Permafrost Thawing: An Exclusive Interview with Ecologist, Dr. Edward Schuur, Univ. of Florida

In the July 16, 2006 edition of SCIENCE a research team in which Dr. Edward A. Schuur of the University of Florida participated, reported new findings about the reservoir of carbon stored in the permafrost in Siberia. The researchers specifically addressed loess soil, known as ”yedoma” in Siberia, a wind and water born dust frozen in permafrost in depths up to 50 m (~164’). The concentration of carbon in the deep yedoma deposits was much higher than expected compared to deep soils elsewhere.

SMO: Dr. Schuur, your paper estimates the varying reservoirs of carbon in gigatons (Gt)

oceans 40,000 Gt
soils 1,500 Gt (all soils globally, including tundra to a depth of 1 m (3.3’)
vegetation 650 Gt

Could you please explain how the mass of carbon is measured and estimated in the atmosphere and in the other pools?

DR. SCHUUR: Mass of carbon is the concentration times the volume. In the case of yedoma, we need to know the thickness of the yedoma (av = 25m), the bulk density (weight of dry soil per volume of soil, in other words kg of soil per cubic meter) and then the carbon concentration, which we can measure on an elemental analyzer. The elemental analyzer combusts the soil sample and measures the amount of carbon dioxide that is released upon combustion. We take soil samples from a range of geographic locations and vertically throughout the yedoma to describe a large area. A similar approach is used for ocean, atmosphere too.

SMO: Please elucidate on carbon reservoirs in the Arctic and how your team’s discovery fits in

DR. SCHUUR: There are two comparisons in our paper: the first comparison is between deep permafrost yedoma (~500gt) and the surface values that are typically used for northern ecosystems ~450gt. The latter value is focused on 1m depth. So, we are saying that there is another, more or less equivalent (large) amount stored deeper below.

The second comparison is an estimate carbon pools for >10,000 years ago when there were ice sheets at the last glacial maximum. The first comparison is the most relevant for current and future changes.

SMO: Most scientist believed that the organic material locked beneath the permafrost in Siberia, Canada and Alaska was in the form of partially decomposed peat, Sphagnum moss. But your study seems to indicate that the yedoma is also carbon repository.

a) How was this overlooked before?

b) Where did the yedoma come from? What plants or animals? When?

c) How was it sequestered in permafrost?

DR. SCHUUR: We are studying soils that are deeper than the traditional 1m depth that many soil studies focus on. Because carbon enters soil as plants and animals die and decompose, it is reasonable in most places to focus on the surface because that is where the biological activity is.

The reason that yedoma is different is that the surface of the soil was rising because in the glacial/interglacial periods, dust was falling and accumulating on the surface. Even though it was only mm to cm falling per year, over decades, this adds up to a lot of material, up to 53m (174’) thick in some places.

As the surface of the soil rose, carbon that was in the soil became trapped in permafrost (permanently frozen) before it had time to decompose fully. As a result you can see intact plant roots preserved deep in the frozen soil. This happened at a time where the ecosystem was steppe-tundra with lots of grasses and herbivores (think mammoth, bison, etc., other Pleistocene mega fauna)

This process resulted in carbon trapped much deeper than is expected in many places, and cut off from decomposition by microbes because it was frozen.

SMO: In regions at the southern extreme of continuous permafrost, how fast is it melting and what CO2 contributions to the atmosphere is this making today?

DR.SCHUUR: This is the $64,000 question. There is permafrost thawing (that is the word that permafrost scientists prefer rather than melting) occurring, and we are trying to estimate how fast it might be coming out. This paper is mostly about the size of the pool, and given how large it is, it is something that we should be worried about if it decomposes. Our lab experiments show that this old frozen carbon can be decomposed when thawed, now it is a matter of making projections into the future with the use of models.

SMO: If the melting is an accelerating positive feedback loop, can you make any estimates of how much faster the out gassing might be with a given temperature or atmospheric CO2 level increase?

DR. SCHUUR: Again this is the current and future research figuring out how much of a climate impact this pool will have using g/c/ms and future scenarios.

SMO: What are the most important actions that you believe should be taken to halt or retard the melting of the permafrost layer?

DR. SCHUUR: Permafrost stability (and preservation of carbon therein) is affected by climate change. Currently, human-caused changes in atmospheric greenhouse gases are likely to affect global climate, thus anything that we can do to reduce emissions to the atmosphere will help mitigate this problem.

SMO: There is a school of thought which believes that permafrost melting will result in the tundra becoming a carbon sink rather than a carbon source. The theory is that as the polar climate warms, plant communities currently limited by the cold temperatures will expand their range northward. And since plants are carbon sinks, the net effect of carbon and methane release from the melting permafrost in the tundra will be cancelled.

