Cirque Research Articles

Palaeoglaciation in the Low Latitude, Low Elevation Tropical Andes, Northern Peru

Characterising glaciological change within the tropical Andes is important because tropical glaciers are sensitive to climate change. Our understanding of glacier dynamics and how tropical glaciers respond to global climate perturbations is poorly constrained. Studies of past glaciation in the tropical Andes have focused on locations where glaciers are still present or recently vacated cirques at high elevations. Few studies focused on lower elevation localities because it was assumed glaciers did not exist or were not as extensive. We present the first geomorphological evidence for past glaciations of the Lagunas de Las Huaringas, northern Peru, at elevations of 3,900–2,600 m a.s.l. Mapping was conducted using remotely-sensed optical imagery and a newly created high-resolution (∼2.5 m) digital elevation model (DEM). The area has abundant evidence for glaciation, including moraines, glacial cirques, hummocky terrain, glacial lineations and ice-sculpted bedrock. Two potential models for glaciation are hypothesised: 1) plateau-fed ice cap, or 2) valley glaciation. Assuming glaciers reached their maximum extent during the Local Last Glacial Maximum (LLGM), between 23.5 ± 0.5 and 21.2 ± 0.8 ka, the maximum reconstructed glacial area was 75.6 km2. A mean equilibrium line altitude (ELA) of 3,422 ± 30 m was calculated, indicating an ELA change of −1,178 ± 10 m compared to modern snowline elevation. There is an east to west ELA elevation gradient, lower in the east and higher in the west, in-line with modern day transfer of moisture. Applying lapse rates between 5.5 and 7.5°C/km provides a LLGM temperature cooling of between 6.5–8.8°C compared to present. These values are comparable to upper estimates from other studies within the northern tropical Andes and from ice-core reconstructions. The mapping of glacial geomorphology within the Lagunas de las Huaringas, evidences, for the first time, extensive glaciation in a low elevation region of northern Peru, with implications for our understanding of past climate in the sub-tropics. Observations and reconstructions support a valley, rather than ice cap glaciation. Further work is required to constrain the timing of glaciations, with evidence of moraines younger than the LLGM up-valley of maximum glacier extents. Numerical modelling will also enable an understanding of the controls of glaciation within the region.

A combination of cosmogenic and Schmidt hammer exposure dating in the study of the deglaciation timing of Sierra de Guadarrama National Park (Spain)

ABSTRACT The objective of the work is to calibrate the Schmidt hammer exposure dating (SHD) method in the Sierra de Guadarrama National Park in correlation with the dates previously obtained by Cosmogenic Radiation Exposure (CRE) dating methods. The dates were recalculated according to the new production models of 36Cl and 10Be cosmogenic isotopes. For this purpose, three glacial cirques were selected (Dos Hermanas, Laguna and Pepe Hernando), located on the eastern slope of Peñalara Peak, Spain (40°51'N, 3°57'O; 2428 m), the highest altitude of this mountain range. The application of the SHD method seems to be influenced neither by the different altitude of the samples nor by their height with respect to the current ground level. The degree of roughness of the rock surfaces (gneiss) has a slight influence, but does not change the actual volume of the results. The results of this work show a clear relationship between the CRE ages and the SHD R-values. The oldest landforms (31–19 ka) give mean values R < 50, both for moraine boulders and polished bedrock. The boulders of a rock glacier (16–15 ka) and the boulders of the innermost moraine yielded higher values: R-value >50. The youngest polished bedrock surface, located under the Peñalara Peak (12–11 ka), yielded R-value >60.

