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Cryospheric Sciences

Imaggeo on Mondays: Drumlins Clew Bay

Imaggeo on Mondays: Drumlins Clew Bay

During ice ages landscapes are sculpted by the power of advancing glaciers. From rock scratches, to changing mountains and the formation of corries, cirques and aretes, through to the formation of valleys and fjords, the effects of past glaciations are evident across the northern hemisphere landscape.

Perhaps not so familiar, drumlin fields are also vestiges of the erosive power of ancient ice sheets. Glacial deposits tend to be angular and poorly sorted, meaning they come in lots of different sizes and shapes. The extreme of this are glacial erratics. Drumlins are are elongated hills made up of glacial deposits and they represent bedforms produced below rapidly moving ice. Our Imaggeo on Monday’s image this week is of Clew Bay in western Ireland and shows the streamlining of drumlins into an extensive drumlin field of glacial sediment. The drumlins here formed during the rapid thinning of the fast moving central parts of the western sector of the British-Irish Ice Sheet, in a process known as deglacial downdraw – probably between 18,000 and 16,000 years ago. The ice was streaming through bays in western Ireland both during and at the end of the Last Glacial Maximum (also known as LGM). This was the time in which the ice sheets covered most of northern America, Europe and Asia. In Clew Bay the ice was a minimum of 800m thick and flowing out into a series of tidewater glaciers situated along the length of Ireland’s western shelf.

By Prof. Peter Coxon, Head of Geography, School of Natural Sciences, Trinity College Dublin & Laura Roberts

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under

Imaggeo on Mondays: Retreating Glacier

Credit: Przemyslaw Wachniew (distributed via imaggeo.egu.eu)

Credit: Przemyslaw Wachniew (distributed via imaggeo.egu.eu)

The Svalbard archipelago is considered to be one of the best places to study the geological history of the Earth because its rocks represent every geological period. This image shows a view from the peak of Fugleberget (569 m a. s. l.; 77º 00’ N, 15º 30’ E) on the south-western coast of the island of Spitsbergen. Glaciation of this geologically diverse area gave rise to a variety of geomorphic features. The most prominent of them, depicted in the picture, is the Hornsund Fjord that cuts through metamorphic and sedimentary rocks ranging from the Proterozoic (up to 2.5 billion years old!) to the Cretaceous Age (older than 66 million years). A spectacular example of glacial erosion can be seen on both sides of the fjord in the cliffs formed of Paleozoic carbonate rocks. Nowadays, this landscape is changing because glaciers are retreating in response to the rapid warming of the Arctic. Patterns of glacial retreat can be recognized at the margin of the Hans Glacier, which descends to the fjord below. Floating parts of the glacier are unstable as they readily break up, form crevasses, and eventually calve in to the fjord, as recorded in the photograph. The 1.5 km long calving front is retreating faster than the grounded parts of the glacier. As glaciers move, they can leave behind large amounts of dirt and rocks, known as moraines. Reduction in the thickness of Hans Glacier, is reflected by the height of the lateral moraine, which can be seen above the ice edge as an elongated ridge with an irregular surface. Retreating glaciers expose new areas of land and water, which affects fluxes of energy and matter in the arctic environment.

By Przemyslaw Wachniew, AGH University of Science and Technology in Kraków .

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Geosciences Column: Fire in ice – the history of boreal forest fires told by Greenland ice cores.

Burning of biomass contributes a significant amount of greenhouses gases to the atmosphere, which in turn influences regional air quality and global climate. Since the advent of humans, there has been a significant increase in the amount of biomass burning, particularly after the industrial revolution. What might not be immediately obvious is that, (naturally occurring) fires also play a part in emitting particulates and greenhouse gases which can absorb solar radiation and contribute to changing Earth’s climate. Producing a reliable record of pre-industrial fire history, as a benchmark to better understand the role of fires in the carbon cycle and climate system, is the focus of research recently published in the open access journal, Climate of the Past.

Forest fires.  Credit: Sandro Makowski (distributed via imaggeo.egu.eu) http://imaggeo.egu.eu/view/916/

Forest fires. Credit: Sandro Makowski (distributed via imaggeo.egu.eu)

Did you know the combustion of biomass can emit up to 50% as much CO2 as the burning of fossil fuels? The incomplete burning of biomass during fires also produces significant amounts of a fine particle known as black carbon (BC). Compare BC to more familiar greenhouse gases such as methane, ozone and nitrous oxide and you’ll find it absorbs more incoming radiation than the usual suspects. In fact, it is the second largest contributor to climate change.

