Hitting the Tundra

It has been cloudy in the last couple of days. Jonathan Ajo-Franklin from LBNL joined the spirited gang of Arctic geophysicists and with his arrival the seismic acquisition has started. Surely the lemmings and the inhabitants of the quiet tundra have noticed our new activity.

Alessio hits the ground with the sledgehammer while Jonathan carefully observes the seismic wave being recorded by the geophones. Glen, our great bear guard, learns about seismic too. 

 For the entire day we have been repeatedly hitting the tundra with a 30 lbs sledgehammer. Today, we swung the sledgehammer approximately 600 times to introduce seismic energy into the subsurface. The seismic energy traveled in the frozen ground and was recorded by a number of little geophones, which were accurately buried within the snowpack.We are carrying out both surface refraction and MASW (multi-channel analysis of surface waves) methods.

It is time to move the seismic line. The team digs the geophones out from the snowpack. 

 The seismic experiment will allow us to measure the seismic velocities within the permafrost. This is a precious information that can be used to discern the physical properties of the subsurface. As with all the other methods we have applied in this campaign, it allows us to interrogate the  permafrost without really directly touching it.

We have now two more days left until the end of this very intensive geophysical campaign in which we collected a tremendous amount of information.
We have all learned a lot  - about geophysics, about the tundra, about the North, and about each other. 

John patiently completes the GPR survey while the rest of the team focuses on the seismic and the electromagnetic methods.

Written by Alessio Gusmeroli (UAF) 

Reflections on the Tundra

Written by Alessio Gusmeroli (UAF)

It is really flat up here. No matter where you look, there are no hills and there are no mountains. The topography is as boring as it gets. This is noticeable if you are a glaciologist (as am I) - used to working narrow valley field sites that are filled by ice and surrounded by rugged peaks and spectacular mountains.

The flat Arctic Coastal Plain

The glory of the Arctic coastal plain does not come right away. It comes with careful inspection. One must stop, listen and look very carefully. If you do that, you hear the sound of the wind, you hear a myriad of snow granules constantly in motion. You notice the role of the wind in creating snow sculptures on the surface. You see beautiful moving snow dunes that resemble their sand relatives. 

The way snow fills the coastal plain is indeed one of the first things we have been learning about in this fieldwork. The presence of snow and the possibility to use snow machines is facilitating all our field operations. With Susan, John, Baptiste and Craig we have been running a variety of "motorized" geophysical experiments, in which the geophysical device is towed across the tundra by the snowmachine. 

The ground penetrating radar, for example is giving us a good idea on what lies beneath the snow pack. First, we see that the snowpack is thicker above ground depressions (i.e., polygonal troughs); second, based on the reflections in the radar data we see that the permafrost that lies at depths greater than 1 m is anything but homogeneous. We have noticed a number of reflectors, likely part of a network of ice wedges and intervening layers. We will be learning a lot more about the deeper ground ice and its relationship to active layer and snow variability once we assemble and jointly interpret the entire datasets. 

Undertaking geophysical fieldwork in the cold has always its peculiarities. We have to fiddle with many tiny little cables that connect into instruments. Some of these often break. Patience and resistance to frustration is something you quickly learn when you work with instruments and delicate cables in the cold. As always, it is a privilege to work up here in the magnificent, bright, Arctic spring with such a nice group of people.

Delicate fiber optic cables connect the radar antenna to the recording console

Team standing ON the Arctic Ocean (sea ice extends out ~4 miles from shore". From left to right: Baptiste Dafflon, Craig Ulrich, Susan Hubbard, John Peterson and me (Alessio Gusmeroli)

White and Bright in Barrow

We’ve competed two days of geophysical acquisition at the same location where we worked last September.  The conditions are quite different – everything is white, white, white; with the snow cover there is little evidence of polygonal ground; and  daytime temperatures  are quite cold (~20F with wind chill). With 24  hours of sunlight, the midnight light is brighter than it gets on sunny days in Berkeley!

