Wednesday, 31 December 2008

Accelerated recession of Swiss glaciers

Evidence has emerged that several large Swiss glaciers are in 'full' retreat. The work has been completed by the Swiss Federal Institute of Technology and suggests that the negative mass balance trend is getting steeper (see graph). Two factors primarily determine the mass balance of a glacier - winter precipitation in the form of snow, and the efficacy of summer melting. Evidence suggests that for the glaciers studied, winter snowfall has changed little. Conversely, the summer melt season has increased in length.

In the study, glaciologists determined the total volume of ice in Swiss glaciers at 74 cubic kilometres in 1999. This was determined partly by direct measurement and partly by modeling. This figure is thought to have been reduced by 13% between 1999 and the present day. There is less concern about the medium term fate of the larger glaciers such as the Aletsch (see photo) as these contain 80% of all the ice in the Swiss glaciers. Of greater concern is the short term fate of small glaciers - many of these are unlikely to survive more than a few years. Aside from the obvious impacts on landscape and tourism, many Swiss glaciers play an important role in water supply and the generation of hydro-electric power.

Tuesday, 17 June 2008

Future research into frost weathering

Despite considerable progress in understanding frost weathering in recent years, a new publication by Matsuoka and Murton (2008) identifies six key research questions on which to focus future research:
  1. Why and when does explosive cracking occur?
  2. Are hard intact rocks damaged only by frost?
  3. How can episodic rockfalls or rock avalanches associated with permafrost degradation be predicted?
  4. What are the rates of and controls on ice segregation and bedrock heave in permafrost regions?
  5. What was the role of frost weathering in the evolution of mid-latitude Quaternary periglacial lowlands?
  6. How and to what extent does frost weathering contribute to long-term erosion of cold mountains?

The authors suggest that answers will be found with the help of new techniques (eg rock sensors to detect fluid and ice presence, 3D microtopography scanning) as well as multi-technique approaches. They also recommend particular attention be paid to distinguishing both temporal and spatial scales. The image shows frost shattered bedrock in Norway, and the development of incipient ground.

Matsuoka, N. and Murton, J. (2008). Frost weathering: Recent adavnces and future directions. Permafrost and Periglacial Processes 19, 195-210.

Thursday, 22 May 2008

Paraglacial slope evolution in the Karakoram Mountains

Massive volumes of unconsolidated slope deposits on the flanks of glaciated valleys in the Karakoram Mountains are interpreted by Iturrizaga (2008) as being largely controlled by moraine re-working and mass movement induced by glacial processes. Production of debris due to weathering processed is deemed to be relatively insignificant. Talus cones that are traditionally viewed as having a periglacial origin are re-interpreted as landforms controlled by glacial activity. This paper is one of a growing number that has focussed attention on the important role of paraglacial processes on landform evolution in glacial environments. The image shows debris flanked slopes in Fåbergstølsdal, Norway, also interpreted by Ballantyne and Benn (1996) as being of paraglacial origin.

Ballantyne, C. K. and Benn, D. I. (1996). Paraglacial slope adjustment during recent deglaciation and its implications for slope evolution in formerly glaciated environments. In: M. G. Anderson and S. M. Brooks (eds). Advances in Hillslope Processes, John Wiley and Sons, Chichester. Volume 2, 1173-1195.
Iturrizaga, L. (2008). Paraglacial landform assemblages in the Hindukush and Karakoram Mountains. Geomorphology 95(1-2), 27-47.

Tuesday, 20 May 2008

Stone runs in the Falkland Islands: Periglacial or tropical?

Excavations of blockstreams (‘stone runs’) on the Falkland Islands reveal an inverted weathering profile that may be indicative of a tropical, rather than periglacial origin for these features. Apparent accumulations of blocks may, in fact, represent the in situ, regolith-stripped remnant of a Tertiary surface. A multi-phase evolution is presented by André et al (2008), that includes chemical weathering, mantle stripping, mass movement and soil forming processes. It is accepted that these polygenetic landforms may have undergone re-working and weathering by subsequent periglacial activity during the late stage Quaternary. The image shows blockstreams on Hardangervidda in Norway (Photo: DTN). For further details, read the full paper:

André, M-F., Hall, K., Bertran, P. and Arocena, J. (2008). Stone runs in the Falkland Islands: Periglacial or tropical? Geomorphology 95(3-4), 524-543.