New hydrogeological results on the Groundwater Dependent Ecosystem of the Pilato Lake (Sibillini Mts, Central Italy)

Located at an altitude of about 1950 m a.s.l. in a glacial cirque of Mount Vettore (Monti Sibillini National Park - Central Italy), Pilato Lake is one of the few glacial lakes existing in the Apennines. Due to the endemic presence of the crustaceous Chirocephalus marchesonii, the Pilato Lake was in the past mainly studied from the biological viewpoint, but hydrogeological information on this groundwater dependent ecosystem is scarce. Furthermore, for investigating the lake drying in the recent 2017, 2019 and 2020 summers, the seasonal lowering of lake levels during 2010, 2012 and 2014-2020 was reconstructed. It resulted that in the preseismic years, the lake emptying was slower than in the post-seismic time. It is then supposed that seismic quaking induced an increase in permeability and, consequently, increased infiltration velocity through the lake sustaining surficial (detrital and glacial) and/or bedrock deposits towards the subsurface. More frequent summer dryings of the lake are then supposed for the next future. The hydrogeological conceptual model of the study area showed that the refilling process of the lake is driven by snow and rain precipitations. The air temperatures during 2017-2020 and their effects on evaporation from lake and on actual evapotranspiration were estimated. The infiltration through sustaining sediments was calculated and the estimation with time of lake wet surface and lake volume variations, and then bulk permeability of sustaining sediments, were evaluated as well.

Morphological differences of longitudinal profiles between glacial cirques and non-glacial valley heads, described by mathematical fitting

Glacial cirques have specific concave longitudinal profiles different from those of valley heads without glacial imprint. The degree of deepening of valley heads can be used to determine the extent of past mountain glaciation and serve as a tool in palaeoenvironmental reconstructions. The aim of the present paper is to compare longitudinal profiles of glacial cirques and non-glaciated valley heads. For this purpose, we analyzed an alpine area with classic well-developed glacial cirques in the Central Alps (Austria) and a mid-mountain area of the High Sudetes (Czech Republic/Poland) with both cirques and non-glaciated valley heads. We described each valley head by c-value function fitting using longitudinal profiles obtained from detailed laser-derived digital elevation models and tested them statistically. The results show, with high accuracy of fitting, significant differences between c-values of glacial cirques and those of non-glacial valley heads. This newly presented approach could be useful for distinguishing between valley heads of fluvial origin and glacial cirques, as well as for evaluating the degree of cirque development.

Role of rock glaciers and other high-altitude depositional units in the hydrology of the mountain watersheds of the Northern Patagonian Andes

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.

Factors influencing the ground thermal regime in a mid-latitude glacial cirque (Hoyo Empedrado, Cantabrian Mountains, 2006–2020)

Air and near-surface ground temperatures were measured using dataloggers over 14 years (2006–2020) in 10 locations at 2262 to 2471 m.a.s.l. in a glacial cirque of the Cantabrian Mountains. These sites exhibit relevant differences in terms of substrate, solar radiation, orientation, and geomorphology. Basal temperature of snow (BTS) measurements and electrical resistivity tomography of the talus slope were also performed. The mean annual near-surface ground temperatures ranged from 5.1 °C on the sunny slope to 0.2 °C in the rock glacier furrow, while the mean annual air temperature was 2.5 °C. Snow cover was inferred from near-surface ground temperature (GST) data, estimating between 130 and 275 days per year and 0.5 to 7.1 m snow thickness. Temperature and BTS data show that the lowest part of the talus slope and the rock glacier furrow are the coldest places in this cirque, coinciding with a more persistent and thickest snow cover. The highest temperatures coincide with less snow cover, fine-grained soils, and higher solar radiation. Snow cover has a primary role in controlling GST, as the delayed appearance in autumn or delayed disappearance in spring have a cooling effect, but no correlation with mean annual near-surface ground temperatures exists. Heavy rain-over-snow events have an important influence on the GST. In the talus slope, air circulation during the snow-covered period produces a cooling effect in the lower part, especially during the summer. Significant inter-annual GST differences were observed that exhibited BTS limitations. A slight positive temperature trend was detected but without statistically significance and less prominent than nearby reference official meteorological stations, so topoclimatic conditions reduced the more global positive temperature trend. Probable existence of permafrost in the rock glacier furrow and the lowest part of the talus slope is claimed; however, future work is necessary to confirm this aspect.

