GeoLog

permafrost

Imaggeo on Mondays: A massive slump

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.

Imaggeo on Mondays: Vanishing Lakes and Dry Arctic Landscapes

The Koukdjuak Plains (south-west Baffin Island, Canada) form a vast postglacial marine plain that borders the Foxe Basin, an area that has been progressively uplifted due to glacio-isostatic rebound following the end of the last glaciation about 6600 years ago. The weight of glaciers on the Earth’s crust causes the ground to be depressed, which, once the glacier melts, bounces back (at a geological pace) as the weight is lifted and the crust reaches a new equilibrium. The rate of rebound in this area can reach 1 cm per year, which is pretty fast for isostatic rebound!

The Foxe Basin and Koukdjuak Plains. Credit: NASA Visible Earth/Jacques Descloitres, MODIS Land Rapid Response Team

Rapid warming of the Arctic and extensive permafrost melt is causing many Arctic lake basins to be breached and drained. This is responsible for the widespread drying of lowland Arctic landscapes. Permafrost in this part of Canada has a high ground ice content, making the region particularly sensitive to a warming climate. As this melts, channels in the permafrost open, and can cause lakes to drain in less than a day!

“The drying Arctic” by Reinhard Pienitz, distributed by the EGU under a Creative Commons Licence.

In the Koukdjuak Plains, the carbonaceous bedrock of the Paleozoic Hudson Platform, one of the largest rock units in western Canada, is overlain by marine clays and glacial tills. These are topped with fine-grained lacustrine deposits, cracked following the drainage of the lake.

Reinhard Pienitz is reconstructing the paleoclimatic history of the Foxe Basin and took this photo while completing paleolimnological fieldwork (lake sediment coring). He explains that “extensive dry-ups of northern lakes like these can be observed in lowland areas across the Canadian Arctic, and [they] profoundly modify the hydrology and wildlife habitats of these northern landscapes”.

Reference:

Marsh, P., Russel, M. ,Pohl, S., Haywood, H. and Onclin, C. Changes in thaw lake drainage in the Western Canadian Arctic from 1950 to 2000, Hydrological Processes (23)1, 145-158 (2009).

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their images to this repository and since it is open access, these photos can be used by scientists for their presentations or publications as well as by the press and public for educational purposes and otherwise. If you submit your images to Imaggeo, you retain full rights of use, since they are licensed and distributed by the EGU under a Creative Commons licence.