GeoLog

glaciers

Imaggeo on Mondays: Tongue of a small giant

Imaggeo on Mondays: Tongue of a small giant

In a world where climate change causes many mountain glaciers to shrink away, bucking the ‘melting’ trend is not easy. In today’s post, Antonello Provenzale, a researcher in Italy, tells us of one glacier in the Alps which is doing just that.

Mountain glaciers are retreating worldwide, with the possible exception of the Karakoram area. For most glaciers, ablation (ice melt) during the warm season is stronger than the accumulation of new ice by snowfall. As a result, while glacier ice flows downhill, the accelerated melting at lower elevation forces the terminus of the glacier to retreat uphill, with a net loss of ice volume.

Such behavior is especially evident on the southern flank of the Alps, where many mountain glaciers have dramatically reduced their dimensions, often fragmenting into smaller, detached pieces.

An important exception is represented by the Miage glacier in Val Veny, Val d’Aosta, northwestern Italy, at the base of the Mount Blanc massif. This glacier is covered with a thick layer of debris, which protects the underlying ice from the direct heating by sunlight. The rocks which make up the debris are poor heat conductors and thus preserve the ice beneath them, making this glacier particularly stable.

This glacier is so stationary that vegetation and trees have grown on its margins and on the debris. Several ponds punctuate the surface of the glacier, as well as some areas on its sides. The Miage lake, for example, is directly in contact with the slowly flowing ice and it is sometimes run by large outburst waves generated by huge blocks of ice and rock falling into the lake water.

This picture was taken in September 2014, during a field excursion of the Italian Glaciological Committee. The image is a composition (stitch) of several images taken with a moderate wide angle lens on a rangefinder digital camera.

By Antonello Provenzale studies Geophysical Fluid Dynamics, Earth System processes and Geosphere-Biosphere interactions at the Institute of Geosciences and Earth Resources of the National Research Council of Italy.

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: Why does a Norwegian glacier look blue?

Imaggeo on Mondays: Why does a Norwegian glacier look blue?

This picture shows the outlet glacier Engabreen running down from the plateau of Svartisen in Norway. Svartisen ice cap comprises two glacier systems of which the Vestre (western) Svartisen is Norway’s second largest glacier. Located right at the polar circle, Svartisen covers a total of 369 km² of the Nordland region. These coastal mountains accumulate a snowpack of 5-7 m depth through the winter season, which feeds the glaciers.

Actually, Svartisen means black ice. However, the ice of the glacier tongue of Engabreen, an outlet glacier of Svartisen ice cap, looks pretty blue in the flat light of a late afternoon in August.  The ice, which is mostly free of air bubbles, transmits the blue colour more than the rest of the visible spectrum of light. Thus, by having to travel a distance of approx. 3 m through the ice body, the blue light is particularly visible.

More than the colour, it is the hydrology and the ice flow of Engabreen which are studied with attention by the Norwegian Water Resources and Energy Directorate (NVE). A tunnel system was built partly underneath the glacier in the 1990’s to collect the waters from Svartisen for hydro power production., The Svartisen Subglacial Laboratory  is located at one end of the tunnel, providing a unique opportunity for direct access to the bed of a temperate glacier. The privileged location means that sub-glacial parameters can be obtained from experiments right at the bottom of a 200 m thick ice pack.

The waters of Holandsfjord have to be crossed to visit the beautiful area of the glacier lake Svartisvatnet and Engabreen. This can be either done by boat shuttle or, as we did, by kayak [ find a magazine article about Kay’s adventure here – in German -].

 By Kay Helfricht, researcher at the Institute for Interdisciplinary Mountain Research of the Austrian Academy of Sciences, Austria

Editor’s note: this text was revised on Tuesday 25th October 2016 following comments from Terje Solbakk.

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: The glacial landscape of Yosemite

 Glacial erratic rocks . Credit: Yuval Sadeh (distributed via imaggeo.egu.eu)

Glacial erratic rocks . Credit: Yuval Sadeh (distributed via imaggeo.egu.eu)

Yosemite National Park, in California, is renowned for its beautiful and striking landscapes. So much so, this is the second time it has feature on the blog this summer. While our last post on the park focused on the ancient volcanic history of its landscape, in this post we fast forward to the Plesitocene (some 110,000 to 12,000 years ago) to discover more about how glaciers shaped Yosemite’s landscape. Indeed, it is the glacier carved landscape which has made the park so famous!

