Degradation of glaciation of the Kazbek-Dzhimarai mountain cluster and individual glaciers in the river basins Urukh, Ardon, Fiagdon, Gizeldon and Genaldon (territory of North Ossetia- Alania)

Работа направлена на исследование темпов деградации оледенения Центрального Кавказа в пределах Горной Осетии с охватом юго-восточных склонов Казбеко-Джимарайского мас- сива на территории Грузии. Основным методом был выбран сравнительный анализ площадей оле- денения, отображенных на государственных топографических картах М 1 : 50 000, выполненных на основе аэрофотосъемки 1957 года и дешифрированных площадях оледенения на космических сним- ках GOOGL 2020 года для той же территории. В процессе работы были применены математиче- ские приемы, позволившие оценку масштабов деградации площади дневной поверхности отдельных ледово-фирновых образований сопровождать оценкой их объемов и средних мощностей. Полученные результаты для территории Горной Осетии хорошо согласуются с результатами проведения ана- логичных работ на других локальных площадях, как на территории России, так и за рубежом, что свидетельствует о глобальности распространения процесса распада горного оледенения, обуслов- ленном потеплением климата планеты. The work is aimed at studying the rate of degradation of glaciation in the Central Caucasus within Mountain Ossetia, covering the southeastern slopes of the Kazbek-Dzhimarai massif on the territory of Georgia. The main method was a comparative analysis of glacier areas displayed on state topographic maps M 1: 50,000, made on the basis of aerial photography in 1957 and decoded glaciation areas on space images of GOOGL 2020 for the same territory. In the course of the work, mathematical methods were applied that allowed the assessment of the scale of degradation of the day surface area of individual ice-fi rn formations to be accompanied by an assessment of their volumes and average thicknesses. The results obtained for the territory of Mountain Ossetia are in good agreement with the results of similar work in other local areas, both in Russia and abroad, which indicates the globality of the spread of the decay of mountain glaciation caused by the warming of the planet's climate.

Modelling future evolution of glaciation in the Central Caucasus

<p>The retreat of glaciers of the Greater Caucasus in the second half of the 20th and early 21st centuries was recorded by a variety of methods, including both direct instrumental observations and remote sensing. It is natural to expect that in the conditions of a gradually warming climate, the general trend of glacier retreat will continue in the future.</p><p>In the foothills of the North Caucasus, an important agricultural region, the problem of expected changes in mountain glaciation is particularly acute, since fluctuations in the flow regime of local rivers depend on the evolution of glaciers: the contribution of glacial runoff to total discharge is very significant. Retreating glaciers can also cause lakes to appear in local depressions in the underlying relief. Their possible breakthrough could cause significant damage to the economy and threaten human lives. The forecast of runoff and lake formation are associated with the projections on the future state of mountain glaciation.</p><p>Here, we present the work in progress to assess the rate of future glacier change in the Central Caucasus throughout the 21st century. The aim is to determine how the characteristics of mountain glaciation (its area, volume, position of the glacier fronts) of the Central Caucasus will change, depending on the climate scenario. In order to accomplish this goal, we use the GloGEMflow model (Zekollari et al., 2019) with an updated radiation block (Rybak et al., 2021, in press) and a set of CMIP5/CMIP6 climate scenarios. The GloGEMflow model features an ice flow block which is calibrated to match the Huss & Farinotti (2012, updated to RGI6.0) glacier geometry data. Validation of the model is based on the assessment of discrepancies arising when comparing data about glaciers boundaries changes for the period from ~2000 (RGI6.0) to 2018 (Department of Glaciology RAS).</p><p>The reported study was funded by RFBR and RS, project number 21-55-100003.</p>

Downscaling CESM2 in CLM5 to Hindcast Pre-Industrial Equilibrium Line Altitude for Tropical Mountains

<p>Highland environments are rarely preserved in the geological record, particularly from as early as the Paleozoic Era. However, several stratigraphic locations are now known which definitely or potentially preserve such environments near the paleoequator during the Late Carboniferous and Early Permian Periods, during which the Earth was in the depths of an icehouse climate like that of the Pliocene and Pleistocene Epochs, the Late Paleozoic Ice Age (LPIA). Several of these locations contain evidence of mountain glaciation at altitudes below 2000 m, leading to questions about the significance of tropical mountain glaciation for global climate during this interval of geologic time. However, climate model simulations for the LPIA have not been able to simulate mountain glaciation like that inferred from the geological record, possibly because of low resolution, incorrect boundary conditions, or climate model bias resulting from incomplete representation of moist convective processes impacting tropical lapse rates. </p><p>The overarching purpose of this study is to develop a climate modeling framework that enables the significance of mountain glaciation for global paleoclimate to be evaluated. Ideally, such a framework would allow low-resolution global model output to be downscaled to the scale of a mountain range to calculate the equilibrium line altitude and similar parameters, enabling evidence of mountain glaciation in the deep past to be used to constrain/tune the low-resolution global models. While this study was designed to inform a specific problem in deep time paleoclimate, its results are likely broadly applicable to assessing how well mountain glaciation is captured by global climate modeling of the past, present, and future.   </p><p>Here, I present a framework in which the CMIP6 pre-industrial control simulation for the Community Earth System Model version 2 (CESM2) at 0.9°x1.25° resolution is used to generate a data atmosphere for the Community Land Model version 5 (CLM5) run at 0.01° resolution in 10 tropical and 1 mid-latitude domain to study the surface mass balance over the domain. For computational reasons, glaciation is assumed to cover a small portion of each grid cell, but surface mass balance still can be evaluated. Topographic boundary conditions come from GMTED2010, but most other information is directly interpolated from the CESM2 simulation. CLM5 simulations require a fixed lapse rate to be assumed, which is varied in each CLM5 simulation across six different values. The CLM5 simulation output along with the mean tropical lapse rate in the CESM2 simulation is then used to evaluate the various biases of this framework in comparison with estimated pre-industrial equilibrium line altitudes for the studied domains.</p><p>This work is supported by the National Science Foundation (USA) under grant EAR-1849754. </p>

The erosion of glaciated mountains: evidence from hypsoclinometry

Mountain glaciation involves the erosion of cirques and troughs, which increase steep slopes but also produce gentle slopes in cirque floors and trough floors. This is expected to increase the variability of slope gradients at related altitudes. Taking a whole mountain range, its distributions of altitude and slope can be analysed to establish a signal of glacial modification. Frequency distributions of altitude (hypsometry) and gradient (clinometry) alone do not seem adequate. Taking these two variables together – hypsoclinometry, plotting slope gradient against altitude – is more promising. Frequency distributions of slope gradient at different altitudes are exemplified here for mountain ranges in British Columbia and Romania, together with altitudinal variations of steep or gentle slopes. Cirque headwalls give the clearest morphometric signature of glaciation. Steep (especially the steepest) slopes are concentrated at cirque altitudes, increasing mean, median, standard deviation (SD) and inter-quartile range (IQR) of gradients, especially above cirque floors. There is only a small increase in SD and IQR at cirque floor altitudes. Hypsometric maxima and increased proportions of gentle slopes at cirque floor altitudes are clear only in mountain ranges densely occupied by cirques. This relates to the small proportion of each cirque (about 28%) occupied by the floor. Concentrations of steep slope aspects in directions favoured by local glaciers provide further evidence of glacial modification. The most general morphometric effect of glaciation, however, is the increase in steep slopes at cirque headwall altitudes. Thus it is possible to rank mountain ranges by degree of glacial modification.