Glaciers distinct from the Greenland and Antarctic ice sheets cover an area of approximately 706,000 square kilometres globally
, with an estimated total volume of 170,000 cubic kilometres, or 0.4 ...metres of potential sea-level-rise equivalent
. Retreating and thinning glaciers are icons of climate change
and affect regional runoff
as well as global sea level
. In past reports from the Intergovernmental Panel on Climate Change, estimates of changes in glacier mass were based on the multiplication of averaged or interpolated results from available observations of a few hundred glaciers by defined regional glacier areas
. For data-scarce regions, these results had to be complemented with estimates based on satellite altimetry and gravimetry
. These past approaches were challenged by the small number and heterogeneous spatiotemporal distribution of in situ measurement series and their often unknown ability to represent their respective mountain ranges, as well as by the spatial limitations of satellite altimetry (for which only point data are available) and gravimetry (with its coarse resolution). Here we use an extrapolation of glaciological and geodetic observations to show that glaciers contributed 27 ± 22 millimetres to global mean sea-level rise from 1961 to 2016. Regional specific-mass-change rates for 2006-2016 range from -0.1 metres to -1.2 metres of water equivalent per year, resulting in a global sea-level contribution of 335 ± 144 gigatonnes, or 0.92 ± 0.39 millimetres, per year. Although statistical uncertainty ranges overlap, our conclusions suggest that glacier mass loss may be larger than previously reported
. The present glacier mass loss is equivalent to the sea-level contribution of the Greenland Ice Sheet
, clearly exceeds the loss from the Antarctic Ice Sheet
, and accounts for 25 to 30 per cent of the total observed sea-level rise
. Present mass-loss rates indicate that glaciers could almost disappear in some mountain ranges in this century, while heavily glacierized regions will continue to contribute to sea-level rise beyond 2100.
Knowledge of supra-glacial debris cover and its changes remain incomplete in
the Greater Caucasus, in spite of recent glacier studies. Here we present
data of supra-glacial debris cover for 659 ...glaciers across the Greater
Caucasus based on Landsat and SPOT images from the years 1986, 2000 and
2014. We combined semi-automated methods for mapping the clean ice with
manual digitization of debris-covered glacier parts and calculated
supra-glacial debris-covered area as the residual between these two maps. The
accuracy of the results was assessed by using high-resolution Google Earth
imagery and GPS data for selected glaciers. From 1986 to 2014, the total
glacier area decreased from 691.5±29.0 to 590.0±25.8 km2 (15.8±4.1 %, or ∼0.52 % yr−1), while
the clean-ice area reduced from 643.2±25.9 to 511.0±20.9 km2 (20.1±4.0 %, or ∼0.73 % yr−1).
In contrast supra-glacial debris cover increased from 7.0±6.4 %, or
48.3±3.1 km2, in 1986 to 13.4±6.2 % (∼0.22 % yr−1), or 79.0±4.9 km2, in 2014. Debris-free
glaciers exhibited higher area and length reductions than debris-covered
glaciers. The distribution of the supra-glacial debris cover differs between
the northern and southern and between the western, central and eastern Greater
Caucasus. The observed increase in supra-glacial debris cover is
significantly stronger on the northern slopes. Overall, we have observed
up-glacier average migration of supra-glacial debris cover from about 3015
to 3130 m a.s.l. (metres above sea level) during the investigated period.
We investigate the concentration and size dependent self-assembly of cadmium selenide nanoparticles at an oil/water interface. Using a pendant drop tensiometer, we monitor the assembly kinetics and ...evaluate the effective diffusion coefficients following changes in the interfacial tension for the early and late stages of nanoparticle adsorption. Comparison with the coefficients for free diffusion reveals the energy barrier for particle segregation to the interface. The formation of a nanoparticle monolayer at the oil/water interface is characterised by transmission electron microscopy.
Surge-Type Glaciers in the Tien Shan (Central Asia) Mukherjee, K; Bolch, T; Goerlich, F ...