The origin and collapse of rock glaciers during the Bølling-Allerød interstadial: A new study case from the Cantabrian Mountains (Spain)

During the Late Pleistocene, the main mountain ranges of the Iberian Peninsula were covered by small icefields and cirque and alpine glaciers. The deglaciation triggered paraglacial processes that generated landforms, mostly within the ice-free glacial cirques. In this research we analyse the deglaciation process in the Muxivén Cirque (42°15′N – 6°16′W), in the upper Sil River Basin, which includes some of the largest relict rock glaciers of the Cantabrian Mountains. We addressed this objective by means of accurate geomorphological reconstructions, sedimentological analysis, Schmidt-hammer surface weathering measurements and a dataset of 10 10Be Cosmic-Ray Exposure ages. Results reveal that after ~16 ka, glaciers retreated to the bottom of the cirques at the headwaters of the valley, leaving the walls free of ice and triggering rock avalanches onto the remnants of these glaciers. This paraglacial process supplied debris to a small glacier within Muxivén Cirque, which transformed in two rock glaciers. These debris isolated the ice inside the rock glaciers only for a very short period of time and ended up melting completely before the Younger Dryas. The lower sector of the largest one stabilized at 14.5 ± 1.5 ka, while the upper sector remained active until 13.5 ± 0.8 ka. Previous to the stabilization of the lower sector of the northern rock glacier, at its margin a high-energy debris avalanche occurred at ~14.0 ± 0.9 ka. These data agree with previous research, corroborating the paraglacial origin of most Iberian rock glaciers during the Bølling-Allerød interstadial.

Post-glacial evolution of alpine environments in the western Mediterranean region: The Laguna Seca record

In an effort to understand how alpine environments from the western Mediterranean region responded to climate variations since the last glacial-interglacial transition, a detailed chronological control and sedimentological analysis, supported by magnetic susceptibility, total organic carbon and C/N data, were carried out on the sedimentary record of Laguna Seca (LS). This is a latitudinal and altitudinally (2259 masl) key alpine wetland site located in the easternmost area of the Sierra Nevada, southern Iberian Peninsula, where sediments accumulated during Heinrich Stadial 1, Bølling-Allerød (B-A) and the Younger Dryas (YD) - previously unrecorded in alpine Sierra Nevada. Climate controlled sedimentation in LS and three coarse-grained and one fine-grained facies association are differentiated, which help us decipher the paleoenvironmental evolution of LS: (1) subaerial cohesionless debris flows during a paraglacial stage; (2) till or nival diamicton during a small glacier/nivation hollow stage; (3) massive mudstone by suspension settling of clays into standing water during a lacustrine stage; and (4) frost-shattering breccia deposited inside the lacustrine stage, probably during the YD, and linked to a periglacial substage. The development of a previously existing small glacial cirque during the Last Glacial Maximum (LGM) in the LS basin at an elevation between 2500 and 2300 m could be supported by the important availability of slope sediments glacially-conditioned such as debris flows, reworked by paraglacial slope processes during the first deglaciation stages, confirming previous studies of landforms in the catchment area and the LGM-Equilibrium Line Altitude estimation above 2400 masl in Sierra Nevada. Mean sediment accumulation rates in the LS sedimentary units (4.21 and 0.28 mm/yr during the paraglacial - small glacier/nivation stage and the lacustrine stage, respectively) confirm that geomorphic activity accelerated just after glaciers retreated due to a slope adjustment and high availability of glacially conditioned sediments. An abrupt change in paleoenvironmental and paleoclimatic conditions occurred in LS at ∼ 15.7 cal kyr BP. This change was probably due to an increase in temperature and precipitation in the western Mediterranean region during the B-A. At LS, this resulted in significant ice-melt, forming a deep-water lake in LS with important organic matter contribution until the end of the Early Holocene (except in the YD when the lake level probably dropped), but elsewhere a general glacier recession in the Sierra Nevada and an expansion of the Mediterranean forest in the southern Iberian Peninsula. Finally, the general long-term aridification that occurred during the Middle Holocene until the present in the western Mediterranean region triggered an important environmental change transforming LS into an ephemeral wetland with an increase in aquatic productivity.

