Monday, July 28, 2014

Wildlife Abounds Across the Tundra

Our NGEE Arctic team has worked in Barrow now for almost three years. Although we stay busy with the work at hand, our scientists often comment on the number of animals that they observe. We have seen caribou, especially, in the winter months, and it is true that we have seen several polar bears over the years all from a safe distance. Today while walking out to our field site I was reminded that the tundra is alive with wildlife; lemmings, various species of birds, including my favorite the snowy owl.






Every year our team gets the pleasure of talking with Denver Holt, an expert in snowy owls, who has been studying them in the Barrow area for more than 20 years. Denver covers many, many miles each summer locating, banding, and studying owl behavior. He always has fascinating stories. Denver runs the Owl Institute in Montana: http://www.owlinstitute.org/

Greenhouse Gas Fluxes from the Tundra – How Are Those Measured?

Earlier in the week I mentioned that our NGEE Arctic team was interested in understanding how changes in landscape topography will impact the flux of CO2 and CH4 from the various polygons we are studying on the Barrow Environmental Observatory (BEO). Recall that we are investigating how ice-rich polygons might evolve in a warming environment and how surface-subsurface interactions, hydrology, biogeochemistry and vegetation dynamics might change for wet versus dry areas. The distribution of water varies dramatically across the landscape and it is likely that the flux of greenhouse gases do as well. Such information is needed for high-resolution models of land-atmosphere interactions and feedbacks to climate; however, how are those fluxes measured?

Scientists on our team are using a number of different approaches to get at this information. One of the best, especially if we want to characterize fluxes for specific locations among polygons, is the chamber-based approach. Using this technique, a clear or opaque chamber is placed over a corresponding collar that has been pressed into the tundra to form an airtight seal. The chamber can be attached to a gas analyzer and the flux of CO2 and CH4 quickly determined. A typical measurement sequence can provide information on net ecosystem exchange and respiration by switching between the two types of chambers and measurements can be completed in 5 to 10 minutes.
Oriana and Bryan, both from LBNL, have been conducting these measurements all week at our replicated field sites and along several transects. We are getting good data from dry and wet areas, and areas like the centers and troughs of polygons and small ponds where standing water is prevalent. Having CO2 and CH4 flux rates from these areas will be good since we have already determined the fraction of the landscape occupied by these geomorphological features. Therefore, upscaling from plot to landscape scales will be fairly straightforward.



 
In addition to measuring greenhouse gases from our polygon sites and transects, we are also collecting data from along the NGEE Arctic tram. This is a 60-meter long set of raised rails on which a cart carrying various sensors travels every 3 hours throughout the day. The sensor measures many components of the energy balance of the tundra plus pictures, thermal images, and albedo. The tram, installed by Bryan and colleagues at BNL and LBNL, has been in place since before snowmelt. Chamber measurements of CO2 and CH4 along the length of the tram, plus repeated measurements of soil moisture, temperature, and thaw depth, will help interpret seasonal changes in energy budgets across the summer and into early winter. In addition, we have an automated chamber nearby that records CO2 fluxes every 30 minutes so we can identify if, and how, CO2 fluxes vary over a 24 hour period.



The NGEE Arctic team will use this information to characterize greenhouse gas fluxes for the Arctic and compare results with an eddy covariance tower at our site. This way we can evaluate small-scale controls on large-scale fluxes, and use that knowledge, once validated, to improve the predictive skill of Earth system models.

Thursday, July 24, 2014

Physiology of Plants on the Tundra...

Earlier in the week I mentioned that this was a cold, cloudy, and wet year compared to the previous two or three seasons that our NGEE Arctic team has worked in Barrow. One of several consequences of that has been a slow start to the growing season for many of the plants that we are studying on the tundra. Plant physiologist Alistair Rogers from Brookhaven National Laboratory has seen this first hand in the data that he has collected as he measured rates of photosynthesis. Alistair comes to Barrow for weeks at a time each summer as part of the NGEE Arctic project to measure processes related to plant physiology. He uses a number of highly sophisticated instruments to make these measurements. Just keeping this equipment in top operating condition takes a considerable effort. However, his hard work is returning many unique insights to the project as we integrate field knowledge into climate models.