Arctic, antarctic, and alpine research,
2017-February, 2/1/2017, 20170201, 2017-02-00, Letnik:
49, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Surge-type glaciers have been observed in several mountain ranges of the world. Though Karakoram and Pamir are the hot spots for the occurrence of surge-type glaciers in High Mountain Asia, few ...surge-type glaciers also exist in Tien Shan. These have not been studied or reported in detail in the recent literature. We have identified 39 surge-type glaciers and five tributary surges in Tien Shan either from available literature or by visual interpretation using available images from the period 1960 until 2014. Out of the 39 glaciers, 9 are confirmed as surge-type, 13 are very probably surge-type, and the remaining are possibly of surge-type. Most of the surge-type glaciers are located in Ak-Shiirak and Central Tien Shan. Compared with the normal glaciers of Tien Shan, the surge-type glaciers are larger, cover higher ranges of elevations, and have shallower slopes. There is no significant difference in aspect. The largest surge events were observed in Central Tien Shan: North Inylchek Glacier (years 1996/1997) and Samoilowich Glacier (years 1992 until 2006) advanced several kilometers. The surge cycle was around 50 years for both of these glaciers. The advance was less pronounced for all other surge-type glaciers during the period ca. 1960–2014. Some of the tributary glaciers behaved differently than the main glaciers in the sense that they continuously advanced during the entire period of our study, whereas the main glaciers have remained stable or retreated.
Results of studying isotopic characteristics of precipitation at the foot of the southern slope of Elbrus, in the Caucasus, are presented. The precipitation sampling was organized at Azau station (at ...an altitude of 2300 m) on an everyday basis. The main precipitation sources for the Elbrus region have been established using the method of HYSPLIT back trajectories. Values of δ
18
O of the precipitation reflect a pronounced relation to the temperature of the surface air layer: Δδ
18
O/Δ
T
= 0.85‰/°C.
Light absorbing particles, such as mineral dust, are a potent climate forcing agent. Many snow‐covered areas are subject to dust outbreak events originating from desert regions able to significantly ...decrease snow albedo. Here, using a combination of Sentinel‐2 imagery, in situ measurements and ensemble detailed snowpack simulations, we study the impact on snow cover duration of a major dust deposition event that occurred in the Caucasus in March 2018. This is, to the best of our knowledge, the first study using ensemble approach and Sentinel‐2 imagery to quantify the impact of a dust event on the snow cover evolution. We demonstrate that the calculation of the impact is strongly affected by the snow model uncertainties but that the March 2018 dust event systematically shortened the snow cover duration in Western Caucasus. The shortening is higher for location with higher accumulation and higher elevation (median values of 23 ± 7 days) than for location at lower elevation (median values of 15 ± 3 days). This is because for sites with higher location and higher accumulation, melt occurs later in the season when more incoming solar energy is available. This highlights the huge impact of a single 1‐day event on snow cover duration, and consequently, on the hydrology of a large region.
Key Points
Dust from Sahara deposited on snow in Caucasus shortened the snow cover duration by 12 to 30 days
The impact of dust deposition was larger at higher elevation
Snow modeling uncertainties quantified by ensemble simulation strongly impact the estimated snow cover duration
A model of the orthographic component of precipitation based on the calculation of the condensation rate of water vapor in the air stream uplifting onto the mountain slope is proposed. The main ...assumptions of the model are as follows: the cooling of the rising air is determined only by the adiabatic process; the orographic component of the vertical component of wind speed is generated by the relief and its weakening with elevation is determined only by atmospheric stratification; the proportion of precipitation from the total mass of the condensed moisture depends only on the air temperature. ERA5 reanalysis, which was previously compared with observational data, is used as the initial data. The proposed model adequately reproduces the spatial and temporal variability of precipitation on the slopes of Elbrus both for short episodes and on the climatic time scale (1985–2018). A comparison of the modeling results with the reconstruction of the annual accumulation of precipitation from the ice core obtained on the western plateau of Elbrus in 2018 has shown a statistically significant positive correlation. However, a similar comparison with the data from the core extracted in 2009 does not give a statistically significant result. This suggests that the proposed model can be used as a tool for conformity between methods of accumulation reconstruction and for substantiation of their physical validity. In addition, this algorithm can be used to calculate monthly and annual sums of precipitation on the mountain slopes of various exposures and to estimate annual accumulation on mountain glaciers.