Cirque lakes of Anatolia

Başta sirk gölleri olmak üzere, buzul gölleri Anadolu’daki yüksek dağlık alanların alpin kuşağındayer alan en önemli gölleri oluşturmaktadır. Anadolu’daki buzul jeomorfolojisi ve Kuvaterner buzullaşmakoşulları hakkında birçok çalışma yapılmış olmasına rağmen sirk gölleri yeterince incelenmemiştir.Bu eksiklikten dolayı bu çalışmada Anadolu’daki tüm sirk göllerinin dağılışı ve morfometriközellikleri CBS tabanlı olarak incelenmiştir. Uydu görüntüleri ve topografya haritaları üzerinden yapılanharitalama çalışmalarında 28 farklı kütle üzerinde toplam 660 adet sirk gölü tespit edilmiştir.Alansal dağılış özelliklerine göre sirk göllerinin çok büyük bir bölümü (%77) Doğu Karadeniz Dağlarıüzerinde bulunmaktadır ve bu dağlık alanlarda sirk gölü/sirk sayısı oranı (G/S oranı) %30’a ulaşmaktadır.Batı ve Orta Toroslar’da buzullaşmaya uğramış birçok kütle ve yüzlerce sirk bulunmasınarağmen sirk gölü sayısı çok azdır ve birçok kütle üzerinde hiç sirk gölü yer almamaktadır (G/S oranı0’dır). Bu durumun oluşmasında litolojik koşullar büyük etkiye sahiptir. Batı ve Orta Toroslar’da buzullaşmayauğramış kütleler karstik birimlerden oluşurken, Doğu Karadeniz Dağları karstik olmayanvolkanik ve intrusif birimlerden oluşmaktadır. Morfometrik hesaplamalara göre Anadolu’daki tümsirk göllerinin ortalama yükseklikleri 2882 metredir ve bu değer Kuvaterner buzul dönemleri kalıcıkar sınırı ölçümleri ile örtüşmektedir. Göl büyüklükleri açısından göllerin ortalama alanları 13.346m2 (0,0133 km2)’dir ve alan sınıflandırmasına göre göllerin neredeyse tamamına yakını küçük gölsınıfı içerisindedir (%99,5). Küresel grid tabanlı iklim verilerine göre sirk gölü alanlarının yıllık ortalamasıcaklığı -0,11°C, yıllık toplam yağış değeri ise 825 mm’dir.

The lowest elevation Pleistocene glaciers in the Carpathians — The geomorphological and sedimentological record of glaciation in the Polonyna Rivna and Borzhava massifs (Ukraine Carpathians)

The Polonyna Rivna (1480 m asl) and Borzhava (1682 m asl) ranges represent medium-high mountain massifs located in the north-western part of the Ukrainian Carpathians, where the legacy of the Pleistocene glaciation has long been unexplored. Based on the first detailed mapping of glacial landforms and sedimentological analysis, we document the presence of freshly-shaped outer moraines and glacial cirques and reconstruct the extent and ice-surface geometry of the six very small (0.09–0.78 km2 area) palaeoglaciers. The specific feature of the area is the presence of extensive mountain-top plateaus that play an important role as additional areas for snowblow accumulation. The equilibrium line altitudes (ELAs) calculated from hypsometry of reconstructed local Last Glacial Maximum (LLGM) using the area x altitude balance ratio (AABR) 1.6 method is exceptionally low at 1138 m asl in the Polonyna Rivna and 1230 m asl in the Borzhava range. Excluding the topographic effect produced by additional snow accumulation the ELA shift upwards between 120 and 180 m which corresponds to 25–53% of the glacier elevation range. The resulted climatic ELA (1282–1352 m asl) together with the mean cirque floor altitude (1194 m asl) and mean elevation of the glacier fronts (994 m asl) represent the lowest values in the entire Carpathian arc. Our data indicate glacier-friendly conditions in the mountain massifs exceeding 1400 m asl in the windward NW part of the Ukrainian Carpathians where due to relatively cold air temperatures and orographic induced precipitation local topolimatic factors dictated the development of marginal glaciation.

