(Soil, Water and Environmental Sciences-Microbial Ecology Laboratory)

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Why arctic permafrost thaw is NOT a methane “time bomb”

Flux chambers used to measure carbon dioxide and methane emissions from Arctic soils.

Flux chambers used to measure carbon dioxide and methane emissions from Arctic soils.

A number of times in recent months I have found myself explaining my research to somebody when they suddenly interject with the comment “Oh, so you’re studying the arctic methane time bomb.” The first time this happened I was confused and not quite sure how to respond, because while I do study processes that could result in methane release from thawing arctic permafrost soils, I wouldn’t call it a time bomb so much as a slow feedback. As I talked to more people, I slowly realized that this comment actually stemmed from a rather profound misconception. There are two possible sources of methane (CH4) release from the arctic that could be triggered by climate change: methane hydrate release, and permafrost carbon thaw. These two potential methane sources stem from very different pools of carbon and are controlled by very different environmental processes. As a result, they have very different sets of risks associated with them. I study permafrost thaw, but most people who have heard anything about the arctic and methane release seem to have heard about methane hydrates. Let me do my best to explain the difference:

Methane hydrates are concentrated solid deposits of frozen methane which are formed under high pressures and low temperatures. Most (<98.75%) methane hydrates are found in deep ocean sediments, but 1% are estimated to exist at depths greater than 300m below arctic permafrost soils. An additional very small amount (likely >0.25%) exist on arctic continental shelves. Rough estimates suggest that there may be approximately 1800 Pg C stored in methane hydrates globally (Ruppel, 2011). While this total quantity of methane is very large (representing more than the total carbon stored in permafrost soils), most of it is well insulated from the warming effects of climate change by a combination of layers of ocean sediment and deep water above it. The paleo-record gives no indication that such deep methane hydrates have been catastrophically released by previous extreme arctic warming (Colose, 2013). The slightly more than one percent of methane hydrates which exist on land or on continental shelves may be at risk of release due to the extreme warming (7-8ºC) projected for the Arctic (IPCC 2013). However, the process of methane release due to warming will be slow and unlikely to release the entire store of methane instantaneously (Ruppel, 2011). Because methane in the atmosphere only has a 10 year lifespan before it is oxidized, such a small and slow release of methane is unlikely to dramatically increase atmospheric methane concentrations (Ruppel, 2011). Furthermore, the methane released from such deep stores has the potential to be consumed my microbial processes and may never reach the surface, further decreasing its impact (Ruppel, 2011). Thus, the risk of catastrophic methane release from hydrates is very low.

A permafrost soil core containing lots of frozen organic material.

A permafrost soil core containing lots of frozen organic material.

In contrast, methane from permafrost organic matter is not stored as methane itself but as organic molecules in frozen soils either on ocean shelves or on land in permafrost. It is estimated that permafrost soils globally hold approximately 1700 Pg C which is more than twice the amount of carbon currently in the atmosphere (Schuur et al 2008). When permafrost soils thaw, the carbon stored in them is exposed to conditions which promote much faster microbial decomposition (Schuur et al 2008). However, the ultimate fate of this carbon depends heavily on environmental conditions. In dry soils, aerobic decomposition proceeds relatively quickly and produces carbon dioxide (CO2) gas. However if permafrost thaw results in wetland formation, anaerobic decomposition proceeds more slowly and produces a mixture of CO2 and CH4 gases. Permafrost thaw may also result in nutrient release and environmental changes that drive a shift in dominant plant communities to species which store more carbon (Schuur et al 2008). Therefore, the net carbon balance of thawing permafrost systems will depend on the amount of carbon uptake due to plant growth as well as the degree and rate of carbon release due to decomposition. Likewise, the rate of CH4 release from these ecosystems will depend on the area of land which is converted to wetlands as a result of permafrost thaw and the length of time which they remain wetlands. If we consider that globally, wetlands are the single largest source of atmospheric methane (177-284 Tg CH4/yr), and that it has been established that permafrost thaw will result in the creation wetlands in many arctic areas (Schuur et al 2008), arctic warming is very likely to increase CH4 emissions to the atmosphere. These emissions will not occur as a sudden release but as a steady long-term increase. In those areas which do not become wetlands, there is a high risk of greatly increased CO2 emissions from thawed permafrost soils.

