Earth`s Cryosphere, 2019, Vol. XXIII, № 2, p. 33-43
CONDITIONS AND PROCESSES OF FORMATION OF A BEADED CHANNEL OF A SMALL RIVER IN PERMAFROST, SHESTAKOVKA RIVER, CENTRAL YAKUTIA
A.M. Tarbeeva1, L.S. Lebedeva2, V.S. Efremov2, I.V. Krylenko1, V.V. Surkov1,
V.V. Shamov2,3, T.N. Lutsenko3
1 Lomonosov Moscow State University, Faculty of Geography,
1, Leninskie Gory, Moscow, 119991, Russia; amtarbeeva@yandex.ru
2 Melnikov Permafrost Institute, SB RAS, 36, Merzlotnaya str., Yakutsk, 677010, Russia
3 Pacific Geographical Institute, FEB RAS, 7, Radio str., Vladivostok, 690041, Russia
Observations over the thermal regime of soils, formation and destruction of river ice were carried out, the hydrological characteristics were obtained, and the geological structure of a small river in Central Yakutia was investigated in order to identify the processes forming the beaded shape of the river channel. This type of a channel is widespread in permafrost regions, characterized by alternation of the channel extensions, ‘beads’, and narrow runs, predetermining the specific thermal, water and ice regime of the river, which leads to alternation of the periods of mixing and stratification of the water, to the presence of pressured unfrozen water in winter, and the appearance of ice mounds and local underwater taliks. Despite the presence of thawed sediments under the channel, thermokarst does not play a significant role in the modern formation of the beads due to the low ice content in the underlying sediments. The maximum water discharges flow above the ice cover, so the expansion and deepening of the pools by the water flow is possible only when anomalously high flow events occur after thawing of ice in the channel. Significant mechanisms of modern deepening and widening of the beads can consist in repeated extrusion and subsequent removal of suspended matter and bottom sediments under cryostatic pressure during freezing of the channel, as well as stresses that occur on the ice-ground contact during freezing, leading to destruction of the banks.
River ice processes, channel processes, thermal regime of a river channel, river taliks, cryostatic pressure, cryogenic processes, Lena-Vilyuy interfluve