AutoCirque: An automated method to delineate glacial cirque outlines from digital elevation models

Cirques are typical erosional landforms of glaciers and have been used as bases for paleoclimate and paleoenvironment reconstruction and for understanding the interactions between glacial erosion, climate, and topography. The availability of high-resolution digital elevation models (DEMs) provides the opportunity to map large populations of cirques for regional and global scale analysis. However, cirque outlines are still mainly determined based on manual digitization, which is time consuming and labor intensive. This paper introduces an automated method to recognize and delineate cirques using DEMs based on a series of hydrological and morphological analyses, including delineating stream network, filtering streams, determining potential cirque threshold points, and delineating cirque outlines. A semi-automated tool is also developed based on user-specified threshold points or cross sections. The related tools are coded in python and imported into ArcGIS as a toolbox, AutoCirque, with user friendly interfaces. Comparison in a test area of the eastern Tian Shan, China, indicated that the population statistics are relatively consistent between manually digitized and auto-delineated cirques. Detailed comparisons for 11 selected cirques indicated that the AutoCirque-delineated and manually digitized cirque outlines are similar in shape with an average boundary offset of approximately one DEM cell size (30 m) and a 70–90% overlap-fit percentage. The derived cirque metrics are also similar, especially for elevation, slope, and aspect related metrics. This toolbox can significantly speed up the analytical processes, remove the subjectivity in delineating cirque outlines, and allow for the comparison of cirque morphology and metrics at regional and global scales.

The Gran Sasso fault system: Paleoseismological constraints on the catastrophic 1349 earthquake in Central Italy

We investigated the late Upper Pleistocene activity of the eight main faults that comprise the active, dip-slip Gran Sasso fault system (GSFS) in the Gran Sasso d'Italia Massif (central Italian Apennines; 2912 m a.s.l.). We carried out novel paleoseismological analyses at four sites of three different fault segments, and reviewed the data of the previous results for three other segments. We carried out several topographic profiles across the offset hillslopes, alluvial fans, glacial cirques, moraines, and valley floor. Through the dozen radiocarbon datings that were combined and cross-checked with many other ages published in previous studies, we have provided robust slip-rates and reconstructed the Holocene seismic history of this fault system. Paleoseismic analyses revealed the presence of three consecutive earthquakes since the onset of the Late Holocene, which were separated by 3.3 ky and 2.2 ky, respectively. The last one occurred in the 13th–14th century CE, a time-span that fits with the catastrophic 1349 seismic sequence.Our review of the macroseismic intensity distribution of this sequence indicates the existence of two distinct mesoseismic areas; a southern one that was already related to the Aquae Iuliae fault rupture (Abruzzi-Campania-Molise borders), and a northern one that robustly matches the hanging-wall of the Gran Sasso fault system. Given the length of this fault system, we estimated Mw 7 for its entire rupture, which accounts for the total destruction of L'Aquila and the neighboring villages. This also accounts for the strong effects and severe damage suffered by several settlements in the para-Tyrrhenian far field, especially to buildings characterized by long fundamental resonance periods, as seen for the monuments of Rome.Although characterized by long recurrence times (2.8 ± 0.5 ky), our results suggest that as for all of the main silent faults of the eastern set of active structures in the central Apennines, this fault system has one of the largest seismogenic potentials of the whole Apennine chain, with seismic risk implications extended even to its far-field.

Geoheritage of the Monchegorsk Igneous Layered Paleoproterozoic Intrusion (Kola Peninsula, Arctic Russia): Evaluation and Geotourism Opportunities