Lab members Gary and RJ sampling a wetland that was created by permafrost thaw.

Lab members Gary and RJ sampling a wetland that was created by permafrost thaw.

So what is the arctic “time bomb,” and why do people confuse it with the possibility of carbon release from arctic permafrost thaw? Last year Whiteman et al (2013) published an article in Nature Commentary describing a “time bomb” consisting of severe global economic impacts from a potential 50 Pg release of methane hydrates either suddenly or over the course of 50 years. The article created a lot of controversy (see articles by Colose, Samenow, and Ahmed) primarily because the authors gave no indication of the likelihood of such an event. While there is not perfect agreement, most scientists consider the likelihood of a sudden catastrophic release of methane hydrates to be very low (Colose 2013). But the prediction of such an extreme event and the ensuing controversy caught the eye of the media. The result is that most people who have heard anything about CH4 release from the arctic have heard about methane hydrates, not the possibility of CH4 release due to the decomposition of organic material in thawing permafrost.

Overall, Arctic warming does have the potential to be a significant positive feedback to global warming, but it is unlikely to come in the form of a sudden, catastrophic release of methane hydrates. The strength and type of the positive feedback will depend primarily on the precise factors controlling the decomposition of carbon compounds released from permafrost soils as they thaw. Decomposition of this material will likely occur very slowly, be incomplete, and produce a mixture of CO2 and CH4 gases. What the precise impacts will be is still very much unknown. That is why groups such as ours are studying the different factors that control the fate of carbon that is released from permafrost.

Moira Hough


Ahmed, Nafeez (2013): http://www.theguardian.com/environment/earth-insight/2013/jul/24/arctic-ice-free-methane-economy-catastrophe

Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell, A. Chhabra, R. DeFries, J. Galloway, M. Heimann, C. Jones, C. Le Quéré, R.B. Myneni, S. Piao and P. Thornton, 2013: Carbon and Other Biogeochemical Cycles. In: Cli-mate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. http://www.ipcc.ch/report/ar5/wg1/
Colose, Chris (2013): http://www.skepticalscience.com/news.php?p=2&t=66&&n=2130

Ruppel, C. D. “Methane hydrates and contemporary climate change.” Nature Education Knowledge 3.10 (2011): 29. http://pm22100.net/docs/pdf/enercoop/energie/gaz/130316_Methane_Hydrates_and_Contemporary_Climate_Change.pdf

Samenow, Jason (2013): http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2013/07/25/methane-mischief-misleading-commentary-published-in-nature/

Schuur, Edward AG, et al. “Vulnerability of permafrost carbon to climate change: Implications for the global carbon cycle.” BioScience 58.8 (2008): 701-714. http://bioscience.oxfordjournals.org/content/58/8/701.short

Whiteman, Gail, Chris Hope, and Peter Wadhams. “Climate science: Vast costs of Arctic change.” Nature 499.7459 (2013): 401-403. http://www.nature.com/nature/journal/v499/n7459/full/499401a.html


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A poem about our sub-Arctic research


Methanogens are very small–

understanding them ain’t so banal.

Their customary dwelling place

is deep within the anaerobic space.

Typically occurring in reduced anoxic environments,

they’re also found in subglacial sediments.

The greenhouse gases they can release

keeps us scientists at unease.

And so many sanguine people hope

to study them in full scope,

in order to build scientific models

that can prevent global debacles.

At the Rich lab we collect peat,

to understand all the heat

contributing to the thaw gradient

at which the permafrost is ambient.

Widely distributed are these methanogens,

they’re also found in Spitsbergen.

High up in the Arctic,

or way down in the Antarctic,

Methanogens are of high importance–

they play a role in the Earth’s disturbance.

There are many reasons to study permafrost,

one of them being the economic costs.

So let’s quantify soil-atmosphere gas exchange

to further assess this climate change!

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Environmental Microbiology in the High Arctic

Swimming in icy cold fjords, Summer barbecues at 4C, insomnia under the midnight sun, polar bears roaming about… I was in no doubt that I was somewhere like nowhere else on Earth. If I was even on Earth at all. The University Centre in Svalbard (UNIS) is the world’s northernmost institution of higher education, located at 78º N in Longyearbyen, Norway. There, I fell in love with the amazing landscape and the diversity of life! The fauna and flora of Svalbard includes more than 1,800 marine invertebrate species, 1,200 terrestrial or freshwater invertebrate species and over 170 higher plant species in addition to the 21 mammal and 28 bird species.

