Schmidt-hammer exposure-age dating (SHD) is a numerical, calibrated-age dating technique based on the degree of weathering of rock surfaces. The Schmidt hammer measures the hardness or strength of a ...rock surface by means of R-values (rebound values), which are produced as the hammer impacts the surface. Age calibration is carried out with reference to at least two surfaces of known age (control surfaces). Mean R-values then yield numerical estimates of the time elapsed since exposure of rock surfaces to subaerial weathering. Under favourable circumstances with a sufficiently large number of impacts, SHD has an age resolution of 300–500 years for rock surfaces exposed during the Holocene and Late Pleistocene, and a current age range of ~25 ka. Accurate independent dating of control surfaces and careful selection of sites to reduce the effects of lithological variability are essential. R-value distributions are an important aid in the interpretation of SHD ages from active and relict, synchronous and diachronous, single and multiple-event surfaces. Important research applications have been made within the fields of Quaternary geochronology, palaeoenvironmental reconstruction, geomorphology and subaerial processes, and landscape dynamics. SHD has been found particularly useful in relation to boulder deposits and bedrock surfaces in glacial and periglacial environments. There is much untapped potential in coastal, temperate and tropical landscapes wherever rock surfaces are exposed to undisturbed rock weathering. The advantages and limitations of SHD compare favourably with the complementary exposure-age technique of terrestrial cosmogenic nuclide dating (TCND). The capability to provide a large number of exposure ages at low cost, and non-destructively in sensitive natural and artefactual settings, are special strengths of SHD.
Mountain depositional landforms are important units for freshwater supply in regions with water deficits and significant droughts during the summer season. In the Northern Patagonian Andes, the cold ...climatic events during the Pleistocene period left a large number of glacial and periglacial depositional landforms, among which a glacial cirque called La Hoya stands out. An analysis of geomorphological landforms, climatic data, soil temperature, flows in springs and streams, electrical conductivity measurements, and stable isotope determination of water, were made to study the hydrological role of these depositional mountain landforms. In this region, precipitations are concentrate during the winter season when an important snow cover accumulates and persists until spring. During winter and spring seasons, part of the snowmelt infiltrates, being kept in solid states inside the depositional landforms, and part of it contributes to the runoff between winter and summer. At the ends of spring and early summer, the snowmelt is the main water contribution to the La Hoya watershed. During late summer and autumn, the most important water contribution is from groundwater discharge. Where glacial ice is absent and the presence of permafrost is limited or non-existent, morphosedimentary units are important landforms for water storage and streams sustenance. This is the case of the city of Esquel, which depends exclusively on the “Los Bandidos” stream for water supply, which is sustained throughout the year by these landforms. The increase in temperature and the decrease in precipitation in this region highlights the importance of the high-altitude depositional landforms for the capture, storage, and distribution of water resources in the Northern Patagonian Andes.
Display omitted
•High-altitude depositional units are reservoirs in regions with water deficits.•Northern Patagonian Andes are in the humid to semiarid climate transitional region.•Glacial and periglacial depositional landforms release the water in warmer seasons.•Groundwater discharge sustains streams in the dry season.•High-altitude depositional landforms constitute effective annual water flow regulators.
Nordenskiöld Land in Central Spitsbergen, Svalbard is characterized as a high latitude, high relief periglacial landscape with permafrost occurring both in mountains and lowlands. Freezing and ...thawing of the active layer causes seasonal frost heave and thaw subsidence, while permafrost-related mass-wasting processes induce downslope ground displacements on valley sides. Displacement rate varies spatially and temporally depending on environmental factors. In our study, we apply Satellite Synthetic Aperture Radar Interferometry (InSAR) to investigate the magnitude, spatial distribution and timing of seasonal ground displacements in and around Adventdalen using TerraSAR-X StripMap Mode (2009–2017) and Sentinel-1 Interferometric Wide Swath Mode (2015–2017) SAR images. First, we show that InSAR results from both sensors highlight consistent patterns and provide a comprehensive overview of the distribution of displacement rates. Secondly, two-dimensional (2D) TerraSAR-X InSAR results from combined ascending and descending geometries document the spatial variability of the vertical and east-west horizontal displacement rates for an average of nine thawing seasons. The remote sensing results are compared to a simplified geomorphological map enabling the identification of specific magnitudes and orientations of displacements for 14 selected geomorphological units. Finally, June to December 2017 6-day sampling interval Sentinel-1 time series was retrieved and compared to active layer ground temperatures from two boreholes. The timing of the subsidence and heave detected by InSAR matches the thawing and freeze-back periods measured by in-situ sensors. Our results highlight the value of InSAR to obtain landscape scale knowledge about the seasonal dynamics of complex periglacial environments.
