Cryoconites as biogeochemical markers of anthropogenic impact in high mountain regions: analysis of polyaromatic pollutants in soil-like bodies

The globalisation and omnidirectional character of anthropogenic processes has challenged scientists around the world to estimate the harmful effects of these processes on ecosystems and human health. Polycyclic aromatic hydrocarbons (PAHs) is one the most infamous group of contaminants, originated both from natural and anthropogenic processes. They could transport to high latitudes and altitudes through atmospheric long-distance transfer and further enter ecosystems of these vulnerable regions by deposition on terrestrial surfaces. An interesting object for tracking transboundary contamination processes in high mountain ecosystems is called cryoconite. Cryoconite, a dark-coloured supraglacial sediment which is abundant in polar and mountain environments, is considered as a storage of various pollutants, including PAHs. Thus, it may pose a risk for local human health and ecosystem through short-distance transfer. Studied cryoconite sediments were collected at the surface of Skhelda and Garabashi glaciers, Central Caucasus high-mountain region, as well as mudflow, moraine material and local soils at the Baksan Gorge in order to examine levels of their contamination. We analysed the content of 15 priority polyaromatic compounds from the US EPA list and used the method of calculation of PAHs isomer ratios with the purpose of identifying their source. To estimate their potential toxicity, Benzo[a]pyrene (BaP) equivalents were calculated. Maximum concentration was defined for NAP (84 ng×g-1), PHE (40 ng×g-1) and PYR (47 ng×g-1), with the minimum concentration for ANT (about 1 ng×g-1). The most polluted material is a cryoconite from Garabashi glacier because of local anthropogenic activities and long-distance transfer. High-molecular weight PAHs are dominated in PAHs composition of almost all samples. The most common sources of PAHs in studied materials are combustion processes and mixed pyrolytic/petrogenic origin. Toxicity levels of separate PAHs did not exceed the maximum permissible threshold concentrations values in most cases. However, the sum of PAHs in BaP equivalents exceed the threshold values in all samples, in some of them more than twice.

Assessment of Climate Change Impact on Snowmelt Runoff in Himalayan Region

The current study was planned to simulate runoff due to the snowmelt in the Lidder River catchment of Himalayan region under climate change scenarios. A basic degree-day model, Snowmelt-Runoff Model (SRM) was utilized to assess the hydrological consequences of change in climate. The SRM model performance during the calibration and validation was assessed using volume difference (Dv) and coefficient of determination (R2). The Dv was found as 11.7, -10.1, -11.8, 1.96, and 8.6 during 2009-2014, respectively, while the R2 is 0.96, 0.92, 0.95, 0.90, and 0.94, respectively. The Dv and R2 values indicating that the simulated snowmelt runoff has a close agreement with the observed value. The simulated findings were also assessed under the different scenarios of climate change: a) increases in precipitation by +20 %, b) temperature rise of +2 °C, and c) temperature rise of +2 °C with a 20 % increase in snow cover. In scenario "b", the simulated results showed that runoff increased by 53 % in summer (April–September). In contrast, the projected increased discharge for scenarios "a" and "c" was 37 % and 67 %, respectively. In high elevation data-scarce mountain environments, the SRM is efficient in forecasting future water supplies due to the snowmelt runoff.

Studies on Three-Dimensional (3D) Accuracy Optimization and Repeatability of UAV in Complex Pit-Rim Landforms As Assisted by Oblique Imaging and RTK Positioning

Unmanned Aerial Vehicles (UAVs) are a novel technology for landform investigations, monitoring, as well as evolution analyses of long−term repeated observation. However, impacted by the sophisticated topographic environment, fluctuating terrain and incomplete field observations, significant differences have been found between 3D measurement accuracy and the Digital Surface Model (DSM). In this study, the DJI Phantom 4 RTK UAV was adopted to capture images of complex pit-rim landforms with significant elevation undulations. A repeated observation data acquisition scheme was proposed for a small amount of oblique-view imaging, while an ortho-view observation was conducted. Subsequently, the 3D scenes and DSMs were formed by employing Structure from Motion (SfM) and Multi-View Stereo (MVS) algorithms. Moreover, a comparison and 3D measurement accuracy analysis were conducted based on the internal and external precision by exploiting checkpoint and DSM of Difference (DoD) error analysis methods. As indicated by the results, the 3D scene plane for two imaging types could reach an accuracy of centimeters, whereas the elevation accuracy of the orthophoto dataset alone could only reach the decimeters (0.3049 m). However, only 6.30% of the total image number of oblique images was required to improve the elevation accuracy by one order of magnitude (0.0942 m). (2) An insignificant variation in internal accuracy was reported in oblique imaging-assisted datasets. In particular, SfM-MVS technology exhibited high reproducibility for repeated observations. By changing the number and position of oblique images, the external precision was able to increase effectively, the elevation error distribution was improved to become more concentrated and stable. Accordingly, a repeated observation method only including a few oblique images has been proposed and demonstrated in this study, which could optimize the elevation and improve the accuracy. The research results could provide practical and effective technology reference strategies for geomorphological surveys and repeated observation analyses in sophisticated mountain environments.