While it is a stunning environment, the high Arctic is is harsh, and the challenges microbiologists face in the high Arctic were due to low biomass, unknown target, unknown selection pressures, the remote fieldwork, low activity of microbes, contamination, and typically only getting one initial sample.


photo 1 photo 2

The general course description as advertised on the University Centre of Svalbard’s website can be found here: http://www.unis.no/STUDIes/Arctic_Biology/ab_327.htm

Course outline

    • 4 lectures per guest lecturer
    • 5d lectures and seminars (some evenings)
    • 7d laboratory practicals (3 themes)
    • 7d fieldwork (3 themes)

Major Topics Covered

    1. Eukaryotic Microbiology
    2. General Ecological Principles
    3. Cryoconite, Glacier and Aerial Microbiology
    4. Terrestrial Microbiology and Nutrient Cycles
    5. Molecular Microbial Ecology (a and b)


    • David Pearce, University of Northumbria & UNIS, Aerial Microbiology, Glacier Microbiology, Hot topics in Arctic Microbiology
    • Malu, University Centre of Svalbard, Arctic Microbiology
    • Giselle Walker, Laboratoire d’Ecologie, Systématique et Evolution, Protistan biogeography and ecology  & Biogeochemical cycles
    • Pete Convey, British Antarctic Survey, Terrestrial Ecology of Arctic and Antarctic systems
    • Antonio Alcami, Universidad Autonoma de Madrid & National Center for Biotechnology (CNB), Viruses in polar marine environments & Metagenomics of viruses in water
    • Chris Laing, University of Exeter, Modeling & Adaptation to low temperatures
    • Lise Øvreås, University of Bergen, Arctic marine microbial diversity & Molecular microbial ecology (soil and marine)
    • Arwyn Edwards, Aberystwyth University, Cryconites & bacterial communities of Svalbard glaciers; Bioinformatics
    • Chester Sands, British Antarctic Survey, Systematics & Bioinformatics
    • Matthias Zielke, Bioforsk Norwegian Institute for Agricultural and Environmental Research, Arctic microbial ecology, C & N-cycles in Arctic soils
    • Marek Situbal, Geological Survey of Denmark and Greenland, Microbial communities on glacier surfaces and ice sheets


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“Tucson” tack

In Swedish Tusen tack means 1000 thanks. I like this because Tusen sounds like Tucson! 

Anywho Tusen tack to everyone in the lab for helping me this summer. I am super excited to be working with such awesome people in the office again!

Cheers to having a great semester:)10438638_273602416177267_626349687097286555_n

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Summer Update: Stable Isotope Ecology

Some may think that summers for grad students are all about fieldwork. This is TRUE! Mostly. It’s also about taking fantastic intensive summer training courses. In June I spent 2 weeks in Salt Lake City, Utah learning about the many ways stable isotopes can be used in ecology and biogeochemistry. It was a fantastic course in which I learned as much as could be packed into my little brain, met many impressive researchers, and made friends with a diverse and wonderful group of graduate students. In short, this course is highly recommended to anybody interested in stable isotopes, and/or biogeochemistry. In long, see below for a course description and list of lectures. Please feel free to ask me if you want to learn more about any of these topics or hear about the fantastic lab sections! Or visit the course website: http://stableisotopes.utah.edu/isocamp.html


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From the course website:

“The concept is to bring students and researchers together from around the world, teaching them about stable isotopes in biogeochemistry and ecology and developing careers in this next generation through lectures, training sessions, and laboratory experiences. IsoCamp facilitates the development of long-lasting friendships and future collaborations.”


