GeoLog

The Lena River flows throughout Russia from its source in the Baikal Mountains out into the Arctic Ocean, where the delta’s landscape is dominated by ice-rich Yedoma and thermokarst lakes. Thermokarst lakes have been identified as a source of carbon release to the atmosphere and Yedoma-like lake sediments are known to release more methane than any other sediment due to their incredibly high carbon content. So what is a thermokarst lake?

The Lena River Delta, dominated by Yedoma uplands and thermokarst lakes. Image taken by LANDSAT (source: NASA).

Thermokarst is a landscape that results from the thawing of both icy permafrost and larger ice masses. In northern Siberia, thermokarst starts to develop at the surface: once the ground subsidises, water accumulates in a series of small basins known as alasses. They continue to grow in size to form thermokarst lakes, which can either drain or coalesce with neighbouring lakes to form even larger ones that can reach several kilometres in diameter. When thermokarst lakes drain, they leave behind much smaller lake remnants that lie with a flat basin with steeply sloping sides. Multiple cycles of thermokarst development can occur within a single thermokarst basin to create a complex thermokarst landscape peppered with lakes and islands.

Kurungnakh Island, which lies within the Lena River Delta, formed during the Pleistocene and is part of the region’s thermokarst landscape. The cliff below exposes the Yedoma, a series of silty permafrost deposits with high ice and carbon contents. Permafrost is soil that is either at or below the freezing point of water and forms in regions where the mean annual temperature is below this. Permafrost soils are very rich in carbon, which is stored as peat and methane. The release of this carbon into the atmosphere has the potential to accelerate climate warming through a positive feedback system. That is, where a small change (the release of methane due to permafrost melt) has the capacity to cause a change of even greater magnitude (the presence of more methane in the atmosphere increases the temperature and accelerates the rate of permafrost degradation, releasing even more methane…).

The most immediately recognisable form of permafrost degradation is the presence of thermokarst – you can get a feel for this in the photo below:

“Kurungnakh Island” by Sebastian Zubrzycki. Distributed by the EGU under a Creative Commons licence.

The pale lower unit is comprised of fluvial sand, overlain by ice-rich permafrost (light grey) and capped with a thin covering of Holocene peat. Fluvial sands in this region are relatively ice-poor, which limits the capacity for further thermokarst development. While there is relatively little capacity for further thermokarst development, it is important to consider other processes associated with permafrost degradation and the rates at which they occur. In doing so, we can better quantify future carbon fluxes from permafrost soils in as the climate warms.

Reference:

Morgenstern, A., Grosse, G., Günther, F., Fedorova, I., and Schirrmeister, L.: Spatial analyses of thermokarst lakes and basins in Yedoma landscapes of the Lena Delta, The Cryosphere, 5, 849-867, doi:10.5194/tc-5-849-2011

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their images to this repository and since it is open access, these photos can be used by scientists for their presentations or publications as well as by the press and public for educational purposes and otherwise. If you submit your images to Imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

After studying ‘Applied Environmental Sciences’ I decided to go with a friend for six months to New Zealand for the southern hemisphere winter. Leaving as soon as my diploma thesis (on epiphytic lichens) was written, we set off into the distance to work and travel. We chose New Zealand as our dream destination because these two islands have so many different landscapes to offer – and this is how I was able to capture this picture:

“Honeycomb Weathering” by Stefanie Boltersdorf (University of Trier, Germany), taken on the Kaikoura Peninsula, New Zealand. This photo is distributed by the European Geosciences Union under a Creative Commons License.

The photo shows honeycomb weathering on the Kaikoura Peninsula, with extends from the East coast of the South Island. Composed of mudstone and limestone, the terraces were once wave-cut platforms and have since been uplifted and deformed (during the Quaternary). The peninsula extends into the sea and encounters the relatively shallow Chatham Rise, an area of ocean floor to the east of New Zealand that was largely dry during the Cretaceous period, but now lies nearly 1000 metres underwater. This area is also one of the region’s most productive fishing grounds, a consequence of the nutrient-rich water that upwells along the coast. At low tide, the ocean gives way to a rocky floor, which is easily navigable by foot for quite some distance – and from there you can have a better view of the local seals and seabirds. At this spot, a branch of the Southern Alps, the so-called Seaward Kaikoura Range, comes close to the sea.

Very early in the morning, after sleeping next to the sea and having breakfast in our small van, ‘Berty’, the tide was very low and we took the opportunity to go for a walk. It was on this adventure we found this stunning structure, peppered with small molluscs that were sheltering in the eroded depressions. These depressions are a consequence of honeycomb weathering – a process initiated when salt meets porous rock. Sea spray delivers salt to the rocks, which, after the water has evaporated, is deposited in the pore spaces. Over time, the salt crystals push the minerals apart and weaken the rock. Small pockets collect seawater and erode into ever-larger depressions, eventually creating this marvellous honeycomb structure.

Although I have been dealing with epiphytic lichens during my diploma thesis, I remained true to them, even after my trip. After my return, and inspired by my trip to the highly lichen-rich New Zealand, I started my PhD thesis – investigating a method of quantitatively and qualitatively assessing nitrogen deposition in lichens, with the help of stable isotopes.