NEEM camp position and representation of boreal vegetation and land cover between 50 and 90 N. Modified from the European Commission Global Land Cover 2000 database and based on the work of cartographer Hugo Alhenius UNEP/GRIP-Arendal (Alhenius, 2003). From Zennaro et al., (2014).

NEEM camp position and representation of boreal vegetation and land cover between 50 and 90 N. Modified from the European Commission Global Land Cover 2000 database and based on the work of cartographer Hugo Alhenius UNEP/GRIP-Arendal (Alhenius, 2003). From Zennaro et al., (2014). Click to enlarge.

The boreal zone contains 30% of the world’s forests, including needle-leaved and scale-leaved evergreen trees, such as conifers. They are common in North America, Europe and Siberia, but fires styles in these regions are diverse owing to differences in weather and local tree types. For instance, fires in Russia are known to be more intense than those in North America, despite which they burn less fuel and so produce fewer emissions. All boreal forest fires are important sources of pollutants in the Arctic. Models suggest that in the summertime, the fires in Siberian forests are the main source of BC in the Artic and shockingly, exceed all contributions from man-made sources!

To build a history of forest fires over a 2000 year period the researchers used ice cores from the Greenland ice sheet. Compounds, such as ammonium, nitrate, BC and charcoal (amongst others), are the product of biomass burning, and can be measured in ice cores acting as indicators of a distant forest fires. Measure a single compound and your results can’t guarantee the signature is that of a forest fire, as these compounds can often be released during the burning of other natural sources and fossil fuels. To overcome this, a combined approach is best. In this new study, researchers measured the concentrations of levoglucosan, charcoal and ammonium to detect the signature of forest fires in the ice. Levoglucosan is a particularly good indicator because it is released during the burning of cellulose – a building block of trees – and is efficiently injected into the atmosphere via smoke plumes and deposited on the surface of glaciers.

The findings indicate that spikes in levoglucosan concentrations measured in the ice from the Greenland ice sheet correlate with known fire activity in the Northern Hemisphere, as well as peaks in charcoal concentrations. Indeed, a proportion of the peaks indicate very large fire events in the last 2000 years. The links don’t end there! Spikes in concentrations of all three measured compounds record a strong fire in 1973 AD. Taking into account errors in the age model, this event can be correlated with a heat wave and severe drought during 1972 CE in Russia which was reported in The New York Times and The Palm Beach Post, at the time.

Ice core. Credit: Tour of the drilling facility by Eli Duke, Flickr.

Ice core. Credit: Tour of the drilling facility by Eli Duke, Flickr.

The results show that a strong link exists between temperature, precipitation and the onset of fires. Increased atmospheric CO2 leads to higher temperatures which results in greater plant productivity, creating more fuel for future fires. In periods of draught the risk of fire is increased. This is confirmed in the ice core studied, as a period of heightened fire activity from 1500-1700 CE coincides with an extensive period of draught in Asia at a time when the monsoons failed. More importantly, the concentrations of levoglucosan measured during this time exceed those of the past 150 years, when land-clearing by burning, for agricultural and other purposes, became common place. And so it seems that the occurrence of boreal forest fires has, until now, been influenced by variability in climate more than by anthropogenic activity. What remains unclear is what the effects of continued climate change might have on the number and intensity of boreal forest fires in the future.

By Laura Roberts Artal, EGU Communications Officer

 

Reference

Zennaro, P., et al.: Fire in ice: two millennia of boreal forest fire history from the Greenland NEEM ice core, Clim. Past, 10, 1905-1924, doi:10.5194/cp-10-1905-2014, 2014.

Imaggeo on Mondays: High altitude glacier monitoring

What a place to work: Spectacular views from the top of the rugged and icy peaks of Tien Shan mountain range. The desire to better understanding global climate change took Leo Sold to this remote area of Central Asia. The frozen slopes of ice and snow in today’s Imaggeo on Mondays photograph hold some of the keys to understanding how the glaciers in this remote region are being affected by a warming climate.