Display omitted
•InSAR detecting thaw subsidence, frost heave and creep in Svalbard•Study of spatial variability of InSAR displacements compared with geomorphology•Identification of specific 2D InSAR patterns for 14 geomorphological units•Detection of seasonal inversion from subsidence to heave using Sentinel-1•Correspondence between displacement and ground temperature seasonal variations
Mountain periglacial environments are important sites of water storage and distribution to downstream areas. The present study was conducted in the “La Hoya” subwatershed, in the Northern Patagonian ...Andes. La Hoya is the main water recharge area of the “Los Bandidos” watershed, from which fresh water is used for human consumption. The aim of this work was to study the hydrogeochemical and isotopic composition of this watershed and evaluate the hydrological and ionic contributions from periglacial landforms, accounting for annual water flow hydrodynamics and climatic trends. Meteorological data, spring and stream flows, electrical conductivity, isotopic content, and major ion concentrations of snow, spring, and stream samples were analyzed from December 2020 to November 2021. Snow melting is the main water contribution to the mountain watershed. Part of the snowmelt drains superficially during the melting season and part of it infiltrates into periglacial landforms, where it is provisionally stored as groundwater. Chemical weathering during groundwater-rock interaction is the main process that regulates water chemical composition, dominating the dissolution of CO2(g) and carbonates, which controls the waters to be of the Ca–HCO3 to Ca–Mg–HCO3 facies type of groundwater. The climate tendency for the last sixty years in this area reflects a decrease in precipitation and an increase in temperatures. This climate trend could affect periglacial environments, modifying the chemical and physical processes that take place in them, which could affect the chemical water quality and the hydrological behavior of the watershed. The chemical and hydrological behavior in watersheds for human consumption should be specially monitored for better use of this resource.
•Periglacial landforms store the snowmelt water until the driest season.•Groundwater-rock interaction controls the hydrochemistry in periglacial watersheds.•CO2 and carbonates dissolution controls the Ca–HCO3 and Ca–Mg–HCO3 chemical facies.•Hydrochemical-isotopic signal varies depending on snowmelt or springs contribution.•Climate change could affect the geochemistry in periglacial mountain areas.
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.
Display omitted
•We produced a new accurate geomorphological map of Sierra Nevada National Park.•Maximum glacier extent during the Last Glaciation reached 104.6km2.•Equilibrium Line Altitude was at 2525m in northern slopes and 2650m in southern.•Mean annual temperatures at the highest lands ranged between −4 and −6°C.•Permafrost conditions developed until elevations of 2500m.
The representation of permafrost and seasonally frozen ground and their projected twenty-first century trends is assessed in the Community Climate System Model, version 4 (CCSM4) and the Community ...Land Model version 4 (CLM4). The combined impact of advances in CLM and a better Arctic climate simulation, especially for air temperature, improve the permafrost simulation in CCSM4 compared to CCSM3. Present-day continuous plus discontinuous permafrost extent is comparable to that observed 12.5 × 10⁶ versus (11.8–14.6) × 10⁶ km², but active-layer thickness (ALT) is generally too thick and deep ground (>15 m) temperatures are too warm in CCSM4. Present-day seasonally frozen ground area is well simulated (47.5 × 10⁶ versus 48.1 × 10⁶ km²). ALT and deep ground temperatures are much better simulated in offline CLM4 (i.e., forced with observed climate), which indicates that the remaining climate biases, particularly excessive high-latitude snowfall biases, degrade the CCSM4 permafrost simulation.
Near-surface permafrost (NSP) and seasonally frozen ground (SFG) area are projected to decline substantially during the twenty-first century representative concentration projections (RCPs); RCP8.5: NSP by 9.0 × 10⁶ km², 72%, SFG by 7.1 × 10⁶, 15%; RCP2.6: NSP by 4.1 × 10⁶, 33%, SFG by 2.1 × 10⁶, 4%. The permafrost degradation rate is slower (2000–50) than in CCSM3 by ∼35% because of the improved soil physics. Under the low RCP2.6 emissions pathway, permafrost state stabilizes by 2100, suggesting that permafrost related feedbacks could be minimized if greenhouse emissions could be reduced. The trajectory of permafrost degradation is affected by CCSM4 climate biases. In simulations with this climate bias ameliorated, permafrost degradation in RCP8.5 is lower by ∼29%. Further reductions of Arctic climate biases will increase the reliability of permafrost projections and feedback studies in earth system models.
