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Hydrological 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: The largest fresh water lake in world

Lake shore in Siberia. Credit: Jean-Daniel Paris (distributed via imaggeo.egu.eu)

Lake shore in Siberia. Credit: Jean-Daniel Paris (distributed via imaggeo.egu.eu)

Most lakes in the Northern hemisphere are formed through the erosive power of glaciers during the last Ice Age; but not all. Lake Baikal is pretty unique. For starters, it is the deepest fresh water lake in the world. This means it is the largest by volume too, holding a whopping 23,615.39 cubic kilometres of water. Its surface area isn’t quite so impressive, as it ranks as the 7th largest in the world. However, it makes up for that by also being the world’s oldest lake, with its formation dating back 25 million years – a time during which mammals such as horses, deer, elephants, cats and dogs began to dominate life on Earth.

Located in a remote area in Siberia, perhaps, most impressive of all is how Lake Baikal came to be. It is one of the few lakes formed through rifting. The lake is in fact, one of only two continental rifted valleys on our planet. Typically, “continental rift zones are long, narrow tectonic depressions in the Earth’s surface”, writes Hans Thybo, lead author of a paper on the subject. The Baikal rift zone developed in the last 35 million years, as the Amurian and Eurasian Plate pull away from one another. Eventually, the stretching of the Earth’s surface, at continental rifted margins, can lead to continental lithosphere splitting and the formation of new oceanic lithosphere. Alternatively, as is the case in Siberia, extensive sedimentary basins can be formed; bound by faults, they are known as grabens. It is by this process that Lake Baikal was formed and now houses around 20% of the world’s fresh water!

But this is not where the amazing facts about today’s Imaggeo on Monday’s picture end. The lake is the origin of the Angara River, along which you’ll find the manmade Bratsk Dam, the world’s second largest dam! The shoreline pictured in this photo by Jean- Daniel Paris, is from this impressive dam. Completed in 1964, this artificial reservoir is home to almost 170 billion cubic meters of water (equivalent to the volume held by 68 million Olympic sized swimming pools!).

However, it’s not the impressive water bodies in this inaccessible location in Siberia that are of interest to Jean-Daniel. In fact, this photograph was taken from a research aircraft, which flew over the region for an investigation that spanned a period of several years. Its aim was to measure how concentrations of CO2 and CO varied across the region. Acquiring this data would allow the team of scientist to better understand the sources of the gases, in this remote area of Russian, due to anthropogenic activities and biomass burning.

Reference

Thybo, H., Nielsen, C.A.: Magma-compensated crustal thinning in continental rift zones, Nature, 457, 873-876, doi: 10.1038/nature07688, 2009

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/.

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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