Thure Cerling Utah Terminology, fractionation, analytical measurement approaches

Todd Dawson Berkeley Isotopes and meteoric, source, and plant waters

Craig Cook Wyoming Intro to IRMS instruments

Ehleringer Utah Plant carbon and related processes in terrestrial ecosystems

Eve-Lyn Hinckley NEON NEON and stable isotopes

Steve Leavitt Arizona Carbon isotopes and the long-term climate record in tree rings

John Roden S Oregon U Leaf water, oxygen isotopes, and the long-term climate record in tree rings

Renee Brooks EPA QA/QC and data analysis

Jed Sparks Cornell Nitrogen transformations within plants and in ecosystems

Seth Newsome New Mexico Body water and animal physiology as integrators of geography and diet

Thure Cerling Utah Reconstructing Diet and Tissue Turnover in Animals

Carly Strasser California Digital Library Data management

Howie Spero UC Davis Biogeochemistry of the Oceans

Brian Popp Hawaii Biology of Oceans

Rebecca Powell Denver Remote sensing

Dave Bowling Utah Carbon Dioxide and the Carbon Cycle

HJ Jost Thermo Fisher Scientific IRIS CO2

Jim Ehleringer Utah Forensics: geospatial applications

Dave Williams Wyoming Biosphere-atmosphere coupling of the water cycle

Elise Pendall Wyoming Soil Biogeochemistry and Stable Isotopes

John Hayes Woods Hole Oceanographic Instrumentation for isotope analysis

Thure Cerling Utah Soils and Carbonates

Hagit Affek Yale D47 analysis

Lesley Chesson Utah Stable isotopes and Food

Kate Freeman Penn State Biomarkers and Environmental Reconstruction

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Dawson and Maggie’s NM Adventure!

Dawson and I  recently had the chance to get out to the CZO field site in Valles Caldera, NM; we were taking some pre-monsoon samples of the site that was burned in a wildfire last summer. We piled ourselves, eight coolers, hundreds of plastic bags and falcon tubes, shovels, GPS, flags, food, and other various gear into Dawson’s car and drove the 8 hours from Tucson to northern New Mexico. It was a long drive, but with the help of “The Monkeywrench Gang” by Edward Abbey  and a stop to eat some delicious Hatch chiles, it went fairly quickly. The scenery was beautiful and we arrived to our cute cabin just as it was getting dark.

The next morning we woke up early and made the hour long trek on the rock and dirt road to Redondo Peak, one of the places that had been burned one year prior and our study site. The road up was almost overrun with Aspen trees, which are traditionally one of the first species to succeed an area after a wildfire. This was the spot where we would take our samples, with the purpose of characterizing the enzyme activity, community composition (using DNA extractions), and microbial biomass. Dr. Jon Chorover and, the incredible field tech, Mark Losleben helped us get started on digging our pits. This turned out to be quite an arduous process. We used shovels, and often a crowbar, to hack at the ground until we reached 40cm–on numerous occassions we would end up prying massive rocks out of the ground, or even hacking roots up to reach the necessary depth. There were six depth intervals from which we took soil samples, and there were 25 sites to be sampled from. Let’s just say that it ended up being quite the workout. A routine set in quickly: dig a pit, gather bags and falcon tubes, sample at each depth and seal in bags/tubes, re-fill pit, gather equipment, move on the next site. Some sites were rocky, other still pure black carbon (ash) from the burn, and some were layers of roots all snarled together. It was pretty exciting just to see the variety of sites, soil profiles, and the regrowth from the previous year.

We did this for two full days, and the last day decided to “beast it out,” and with the help of Jon Chorover and Mark Losleben again, we completed 11 sites on the last morning. After that, we packed up our nearly overflowing coolers with all 157 soil samples in Ziploc bags, as well as the additional 157 falcon tubes housing the soil samples for DNA extraction. After leaving the Valles Caldera and heading back through the red rocks of Jemez Springs, we filled the coolers with ice and drove straight to Tucson–the monsoon clouds chasing us the whole way. It was a great to be home, but the study site was so beautiful that it was still a bit sad to leave. Now we are on the processing phase–finished with sieving and separating soil for the Microbial and Biogeochem constituents, onto DNA extractions, choloroform fumigation for microbial biomass, and enzyme assays.

All in all, it was an extremely successful and fun trip! We learned an insane amount about field work, worked out butts off, and are now back to our typical lab rat lives. 🙂

Digging them pits!

Digging them pits!

Red rocks of the Caldera on our way to Jemez Springs

Red rocks of the Caldera on our way to Jemez Springs


The monsoon following us all the way home!

Soil profile–see the root we hacked on the right?

A view of the road up and the burn site

Nearby wildfire--we were worried it would be so close we wouldn't even get to sample.

Nearby wildfire–we were worried it would be so close we wouldn’t even get to sample.