ABSTRACTWe present a field-based reconstruction of the geomorphology in the Subtropical Andean mountains of the Limarí basin, semiarid central Chile (30–31° S). Fieldwork campaigns and remote-sensing ...analysis served for detailed geomorphological mapping at four formerly glaciated valleys in the heads of the Combarbalá and Río Hurtado sub-basins. We identify a mosaic of glacial, periglacial, and paraglacial landforms. Glacial landforms include a massive dead-ice moraine complex, with thermokarst and debris-filled fractures suggesting former ice-cored moraine degradation. This landform is superimposed by transversal and arcuate ridges suggesting active-ice processes. Periglacial landforms such as rock glaciers, gelifluction, and protalus lobes occur in cirques and U-shaped valleys, but also on moraine deposits. Paraglacial processes are indicated by talus accumulation in those formerly glaciated slopes. The geomorphological imprint is evidence for the interaction and succession between glacial, periglacial, and paraglacial dynamics from the Late Pleistocene to the present.
High-resolution aerial images allow detailed analyses of periglacial landforms, which is of particular importance in light of climate change and resulting changes in active layer thickness. The aim ...of this study is to show possibilities of using UAV-based photography to perform spatial analysis of periglacial landforms on the Demay Point peninsula, King George Island, and hence to supplement previous geomorphological studies of the South Shetland Islands.
Photogrammetric flights were performed using a PW-ZOOM fixed-winged unmanned aircraft vehicle. Digital elevation models (DEM) and maps of slope and contour lines were prepared in ESRI ArcGIS 10.3 with the Spatial Analyst extension, and three-dimensional visualizations in ESRI ArcScene 10.3 software.
Careful interpretation of orthophoto and DEM, allowed us to vectorize polygons of landforms, such as (i) solifluction landforms (solifluction sheets, tongues, and lobes); (ii) scarps, taluses, and a protalus rampart; (iii) patterned ground (hummocks, sorted circles, stripes, nets and labyrinths, and nonsorted nets and stripes); (iv) coastal landforms (cliffs and beaches); (v) landslides and mud flows; and (vi) stone fields and bedrock outcrops.
We conclude that geomorphological studies based on commonly accessible aerial and satellite images can underestimate the spatial extent of periglacial landforms and result in incomplete inventories. The PW-ZOOM UAV is well suited to gather detailed geomorphological data and can be used in spatial analysis of periglacial landforms in the Western Antarctic Peninsula region.
Periglacial processes and landforms together with the presence of permafrost are among the most relevant geomorphological elements in the northern Antarctic Peninsula region. Their distribution ...affects the hydrology and has consequences for the ecosystems of the ice-free areas. In this paper a compilation of the different types of periglacial landforms and processes occurring in the South Shetland Islands is carried out and their spatial distribution is analysed. Furthermore, the relationships of the periglacial landforms with local conditions and permafrost distribution have been taken into account. A total of thirty three types of periglacial landforms were identified and considered in this work. Patterned ground and stone fields are the most common periglacial landforms, which are located within a wide altitudinal range and mainly on platforms. Field studies, aerial photograph and satellite imagery interpretation were implemented to produce detailed maps from ten areas with different geological, geomorphological and relief characteristics, including the largest and most relevant ice-free areas within the archipelago, showing the presence and spatial distribution of periglacial landforms. This work shows that the periglacial environment, primarily conditioned by the regional climatic conditions, has a great diversity in the studied region and that the distribution of the periglacial landforms is also related to local relief and geomorphological characteristics, lithology, hydrogeology, and presence of permafrost where altitude plays an important role. Periglacial phenomena are widespread above 10m a.s.l. and are especially active on slopes and platforms between 30 and 100m a.s.l. The spatial distribution of periglacial landforms helps to identify the presence of permafrost that is dominant above 25–30m a.s.l. and more than 70% of the surface is occupied by active layer-related landforms.
Pleistocene periglacial activity in eastern Australia was widespread and has been predicted to have extended along much of the east coast. This paper describes block deposits in the New England ...Tablelands, Australia, as far north as 30°S. These deposits are characterized by openwork blocks on slopes below the angle of repose. The deposits are positioned where frost cracking was significant and range in area up to 8 ha. Surface exposure dating using the cosmogenic nuclide 36Cl from four block deposits indicate all sites were active late during the last glacial cycle, with a concentration of activity between 15–30 ka. Modern temperature measurements from block deposits highlight the importance of local topography for promoting freezing. Periglacial deposits are likely to have been more extensive than previously recognized at these northern limits, and mean annual temperature more than 8°C colder than today.
PDF