By Stefanie Boltersdorf, with Geo-facts from Sara Mynott

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

 This week’s Imaggeo on Mondays is brought to you by the photographer himself, Antonio Jordán (Univerity of Sevilla, Spain), who describes the impact of forest fires on soil properties.

“Soil water repellency” by Antonio Jordán, distributed by the European Geosciences Union under a Creative Commons licence.

This photo was taken while planning some field experiments: in the image, several water drops are resting on a surface soil layer without infiltrating. This process is known as water repellency. Water repellency is a property of soils which, until recently, has not received much attention despite its geomorphological consequences (limiting water infiltration in soils, increasing runoff rates and enhancing the risk of soil erosion). Vegetation, including tree species such as pines or eucalyptus, or shrubs, such as heather, fungi and other soil microorganisms are the main sources of hydrophobic organic substances in soils. Climate, soil texture and structure may also modulate the degree of hydrophobicity.

Forest fires are a major cause of soil water repellency. During the combustion of litter and soil organic matter, some organic substances from the soil volatilise and escape as part of the smoke. However, another part can be displaced in depth and condense following a hot-to-cold gradient. These organic substances form hydrophobic coatings on the surface of soil particles and aggregates. So, when the soil reaches temperatures between 200ºC and 250ºC, water repellency can be increased or induced. If temperature peaks are higher, combustion and volatilization are more intense, and hydrophobic substances may be completely lost or destroyed.

Therefore, soil scientists use soil water repellency as an index of fire severity. A simple way to determine the degree of water repellency is to measure the time required for infiltration of water drops. The development of a water-repellent soil layer, as seen here, together with the loss of vegetation cover that protects soil may trigger soil erosion processes in sensitive areas just to get the first storms of the wet season.

I took this photograph a few days after a forest fire very close to Montellano (Sevilla, SW Spain). The region is characterised by a dense pine forest, shallow soils and steep slopes. The fire affected between 70 and 80ha, quickly climbing the northern slope of the mountain reaching the top, and progressing down the southern slope within a matter of hours.

By Antonio Jordán, University of Sevilla

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

This week, we are excited to introduce a new monthly blog column called Geotalk, featuring short interviews with geoscientists about their research. To kick-start this regular Q&A series, we talked to Dr Guillermo Rein of Imperial College London about “the largest fires on Earth” and how they can contribute to greenhouse gas emissions.

Dr Rein next to a water vapour vent on top of the 30m-high Bogside bing, near Glasgow, Scotland. This bing is a man-made hill of mining waste, and started to smoulder in 2009, approximately 80 years after the closure of the pit. The spread of the combustion is accompanied by the development of vents ahead of the front. (Image by Dr Ricky Carvel and Dr Guillermo Rein, distributed under a CC BY-SA Creative Commons licence)

First, could you introduce yourself and let us know a bit about your research topic(s)?

I was born in Madrid, and studied engineering at ICAI (Ingeniero Industrial 1999). I then moved to the University of California at Berkeley to study combustion science where I got an MSc (2003) and PhD (2005), both in Mechanical Engineering. After six years at the University of Edinburgh, I am now a Senior Lecturer at Imperial College London. I research on fire dynamics, both in the built and the natural environments. At the EGU General Assembly, I usually talk at the Soil System Sciences sessions about my work on smouldering wildfires of peat and coal, which I claim are the largest fires on Earth. As a scientist and engineer, I want to understand these fires so that I can then solve the problems they pose.

A particular interesting area of your research is that of smouldering fires and related burning of fossil fuels. To start, could you explain to us what the difference is between smouldering fires and the more familiar flaming fires?

In wildfires, there are two types of combustion, smouldering and flaming, and depending on what is burning one dominates over the other. Pyrolysis of biomass always takes place due to the heat released by the wildfire, and it leads to the formation of two chemical products: pyrolysate (gas) and char (solid). In flames, the fuel oxidising is the gaseous pyrolysate so the reaction is airborne. In smouldering, the fuel is the char and the reaction is on the pores of the biomass, not airborne but on the solid itself (thus on the ground and under the ground as well). Smouldering is slow, low-temperature, flameless, and represents the most persistent type of combustion phenomena (easier to ignite and more difficult to suppress than flaming).

My true expertise is smouldering combustion, a rare topic, really. There are very few people who work on that but this might change in the incoming decade. I have coined the term “accidental burning of fossil fuels” referring to the wide spread of smouldering megafires of ancient carbon stored in natural coal and peat deposits, and burning for decades in six continents. It is a rather novel topic quickly attracting scientific attention.

On a video on your website you mention a smouldering fire that has been burning for the last 6,000 years. How is this possible, and how could such fires be extinguished?

That is a talk I gave at UC Berkeley. I always mention the case of the Burning Mountain, Australia. It is remarkable. It is a large coal seam partially exposed to the atmosphere and partially underground. It is now a National Park that one can visit, and it is also a sacred ground for natives. There are very few papers in the scientific literature where it has been studied. One of them from 1974 roughly estimated that, given the current burning rate and the burnt pattern left behind, it had been burning for six millennia. I always add at this point that at least the British cannot be blamed for it.