 
Alistair has made a number of observations in the last two years, and he has published a couple of nice papers highlighting rates and underlying biochemistry of photosynthesis for tundra vegetation. Most recently while conducting this research he noticed that plant growth was slow or delayed this year compared to previous years, as was the expansion of leaves that he was relying on for many of his measurements. It was a challenge to find leaves of a suitable size for his gas exchange cuvette. Alistair also noticed the leaves were not as green as they were at this time last year possibly due to cold temperatures, limited thaw depth for root development, and a general lack of nitrogen uptake by the plants. Since photosynthesis is strongly dependent on leaf nitrogen, Alistair has observed that rates are somewhat lower than last year. It will be interesting to see if photosynthesis rates recover to expected levels as the season progresses (and hopefully warms) and as plants continue to grow and mature.


 


It is important to know that the growing season in Barrow is short, typically just three months or so. Not much time for soils to warm, thaw, and biology to come alive on the tundra.  Plants are particularly challenged this year. Although only the latter part of July, temperatures are expected to soon peak and then decline as we get into August. Winter is on the horizon. A few plants are flowering, but even that seems to be less than what I recall in past years.
 


 
It would appear that plants have a challenging time growing in this harsh and highly variable environment. Alistair's research is helping us understand how plants cope and adapt to change in an Arctic environment. Knowledge from his studies will be useful as we seek to improve predictions of climate using Earth System Models.

Wednesday, July 23, 2014

Frozen Solid - Permafrost Beneath the Tundra

It's hard to imagine that soils can be frozen for hundreds of years. But try to dig a hole into the Arctic tundra and you'll quickly find that the job is almost impossible due to permafrost; soil frozen solid.

Permafrost is technically defined as soil that is frozen for two or more consecutive years. It can be found throughout much of the North Slope, occurring at several inches to many feet below the soil surface. In Barrow, the depth to permafrost averages 18 inches (plus or minus), but does vary depending on landscape position (e.g., slope and aspect), water saturation, vegetation cover, and thickness of any moss or organic layer.
Today while working on the Barrow Environmental Observatory (BEO), it was all I could do to get a shovel into the ground to a depth of 6 to 8 inches. Having dug a hole, it was easy to see that the upper soil was largely composed of recent organic matter, with gray to black mineral soil deeper in the soil profile, and then frozen soil. A quick measurement with a temperature probe confirmed that soil temperatures were close to zero and considerably colder than that at depth. Sensors placed deep into the permafrost at our field site show that temperatures can be as low as -9 C and stay that temperature year round.




The layer of soil above permafrost is referred to as the active layer. This layer will continue to thaw and deepen throughout the season. By the end of September the active layer will be thicker than it is today and mark the true depth to permafrost.

One of the questions that the NGEE Arctic project is trying to understand is just how much rising temperatures will continue to thaw permafrost (or deepen the active layer) in the coming decades. This information needs to be incorporated into models if we are to predict changes to Arctic ecosystems in the future. Assuming that warmer temperatures will accelerate thaw depth, this may have significant consequences for the release of CO2 and CH4 from tundra landscapes. This can occur directly through an acceleration of microbial processes responsible for CO2 and CH4 production or indirectly through changes in landscape topography and water distribution. Our team is studying this latter dynamic by looking at CO2 and CH4 fluxes from low- and high-center polygons. High-center polygons form as a result of long-term changes in ice content due to rising temperature and they can have very different soil and vegetation characteristics than more common low-center polygons.

I'll show how we measure the flux of greenhouse gases from polygons on the tundra later this week...

Tuesday, July 22, 2014

Summer Science in Barrow...

