Water, Water Everywhere…But Where Does It Go?

One of the organizing themes of the NGEE Arctic project is hydrology. It is important both for our field and laboratory measurements and especially for our modeling. We are exploring the question of how water distribution across polygonal landscapes will be impacted as permafrost thaws and topography changes due to melting ground ice and ice wedges underlying polygons. Our hydrologists and their modeling colleagues are finding that a key uncertainty in determining water distribution, in addition to topography in these low gradient environments, is the saturated hydraulic conductivity (Ksat) of soils. Knowing Ksat allows us to better understand the movement of water through saturated media and facilitates accurate modeling of water flow in soils. Modelers on our team need this information for the parameterization of our fine-scale models of low- and high-center polygons and for use in our global land surface models.

Today Cathy, Go, Larry, and I left our apartment and stepped out into the windy, cold, and unusually rainy weather. It was slightly annoying at the time, but surely the weather would get better right? As we pulled sleds full of our equipment to the field we soon realized that the sun was not going to appear, that the winds were not going to subside, and that the rain was not going to stop. On the contrary, this was going to be (not withstanding mosquitos) one of the more miserable days on the tundra that I have experienced in the last three years.

 

Once at the field site Cathy unpacked our Guelph Permeameter that she had purchased some time ago from Soil Moisture Equipment (Santa Barbara, CA). The equipment can be transported, assembled, and operated presumably by one person. However, we found that in rainy weather with winds upwards to 20 mph that two people were needed to stabilize the unit, position the tripod, and get it ready for operation. Once assembled, the permeameter enabled measurements of Ksat to be determined in 35 minutes to an hour. Although all the calculations still need to be completed, it is clear that Ksat values for the silty soils commonly found across our field sites on the Barrow Environmental Observatory (BEO) are low. This means that water movement, especially lateral movement, is very slow. Our team has noticed this in trying to collect samples for water chemistry, etc. It is simply difficult to get water from these soils. We think that once incorporated into models, the consequences of low Ksat – now that we have direct measurements – will become evident in the distribution of water across the landscape and the cascade of other processes of biogeochemistry and vegetation dynamics. We should know more about this before too much longer… 

 

 

 

Available Forms of Nitrogen for Tundra Plants and Microbes…

Yesterday was a productive day for all NGEE Arctic teams working on the tundra. Today our group left the Herman House apartment with a couple of goals. One was to complete surface and pore water sampling for geochemistry; another was to continue vegetation resurveys for the purpose of fine-scale mapping of plant functional types (PFTs) across polygons. Mallory and I also wanted to finish sampling of soils that she began two days ago for analysis of nitrogen availability. While Mallory has not yet developed the full scope of her PhD studies, she is interested in better understanding the interplay between soil organic matter decomposition and the forms of nitrogen ultimately made available for plants and microbes. More specifically Mallory would like to combined advanced analytical methods with some aspect of plant and microbial biology, and therein characterize the pool size and diversity of low molecular weight (LMW) nitrogenous compounds in soils. There is a considerable amount of published literature on nitrate and ammonium availability in tundra soils, but LMW compounds that can be used by plants and microbes as a source of nitrogen are also important. However, they have not been fully characterized. Working with Bob Hettich and Rich Norby at ORNL and as a student through the Bredesen Center for Interdisciplinary Studies and Graduate Education, Mallory has the opportunity to merge powerful mass spectroscopic approaches (MALDI and electrospray ionization sources) and field ecology, into a single program of study. But before she can do this, Mallory needed to obtain a range of samples from the Barrow Environmental Observatory (BEO) so she could conduct preliminary studies to refine her techniques and then, equally important, the questions that Mallory would like to tackle will also need to be developed. She identified plots within low- and high-center polygons and excavated a small monolith of soil from the upper active layer. She did this at a number of locations making sure that she had adequate replicates and samples for areas that supported the growth of several different plant species. This way Mallory can assess her early work in terms of variation in nitrogenous compounds due to topographic location and species composition. Once samples were collected they were labeled, placed in plastic bags, packed into a cooler, and will be shipped to ORNL later this evening. Mallory will be busy during the coming months and it will be interesting to see how her research develops both with regards to fundamental science and integration of that knowledge into models.

Geochemistry of Methane Formation in Surface and Pore Water Samples…

Today we had 15 people working on the Barrow Environmental Observatory (BEO). Researchers from three DOE national laboratories, the University of Alaska, and scientists from China, Japan, and Germany were collecting data on various topics; soil carbon dynamics, hydrology, and energy balance. It is always rewarding to see this many people working on so many integrated components of the NGEE Arctic project.

