97 research outputs found
Changes in Eurasian glaciation during the past century: glacier mass balance and ice-core evidence
No full textGlaciers of both the Arctic and mid-latitude mountain systems within Eurasia have retreated intensively during the past century. Measured and reconstructed glacier mass balances show that glacier retreat began around the 1880s. The mean annual mass-balance value for 1880–1990 was −480 mm a−1 for glaciers with maritime climatic conditions, and −140 mm a−1 for continental glaciers. It can be concluded that warming in the Caucasus occurred during at least the last 60 years, according to the distribution of crystal sizes in an ice core from the Dzhantugan firn plateau. Temperatures measured in 1962 at 20 m on the Gregoriev ice cap, Tien Shan, were −4.2°C while in 1990 they were −2°C, a warming of 2.2°C over 28 years. Changes in the isotopic composition of glacier ice during the 20th century indicate recent and continuing warming in different regions of Eurasia. The δ18O records reveal an enrichment at the Gregoriev ice cap during the last 50 years, while surface temperatures at the Tien Shan meteorological station have increased 0.5°C since 1930.</jats:p
Changes in Eurasian glaciation during the past century: glacier mass balance and ice-core evidence
No full textGlaciers of both the Arctic and mid-latitude mountain systems within Eurasia have retreated intensively during the past century. Measured and reconstructed glacier mass balances show that glacier retreat began around the 1880s. The mean annual mass-balance value for 1880–1990 was −480 mm a−1 for glaciers with maritime climatic conditions, and −140 mm a−1 for continental glaciers. It can be concluded that warming in the Caucasus occurred during at least the last 60 years, according to the distribution of crystal sizes in an ice core from the Dzhantugan firn plateau. Temperatures measured in 1962 at 20 m on the Gregoriev ice cap, Tien Shan, were −4.2°C while in 1990 they were −2°C, a warming of 2.2°C over 28 years. Changes in the isotopic composition of glacier ice during the 20th century indicate recent and continuing warming in different regions of Eurasia. The δ
18O records reveal an enrichment at the Gregoriev ice cap during the last 50 years, while surface temperatures at the Tien Shan meteorological station have increased 0.5°C since 1930.</jats:p
Large-scale drivers of Caucasus climate variability in meteorological records and Mt El'brus ice cores
Get PDFA 181.8 m ice core was recovered from a borehole drilled into bedrock on the western plateau of Mt El'brus (43 degrees 20'53.9 ' N, 42 degrees 25'36.0 ' E; 5115m a.s.l.) in the Caucasus, Russia, in 2009 (Mikhalenko et al., 2015). Here, we report on the results of the water stable isotope composition from this ice core with additional data from the shallow cores. The distinct seasonal cycle of the isotopic composition allows dating by annual layer counting. Dating has been performed for the upper 126 m of the deep core combined with 20 m from the shallow cores. The whole record covers 100 years, from 2013 back to 1914. Due to the high accumulation rate (1380 mm w.e. year(-1)) and limited melting, we obtained isotopic composition and accumulation rate records with seasonal resolution. These values were compared with available meteorological data from 13 weather stations in the region and also with atmosphere circulation indices, back-trajectory calculations, and Global Network of Isotopes in Precipitation (GNIP) data in order to decipher the drivers of accumulation and ice core isotopic composition in the Caucasus region. In the warm season (May-October) the isotopic composition depends on local temperatures, but the correlation is not persistent over time, while in the cold season (November-April), atmospheric circulation is the predominant driver of the ice core's isotopic composition. The snow accumulation rate correlates well with the precipitation rate in the region all year round, which made it possible to reconstruct and expand the precipitation record at the Caucasus highlands from 1914 until 1966, when reliable meteorological observations of precipitation at high elevation began
TRANSFORMATION OF THE INITIAL ISOTOPIC COMPOSITION OF PRECIPITATION IN CAVES OF THE SOUTH-WESTERN CAUCASUS
No full textThe paper presents preliminary results and interpretation from an ongoing research project in the Novy Afon and Abrskil caves of Abkhazia. The research have demonstrated that δ18O and δD analyses of drip and ground waters in two caves in the South-Western Caucasian region allows to better understand interaction between isotopic composition of precipitation, soil, and vadose zone. Drip and ground water samples from the caves were compared with the present-day Global (GMWL) and the Local Meteoric Water Lines (LMWL). They fall along the GMWL and LMWL and are tied by equation δD = 5.74δ18O - 6.98 (r2 = 0.94). Drip water isotopic composition is similar to that from lakes and pools. The incline of δ18O - δD line differs from GMWL and LMWL. It reflects a possible result from secondary condensation and evaporation and water-rock interaction, and depends on the climate aridity level
TRANSFORMATION OF THE INITIAL ISOTOPIC COMPOSITION OF PRECIPITATION IN CAVES OF THE SOUTH-WESTERN CAUCASUS
No full textDISCOVERY OF COLD ICE IN A NEW DRILLING SITE IN THE EASTERN EUROPEAN ALPS
No full textDuring autumn 2011 we extracted the first ice cores drilled to bedrock in the eastern European Alps from a new drilling site on the glacier Alto dell’Ortles (3859 m, South Tyrol, Italy). Direct ice core observations and englacial temperature measurements provide evidence of the concomitant presence of shallow temperate firn and deep cold ice layers (ice below the pressure melting point). To the best of our knowledge, this is the first cold ice observed within a glacier of the eastern European Alps. These ice layers probably represent a unique remnant from the colder climate occurring be- fore ~1980 AD. We conclude that the glacier Alto dell’Ortles is now changing from a cold to a temperate state. The occurrence of cold ice layers in this glacier enhances the probability that a climatic and environ- mental record is fully preserved in the recovered ice cores
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