Changes and representativeness of mountain glaciation parameters

Abstract

The study was aimed at analysis of changes in the area Fgl, the number Ngl and statistical parameters of distribution for different aggregates of glaciers over two periods: 1946–1975 and 1976–2005. The determined changes in the above parameters of glaciers located in river basins of the following mountain regions: the North Caucasus (Baksan, Chegem, Cherek, Malka, Teberda, Terek), Alay ridge (Akbura, Isfara, Isfayram, Shahimardan, Sokh), Altay (Aktru, Chuya, Katun) and Pamir (Gunt), are presented in the article. For better reliability of the height parameters of the glacier aggregates at the scale of the river basins, the maximum, minimum and average height values of individual glaciers were weighed by area. The trustworthiness of changes of the weighed height parameters confirms consistency with the linear relationship adopted at the scale of the river basin between the dimensions of the glaciers and the average weighed heights of beginning, end and average altitude of individual glaciers. Definition of the concept and the scale of representativeness of local measurements of glacier mass balance in the WGMS database is the actual glaciological problem. The proposed quantitative substantiation and the results of the selection of a group of representative glaciers are, in general, based on the use of parameters of dynamical state of individual glaciers distributed over several intervals from the minimum to maximum area values. The parameters of each glacier included: total area, volume, maximum and minimum height difference, index of morphological type, average thickness, orientation and slope of the surface. The sequence of determining the composition of a sample of representative glaciers on the example of glaciations in the basins of the Kyzylsu Western (Pamir) and Katun (Altai) rivers is described. Important part of the work was performed to reveal the possibilities to use local values (Ab – ablation/Bs – summer mass balance) measured on a priori reference/representative glaciers in the WGMS database as an additional argument for modeling and calculation of river runoff at the scale of river basins for June–September and other time intervals. Adding of local values of Ab/Bs as a complementary argument to the regression equations for regional calculations of runoff of the rivers of a snow-glacial feeding in the North Caucasus, Pamir-Alai and Altai was found to be efficient in only limited number of cases. The hydrological representation of the glacier is a new characteristic of practical importance for solving problems of hydrology and glaciology in river basins of snow-glacial type of the flow formation, which include almost all Alpine river basins. The method of revealing the hydrological representativeness of local Ab/Bs measurements described in the paper may be used for glaciers from the existing WGMS network.