1 research outputs found
Development of proglacial lakes and evaluation of related outburst susceptibility at the Adygine ice-debris complex, northern Tien Shan
The formation and development of glacial lakes in mountainous
regions is one of the consequences of glacier recession. Such lakes may drain
partially or completely when the stability of their dams is disturbed or as
a consequence of impacts. We present a case study from the Central Asian
mountain range of Tien Shan – a north-oriented tributary of the Adygine
Valley, where the retreat of a polythermal glacier surrounded by permafrost
has resulted in the formation of several generations of lakes. The aim of
this study was to analyse the past development of different types of glacial
lakes influenced by the same glacier, to project the site's future
development, and to evaluate the outburst susceptibility of individual lakes
with an outlook for expected future change. We addressed the problem using a
combination of methods, namely bathymetric, geodetic and geophysical on-site
surveys, satellite images and digital elevation model analysis, and modelling
of glacier development. Based on this case of the glacial lakes being of
varied age and type, we demonstrated the significance of glacier ice in lake
development. Lake 3, which is in contact with the glacier terminus, has
changed rapidly over the last decade, expanding both in area and depth and
increasing its volume by more than 13 times (7800 to 106 000 m3). The hydrological connections and routing of glacier meltwater have
proved to be an important factor as well, since most lakes in the region are
drained by subsurface channels. As the site is at the boundary between
continuous and discontinuous permafrost, the subsurface water flow is
strongly governed by the distribution of non-frozen zones above, within, or
beneath the perennially frozen ground. In the evaluation of lake outburst
susceptibility, we have highlighted the importance of field data, which can
provide crucial information on lake stability. In our case, an understanding
of the hydrological system at the site, and its regime, helped to categorise
Lake 2 as having low outburst susceptibility, while Lake 1 and Lake 3 were labelled as
lakes with medium outburst susceptibility. Further development of the site
will be driven mainly by rising air temperatures and increasingly negative
glacier mass balance. All three climate model scenarios predicted a
significant glacier areal decrease by 2050, specifically leaving 73.2 %
(A1B), 62.3 % (A2), and 55.6 % (B1) of the extent of the glacier in 2012.
The glacier retreat will be accompanied by changes in glacier runoff, with
the first peak expected around 2020, and the formation of additional lakes.</p