Abstract
This study describes the analysis of changes in area and volume of the Mt. Elbrus glacier system, Central Caucasus from 1997 to 2017. It is based on helicopter-borne ice thickness measurements, comparison of high-resolution imagery and two digital elevation models (DEMs) with 10 meter resolution. More than 250 km of ground-penetrating radar (GPR) profiles of ice thickness with reliable reflections were obtained. The total volume of Mt. Elbrus glaciers was 5.03±0.85 km3 of ice in 2017. Our results show that 68% of the total ice volume is concentrated below 4000 m a.s.l. where the average ice thickness was 44.6±7.3 m, 18% of the volume lies within 4000-4500 m a.s.l. (thickness of 41.2±7.3 m), and just 14% lies above 4500 m a.s.l. (thickness of 29.7±6.65 m). The glacier-covered area of Mt. Elbrus decreased from 125.76±0.65 km2 in 1997 to 112.20±0.58 km2 in 2017, a reduction of 10.8%. Over the same period the volume decreased by 22.8%. The mass balance of the Elbrus glaciers decreased by -0.55±0.04 m w.e. a-1 from 1997 to 2017. Mass balance on west-oriented glaciers is less negative than on east-and south-oriented glaciers where mass balance is most negative. The mass balance of the east-oriented Djikiugankez glacier decreased at the fastest average rate (-0.97±0.07 m w.e. a-1). This glacier contains 28% of the total Elbrus glacier system ice volume, most of which is concentrated below 4000 m a.s.l. Only one small glacier on the western slope demonstrated mass gain. Our results match well with the long term direct mass balance measurements on the Garabashi glacier on Elbrus which lost 12.58 m w.e. and 12.92±0.95 m w.e. between 1997 and 2017 estimated by glaciological and geodetic method, respectively. The rate of Elbrus glacier mass loss tripled in 1997-2017 compared with the 1957-1997 period.
Highlights
Mountain glacier recession is considered to be unequivocal evidence of climate change
The Elbrus glaciers were characterized by different relative surface area reductions
From manual drawing of bedrock topography based on expertize (Fischer and Kuhn, 2013) to more complex interpolation and cross validation techniques (Lapazaran et al, 2016b). Another method involves using a distributed ice thickness model, which can be validated and adjusted with available measurements (Feiger et al, 2018). Such an approach enables ice thickness estimation on parts of a glacier not covered by the ground-penetrating radar (GPR) survey
Summary
Mountain glacier recession is considered to be unequivocal evidence of climate change. Glacier melt water released from ice loss contributes to sea level rise and modifies downstream river runoff (Huss and Hock, 2018). Knowledge of glacier mass changes is still limited. Assessments of rates of change of global and regional glacier masses may contain considerable uncertainties (Gardner et al, 2013; Zemp et al, 2019). A glacier adjusts its geometry (area and length) in response to climatic changes, but this adjustment is controlled by its dynamic response (Vincent et al, 2017). Mountain glacier mass balance is driven directly by meteorological variables and serves as a good climate indicator. Glacier mass change estimates are usually based on time series
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