The First Rock Glacier Inventory for the Greater Caucasus

Rock glaciers are an integral part of the periglacial environment. At the regional scale in the Greater Caucasus, there have been no comprehensive systematic efforts to assess the distribution of rock glaciers, although some individual parts of ranges have been mapped before. In this study we produce the first inventory of rock glaciers from the entire Greater Caucasus region—Russia, Georgia, and Azerbaijan. A remote sensing survey was conducted using Geo-Information System (GIS) and Google Earth Pro software based on high-resolution satellite imagery—SPOT, Worldview, QuickBird, and IKONOS, based on data obtained during the period 2004–2021. Sentinel-2 imagery from the year 2020 was also used as a supplementary source. The ASTER GDEM (2011) was used to determine location, elevation, and slope for all rock glaciers. Using a manual approach to digitize rock glaciers, we discovered that the mountain range contains 1461 rock glaciers with a total area of 297.8 ± 23.0 km2. Visual inspection of the morphology suggests that 1018 rock glaciers with a total area of 199.6 ± 15.9 km2 (67% of the total rock glacier area) are active, while the remaining rock glaciers appear to be relict. The average maximum altitude of all rock glaciers is found at 3152 ± 96 m above sea level (a.s.l.) while the mean and minimum altitude are 3009 ± 91 m and 2882 ± 87 m a.s.l., respectively. We find that the average minimum altitude of active rock glaciers is higher (2955 ± 98 m a.s.l.) than in relict rock glaciers (2716 ± 83 m a.s.l.). No clear difference is discernible between the surface slope of active (41.4 ± 3°) and relict (38.8 ± 4°) rock glaciers in the entire mountain region. This inventory provides a database for understanding the extent of permafrost in the Greater Caucasus and is an important basis for further research of geomorphology and palaeoglaciology in this region. The inventory will be submitted to the Global Land Ice Measurements from Space (GLIMS) database and can be used for future studies

Strong acceleration of glacier area loss in the Greater Caucasus between 2000 and 2020

An updated glacier inventory is important for understanding glacier behaviour given the accelerating glacier retreat observed around the world. Here, we present data from a new glacier inventory for two points in time (2000, 2020) covering the entire Greater Caucasus (Georgia, Russia, and Azerbaijan). Satellite imagery (Landsat, Sentinel, SPOT) was used to conduct a remote-sensing survey of glacier change. The 30 m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM; 17 November 2011) was used to determine aspect, slope, and elevations, for all glaciers. Glacier margins were mapped manually and reveal that in 2000 the mountain range contained 2186 glaciers with a total glacier area of 1381.5 ± 58.2 km2. By 2020, the area had decreased to 1060.9 ± 33.6 km2 a reduction of 23.2 ± 3.8 % (320.6 ± 45.9 km2) or −1.16 % yr−1 over the last 20 years in the Greater Caucasus. Of the 2223 glaciers, 14 have an area > 10 km2, resulting in the 221.9 km2 or 20.9 % of total glacier area in 2020. The Bezengi Glacier with an area of 39.4 ± 0.9 km2 was the largest glacier mapped in the 2020 database. Glaciers between 1.0 and 5.0 km2 accounted for 478.1 km2 or 34.6 % in total area in 2000, while they accounted for 354.0 km2 or 33.4 % in total area in 2020. The rates of area shrinkage and mean elevation vary between the northern and southern and between the western, central, and eastern Greater Caucasus. Area shrinkage is significantly stronger in the eastern Greater Caucasus (−1.82 % yr−1), where most glaciers are very small. The observed increased summer temperatures and decreased winter precipitation along with increased Saharan dust deposition might be responsible for the predominantly negative mass balances of Djankuat and Garabashi glaciers with long-term measurements. Both glacier inventories are available from the Global Land Ice Measurements from Space (GLIMS) database and can be used for future studies

Brief communication: Supraglacial debris-cover changesin the Caucasus mountains

Debris cover on glaciers can significantly alter melt, and hence, glacier mass balance and runoff. Debris coverage typically increases with shrinking glaciers. Here, we present data on debris cover and its changes for 559 glaciers located in different regions of the Greater Caucasus mountains based on 1986, 2000 and 2014 Landsat and SPOT images. Over this time period, the total glacier area decreased from 691.5km2 to 590.0km2 (0.52%yr-1. Thereby, the debris covered area increased from ~11 to ~24% on the northern, and from ~4 to 10% on the southern macro-slope between 1986 and 2014. Overall, we found 18% debris cover for the year 2014. With the glacier shrinkage, debris-covered area and the number of debris-covered glaciers increased as a function of elevation, slope, aspect, glacier morphological type, Little Ice Age moraines, and lithology