Comparison of Data from Rain Gauges and the IMERG Product to Analyse Precipitation in Mountain Areas of Central Italy

In central Italy, particularly in the Umbria-Marche Apennines, there are some complete, high-altitude weather stations, which are very important for assessing the climate in these areas. The mountain weather stations considered in this study were Monte Bove Sud (1917 m.a.s.l.), Monte Prata (1816 m.a.s.l.) and Pintura di Bolognola (1360 m.a.s.l.). The aim of this research was to compare the differences between the precipitation measured by the rain gauges and the data obtained by satellite using the IMERG algorithm, at the same locations. The evaluation of possible errors in the estimation of precipitation using one method or the other is fundamental for obtaining a reliable estimate of precipitation in mountain environments. The results revealed a strong underestimation of precipitation for the rain gauges at higher altitudes (Monte Bove Sud and Monte Prata) compared to the same pixel sampled by satellite. On the other hand, at lower altitudes, there was a better correlation between the rain gauge value and the IMERG product value. This research, although localised in well-defined locations, could help to assess the problems in rain detection through mountain weather stations.

Snow Avalanche Assessment in Mass Movement-Prone Areas: Results from Climate Extremization in Relationship with Environmental Risk Reduction in the Prati di Tivo Area (Gran Sasso Massif, Central Italy)

Mass movements processes (i.e., landslides and snow avalanches) play an important role in landscape evolution and largely affect high mountain environments worldwide and in Italy. The increase in temperatures, the irregularity of intense weather events, and several heavy snowfall events increased mass movements’ occurrence, especially in mountain regions with a high impact on settlements, infrastructures, and well-developed tourist facilities. In detail, the Prati di Tivo area, located on the northern slope of the Gran Sasso Massif (Central Italy), has been widely affected by mass movement phenomena. Following some recent damaging snow avalanches, a risk mitigation protocol has been activated to develop mitigation activities and land use policies. The main goal was to perform a multidisciplinary analysis of detailed climatic and geomorphological analysis, integrated with Geographic Information System (GIS) processing, to advance snow avalanche hazard assessment methodologies in mass movement-prone areas. Furthermore, this work could represent an operative tool for any geomorphological hazard studies in high mountainous environments, readily available to interested stakeholders. It could also provide a scientific basis for implementing sustainable territorial planning, emergency management, and loss-reduction measures.

Upslope migration of snow avalanches in a warming climate

Snow is highly sensitive to atmospheric warming. However, because of the lack of sufficiently long snow avalanche time series and statistical techniques capable of accounting for the numerous biases inherent to sparse and incomplete avalanche records, the evolution of process activity in a warming climate remains little known. Filling this gap requires innovative approaches that put avalanche activity into a long-term context. Here, we combine extensive historical records and Bayesian techniques to construct a 240-y chronicle of snow avalanching in the Vosges Mountains (France). We show evidence that the transition from the late Little Ice Age to the early twentieth century (i.e., 1850 to 1920 CE) was not only characterized by local winter warming in the order of +1.35 °C but that this warming also resulted in a more than sevenfold reduction in yearly avalanche numbers, a severe shrinkage of avalanche size, and shorter avalanche seasons as well as in a reduction of the extent of avalanche-prone terrain. Using a substantial corpus of snow and climate proxy sources, we explain this abrupt shift with increasingly scarcer snow conditions with the low-to-medium elevations of the Vosges Mountains (600 to 1,200 m above sea level [a.s.l.]). As a result, avalanches migrated upslope, with only a relict activity persisting at the highest elevations (release areas >1,200 m a.s.l.). This abrupt, unambiguous response of snow avalanche activity to warming provides valuable information to anticipate likely changes in avalanche behavior in higher mountain environments under ongoing and future warming.

