Inexistence of permafrost at the top of the Veleta peak (Sierra Nevada, Spain)

Characteristics of the Siberian coal basins permafrost: An example of Ytymdja depression

Ytymdja depression is one of the Mesozoic structures with discovered large coal deposits of the Aldan Upland. Lack of industrial development and farness from agglomerations explain the knowledge gap about the environmental conditions of the Ytymdja depression. A field monitoring network with existing deep boreholes was absorbed to investigate permafrost conditions and to assess potential impacts of local factors and climate change. This paper describes analyse temperatures at the depth down to 240 m by these boreholes with air and ground temperatures of the Ytymdja depression to determinate permafrost conditions. The research was carried out in a 1800 km² area of the South Yakutia, Siberia, using satellite imagery-based classification. The field investigations and analysis of ground temperatures indicated that permafrost underlies of the ground entire area of Ytymdja depression, but likely absent under large rivers. Permanent negative temperatures have been detected in the borehole, which shows evidence of the existing of widespread permafrost conditions nowadays in the coal basins in Siberia. Permafrost temperatures vary between -3.1 °C and -1.5 °C at 35 m below the surface, and annual ground temperatures at 1 m depth ranged from -4.9 °C to -1.2 °C. Thermal conductivity of rocks determined by individual core samples varies from 1.1 to 2.9 W m^-1 °C^-1 with geothermal heat flux in the permafrost zone of 0.02 W m^-2 and an increase in the zone below permafrost to 0.03 W m^-2. Spatial modelling for the entire territory of the Ytymdja depression deduced a continuous permafrost distribution with a thickness between 106 and 251 m. The considerable thickness of permafrost probably prevents the emission of greenhouse gases from coal seams into the atmosphere, but detailed studies in this direction have yet to be carried out.

Long-term ecological changes in Mediterranean mountain lakes linked to recent climate change and Saharan dust deposition revealed by diatom analyses

Anthropogenic climate change and the recent increase of Saharan dust deposition has had substantial effects on Mediterranean alpine regions. We examined changes in diatom assemblage composition over the past ~180 years from high-resolution, dated sediment cores retrieved from six remote lakes in the Sierra Nevada Mountains of Southern Spain. In all lakes, changes in diatom composition began over a century ago, but were more pronounced after ~1970 CE, concurrent with trends in rising regional air temperature, declining precipitation, and increased Saharan dust deposition. Temperature was identified as the main predictor of diatom assemblage changes, whereas both Saharan dust deposition drivers, the Sahel precipitation index and the winter North Atlantic Oscillation, were secondary explanatory variables. Diatom compositional shifts are indicative of lake alkalinization (linked to heightened evapoconcentration and an increase in calcium-rich Saharan dust input) and reduced lake water turbulence (linked to lower water levels and reduced inflows to the lakes). Moreover, decreases in epiphytic diatom species were indicative of increasing aridity and the drying of catchment meadows. Our results support the conclusions of previous chlorophyll-a and cladoceran-based paleolimnological analyses of these same dated sedimentary records which show a regional-scale response to climate change and Saharan dust deposition in Sierra Nevada lakes and their catchments during the 20th century. However, diatom assemblages seem to respond to different atmospheric and climate-related effects than cladoceran assemblages and chlorophyll-a concentrations. The recent impact of climate change and atmospheric Saharan deposition on lake biota assemblages and water chemistry, as well as catchment water availability, will have important implications for the valuable ecosystem services that the Sierra Nevada provides.

Contamination of Arctic Lakes with Persistent Toxic PAH Substances in the NW Part of Wedel Jarlsberg Land (Bellsund, Svalbard)

The expansion of glacier-free areas in polar regions favours the appearance of lakes in the non-glaciated parts of glacier basins. This paper presents the differentiation of organic compound concentrations in fifty-four Arctic lakes collected in four locations (Logne Valley, in the vicinity of the Scott, Renard and Antonia glaciers). We cover meteorological measurements, chemical analysis of sixteen dioxin-like compounds (Polycyclic Aromatic Hydrocarbons (PAHs)), formaldehyde (HCHO), sum parameters of phenolic compounds (∑phenols) and dissolved organic carbon (DOC). The most contaminated with PAH compounds were lakes exposed to the influence of the Greenland Sea (Logne Valley lakes) and to the prevailing winds (Scott and Renard lakes). Interpretation of the PAH compounds results allowed for identification of pyrogenic sources as the main sources of PAH compounds in the year 2012. The highest levels of HCHO and ∑phenols were observed for the Scott lakes, while the highest DOC levels were noted in Antonia lakes.

