GeoLog

moulin

Imaggeo on Mondays: Moulin on the Athabasca Glacier

Moulin . Credit: Stephanie Grand (distributed via  imaggeo.egu.eu)

Moulin . Credit: Stephanie Grand (distributed via imaggeo.egu.eu)

The Athabasca Glacier is located in Jasper National Park, in the Canadian Rockies. It is the largest of seven named distributary glaciers carrying ice away from the Columbia Icefield, the largest icefield in the Rocky Mountains. This picture shows a summer meltwater stream running on the surface of the ice disappear in a moulin – a vertical shaft forming part of the glacier’s internal plumbing system. After entering the moulin, the meltwater may flow through englacial streams before reaching the bottom of the glacier, where it forms a glacial deposit known as a kame (see this video for a description of kame formation processes filmed on location at the Athabasca glacier).

Easily accessible from the highway, the Athabasca glacier is one of the most striking places to observe first-hand the effects of climate change. Warmer temperatures have caused an acceleration of ablation processes such as surface melting and erosion, as shown in this picture. The toe of the glacier is currently retreating between 10 and 25 m each summer and the surface of the glacier is dropping down by more than 5 meters per year. It is expected that the Athabasca glacier will disappear completely within a generation.

Collectively, glaciers in Western Canada and Alaska are estimated to lose 20 to 30 per cent as much as what is melting annually from the Greenland Ice Sheet, compounding disruptions in ocean circulation patterns and global sea levels. The disappearance of these mountain glaciers also has implications for hydropower generation capacity and fisheries.  ​

By Stéphanie Grand, Lecturer at the Institute of Earth Surface Dynamics at the University of Lausanne

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: Carving polar canyons

This week Ian Joughin, a research scientist from the Polar Science Center at the University of Washington, takes us on the polar express to put glacial processes into perspective and find out what makes a moulin…

“Water filled canyon” by Ian Joughin, distributed by the EGU under a Creative Commons licence.

“Water filled canyon” by Ian Joughin, distributed by the EGU under a Creative Commons licence.

This canyon formed when a melt lake on the surface of the Greenland Ice Sheet overflowed and created a stream that extended out toward a crevasse field. This outflow stream filled a crevasse, causing it to fracture under the pressure of the liquid, creating a hydrofracture that ran through the full thickness of the ice sheet. This fracture created a conduit to the base of the ice sheet, known as a moulin, through which the surface water drained to the bed.

Surface water entering a moulin on Athabasca Glacier (a much smaller Moulin than the one what would have drained the Greenland lake). (Credit: Wikimedia Commons user China Crisis)

Surface water entering a moulin on Athabasca Glacier. (Credit: Wikimedia Commons user China Crisis)

Over the course of several years, the turbulent overflow stream melted the ice down to create this canyon. By the time this photo was taken, snow had dammed canyon near the lake outlet, meaning it no longer actively drained the lake.

Most of the water in the photo is from melt at the sides of the canyon. The ice is flowing at approximately 100 m/yr, slowly moving the stream outlet toward higher ground so it is unlikely that the lake will overflow at this location again. And instead, we have found a new canyon forming in a lower part of the lake basin.

By Ian Joughin, University of Washington

The EGU’s open access geoscience image repository has a new and improved home at http://imaggeo.egu.eu! We’ve redesigned the website to give the database a more modern, image-based layout and have implemented a fully responsive page design. This means the new website adapts to the visitor’s screen size and looks good whether you’re using a smartphone, tablet or laptop.

Photos uploaded to Imaggeo are licensed under Creative Commons, meaning they can be used by scientists, the public, and even the press, provided the original author is credited. Further, you can now choose how you would like to licence your work. Users can also connect to Imaggeo through their social media accounts too! Find out more about the relaunch on the EGU website.