Monchegorsk is an intrusion complex of basic and ultrabasic rocks of the Paleoproterozoic age. This complex formed during active magmatic mobility that took place in NE Scandinavia 2.5 Ga years ago. These were the subject of intensive exploration and exploitation at the beginning of the 20th century, the latter carrying on through to the beginning of the 21st century. This contributed to the creation of some different forms of post-industrail mining infrastructure in the area. Many mining settlements, including Monchegorsk, mining plants, adits and quarries were established during this time, the relics of which are still present today. The Monchegorsk intrusions complex is formed by several fragmented massifs: Traviannaya, Kumuzhia, Nittis, Sopcha, Nyud, Poaz, and Monchetundra, the highest elevations of which reach up to 1000 m above sea level. These massifs form a landscape of “islands” and mountain ranges that have influence upon the regional landscape over several tens of kilometers. Their geography is characterized by numerous reliefs, glacial cirques, rocky thresholds with waterfalls and trough lakes. The potential of this region lies in the heritage of historical exploitation, numerous monuments of which have been preserved to this day. An important value is a landscape resulting from the relief of these mountains, highlighted by glacial activity in the Pleistocene. There are also interesting examples of Arctic fauna and flora, and of the rocks that form the bedrock in this intrusion. Some of the mineralization of these outcroppings can also be admired in the collections of the local museum that serves as a geocenter. The possibility of admiring relatively easily accessible views (the international route St. Petersburg–Murmansk–Kirkenes passes through the middle of the hills) and the interesting geology of the area abounding in rocks of mineralogical significance, their exposures, and history, along with the possibility of observing various post-industrail forms, make this area of great tourist potential. This article describes the most interesting exposures of outstanding tourist value and proposes routes connecting these points. It also discusses the problem of securing these exposures and the necessary tourist infrastructure, which is currently lacking.

MAT: GIS-Based Morphometry Assessment Tools for Concave Landforms

The rapid development of remote sensing technology for obtaining high-resolution digital elevation models (DEMs) in recent years has made them more and more widely available and has allowed them to be used for morphometric assessment of concave landforms, such as valleys, gullies, glacial cirques, sinkholes, craters, and others. The aim of this study was to develop a geographic information systems (GIS) toolbox for the automatic extraction of 26 morphometric characteristics, which include the geometry, hypsometry, and volume of concave landforms. The Morphometry Assessment Tools (MAT) toolbox in the ArcGIS software was developed. The required input data are a digital elevation model and the form boundary as a vector layer. The method was successfully tested on an example of 21 erosion-denudation valleys located in the young glacial area of northwest Poland. Calculations were based on elevation data collected in the field and LiDAR data. The results obtained with the tool showed differences in the assessment of the volume parameter at the average level of 12%, when comparing the field data and LiDAR data. The algorithm can also be applied to other types of concave forms, as well as being based on other DEM data sources, which makes it a universal tool for morphometric evaluation.

Climate-driven soil erosion processes in alpine environments over the last century: Evidence from the Taibai Mountain (central China)

Over the last century, climate warming has increased vegetation coverage in alpine regions, having major implications for associated terrestrial and aquatic ecosystems. Due to the remoteness of mountainous regions, there is a paucity of monitoring data regarding the response of catchment processes to climate change. Particle size distribution, magnetic properties, and elemental contents were investigated in 210Pb-dated sediment cores (34 cm in length) collected from two hydrologically-connected cirque lakes in the Taibai Mountain (the highest mountain in east mainland China). Both lakes have experienced directional environment changes since the 1980s, suggested by concurrent increases in magnetic susceptibility and organic matter. Prolonged growth season under a scenario of warmer climate has promoted vegetation development and soil conservation, subsequently increasing the contribution of terrestrial detritus derived from top soils that are rich in magnetic minerals and organic matter. Contents of clay and silt remained high throughout the two sediment cores, suggesting that depositional environment was relatively stable in both lakes. However, few peaks in coarse particles probably resulted from the cold and wet climate between the 1940s and the 1970s. During the relatively cold and wet episodes, prolonged snow-packs and enhanced melt-water discharge would strengthen bedrock weathering and erosion intensity, subsequently increasing the influxes of coarse particles. This is the first study to reveal decadal-scale changes in catchment processes of the Taibai Mountain, and the results highlight positive effects of climate warming on environmental protection of our study site and other similar alpine mountains through promoting water and soil conservation.