Comparison of hydrochemistry and organic compound transport in two non-glaciated high Arctic catchments with a permafrost regime (Bellsund Fjord, Spitsbergen)

An increase in air temperature related to climate change results in the retreat of glaciers, the degradation of permafrost, and the expansion of glacier-free areas in the polar regions. All these processes lead to changes in the Arctic landscape. They influence the hydrochemistry of streams and rivers fed by glaciers and thawing permafrost. In this study, we examine eighty two water samples from two non-glaciated catchments with snow-permafrost regime: the Tyvjobekken Creek and the Reindeer Creek (NW Wedel-Jarlsberg Land, Spitsbergen). We cover hydrometeorological measurements, fluctuations of physicochemical parameters (pH, specific electrolytic conductivity (SEC)), and the presence of selected organic compounds (dissolved organic carbon (DOC), formaldehyde (HCHO), ∑phenols). The obtained levels of DOC (0.061-0.569mgCL^-1) and HCHO (<LOD-0.140mgL^-1) in water samples of these two high Arctic creeks confirm the role of the melting permafrost as a rich source of terrestrial organic carbon and organic pollutants, as well as the impact of rainfall on surface water chemistry. It was found that fluctuations of physicochemical indices (pH, SEC, DOC) were related to changes in mean daily discharge of Reindeer Creek (0.012-0.034m³s^-1) and Tyvjobekken Creek (0.011-0.015m³s^-1) (r>0.40). The Tyvjobekken Creek catchment, in contrast to Reindeer Creek catchment, turned out to be resistant to rapid changes in meteorological conditions (r<0.10) and surface runoff. The processes of permafrost thawing, calcium carbonate dissolution, and biogeochemical "breathing" of soils proved to be crucial for the development of water chemistry. In conclusion, the surface water chemistry of the Reindeer Creek was found to result from the mutual influence of hydrometeorological indices and the biogeochemical environment of the catchment.

Impacts of climate warming on the frozen ground and eco-hydrology in the Yellow River source region, China

The Yellow River source region is located in the transition region between permafrost and seasonally frozen ground on the northeastern Qinghai-Tibet Plateau. The region has experienced severe climate change, especially air temperature increases, in past decades. In this study, we employed a geomorphology-based eco-hydrological model (GBEHM) to assess the impacts of climate change on the frozen ground and eco-hydrological processes in the region. Based on a long-term simulation from 1981 to 2015, we found that the areal mean maximum thickness of seasonally frozen ground ranged from 1.1-1.8m and decreased by 1.2cm per year. Additionally, the ratio of the permafrost area to the total area decreased by 1.1% per year. These decreasing trends are faster than the average in China because the study area is on the sensitive margin of the Qinghai-Tibet Plateau. The annual runoff exhibited variations similar to those of the annual precipitation (R²=0.85), although the annual evapotranspiration (ET) exhibited an increasing trend (14.3mm/10a) similar to that of the annual mean air temperature (0.66°C/10a). The runoff coefficient (annual runoff divided by annual precipitation) displayed a decreasing trend because of the increasing ET, and the vegetation responses to climate warming and permafrost degradation were manifested as increases in the leaf area index (LAI) and ET at the start of the growing season. Furthermore, the results showed that changes to the frozen ground depth affected vegetation growth. Notably, a rapid decrease in the frozen ground depth (< -3.0cm/a) decreased the topsoil moisture and then decreased the LAI. This study showed that the eco-hydrological processes in the headwater area of the Yellow River have changed because of permafrost degradation, and these changes could further influence the water resources availability in the middle and lower reaches of the basin.

Spatial characterization of glacial and periglacial landforms in the highlands of Sierra Nevada (Spain)

Sierra Nevada constitutes the southernmost and highest massif in the Iberian Peninsula, with elevations exceeding 3000m. Two large glacial advances were recorded during the Last Glaciation and several minor advances occurred until the Early Holocene. Since then, periglacial activity has prevailed above 2500m. Here, we present a new and more accurate geomorphological map of the highlands of Sierra Nevada, integrating in a GIS environment i) high resolution satellite imagery, ii) topographic data, and iii) field observations. This approach has allowed a better characterization of the spatial extent of cold-climate morphogenic processes and associated landforms formed during the Last Glaciation and subsequent deglaciation. Despite its extension and high altitude, the steep relief of Sierra Nevada and its southern location conditioned a significantly lower glaciated surface (104.6km²) with respect to other Iberian massifs. We have also inferred the paleoclimatic conditions of the study area through the calculation of Equilibrium Line Altitudes (ELAs). The distribution of the lowest moraines suggests an ELA for the maximum glacial extent at 2525m in the northern slope and 2650m in the southern side, increasing towards the east. Local ELA differences are related to: (i) the influence of the warmer Mediterranean Sea in contrast to the cooler Atlantic Ocean, (ii) the climate with more continental characteristics on the northern slope, and (iii) the microscale control of the local topography. Mean annual air temperatures in the ice-free summit plateaus were between -4/-6°C during the maximum local glacial extent, determining permafrost conditions with intense periglacial dynamics. Rock glaciers and protalus lobes developed until 2500m, the lowest boundary for permafrost regime. The distribution of other glacial and periglacial landforms within the limits of the maximum ice extent provides evidence to better understand the extent of subsequent glacial stages and post-glacial landscape evolution in Sierra Nevada.