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Imaggeo on Mondays: The Final Effort

22 Sep

We’ve all been there: long hours in the field, a task that seems never ending but which has to be finished today. This week’s Imaggeo on Mondays image is brought to you by Patrick Klenk who highlights the importance of how ‘getting the job done’ relies on good team work!

Two years ago I posted this picture to imaggeo as a tribute to everyone who ever experienced the perils and pitfalls of outdoor field experiments and especially to the colleagues who help you to pull through in the end. It is their scientific spirit which allows to add that indispensable calibration measurement making the difference between a heap of nice-to-look-at data and a quantifiable dataset — even if this means staying on for that extra hour in quickly fading daylight while the cold of a late autumn night encroaches already relentlessly upon your exposed field site.

Final Effort (Credit: Patrick Klenk via imaggeo.egu.eu)

Final Effort (Credit: Patrick Klenk via imaggeo.egu.eu)

In this particular case, we started out on a bright late autumn day, planning to quickly complete a week-long series of Ground-Penetrating Radar  (GPR) experiments on our ASSESS test site in the vicinity of Heidelberg, Germany.  Most certainly, we intended to be finished long before this picture was taken — but alas, as most environmental scientists who are concerned with experimental field studies can probably relate to, outdoor experiments often do not work out exactly as planned and especially timetables get overturned more often than not. In the end, this field day turned out to be the last usable field day for that season and only through the final team effort pictured here we were able to successfully complete a quite involved series of GPR experiments.

The aim of these GPR experiments is to quantify near-surface soil hydraulic properties through the observation of soil water dynamics with non-invasive measurement methods directly at the field scale.  To date, the quantification of soil hydraulic properties remain the holy grail of soil sciences, since they are difficult to determine but widely required for a range of applications such as precision agriculture or the prediction of contaminant flow through the subsurface. Traditional approaches, which determine soil hydraulic properties e.g. from soil samples in the laboratory, suffer from their high cost, their destructive nature and from issues of transferability of the results back to the field. We specifically designed our test-site with a complicated but known subsurface structure to allow for the development of quantitative, high-resolution observations of soil water dynamics with GPR.  In brief, our approach compares GPR observations of soil water dynamics related processes such as: water sprinkling from above the surface (infiltration) or a varying water table depth (achieved by pumping water in and out of the structure from below: imbibition and drainage) to numerical simulations of both subsurface water flow and the expected GPR response. Our research then focuses (i) on observation based estimation methods of the parameters which are needed by the models we use to calculate physical property distributions (inversion) and (ii) on data assimilation methods (i.e. a form of continuously integrating modelled states of a physical system with available observational data) to optimally combine all available information for quantifying the soil properties in question.

 

Patrick is a physicist, currently working as a postdoc with the soil physics group at the Institute of Environmental Physics, Heidelberg University, Germany, on novel approaches for developing Ground-Penetrating radar for quantitative soil hydrology.

 

By Patrick Klenk, postdoctoral researcher at the Institute of Environmental Physics, Heidelberg University, Germany

 

References

Buchner, J.S., Wollschläger U., Roth K. (2012), Inverting surface GPR data using FDTD simulation and automatic detection of reflections to estimate subsurface water content and geometry, Geophysics, 77, H45-H55, doi:10.1190/geo2011-0467.1.

Dagenbach, A., J. S. Buchner, P. Klenk, and K. Roth (2013), Identifying a soil hydraulic parameterisation from on-ground GPR time lapse measurements of a pumping experiment, Hydrol. Earth Syst. Sci., 17(2), 611–618,doi:10.5194/hess-17-611-2013.

Klenk, P., Jaumann, S., and Roth, K. (2014): Current limits for high precision GPR measurements, in ‘Proc. 15th International Conference on Ground Penetrating Radar (GPR2014), 30 June-04 July 2014, Brussels, Belgium, available online shortly.

Klenk, Patrick,  Developing Ground-Penetrating Radar for Quantitative Soil Hydrology, PhD-Thesis, Heidelberg University, 2012, http://www.ub.uni-heidelberg.de/archiv/14329.

 

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

 

 

Imaggeo on Mondays: Paramo Soil

15 Sep

Paramo Soil. (Credit: Martin Mergili,via imaggeo.egu.eu)

Paramo Soil. (Credit: Martin Mergili,via imaggeo.egu.eu)

What lies between 3000m and 4800m above sea level in the mountains of the Andes? A very special place dominated by an exceptional ecosystem: The Páramo. Picture lush grasslands with a unique population of flora and fauna, some of which is found nowhere else on Earth.

Páramos stretch from Ecuador to Venezuela, across the Northern Andes and also occur at high elevation in Costa Rica. The climate here is changeable; dowsing rains can be immediately followed by clear skies and blazing sunshine. Overall, the areas experience low average temperatures and rates of evaporation but moderate amounts of precipitation. It is this changeable climate that means the Páramo is thought to be an evolutionary hot spot, where biodiversity is budding faster than at any other place on Earth.

However, were it not for the traditional Andean clothing the girl is wearing in our Imaggeo on Monday’s image, you wouldn’t immediately know this photograph was taken close to the equator. Martin Mergili visited the Páramos of Ecuador, back in 2007, as a PhD student of the University of Innsbruck (Austria) on a field trip around the South American country. Martin gives a detailed account of how the Páramo soil pictured in the image came to be:

‘Whilst 100 km to the east, in the lowlands of the Amazon rainforest, organic matter is rapidly decomposed and soils may be tens of metres deep due to extensive weathering, the reverse is the case here, 3000 m higher up. In the tropical highlands of the Páramo, the year round moist and cool regime slows decomposition and weathering. The obvious result is a rather peaty soil, rich in organic content, supporting pasture grounds used for herding sheep.’

