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. 

 

Temperature on the Tundra...

The spatial heterogeneity of Arctic landscapes presents unique challenges to measuring and modeling a wide variety of land surface processes. One that is of particular importance to the NGEE Arctic project is the distribution of temperatures within active layer soils and permafrost. This applies to both the profile of temperature with depth in the soil and variation in temperature across the microtopography of ice-wedge polygons. Many of our team members would like to have good measurements of temperature not only for understanding its importance in controlling CO₂ and CH₄ flux, but also for validation of our fine-scale models where the challenge is in simulating freeze-thaw processes at fairly high resolution.

Knowing the important role played by temperature in Arctic ecosystems our scientists have deployed a number of temperature probes at field sites on the BEO. Currently we have a dense network of probes that measure temperatures across polygon centers, rims, and troughs to a depth of 1.5 meters. Many of these datasets are available at the NGEE Arctic data portal.

Not surprisingly, every year a suite of new research tasks are added to our existing activities. And when that happens, additional probes also frequently need to be installed. This trip Bob, Go, and Sina each had tasks that required new temperature measurements. Interestingly, their need for new temperature measurements were driven by a range of science questions at fine, intermediate, and large spatial scales.

Sina and Bob were interested in the temperature of shallow soils so they spent much of the last two days installing a dozen Stevens Hydra Probe II sensors within the upper several centimeters of soil at our intensive study sites. Sina placed probes within the soil, ran cables back to the data logger and Bob did the wiring. The data loggers had to be reprogrammed but Bob was able to do that fairly quickly despite surprisingly cold temperatures and intermittent rain. Sina will use these temperature measurements in conjunction with information that she derives from the infrared (IR) camera that is mounted atop a 10-meter tower on the BEO. These measurements taken at two different scales will provide information that will help us interpret spatial heterogeneity in temperatures across the landscape.

Similarly, Go installed temperature and moisture probes at 15 to 20 locations on the BEO last fall. Yesterday and today he downloaded data from each of those and recorded their position with GPS. Go was happy with the quality of data that he has acquired and with the lack of problems encountered given that the probes were left in place over the winter. However, despite his best efforts one or two of the data loggers had been damaged by lemmings or foxes. This kind of damage plagues all researchers, but seems to be an especially acute problem in the Arctic. We should be pleased that only one or two data loggers needed to be replaced. Go plans to continue measuring temperatures at broad spatial scale across the BEO for several more years so he can evaluate surface temperatures from the NASA Soil Moisture Active Passive (SMAP) mission (http://www.nasa.gov/smap/). This will help the NGEE Arctic project in several ways, but most importantly in translating what we measure at fine scales to spatial scales relevant to climate models.

Boardwalks Get an Upgrade...

One of the benefits of working on the Barrow Environmental Observatory (BEO) is that access to our field sites is relatively easy thanks to several kilometers of existing boardwalk and trail mat. This network of walkways was installed in 2005 in support of the NSF-sponsored Biocomplexity Experiment. Since that time the combination of raised wooden boardwalks and trail mat has protected the tundra from repeated foot traffic. Beginning in 2012, the NGEE Arctic project has added to this infrastructure especially in support of accessing our intensive study sites that distributed across the tundra.

             

Heavy use of the boardwalk and trail mat by countless scientists who walk these trails daily has taken its toll, and certain sections of the trail were in need of repair. The boardwalk was unlevel and some of the trail mat was under water.

Last fall, and earlier this spring UIC Science, landlords of the BEO, made a commitment to upgrading the trail. A crew led by Araina Danner certainly did their homework and the trail is vastly improved since last year. All raised boardwalks have been leveled and made straight, and trail mat rerouted in an attempt to avoid standing water. The end result is a much better surface for walking back and forth from the field sites. Because of this there is a noticeable absence of disturbance along the trail such as was beginning to be a problem towards last fall.

Nice job by Araina and others with UIC Science who helped make those improvements possible.

 

Getting Away from the Office...

In most years I would have travelled to Barrow two or three times already for field research, but not this season. Various activities including writing the NGEE Arctic Phase 2 proposal kept me and many others at their desks. Now that those responsibilities are behind me I can fortunately enjoy time on the tundra with colleagues from around the country. And if today is an example of what the next couple of weeks will hold then I am confident that June will be a busy month.

First thing this morning I picked up Bob, Go, and Sina, all with the University of Alaska Fairbanks, from the Barrow airport. Bob and Go have been involved with the NGEE Arctic project for several years. Sina, on the other hand, is enjoying her first year as a post-doc from Germany with the project. You might have seen her blog post earlier in the season when she and Bob installed a high-resolution infrared (IR) camera atop a 10-meter tower on the Barrow Environmental Observatory (BEO). She is back this week to download data and make adjustments to the tower and camera now that they have been in place for a month or two.

Bryan, Ori, and Ian are also back in Barrow (LBNL). Bryan and Ori are veterans while Ian was in Barrow earlier in the season, but otherwise this is his first summer on the project. These three will be making adjustments to the NGEE Arctic tram that was installed on the BEO in May. The tram, complete with 65-meter track and cart carrying multi sensors for energy balance measurements, delivered a lot of great information last season and we look forward to similar insights this year. The tram including the cart and the rails were redesigned over the winter with help from Keith and Shawn (BNL). Bryan, Ori, and Ian will also be checking up on two solar panels installed for a geophysical ERT array and evaluating a micro-plot warming technique that they and Margaret Torn (LBNL) developed over the winter. We plan to deploy that technique in July and August to look at CO₂ and CH₄ flux from active layer soils that are warmed by -4 degrees centigrade. This will be done to address a specific hypothesis about rates of greenhouse gas emissions from decomposing organic matter in thawing soils. Such information will be used to improve the representation of soil organic matter decomposition in models. Stay tuned for an update on that experiment later in the summer.

For now, it’s good to be back in Barrow…