We’ve focused to date on EM and radar using different systems, frequencies and acquisition modes – the figures below show 100MHz Sensors and Software radar being acquired by pulling it manually and with a snowmobile. The snowmobiles have been great for pulling around equipment and people (and lets admit it, the snowmobiles have been downright fun). We are starting to recognize geophysical signatures of ice wedges permafrost variability but have lots more to learn.

It has been great to be here with Stan, Cathy, Alex and Anna, who are working on the neighboring plots installing hydrological wells. Everyone is working hard and in good spirits.

First NGEE Geophysical Winter Campaign

The NGEE geophysical team is on the way to Barrow for its first ‘winter campaign’.  Last September, the team  conducted its first ‘active layer characterization campaign’, which  included acquisition of a variety of geophysical and point measurements along a permafrost gradient where lidar data were also available. Analysis of the datasets, individually and in combination, revealed the utility of the methods for characterizing critical active layer and land-surface properties and their relationships; results were presented at the EGU meeting in Vienna two weeks ago.

Team (standing in the Arctic Ocean) from left to right:
Stan Wullschleger (ORNL), Baptiste Dafflon (LBNL),
Craig Ulrich (LBNL), Susan Hubbard (LBNL),
John Peterson (LBNL)and Alessio Gusmeroli (UAF), Sept 2011. For this May
campaign, Jonathan Ajo-Franklin (LBNL) will also join us.

First Geophysical Field Campaign

The objectives of this campaign are threefold: (1) to characterize the ground ice beneath the active layer at the same location as the previous campaign; (2) to test a new seismic methodology for quantifying ground ice characteristics; and (3) to collect a variety of geophysical data in a nearby area to provide a foundation for other measurements that will be made by other NGEE groups during the upcoming growing season. 

We are excited to again be working in Barrow together again, worried about the instrumentation performance in this cold weather, and curious to explore the geophysical responses to the frozen ground. Stay tuned!

First geophysical field campaign!

The NGEE geophysical team had their first field day today, with an objective to explore subsurface soil variability just prior to freeze in a field site in Barrow that displays different thermokarst characteristics. Baptiste Dafflon, Craig Ulrich, John Peterson and Susan Hubbard from LBNL were joined by Alessio Gusmeroli from UAF. We arrived to a dusting of snow and what seems like an incipient freeze – everyone was bundled for field work. After hauling lots of equipment out to the site, we collected surface electromagnetic data along some key transects and tested the ground penetrating radar responses. We initiated the collection of active layer depth, temperature, and TDR moisture probing along the geophysical transects. Tomorrow Stan Wullschleger from ORNL will join us, and we will start the electrical data acquisition. We are exciting to see what these data yield!

Features, features everywhere

Continuing our site selection activities, yesterday the NGEE team flew by charter plane from Nome to Barrow, flying over or stopping at: Council, Kougarok, Kotzebue, Selewik, the Brooks Range, Ivotuk, and Atqasuk. Although in the early stages of NGEE we propose to focus our field activities on the Barrow and Council 'end-member' sites, we envision that later stages of the project will include a gradient study along a transect similar to what we flew. The beauty, vastness, and remoteness of the landscape was awe inspiring.

Over and over again, we witnessed a variety of permafrost degradation features in close proximity to each other. Being able to see these features from above - and in relation to the larger scale geology, topography and river systems - allowed us to speculate about key factors and interplay of processes that control the evolution of these features. The 'uniformity of the heterogeneity' was striking, and suggests that there is a rhyme and reason to the expressions. This is encouraging, because development of a next generation landscape simulator will require an understanding of the permafrost evolution as well as its impact on climate.

Last night (after dinner, at 11 PM at 'night', when there is still plenty of light to work....), Craig Tweedie gave the team a mini-tour of several experiments in progress in the area. This morning we will meet with community leaders in Barrow and spend the rest of the day scouting for field sites and visiting the Barrow ARM site. In contrast to Nome, the weather is gloomy here. I guess that is to be expected, for the farthest northern city in the US!