The Páramos support the local human population by providing the main source of water in the Andean valleys whilst the grasslands provide extensive fodder for grazing cattle or sheep. To provide fresh appetising grasses farmers regularly burn the natural vegetation. To what extent the soil of the Páramos is altered as a result of this practice is not clear, but it might provide an explanation for the presence of the dark grey layer seen in the photograph.’Alternatively’, explains Martin, ‘as the area is influenced by significant volcanic activity, this layer might well be the result of ash falls.’

A further feature of interest is the sequence of undulating layers below the organic soil: still part of the soil, it represents a set of volcanic or sedimentary strata with varying resistance to weathering and erosion, probably influenced by tectonic forces. A metre below the bottom of the image, you would come across unweathered rocks.

Páramo El Ángel in Ecuador with Espeletia plants (Credit: Martin Mergili via http://www.mergili.at/worldimages/)).

Páramo El Ángel in Ecuador with Espeletia plants (Credit: Martin Mergili via http://www.mergili.at/worldimages/)

By Laura Roberts Artal, EGU Communications Officer and Martin Mergili, BOKU University, Vienna

References

Buytaer. W., Sevink. J., De Leeuw. B., Deckers. J.:   Clay mineralogy of the soils in the south Ecuadorian paramo region, Geoderma, 127, 144-129, 2005

Hofstede. R. G.M.: The effects of grazing and burning soil and plant nutrient concentration in Colombian paramo grasslands, Plant and Soil, 173, 1, 111-132, 1995

 

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

Imaggeo on Mondays: Trapped air

8 Sep

Can you imagine walking into the depths of an icy, white, long and cavernous channel within a thick glacier? That is exactly what Kay Helfricht did in 2012 to obtain this week’s Imaggeo on Mondays photograph.

Tellbreen Glacier is a small glacier (3.5Km long) in the vicinity of the Longyearbyen valley in the Svalbard region of Norway. Despite its limited size, it is an important glacier. One of the key parameters scientist use to understand how glaciers are affect by a warming climate is how the melt water is transported through to the front of the glacier. The majority of models utilise data from temperate or polythermal glaciers, i.e., glaciers which have free water within the icy matrix. Tellbreen is a cold glacier, meaning the basal layers of ice are frozen to the glacier bed; despite the traditional view that cold glaciers are not able to store, transport and release water, Baelun and Benn, 2011 found Tellbreen does this year round.

Trapped air. (Credit: Kay Helfricht via imaggeo.egu.eu)

Trapped air. (Credit: Kay Helfricht via imaggeo.egu.eu)

Kay visited Tellbreen whilst at the Artic Glaciology course at the University Centre in Svalbard. ‘Each weak one excursion led us to glaciers in the vicinity of Longyearbyen’ says Kay, ‘this day we visited the glacier Tellbreen. Near the tongue of the glacier the outlet of an englacial channel enabled us to explore the inside of the glacier. We went for some tens of meters into the channel.’

What the group found were that the walls of ice either side of the channel contained impurities, from stones to gravel, as well as mud and also water. The image above shows ‘air trapped in the ice-walls of the conduit at a time when the conduit would have been filled with meltwater of the glacier’ explains Kay. Air accumulated in bubbles at the roof of the conduit. When the water in the conduit started to refreeze along the side-walls, these smooth lenticular bubbles were trapped and stored in the ice. Studying the bubbles and other impurities in the ice can give hints on the history of the glaciers ice flow and its thermal regime over several decades.

References

Baelum. K., Benn. D.I.: Thermal structure and drainage system of a small valley glacier (Tellbreen, Svalbard), investigated by ground penetrating radar, The Cyosphere, 5, 139-149, 2011

Naegeli. K., Lovell. H., Zemp. M., Benn, I. The hydrological system of Tellbreen, a cold-based valley glacier on Svalbard, investigated by using a systematic glacio-speleologicalapproach, Geophysical Research Abstracts, 16, EGU2014-6149, 2014 (conference abstract)

 

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

Imaggeo on Mondays: A massive slump

1 Sep

One of the regions that has experienced most warming over the second half of the 20th century is the Potter Peninsula on King George Island in Antartica. It is here that Marc Oliva and his collaborators are studying what the effects of the warming conditions on the geomorphological processes prevailing in these environments.

“Permafrost is present almost down to sea level in the South Shetland Islands, in Maritime Antarctica” says Marc, “in some recent deglaciated environments in this archipelago, the presence of permafrost favours very active paraglacial processes”.

Permafrost is defined as the ground that remains frozen for periods longer than two consecutive years and constitutes a key component of the Cryosphere. However, it is not fully understood how it reacts to climate variability. In this sense, there is an on-going effort to improve our knowledge on these topics by carrying out long–term monitoring of permafrost, as well as of geomorphological processes, in order to better understand the response of the terrestrial ecosystems to recent warming trends.

This weeks’ Imaggeo on Mondays picture shows a massive slump and the exposed permafrost in the shoreline of a lake in Potter Peninsula (King George Island, Maritime Antarctica). Following the deglaciation of this ice-free area paraglacial processes are very active transferring unconsolidated sediments down-slope to the lake.

Slump-permafrost, Potter Peninsula, Antarctica. (Credit: Marc Oliva via imaggeo.egu.eu)

Slump-permafrost, Potter Peninsula, Antarctica. (Credit: Marc Oliva via imaggeo.egu.eu)

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

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