High altitude glacier monitoring Credit: Leo Sold (distributed via imaggeo.egu.eu)

High altitude glacier monitoring Credit: Leo Sold (distributed via imaggeo.egu.eu)

Glacier changes are known to be excellent indicators of climatic change and are therefore monitored around the world. However, some regions have a much higher coverage of measurements than other, often remote areas. Additionally, long time-series of glacier measurements are rare even on the global scale but are indispensable for a sound data basis to study future glacier changes. Thus, having a long-term measurement series in a region like the Tien Shan is a real asset for the work of glaciologists. Central Asia has a long tradition of glacier monitoring but unfortunately many ongoing monitoring programs were interrupted in the mid-1990s after the collapse of the Soviet Union. Although the suspended time-series already provide a great source of information, their continuation is fundamental for conducting future studies on Central Asian glaciers.

This image was taken in summer 2013 on the Suek Zapadniy glacier located in the Inner Tien Shan, Kyrgyzstan.Because snow-covered crevasses cannot always be identified at the snow surface the two researchers are roped up while taking snow depth measurements at 4500m above sea level. The monitoring of Suek Zapadniy glacier is part of the wider CATCOS project (Capacity Building and Twinning for Climate Observing Systems), which aims at improving the coverage with climate-related observations in areas were measurements are rare. It is funded by the Swiss Agency for Development and Cooperation (SDC) and is coordinated by the Swiss Federal Office of Meteorology and Climatology (MeteoSwiss). Within this project, the University of Fribourg (Switzerland) and the WGMS (World Glacier Monitoring Service) re-established a glacier monitoring programme on multiple glaciers in the Tien Shan and Pamir range in Kyrgyzstan, in close collaboration with the GFZ Potsdam (German Research Center for Geoscience, Potsdam), leading the CAWa Project (Central Asian Waters), and the Central-Asian Institute for Applied Geoscience (CAIAG) located in Kyrgyzstan. Notably, the project also focuses on capacity building – meaning, field campaigns involve on-site training of researchers in Kyrgyzstan and Switzerland.

The subset of glaciers chosen for the monitoring program is based on the availability of previous or historical data, the accessibility, and their distribution across the region. Annual mass balance measurements have been carried out since the summer of 2010. Their aim is to establish the difference between the amount of snow that is accumulated on the glacier during winter and the amount of ice melted during the summer months. Integrated over the entire glacier area, this provides a measure for the mass change of a glacier and, thus, for its response to climate changes. In the low-altitude areas of a glacier where summer melting exceeds the quantity of snow accumulated in winter, mass balance measurements involve drilling and maintenance of ablation stakes. These stakes are commonly made of plastic and are inserted into the glacier at a known depth, providing a bench mark against which the glacier thickness changes can be measured. In high altitudes snow can outlast the entire year, allowing the glacier to gain mass. The accumulation is measured as snow depth and its density by means of digging snow pits. Together, ablation and accumulation measurements provide the glacier mass balance. Since 2010 Suek Zapadniy glacier loses 0.4m water equivalent each year, referring to the water level if snow and ice was melted and distributed over the glacier.

“Ideally, summer measurements at the end of the hydrological year would be complemented by winter accumulation measurements in spring. However, reaching such remote areas involves an immense logistical effort under difficult conditions,” explains Leo.

Black Abramov glacier. Before the fall of the Soviet Union, Abramov glacier provided one the the longest continuous glacier mass balance records, dating back to 1968. In 2011, a global research network re-established a monitoring program in cooperation with local partners. The picture highlights the important role of surface albedo in terms of glacier ablation. Credit: Leo Sold (distributed via imaggeo.egu.eu

Black Abramov glacier. Before the fall of the Soviet Union, Abramov glacier provided one the the longest continuous glacier mass balance records, dating back to 1968. In 2011, a global research network re-established a monitoring program in cooperation with local partners. The picture highlights the important role of surface albedo in terms of glacier ablation. Credit: Leo Sold (distributed via imaggeo.egu.eu

By Laura Roberts, EGU Communications Officer and Leo Sold, PhD Student at the University of Fribourg

If you pre-register for the 2015 General Assembly (Vienna, 12 – 17 April), you can take part in our annual photo competition! From 1 February up until 1 March, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

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