During the last ice age, the high peaks and valleys of the Sierra Nevada (of which Yosemite belongs to) were covered by ice.  A vast continental ice sheet spread across much of the United States and Canada. Local climate variations as well as the geographical position of Yosemite meant that the accumulation of ice in the region was particularly unique, and didn’t belong to the vast continental ice sheet. Nevertheless, glaciers dominated the landscape during this time and the scars left behind by their presence resulted in a range of landforms observable today: including chatter marks (gouges left in granite by moving glaciers), glacier polish (shiny patches of granite), exfoliation (layered cracking of rocks which resembles onions peeling), and many others.

As glaciers move, they accumulate debris underneath their surface. As the vast frozen rivers advance, they carry the debris, which can range from pebble-sized rocks through to house-sized boulders, along with it. As the climate in the Yosemite region began to warm as the ice age came to an end, the glaciers slowly melted. Once all the ice was gone, the rocks and boulders, known as glacial erratics, were left behind.

One of the best examples of glacial erratics can be seen at Olmstead Point, near Mt. Hoffmann, in Yosemite National Park, as photographed by Yuval Sadeh. Yuval reminisces about the moment he reached the spot where the boulders are strewn across the landscape:

“I remember walking on this extremely smooth scraped surface, watching the glacial erratics rocks which looks like a giant artist placed them gently on the bedrock. Although the glacier melted many years ago, out there on the glacier carved surface it seems that time is standing still ever since.”

Imaggeo on Mondays: Heavy machinery

Imaggeo on Mondays: Heavy machinery

How do you get heavy machinery, such as a drill spool onto an ice sheet? This week’s imaggeo on Mondays’ photography captures the freighting of components of a hot water drill to directly access and observe the physical and geothermal properties at the ice-bed interface. In the image, SAFIRE principal investigator Bryn Hubbard and post-doc Sam Doyle help fly in the drill spool at the start of the Summer 2014 field campaign on Store Glacier, Western Greenland.

Freighting several tons of equipment onto the Greenland Ice Sheet for the sake of science may be slightly intense, but in doing so, it reveals an environment that is complex in history and dynamics.

The Greenland Ice Sheet is losing mass at an increasing rate, and since 2010 has contributed 1 mm/year to global sea level rise. The large majority of changes occur within the drainage basins of marine-terminating glaciers (those which end at the lands edge and drain into the sea), which flow rapidly and drain 88% of the ice sheet. While the surface melt processes of glaciers has been well-studied and quantified, very little is known about what happens below the glacier surface, especially where the ice meets the bedrock.

Recent studies from Greenlandic outlet glaciers have emphasized meltwater-enhanced basal lubrication as an increasingly important mechanism to explain the flow of ice down a glacier. In essence, meltwater generated at the glacier surface will eventually find its way down to the glacier bed through crevasses that connect these two systems. The sudden influx of water increases the pressure within the environment, causing the glacier to “lift” off the bed and flow faster. However, the mechanism is largely an untested theory, and its specifics at the ice-bed interface are still largely unknown, especially on fast-flowing outlet glaciers. In order to achieve accurate predictions of sea level rise in the near future, we need to fully understand the dynamics occurring at the ice-bed interface and its complex response to climate-induced ice melt.
Obviously, a great method to tackle this research question is to air freight tons of heavy machinery onto the Greenland Ice Sheet, and to gain access to the bed of the ice sheet by drilling a 600-metre tunnel with hot water. This is part of the Subglacial Access and Fast Ice Research Experiment (SAFIRE), a collaboration between the Scott Polar Research Institute at the University of Cambridge and Aberystwyth University in Wales.

The SAFIRE project has two specific goals: 1. to identify and characterise the mechanical and hydrological conditions at the base of a large outlet glacier in Greenland, using instruments installed in boreholes drilled to the bed; and 2. to determine the role of basal processes in governing ice flow and iceberg calving. With no previous observation ever made in a subglacial environment of this type of glacier, this project breaks new ground, and from the unique datasets acquired from instruments deployed in boreholes and on the glacier’s surface, higher order numerical ice-flow models can be written and constrained.

Our work is mainly on Store Glacier, which is a large tidewater glacier in the Uummannaq region of northwestern Greenland. Store has a large drainage basin (35,000 km2) and flows up to 5 km/year at the glacier terminus, discharging extremely large volumes of ice into the ocean every day. Since 2014, we have been working on-site at a campsite ~30 km from the terminus, and our results characterise an extremely dynamic and warm basal environment over a deformable sediment bed. A detailed analysis of these unexpected results will be forthcoming in the near future.

By TJ Young, Scott Polar Research Institute / British Antarctic Survey 

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/.

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