InSAR-based characterization of rock glacier movement in the Uinta Mountains, Utah, USA

Rock glaciers are a prominent component of many alpine landscapes and constitute a significant water resource in some arid mountain environments. Here, we employ satellite-based interferometric synthetic aperture radar (InSAR) between 2016 and 2019 to identify and monitor active and transitional rock glaciers in the Uinta Mountains (Utah, USA), an area of ∼3000 km2. We used mean velocity maps to generate an inventory for the Uinta Mountains containing 205 active and transitional rock glaciers. These rock glaciers are 11.9 ha in area on average and located at a mean elevation of 3308 m, where mean annual air temperature is −0.25 ∘C. The mean downslope velocity for the inventory is 1.94 cm yr−1, but individual rock glaciers have velocities ranging from 0.35 to 6.04 cm yr−1. To search for relationships with climatic drivers, we investigated the time-dependent motion of three rock glaciers. We found that rock glacier motion has a significant seasonal component, with rates that are more than 5 times faster during the late summer compared to the rest of the year. Rock glacier velocities also appear to be correlated with the snow water equivalent of the previous winter's snowpack. Our results demonstrate the ability to use satellite InSAR to monitor rock glaciers over large areas and provide insight into the environmental factors that control their kinematics.

Assessing the ecological value of dynamic mountain geomorphosites

Geoheritage is a component of geodiversity constituted by all the elements of geodiversity recognized by society for their particular values. The definition of these values, including the importance of geoheritage for biodiversity, plays a key role in the process of heritage recognition and geoconservation policymaking. In mountain environments, dynamic geomorphosites have a strong influence on plant diversity because the active geomorphological processes responsible for their formation act as renovators for habitats of pioneer species. In this paper, we propose criteria to assess the ecological value of dynamic mountain geomorphosites. We show that the interest of plant communities (species richness and presence of rare or protected species) and the influence of geomorphological processes on plant communities (disturbances, surface movement and soil) are fundamental criteria for assessing the ecological value in an exhaustive and objective way and that the question of the scale (local and national scales) is also a crucial parameter. We then illustrate this methodological proposal by evaluating the ecological value of three dynamic geomorphosites and a talus slope in the western Swiss Alps.

Local Perceptions of Climate Change and Adaptation Responses from Two Mountain Regions in Tanzania

Mountain environments and communities are disproportionately impacted by climate change. Changes in temperature are greater than at lower elevations, which affect the height of the cloud base and local rainfall patterns. While our knowledge of the biophysical nature of climate change in East Africa has increased in the past few years, research on Indigenous farmers’ perceptions and adaptation responses is still lacking, particularly in mountains regions. Semi-structured interviews were administered to 300 farmers on Mount Kilimanjaro (n = 150) and the Udzungwa Mountains (n = 150) in Tanzania across gender and wealth groups. Respondents in both mountains reported not only changes in rainfall and temperature, corresponding with meteorological data, but also a greater incidence of fog, wind, frost, and hailstorms—with impacts on decreased crop yields and increased outbreaks of pests. The most common adaptation strategies used were improved crop varieties and inputs. Wealthier households diversified into horticulture or animal rearing, while poorer households of Hehe ethnicity diversified to labour and selling firewood. Despite being climate change literate and having access to radios, most respondents used Indigenous knowledge to decide on planting dates. Our findings highlight how context and culture are important when designing adaptation options and argue for greater involvement of local stakeholders in adaptation planning using a science-with-society approach. Place-based results offer generalisable insights that have application for other mountains in the Global South.

Assessing and Projecting Surface Air Temperature Conditions Required To Sustain Permafrost in Japan

Permafrost covers a wide area of the Northern Hemisphere, including high-altitude mountainous areas even at mid-low latitudes. There is concern that the thawing of mountain permafrost can cause slope instability and substantially impact alpine ecosystems. However, permafrost in mountainous areas is difficult to observe, and detailed analyses have not been performed on its current distribution and future changes. Here, we show that the surface air temperature required to sustain Japan's mountain permafrost is estimated to decrease rapidly at present; most mountain permafrost in Japan is projected to disappear by the second half of the 21st century, and disappear very quickly in some places from approximately 2020–2030, regardless of climate scenarios. Our projections indicate that climate change has a considerable impact on mountain environments and that even if climate stabilization is achieved, Japan's mountain permafrost may almost disappear. It is important to consider measures to adapt to the changing mountain environment.