Glaciation in the highest parts of the Ukrainian Carpathians (Chornohora and Svydovets massifs) during the local last glacial maximum

The Chornohora and Svydovets massifs represent the highest part of the Ukrainian Carpathians (2061 m a.s.l.) and the north-eastmostmountain area in Europe, which was subject to mountain glaciation during the Quaternary. This region represents one of the least explored areas in terms of glacial geomorphology in Europe, which is crucial for validating the inferred zonal/meridional mode of atmospheric circulation on the continent during glacial stages. Based on new mapping of glacial landforms and sediments, we reconstruct the extent and ice-surface geometry as well as establish equilibrium line altitudes (ELAs) using the Area-Altitude-Balance-Ratio method for 40 palaeo-glaciers in the study area during the local Last Glacial Maximum (LLGM). Additionally, we list the inventory and morphometric characteristics of glacial cirques in the studied massifs (n = 77), which together with the local ELA pattern are discussed in the context of palaeo-wind directions and dominant precipitation patterns during the LGM. ELA values for the Svydovets (1401 m a.s.l.) and Chornohora (1516 m a.s.l.) massifs were much lower than those for the Rodna Mountains (1697 m) in the Northern Romanian Carpathians located 80 km to the southeast, and for the Tatra Mountains (1580 m) located 350 km to the northwest. In the Ukrainian Carpathians both glacier ELA and cirque elevations show a rising trend towards the southeast of 4 m km−1 controlled by preferential moisture transport from the northwest. This suggests that the dominant W-NW precipitation regime in effect during the LGM was similar to present-day conditions. This supports a previous glacial-geomorphologic reconstruction from the Rodna Mountains in Northern Romania and is in line with both model simulations and regional palaeo-wind proxies that show an enhanced mid-latitude North Atlantic zonal circulation pattern over central Europe during the LGM.

Tropical glacier reconstructions during the Last Glacial Maximum in Costa Rica

Numerous high elevation tropical mountains around the world show evidence of past glacial activity during the Last Glacial Maximum (LGM). Cerro Chirripó in Costa Rica exhibits paleoglacial landforms such as glacial cirques, moraine deposits and polished and striated bedrock surfaces. We used aerial imagery (1:25000) and contour lines to develop a Digital Elevation Model (DEM) for the LGM. We determined paleo-equilibrium line altitudes (paleo-ELAs) using Area-Altitude Balance Ratio (AABR) during the LGM for Cerro Chirripó in Costa Rica. Additionally, a Generalized Linear Model (GLM) was performed to statistically analyze the paleoglacier volumes and ice thickness combined with ten land surface parameters (LSP). Our results identified thirty-one paleoglaciers covering an area of 28.26 km2 during the global LGM, with a maximum ice thickness of 178 meters in Cerro Chirripó, a total volume of 13863 × 105 m3 and a mean paleo-ELA of 3490 meters. In addition, Area and Slope were the LSP with the highest statistical correlation to explain the paleoglacier volumes, while Area and Diurnal Anisotropic Heating were best for the paleoglacier ice thickness. As one of the first studies in the tropical high mountain environments, this work expands the geographic scope of glacier volume and thickness reconstructions during the maximum expansion of the LGM.

The Lowest Elevated Pleistocene Glaciers in the Carpathians – Geomorphological and Sedimentological Record of Glaciation in the Polonyna Rivna and Borzhava Massifs (Ukraine Carpathians)

The Polonyna Rivna (1480 m asl) and Borzhava (1682 m asl) ranges represent the medium-high mountain massifs located in the north-western part of the Ukrainian Carpathians, where the legacy of the Pleistocene glaciation has long been unexplored. Based on the first detailed mapping of glacial landforms and sedimentological analysis, we document the presence of freshly-shaped outer moraines and glacial cirques and reconstruct the extent and ice-surface geometry of the six very small (0.09–0.78 km2 area) palaeoglaciers. The specific feature of the area is the presence of extensive mountain-top plateaus that play an important role as additional areas for snowblow accumulation. The equilibrium line altitudes (ELAs) calculated from hypsometry of reconstructed maximal glacier extent using the area x altitude balance ratio (AABR) 1.6 method is exceptionally low at 1138 m in the Polonyna Rivna and 1230 m in the Borzhava range. Excluding the topographic effect produced by additional snow accumulation the ELA shift upwards between 120 – 180 m which corresponds to 25 – 53% of the glacier elevation range. The resulted climatic ELA (1282–1352 m) together with the mean cirque floor altitude (1194 m) and mean elevation of the glacier fronts (994 m asl) represent the lowest values in the entire Carpathian arc. Our data indicate glacier-friendly conditions in the mountain massifs exceeding 1400 m asl in the windward NW part of the Ukrainian Carpathians where due to relatively cold air temperatures and orographic induced precipitation local topolimatic factors dictated the development of marginal glaciation.