It is very difficult to suppress large smouldering fires like this one because it requires total flooding, fuel removal, or smothering. You can imagine that flooding or removing a massive portion of soil in a remote location is not always viable or desirable. Smothering is often attempted but it requires very long holding times (several years of continuous application) and is prone to sealing failures. However, more advanced techniques can be developed in the near future by combining technologies already used in seismic and petroleum engineering.

Is it possible to reduce the atmospheric carbon emissions related to smouldering fires? If so, how?

The problem with smouldering fires is that peat and coal are made of ancient carbon stored in the soil. This massive amount of carbon is slowly released to the atmosphere during fires creating pollution, haze episodes, and climate change. Moreover, it destroys accidentally valuable energy and ecological resources without any benefit to anyone whatsoever. The best way to avoid this is prevention: avoid smouldering fires from igniting to begin with (mainly via keeping organic soils moist, avoiding drainage, and keeping ignition sources away). When prevention fails, monitoring and suppression are the next tasks. But current monitoring and suppression technologies for smouldering fires are costly, rudimentary and rather inefficient. We need something better, and advanced science can feed and develop the needed technology.

Last but not the least, can you tell us a bit about your future research plans?

My research aim in the long term is to develop detection, monitoring and suppression technologies. Current knowhow comes 90% from flaming wildfires and unfortunately it does not work well for smouldering. However, before that happens, the science that allows us to understand these fires and provides a larger framework of knowledge must be developed first. My immediate plans are to contribute to this framework. With my team, I study peat and coal fires in the laboratory and in the field, including the chemistry of smouldering, the required ignition conditions, the spread patterns, the emissions, and so on.

One of my most pressing current objectives is to convince the scientific community that smouldering creates a positive feedback mechanism to climate change. This is because warmer organic soils and moisture deficiency create and accelerate smouldering hotspots, thus leading to the burning of more ancient carbon, closing the loop when the climate warms up and dries more organic soils. The theory and laboratory results are clear. I am now working on a paper putting everything together.

A lone tree destroyed by the 2006 Rothiemurchus peat fire in Scotland, UK. The trunk and lower branches have been charred by flames but the soil has been destroyed by a smouldering fire, exposing the trees roots and ultimately leading to the death of the tree. (Image by Dr Guillermo Rein and Dr Claire Belcher, distributed by EGU under a Creative Commons licence.)

Abstract submission for the EGU General Assembly 2012 (EGU2012) is now open. The General Assembly is being held from Sunday 22 Apr 2012 to Friday 27 Apr 2012 at the Austria Center Vienna, Austria.

You can browse through the Sessions online.

Each Session shows the link Abstract Submission. Using this link you are asked to log in to the Copernicus Office Meeting Organizer. You may submit the text of your contribution as plain text, LaTeX, or MS Word content. Please pay attention to the First Author Rule.

The deadline for the receipt of Abstracts is 17 January 2012. In case you would like to apply for support, please submit no later than 15 December 2011. Information about the financial support available can be found on the Support and Distinction part of the EGU GA 2012 website.

Further information about the EGU General Assembly 2012 on it’s webpages. If you have any questions email the meeting organisers Copernicus.

High Altitude Wetland in the Alps, Switzerland. Image by Christine Schleupner, distributed by EGU under a Creative Commons License.

High altitude wetlands are scenic and unique ecosystems that fulfill important hydrological functions and provide many ecosystem services. They also serve as geo-archives and play a role in greenhouse-gas emissions, just to name a few things.

The photograph has been taken at the Riffelsee (2770 m) near Zermatt, Switzerland. The small lake surrounded by wet-meadows and cottongrass is famous for its reflection of the Matterhorn. In a current project at the Research Unit Sustainability and Global Change in Hamburg distribution and services of such wetlands are evaluated and integrated into interdisciplinary models.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

The public call for sessions for the European Geosciences Union General Assembly 2012 has been issued. The EGU GA 2012 will be held at the Austria Center Vienna (ACV) from 22 April to 27 April 2012. The details are below, the web page to visit to submit sessions is Call for Sessions page of the EGU General Assembly 2012 website.

We hereby invite you, from now until 16 Sep 2011, to take an active part in organizing the scientific programme of the conference.

Please suggest (i) new sessions with conveners and description and (ii) modifications to the skeleton programme sessions. Explore the Programme Groups (PGs) on the left hand side, when making suggestions. Study those sessions that already exist and put your proposal into the PG that is most closely aligned with the proposed session’s subject area.

If the subject area of your proposal is strongly aligned with two or more PGs, co-organization is possible and encouraged between PGs. Only put your session proposal into one PG, and you will be able to indicate PGs that you believe should be approached for co-organization.

If you have questions about the appropriateness of a specific session topic, please contact the Officers for the specific EGU2012 Programme Group. To suggest Union Symposia, Great Debates, Townhall Meetings or Short Courses, please contact the Programme Committee Chair (Gert-Jan Reichart).

In case any questions arise, please contact EGU2012 at Copernicus.