yet seen all the data collected on chamber performance, but Alistair and others will be here in a few days to assess performance and then disassemble chambers for the winter. If the results look encouraging the ZPW design gives us a viable option for continued testing and possible deployment of a technique that could help our NGEE Arctic team better understand growth and physiological acclimation of plants to warming temperatures. Stay tuned…

Cores for a Colleague…

One of my tasks this week while in Barrow is to collect a series of soil samples from low- and high-center polygons. A colleague, Elizabeth Herndon, a former post-doc at ORNL, now Assistant Professor at Kent State University requested samples of active layer soils for a geochemistry study that she is doing across a latitudinal transect. My guess is that samples provided by the NGEE Arctic project represent the northern anchor to that transect.

I was glad to help and therefore set about to formulate a strategy whereby soil cores could be collected from frozen soil using a slide hammer and a split-core sampler. I organized everything into a small sled and walked several kilometers with sled in tow to our NGEE Arctic “intensive” field site on the Barrow Environmental Observatory (BEO). Two or three inches of fresh snow made this a fairly easy task.

Once representative polygons had been located, cores were collected from several different micro-topographic positions across the polygons including centers, rims, and troughs. The cores varied in length from 15 to 30 cm and in composition with generally an organic-rich upper layer and a deeper layer of mineral soil. There were obvious differences in these characteristics among micro-topographic positions in the landscape. Fortunately, the split-core design of the sampler facilitated retrieval of the soil core and made it fairly easy to visualize the sample and record a quick characterization into my lab notebook. Photographs were taken of all cores.

One interesting observation made while collecting 15 soil cores was that these active layer soils were freezing from the top, down, and also from the bottom, up. This is not entirely surprising given the nature of permafrost, but what it meant for many of the samples is that the middle portion of the soil core was still thawed. This can lead to a soil appearing frozen and presumably devoid of biological activity when, in reality, this layer can be warmer than soils above and below it with maintenance of possible microbial metabolism into the winter. The question that many scientists are trying to answer, including those on the NGEE Arctic team, is what significance might this make to annual carbon budgets of tundra ecosystems and CO₂ and CH₄ fluxes either during the fall-winter transition or to fluxes in the early spring? We are currently conducting chamber-based measurements of carbon fluxes in the field, coupled with controlled freeze-thaw experiments in the laboratory. What we hope to provide is a multi-scale, quantitative assessment of this phenomenon and representation of such in models.

At the end of the day all soil cores were loaded into the sled and everything was pulled back to the road and a waiting vehicle. The cores were placed into a freezer at the Barrow Arctic Research Center (BARC) and will be shipped to Elizabeth in a few days. It will be interested to see the results of her analysis.