Any plant ecologist knows that field research requires patience and an ability to cope with changing weather conditions.  Like this morning when we woke to snow and temperatures slightly below freezing.  Such is summer science in Barrow, Alaska.  It looked all the more frigid while driving out of town along the Arctic Ocean.  Although the waters have generally been clear of ice, a shift in winds caused sea ice to move towards shore.  Just visual evidence that this is a harsh, remote, and beautiful region of the world.  Now, off to the field…


Monday, July 21, 2014

Scientists Come and Go from Barrow...

Summer, if there is one in Barrow, is marked by the coming and going of researchers. A constant flux of scientists who spend weeks at a time studying the landscapes, plants, and animals in and around this Inupiat community 330 miles north of the Arctic Circle.

Today I join that long procession of scientists as I depart Knoxville for the North Slope of Alaska. It will be a long trip taking 16 hours and covering 4600 miles as I make my way to Chicago, Anchorage, Fairbanks, Prudhoe Bay, and eventually Barrow. Hopefully my travels will be uneventful, although NGEE Arctic scientists have experienced delays in recent weeks largely due to fog along the coast of the Arctic Ocean. This made landing difficult and a few of our colleagues spent several days in Anchorage earlier in the month waiting for conditions to improve. They finally made it to Barrow and many are there now conducting various measurements in support of the project.
Conditions this year for field measurements have not been ideal. It has been unusually cold and wet. Air temperatures have been restricted to the 30's with just a handful of days warming into the 40's. It snowed as recently as last week. It has also been rainy, with this being the wettest summer by far in our four years working in Barrow. None of this seems to slow down our researchers, however, as they have been actively working in the field since May measuring snowmelt and water table depths; geophysics; fluxes of energy, CO2, and CH4; components of soil evaporation and transpiration; spectral reflectance of vegetation; and leaf gas exchange. It has been a busy year!

I'll provide daily updates for the next 10 days as our project scientists undertake various research activities at our field sites on the Barrow Environmental Observatory (BEO). To the extent possible I'll do my best to relate those to the objectives of the NGEE Arctic project and to our goal of improving climate models.
You can expect to hear more from me once I get to Barrow and join my colleagues...




Monday, July 14, 2014

Another Fun Day with the Students...

Today was Day 2 for the Nuna 2014 Summer Camp being held at Ilisagvik Community College in Barrow, Alaska. Alessio reminds me that working with middle school students is not a simple undertaking. One must remain mindful of group dynamics, and find a balance with play and work. Alessio is making it a priority to share his enthusiasm for science. So far that approach seems to be working as the students are having a great time. The students are busy and spending a lot of time outdoors.

As a result, Day 2 was epic. Alessio and the students started off by preparing a permafrost sample. Each student prepared a mixture of soil and water and put it in the freezer. With this they were simulating ice rich vs. ice poor permafrost. After “making permafrost”, the students headed out to the NGEE Arctic field sites on the Barrow Environmental Observatory (BEO). This time Alessio tried to focus their activities on plants and animals. They discussed the importance of water, and how surface hydrology is conditioned by the ice wedge polygons discussed the day before. Kids love being outside. It was easy to see how the distribution of plants was controlled by water with sedges and forbs in water inundated areas with grasses and short woody shrubs on the drier upland areas. Not many animals were present, but Alessio and the students talked about how birds and other animals might nest on areas that were “high and dry” as opposed to areas that flooded easily.

In the afternoon the students did something very special. David Masak, a smiley man in his fifties who work for Ilisagvik, asked his dad if they could see his meat-cellar, four meters below ground, dug in permafrost. This was quite an experience, for Alessio and for the students. The cellar was dug in 1969 with an icepick, it took 3 months to dig, and since then, has provided shelter for the wild game. The students truly enjoyed the experience. First they could touch permafrost and observe it very closely. Second, they obtained a glimpse of Inupiat culture, and finally third the roof of the cellar was full of beautiful hoarfrosts which fascinated many of the students.

Alessio writes that it was a long but good day. Everyone had fun. Tomorrow is another day.