Supraglacial debris cover assessment in the Caucasus Mountains, 1986-2000-2014

The database contains glacier outlines from 1986-2000-2014. During the investigation Landsat (Landsat 5 TM, Landsat 7 ETM+, Landsat 8 OLI) and SPOT satellite imagery were analyzed to generate glacier outlines using manual and semi-automated methods

Late Quaternary glacier-climate reconstructions from the Southern Alps, New Zealand

One of the outstanding problems in modern geoscience is identifying the cause of past climate changes, particularly the drivers of rapid climate change during Quaternary glacial cycles. Changes in the physical geography of Earth’s surface during the Late Quaternary are mainly dependent on glacial dynamics – periods of rapid warming produced significant amounts of meltwater that reshaped the landscape, changed global sea-level and influenced climate. Identifying the timing of key climate transitions during past warming episodes, such as the last glacial termination, may help to understand the future evolution of Earth’s climate system (e.g. Denton et al., 2021). In this thesis, using geomorphological mapping and sixty-six cosmogenic 10Be surface exposure ages obtained from ice sculpted bedrock surfaces and deposited moraine landforms, I constrain the local Last Glacial Maximum and subsequent timing of last glacial termination in the Ahuriri River valley, Southern Alps, New Zealand (44°15′S, 169°36′E). Using the maximum elevation of lateral moraine (MELM) and accumulation area ratio (AAR) methods, along with application of a temperature lapse rate, I estimate the equilibrium-line altitude (ELA) and associated temperatures from the same periods. The largest glacial event in the Ahuriri River valley occurred at 19.8±0.3 ka when the former Ahuriri Glacier reached its maximum extent, which coincides with the global Last Glacial Maximum. By 16.7±0.3 ka, ice had retreated ~18 km up-valley from the LGM position and deglaciation was accompanied by the formation of a shallow proglacial lake. Surface exposure ages from moraines situated in a tributary of the upper Ahuriri River valley indicate that a subsequent advance of the palaeo glacier culminated at 14.5±0.3 ka, while the next readvance or still stand occurred at 13.6±0.3 ka. About 1000 yr later (12.6±0.2 ka), the former glacier built another prominent terminal moraine ridge in the lower section of the upper right tributary valley. Reconstructions of past glacier geometries indicate that the local ELA was depressed by ~880 m and climate was 5±1 °C colder than present (1981–2010) at 19.8±0.3 ka, while ELA was depressed by ~770 m and climate was 4.4±0.9 °C colder at 16.7±0.3 ka. Subsequent estimations suggest ELA elevations at 14.5±0.3 ka, 13.6±0.3 ka, and 12.6±0.2 ka were ≤700 m, ≤630 m, and ~360 m lower than today. This equates to air temperatures of ≤3.9 °C, ≤3.5 °C, and 2.3±0.7 °C colder than today, assuming no changes in past precipitation. The results reported here provide the first dataset of Late Quaternary glacial maximum extent and deglaciation along with quantitative paleoclimate reconstructions from the Ahuriri River valley, Southern Alps, New Zealand. The small amount of warming estimated in this study between 19.8±0.3 and 16.7±0.3 ka differs somewhat from glacial reconstructions in other major valleys in the Southern Alps, specifically from Rakaia River valley (e.g. Putnam et al., 2013a) where a much larger amount of warming may have occurred during the same time. Robust constraints of glacier changes in the Ahuriri valley between 14.5±0.3 and 12.6±0.2 ka confirm that an early glacier readvance occurred in New Zealand at this time, which has been previously recognised with only limited evidence (e.g. Kaplan et al., 2010; Putnam et al., 2010a). The reconstructed ELA suggests that the coldest part of the Late Glacial reversal occurred at 14.5±0.3 ka. The new constraints from glacial records in the Ahuriri River valley presented in this study offer the opportunity to test hypotheses about the climate system, to better understand the processes that drove ice retreat and readvance during the Last Glacial Maximum and subsequent termination.</p

Analysis of Regional Changes in Geodetic Mass Balance for All CaucasusGlaciers over the Past Two Decades

National audienc

Supra-glacial debris cover changes in the Greater Caucasus from 1986 to 2014

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

Glacial geomorphology of the Ahuriri River valley, central Southern Alps, New Zealand

No description supplie

Supraglacial debris cover assessment in the Caucasus Mountains, 1986-2000-2014

The database contains glacier outlines from 1986-2000-2014. During the investigation Landsat (Landsat 5 TM, Landsat 7 ETM+, Landsat 8 OLI) and SPOT satellite imagery were analyzed to generate glacier outlines using manual and semi-automated methods