Thermokarst Exploration near Council

Today the NGEE team spent the day exploring the geomorphology, hydrology and vegetation near Council. We were able to observe an outstanding array of features indicative of the transitional nature of this landscape. On the hillslopes, we witnessed solifluction (or active layer detachment and transport) as well as shrubification. On flatter ground, we walked through many different thermokarst features, stepping from wet sedges in the middle of the thermokarsts (the first step is always a surprise...) to higher and dryer shrubs on the banks of the features.

We used a probe to measure the spatial variation in the active layer thickness , which often ranged from 30cm on the banks to >1m in the center of the thermokarsts; this variation is expected to drive a variety of above ground vegetation and below ground microbial ecosystem processes that feedback to climate. Not only were the transitions in moisture, vegetation, and active layer sharp, but the heterogeneity of features within a small distance was striking: thermokarsts, drained lakes, and patterned ground formations were all evident in close proximity. Witnessing textbook examples of such a variety of permafrost degradation features first-hand was awesome - it fostered plenty of team discussion about where to select sites for detailed study.

After investigating lodging possibilities for a field camp in Council and experiencing the generous hospitality of Council townspeople, we headed back for our last night in Nome. On the way back, we spotted reindeer and grizzly bear, as well as several large birds and small critters. What a day.

Tomorrow early morning we board a small charter plane to survey this and several other areas from the air – we expect another exhilarating day of observing these features from another perspective.

All photos in this post were taken by Roy Kaltschmidt and are under copyright by Lawrence Berkeley National Lab

Welcome to Nome

Posted by Sam Wright on behalf of Susan Hubbard

The majority of the NGEE team flew this morning from Anchorage to Nome,  Alaska. Nome is located on the Seward Peninsula, about 75 miles from the town of Council, where the NGEE team is considering developing one of two field study sites. Compared to the Barrow study site (which the team will visit later this week), the Council region is warmer and the permafrost is thinner.  A study site in this region will allow us to examine ecosystem-climate feedbacks associated with a transitional landscape where the permafrost is discontinuous and the expansion of shrubs to tundra is already occurring. Stan and Larry, who had arrived in Nome the day before, met us at the airport with vehicles.  We arrived to a beautiful day – bright blue sky and warmer temperatures than many of the summer days I experience in Berkeley.  It was an auspicious start to our weeklong site selection venture!

Our main activity today was a meeting with several of the Nome community leaders. Larry had arranged the meeting, and he initiated the discussion by describing the NGEE project to the leaders and then asking for their feedback.  Four hours of very interesting conversation followed.  The leaders asked excellent questions and offered assistance in terms of data, introductions, and community outreach. They thought our key scientific question - of how permafrost degradation impacts water distribution, nitrogen allocation, organic carbon decomposition and energy balance - was indeed worthy of study. Most importantly, listening to them provided really valuable insights about how climate change and the coupled processes that we plan to study can really impact a community. We heard accounts of how the landscape, flora and fauna had changed since the days that they or their parents were younger. They told us how Felt Leaf Willow and Cottonwood, which grow well in thawed soils, has become much more pervasive in their landscape.  Terrain that ‘used to be smooth when I was young is now humpty-dumpty’, which referred to the microtopograhy created through thermokarsting.  We heard about changes in the fish species, how moose had replaced caribou within their lifetime, and how areas that once yielded salmonberries now yield blueberries. With a population that includes large mammal hunters, reindeer herders, and fisherman, it is clear that these changes have impacted the livelihood of the town members. These changes also have feedbacks to the processes that we are intending to study in ways that we had not considered.  For example, beavers, which very have recently become much more common in the area due to warming, are building dams that are altering surface water flows.  Although we had envisioned choosing our study plots within the Council site based primarily on geomorphology (i.e., pre-, active- and post- permafrost degradation), it was clear through these conversations that there are many other factors that could indicate the state of the landscape transition, and we discussed different avenues for soliciting this deep local ecological knowledge for use within NGEE.

We wrapped up our meeting by talking with logistical providers who had also joined the meeting, and looking at maps and areal images of the different areas around Council that we will visit tomorrow.  We are all excited about getting out to the field - it is bound to be an interesting day in this fascinating region!