David, Baohua, Mallory, Ziming, and I left our apartment in Barrow shortly before 8:00am and stopped by the Barrow Arctic Research Center (BARC) and our storage room in Building 553 before heading to the field. Once we made the 2 km hike to our field site, Baohua and Ziming got busy collecting surface and pore water samples. They used a combination of techniques to obtain water samples from various depths in the soil using macrorhizons, etc. These were inserted into the soil of low- and high-centered polygons yesterday, placed under modest suction, and by this morning had accumulated 40 to 50 cubic centimeters of water. It was necessary to filter the samples to remove suspended sediments and then Ziming and Baohua analyzed them in the field for electrical conductivity, pH, temperature, and concentration of ferrous iron. One of the primary objectives in collecting these samples is to better understand the process of methanogenesis. Methanogenesis is the formation of methane, a potent greenhouse gas, by microbes known as methanogens. These microbes, under anaerobic conditions, use ferric iron as an electron acceptor. This gives rise to ferrous iron which indicates anoxic conditions that may support methanogenesis. Data from the work of Ziming, Baohua, and David will be integrated with field and laboratory experiments to better understand the geochemical controls on methane formation. Improvements in how models represent this important process are one outcome of this research and an important goal of the NGEE Arctic project.

Early Career Scientists Contribute to NGEE Arctic…

The NGEE Arctic project has been fortunate over the last three years to host a number of post-docs, and PhD and MS students. These include Heather, Lily, Michael, Lydia, Zach, Baptiste, , Shan, Carolin, Melanie, Ingrid, Ali, Chandana, Mark, Andy, Jonathan, Jenny, Santonu, Xiaofeng, Victoria, Taniya, Elizabeth, Nathan, Biao, Andy, Mark, Andrew, and Ben to name just a few. I want to thank all of them for their dedication and for their field, laboratory, and modeling contributions to the project.

This week we are fortunate to have Mallory Ladd and Ziming Yang join us for this trip  to Barrow as new team members. Mallory is starting her PhD as a student with the Bredesen Center for Interdisciplinary Research and Graduate Education (http://bredesencenter.utk.edu/index.php). This program unites complementary resources at the University of Tennessee and Oak Ridge National Laboratory (ORNL). Mallory is working with both Bob Hettich and Rich Norby to assess forms of organic nitrogen in permafrost. She will be applying various analytical techniques to examine nitrogenous compounds in soil and competition for that nitrogen between plants and microbes. Ziming joined the project as a postdoctoral research associate through ORNL’s Postdoctoral Program (http://www.ornl.gov/connect-with-ornl/for-academia/postdoctoral-programORNL) after a successful PhD program at Arizona State University. While at ASU Ziming obtained his PhD degree in organic chemistry in the Department of Chemistry and Biochemistry. Ziming is working with Baohua Gu and will examine the geochemical controls on methane flux from thawing permafrost. He will have both a field and a laboratory component to his research, as will Mallory. It is hoped that the work of both Mallory and Ziming will allow us to better understand and integrate novel aspects of carbon adn nitrogen biogeochemistry into models.

I will focus on Mallory's and Ziming's specific research later in the week and what they are individually doing while in Barrow while working on the NGEE Arctic project.

 

Pic of the Trip…

Our trip to Seward Peninsula is over and, with the exception of Cathy, Larry, and Joel, everyone is leaving Nome. Most people are traveling home; David and I, however, will catch a flight on Wednesday to Barrow where we will meet others from ORNL for a week of field work on the Barrow Environmental Observatory (BEO). This week on the Seward Peninsula has been terrific. Our team always enjoys being together; it’s a great group. Discussions can be wide-ranging when you get this many people together but everyone gets along and we always have a long list of things to do. The drive and the time in the field all contribute in a positive way to our to-do list.

Here are few photos that people contributed throughout the week that did not make it into my evening postings to the blog. The pictures show the lighter side of science and the scenery that was around us all week. I hope you enjoy them. My thnaks to David, Shawn, Cathy, and others for sending me photos. I’ll continue posting to the blog in a few days once we are settled into Barrow. Be safe…

 

 

Interesting Geomorphological Features in the Landscape…

According to Wikipedia, solifluction is a gradual mass wasting slop process, occurring in periglacial environments. It is the slow downslope movement of water-saturated sediment due to recurrent freezing and thawing of ground. The lobes formed through the solifluction process are quite distinctive and easy to see as you drive through the area.

 

We have seen evidence of solifluction at several locations this week and today we took the opportunity to visit one such site on a modest hillslope just 15 to 20 miles outside Nome on the Teller Road. Joel and Eitan spend the afternoon excavating a small section of an advancing lobe trying to better characterize thaw depth, ice content, soil texture, and moisture content. Larry, David, and Cathy took time to collect soil cores from across the lobes and adjacent areas, as well as quantify the spatial variation in thaw depth across the area. Since one of these solifluction features can cover an entire hillslope I took the afternoon to walk each lobe and examine the distribution of water and vegetation along the advancing front. It was clear that the lobes were fairly massive with most of them being multiple meters in height. The advancing faces of these features were heavily colonized by willow shrubs. These shrubs were quite productive and seemed to thrive in areas of physical disturbance. Downslope of the advancing face the soils were saturated and vegetation was largely sedges and forbs. So these geomorphological features created a highly variable environment for vegetation cover. The implications for albedo, energy balance, and the carbon cycle of these solifluction features are unknown, but they represent interesting features in the landscape. While the solifluction process itself may not be of interest to our NGEE Arctic team, the mechanisms that promote shrub expansion are and we will want to return to this and other disturbed areas in order to learn more. 