DR. SCHUUR: This is an important point and cannot be ignored. It depends on the rate of plant response and soil microbe response. In the yedoma soils there is far more total carbon than can be offset by plant growth, but then that depends on how extensively/fast the soil thaws. In general though there is so much carbon in yedoma down deep (~500gt), that if you consider the total land plant biomass (~650gt) worldwide that you can see that if all the yedoma thawed that there is no way to grow enough plants to offset.

SMO: Wildcard. Here you can ask your own question and answer it if you wish.

DR. SCHUUR: Here's a comment regarding surprises in climate change research. One aspect about this yedoma pool is that we are saying that this is 500 billion tons of carbon that was not really considered before. One extension of this is to think that if this surprise is out there, might there not be other surprises in the earth carbon cycle/climate system that can have a significant impact on our climate trajectory? This research makes me think that there are more surprises out there, and some we might only discover as they change in response to changing climate.

Ted Schuur, Ph.D.
Asst. Professor of Ecosystem Ecology
Department of Botany
University of Florida
Gainesville, FL, 32611-8526

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Permafrost Thawing: Temperate Tantrums

Here Comes the Sun

During this summer of searing heat waves, we don’t need to tell Americans that things are heating up. In a report issued this June by the prestigious National Academy of Sciences, “A panel of top climate scientists told lawmakers that Earth is heating up and that "human activities are responsible for much of the recent warming. Their 155-page report said average global surface temperatures in the Northern Hemisphere rose about 1 degree during the 20th century.-- Earth is the hottest it has been in at least 400 years, maybe more.”

In big brush strokes, the climate of our Earth has changed dramatically since it was formed. Our planet had experienced hotter periods and colder periods. The outcome is determined by the amount of solar energy input vs. the amount of solar energy reflected and heat radiated. See our article on Earth’s Radiation Budget for how this balance is established..

The Heat is On

Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades. The Earth's average near-surface atmospheric temperature rose 0.6 ± 0.2 °Celsius (1.1 ± 0.4 °Fahrenheit) in the 20th century. The prevailing scientific opinion on climate change is that "most of the warming observed over the last 50 years is attributable to human activities." Source

It is widely believed by many scientists that what seems to be a relatively small increase in sea temperature is negatively effecting coral reefs (coral bleaching) and is accentuating the severity of hurricanes. But the impacts on high latitudes are just now starting to get attention.

Polaritis

What may be until now a largely overlooked consequence of global warming is the effect of rising temperatures in the Arctic and Antarctic. As glaciers melt, sea level rises and a darker, more absorbent surface is exposed. Likewise, as sea ice melts, it loses the reflectivity of frozen snow and ice, therefore the darker water surface absorbs more solar energy.

But perhaps of even greater concern is the impact of warming on the high latitude tundras of Siberia, Alaska and Canada. The soil beneath the surface has been mostly frozen for about 10,000 years and over this period it has been accumulating partially decomposed plant and animal matter from the surface. We are not talking about an insignificant area.

Permafrost is found on both land and continental shelves in the Arctic, and it comprises almost 24% of the Northern Hemisphere’s land, covering approximately 22.8 million square kilometers.Source

What is significant is that a half degree change in average global temperature may make us sweat a little (or a lot) more in the temperate climes, at the southern edge of the permafrost regions, there is frozen subsurface permafrost soil that is just barely above freezing. In this case a half a degree means the difference between solid and liquid. And this difference in phases is huge. As the permafrost thaws it allows bacteria and other decomposers to get busy. The outcome is the release of carbon dioxide and methane (10 times more effect than carbon dioxide as a greenhouse gas).

This is what scientists mean when they talk about “tipping points”—a small change can initiate large scale, irreversible changes. What we have here is a positive feedback loop. The end products of the reaction (thawing and the release of carbon dioxide) increase atmospheric warming which stimulates more permafrost thawing. There is reason to believe that this may be an “accelerating” positive feedback loop in which the faster the permafrost melts, the faster the permafrost melts.

Now new research provides an unexpected surprise. Locked beneath the permafrost of northeastern Siberia, there is approximately 75 times the amount of carbon released every year through our burning of fossil fuels.

See the next article for an interview with Dr. Ted. Schurr of the University of Florida, a member of the team who made this startling discovery.

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Gallon Drunk MetroSantaCruz

Gallon Drunk

'Fuel efficiency" may not be a buzz-phrase for Venezuelans who guzzle gas at an astonishing 12 CENTS A GALLON. But for cost-conscious commuters in Santa Cruz, who are now paying upward of $3.30 a gallon (yes, that's more than it takes someone in Venezuela to fill their entire tank), every cent counts. Saving both money and the environment were what self-described commuter advocate DR. RON S. NOLAN had in mind three months ago when he co-founded SOLAR METRO ONLINE, which provides information on solar energy and transportation issues. The site's most popular section is its daily updates on gas prices at 22 stations in Aptos, Capitola, Soquel and SANTA CRUZ

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