Climate sensitivity and geomorphological response of cirque glaciers from the late glacial to the Holocene, Sierra Nevada, Spain

Through a detailed geomorphological study, including thourough mapping of the geomorphic features as well as 10Be Cosmic-Ray Exposure (CRE) dating, the geomorphological evolution of the Mulhacén cirque since the maximum ice extent of the last glacial cycle until nowadays was determined. This glacial cirque is shaped on the northern face of the Mulhacén peak (3479 m a.s.l. 37°03′12″N/3°18′41″W), Sierra Nevada, southern Spain. It includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle. Furthermore, the sequence of glacial oscillations from this site was compared to that of other cirques of the massif, evidencing that: (i) new glaciers formed in these cirques during the Younger Dryas (YD), and (ii) disappeared at 11.7 ± 1.0 ka. Depending on the altitude, orientation and height of the cirque walls, the final deglaciation of the cirques generated a diversity of landscapes, including a wide range of glacial and periglacial landforms, such as polished surfaces, sequences of moraines, proto-rock glaciers or large rock glacier systems. No glaciers existed in the Sierra Nevada during the Middle Holocene. Only the cirques whose summits exceed 3300 m, are north-exposed and whose walls exceed 300 m high (i.e. Mulhacén and Veleta) hosted glaciers during Neoglacial phases, including the Little Ice Age (LIA) (approx. 1300–1850 CE). During these periods, climate oscillations favoured the formation of small glaciers in these cirques, which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs. The existence of glaciers impeded the formation of permafrost-related landforms, such as rock glaciers and protalus lobes until the end of the LIA, when they started to form. These results are compared with the deglacial evolution in 55 cirques from Iberian mountains as well as from glacial cirques from other mid-latitude mountains and subpolar regions. The chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns, with no significant differences at regional scale. For each mountain range, the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases.

Current glacier recession causes significant rockfall increase: the immediate paraglacial response of deglaciating cirque walls

Abstract. In the European Alps, almost half the glacier volume has disappeared over the past 150 years. The loss is reflected in glacier retreat and ice surface lowering even at high altitude. In steep glacial cirques, surface lowering exposes rock to atmospheric conditions probably for the very first time in several millennia. Instability of rockwalls has long been identified as one of the direct consequences of deglaciation, but so far cirque-wide quantification of rockfall at high resolution is missing. Based on terrestrial lidar, a rockfall inventory for the permafrost-affected rockwalls of two rapidly deglaciating cirques in the Central Alps of Austria (Kitzsteinhorn) is established. Over 6 years (2011–2017), 78 rockwall scans were acquired to generate data of high spatial and temporal resolution. Overall, 632 rockfalls were registered, ranging from 0.003 to 879.4 m3, mainly originating from pre-existing structural rock weaknesses. A total of 60 % of the rockfall volume detached from less than 10 vertical metres above the glacier surface, indicating enhanced rockfall activity over tens of years following deglaciation. Debuttressing seems to play a minor effect only. Rather, preconditioning is assumed to start inside the randkluft (void between cirque wall and glacier) where measured sustained freezing and ample supply of liquid water likely cause enhanced physical weathering and high quarrying stresses. Following deglaciation, pronounced thermomechanical strain is induced and an active layer penetrates into the formerly perennially frozen bedrock. These factors likely cause the observed paraglacial rockfall increase close to the glacier surface. This paper, the first of two companion pieces, presents the most extensive dataset of high-alpine rockfall to date and the first systematic documentation of a cirque-wide erosion response of glaciated rockwalls to recent climate warming.