 

Taking Time to Talk…

The last few days have been busy with trips out the Kougarok, Council, and Teller Road. We have, however, seen a lot of potential field sites and discussed a number of scientific questions that will require careful consideration before making final decisions. Today everyone met in the commons area of the Dredge No. 7 and we began to focus on important outcomes from this week. We first discussed a strategy for characterizing the landscape on the Seward Peninsula, both for use in our measurements and models, and then using that scheme to help identify a few critical field sites. That proved to be a great discussion and it went a long ways towards helping outline how we will organize at least the field site selection section of our upcoming Phase 2 renewal proposal. Our team then discussed a number of high-level science questions with an emphasis on a multidisciplinary approach to understanding the causes and consequences of greenhouse gas flux and shrub expansion in the Arctic. We all feel that being able to tackle important questions from a systems perspective is one of the major strengths of our team and we want to make sure that we ask questions that take advantage of our unique scientific and technical capabilities. We ended the morning meeting with a list of action items to pursue when we return to our home institutions.

Peter Has a Party…Birthday Party

Our drive out Teller Road was an exciting one and marked a successful day. We had learned earlier in the week that today was Peter’s birthday so the team had arranged a special dinner at a new restaurant in Nome. Dinner is usually spent at Airport Pizza, but tonight we enjoyed instead a celebratory meal at the Pingo Bakery and Seafood House. It was a great dinner of halibut and salmon served alongside pasta and eggplant. What a rare treat after a long day in the field. Having been tipped off that today was Peter’s birthday, the proprietor presented Peter with a small cake topped with a single candle. We had all signed a card for Peter as well today with best wishes from everyone on the trip.

 

Happy Birthday Peter!

 

 

Terrific Trip Out Teller Road…

Our NGEE Arctic team has spent three exciting days in Nome with trips out the Kougarok and Council Roads. Today we met to begin our trip out the Teller Road that goes 75 miles north and to the west of Nome. Everyone gathered in the parking area of the Dredge No. 7 Inn and we had a safety briefing for the day. This is something we do to ensure that we are all aware of what we will be doing and to discuss any logistical or safety concerns. Keeping everyone safe while we drive mile after mile of remote dirt roads is always a priority.

 

With the exception of Larry, no one on our team had traveled out the Teller Road so this was going to be a new experience. We knew of research that had been conducted along the Council and Kougarok Road, but knew relatively little about research in this particular area of the Seward Peninsula. Our hopes were high, however, and we were not disappointed with our first stop of the day that included a large area of tundra undergoing considerable thaw and degradation. There was ample evidence that this area of the Seward Peninsula was once covered with active polygons and here we saw how degradation of the underlying permafrost was transforming the landscape to one of hummocks and hollows, or high-center polygons. It was quite striking. Our team spent a considerable amount of time here. And once our eye was accustomed to seeing evidence of degradation, it was something that we saw consistently along the road for 20 to 25 miles. 

 

Members of the team enjoyed their time at this degrading site with a lot of discussion about what might be controlling such a dramatic change in the landscape. Larry and I commented that working with the NGEE Arctic team, especially because of the multidisciplinary background of all the investigators, the conversations could be quite varied. Small groups tended to form and talk about how hydrology was impacted by a change in landscape topography and, in turn, how that might drive vegetation dynamics and biogeochemistry across these areas. We saw this again in a second area when we stopped to look at solifluction lobes that had formed on a moderate slope. 

 

There was a lot of really great discussion as we stood around the field today and looked at one feature or another. It was rewarding to listen in on all the discussions. What I did not expect was that this conversation continued within individual vehicles, and between the vehicles. The discussion between vehicles occurred because Larry had purchased hand-held radios for the trip. His purchase was primarily motivated as a safety measure and for what we thought would be just minimal exchange of information as we drove. To our surprise what happened this afternoon over the radios was a full scale discussion of the mechanisms controlling shrub expansion at the sites we had visited. A person in one car would make a comment, followed by another and another. We kept our discussion going for several hours. It was pretty fascinating and really exciting as we laid out a framework for shrub dynamics and the controls and consequences of shrubs increasing moving into tundra. Never under-estimate the value of discussion and the willingness of researchers to share their ideas. Larry - thanks for purchasing the radios!