Changes in the map area of 498 glaciers located on the Main Caucasus ridge (MCR) and on Mt. Elbrus in the Greater Caucasus Mountains (Russia and Georgia) were assessed using multispectral ASTER and ...panchromatic Landsat imagery with 15 m spatial resolution in 1999/2001 and 2010/2012. Changes in recession rates of glacier snouts between 1987–2001 and 2001–2010 were investigated using aerial photography and ASTER imagery for a sub-sample of 44 glaciers. In total, glacier area decreased by 4.7 ± 2.1% or 19.2 ± 8.7 km2 from 407.3 ± 5.4 km2 to 388.1 ± 5.2 km2. Glaciers located in the central and western MCR lost 13.4 ± 7.3 km2 (4.7 ± 2.5%) in total or 8.5 km2 (5.0 ± 2.4%) and 4.9 km2 (4.1 ± 2.7%) respectively. Glaciers on Mt. Elbrus, although located at higher elevations, lost 5.8 ± 1.4 km2 (4.9 ± 1.2%) of their total area. The recession rates of valley glacier termini increased between 1987–2000/01 and 2000/01–2010 (2000 for the western MCR and 2001 for the central MCR and Mt.~Elbrus) from 3.8 ± 0.8, 3.2 ± 0.9 and 8.3 ± 0.8 m yr−1 to 11.9 ± 1.1, 8.7 ± 1.1 and 14.1 ± 1.1 m yr−1 in the central and western MCR and on Mt. Elbrus respectively. The highest rate of increase in glacier termini retreat was registered on the southern slope of the central MCR where it has tripled. A positive trend in summer temperatures forced glacier recession, and strong positive temperature anomalies in 1998, 2006, and 2010 contributed to the enhanced loss of ice. An increase in accumulation season precipitation observed in the northern MCR since the mid-1980s has not compensated for the effects of summer warming while the negative precipitation anomalies, observed on the southern slope of the central MCR in the 1990s, resulted in stronger glacier wastage.
In the modern sense, glaciers are a unique large terrestrial biome. They combine autotrophic–heterotrophic ecosystems with the most significant contribution of abiotic processes. The biome serves as ...an important supplier of biogenic elements and climatically active substances accumulated over glacial epochs. The cycle of biogenic greenhouse gases (GHGs) is one of the most important biospheric functions of any large ecosystem. Ablation, which is especially prominent on mountain glaciers, can have a significant impact on the GHG cycle under current warming. We have studied two mountain glaciers located in the European (North Caucasus, 2020) and Asian (Altai, 2021) parts of Russia. The purpose of this work was to estimate the current values of GHG fluxes in the influence zone of the glaciers losing their mass under warming. Due to the accumulation of cryoconites (fine-grained soils, mainly of aeolian genesis) on the ice surface, the ablation zones, on average, serve as weak sources of CO
2
for the atmosphere (15.3 mg CO
2
m
–2
d
–1
), whereas the glacier accumulation zones are weak sinks (–21.5 mg CO
2
m
–2
d
–1
). Young terminal moraines formed over the last 20 years are more significant additional sources of CO
2
(45.2 to 446.3 mg CO
2
m
–2
d
–1
) and methane. The spatial variations in methane fluxes are highly substantial, and its contribution to radiative forcing (–0.4 to +225.6 mg CO
2
-equiv. m
–2
d
–1
) may be comparable to that of CO
2
. Compared to these GHGs, the net fluxes of nitrous oxide in the glacial ecosystems studied are negligible. The contribution of soil-like bodies of young moraines significantly increases the weighted average estimation of CO
2
emission on glaciers from 2 to 1015 kg C km
–2
yr
–1
. The results obtained highlight the role of glaciers as preserving biospheric agents of the GHG exchange in the atmosphere.
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