Fluctuations of unstable mountain glaciers: scale and character

Abstract

The paper describes the characteristics and behavior of unstable glaciers in the Pamirs, central Asia, over the last 30 years. These glaciers are divided into three groups: glaciers with registered surges; glaciers with signs of current instability; glaciers with signs of instability in the recent past. Examples are given to illustrate the nature of glacier fluctuations at a time of general glacier retreat in the Pamirs. A description is given of the evolution of Medvezhiy surging glacier, which was the subject of detailed annual observation from 1963 to 1991. Comparative characteristics of two building-up stages of this glacier, 1964–72 and 1974–88, are produced. On the basis of aerotopographic monitoring and with the aid of computer analysis, the kinematics of the glacier surface during the 1988–89 surge are traced in detail and the role of microsurges in the course of glacier build-up and the glacier surge is established.

Monitoring surging glaciers of the Pamirs, central Asia, from space

“…We define targeted dynamically unstable glacier monitoring as a system of regular and long-term remote-sensing and ground-based observations of spatial–temporal changes (fluctuations) in glacier size, shape and dynamic regime, aimed at timely detection of its activation as well as projection of time, scale and consequences of possible glacier catastrophes. This monitoring system includes regional and local levels; each has its own appropriation, methods and means for observation, data processing and analysis (Kotlyakov and others, 2003a, 2006).…”

“…Such observations are crucially important both for scientific purposes and for the projection of related disastrous phenomena. The notorious collapse of Kolka glacier, Pamirs, central Asia, in 2002 dramatically demonstrates what we might expect from surging glaciers in the absence of a special monitoring service oriented to periodic assessment of their state and surge projection (Kotlyakov and others, 2003a).…”

A surge of North Gasherbrum Glacier, Karakoram, China

“…The glaciers in the Karakoram and in Alaska, USA, represent ∼90% of the known surging glaciers (Hewitt, 1969); in the Pamirs a large number of glaciers are potential surge-type glaciers, with >60 observed surge events (Kotlyakov and others, 1997). In the Karakoram >30 surges have been reported since the 1860s (Hewitt, 1998), and many more probably went unnoticed.…”

Transport conditions of mountain-surging glaciers as recorded in the micromorphology of quartz grains (Medvezhiy Glacier, West Pamir)

“…The transgression led to the creation of an ice dam and a reservoir on the upper segment of the valley, and breaching of the dam caused a glacial flood with serious consequences (Dolgushin & Osipova, 1975;Nowikov, 2002). The next surge was registered in 1973, when the Medvezhiy Glacier flowed down through the valley once again, blocking the Abdukagor River and the estimated snout's transgression was 1,950 metres long (Kotlyakov et al, 1997). The episodes in 1988The episodes in -1989The episodes in and in 2001 were not such great transgressions.…”

“…Samples 1, 3 and 5 provide data on transformation of the quartz grain surface caused by processes in environment of a surging glacier. Samples 2 and 4 allow to supplement data on the characteristics of the source material from the valley's slopes, because these were transported pas- vezhiy Glacier surges, based on Dolgushin & Osipova (1975), Kotlyakov et al (1997), Novikov (2002) and personal observations. * -estimated value of snout's advances; ?…”