Deglaciation Process Research Articles

Characteristics, distribution, and origin of ferruginous deposits within the Late Ordovician glaciogenic setting of Arabia

Ferruginous deposits are iron-rich sediments or sedimentary rocks found in various sizes, shapes, and compositions within sedimentary strata in different depositional settings. This study investigates the characteristics, distribution, and origin of ferruginous deposits found in the Late Ordovician glaciogenic Sarah Formation and surrounding deposits in central Saudi Arabia. Several types of ferruginous deposits have been identified through field observations and laboratory investigations, including thin-section petrography, geochemical, surface, and bulk mineralogical analyses, and computed tomography scans. The identified ferruginous deposits include solid and rinded concretions, pipes, layers, ferricretes, liesegang bands, and fracture infills. They were associated with the periglacial and proglacial facies of the Sarah Formation. For instance, ferruginous deformed layers were mainly observed in subglacial facies, while rinded concretions occurred in bleached glaciofluvial facies. Ferruginous deposits were also found in the uppermost parts of non-glacial facies, such as the shallow marine Quwarah Member of the Qasim Formation and the braided deltaic Sajir Member of the Saq Formation. Compositionally, goethite was the dominant iron oxide mineral in all ferruginous deposits, and it is mostly distributed as cement, filling pore spaces. In comparison to ferruginous deposits reported in different depositional settings on Earth and Mars, the studied ferruginous deposits in an ancient glaciogenic setting exhibit different mineralogical characteristics. Specifically, the studied solid concretions are less abundant and primarily amalgamated, while the rinded concretions appear to be more mature than those reported in other depositional environments. This study suggests that the weathered basement rocks of the Arabian Shield were the primary source of iron. The iron-bearing rocks were eroded and transported by Hirnantian glaciation and deglaciation processes.

Early sea ice decline off East Antarctica at the last glacial-interglacial climate transition.

Antarctic climate warming and atmospheric CO2 rise during the last deglaciation may be attributed in part to sea ice reduction in the Southern Ocean. Yet, glacial-interglacial Antarctic sea ice dynamics and underlying mechanisms are poorly constrained, as robust sea ice proxy evidence is sparse. Here, we present a molecular biomarker-based sea ice record that resolves the spring/summer sea ice variability off East Antarctica during the past 40 thousand years (ka). Our results indicate that substantial sea ice reduction culminated rapidly and contemporaneously with upwelling of carbon-enriched waters in the Southern Ocean at the onset of the last deglaciation but began at least ~2 ka earlier probably driven by an increasing local integrated summer insolation. Our findings suggest that sea ice reduction and associated feedbacks facilitated stratification breakup and outgassing of CO2 in the Southern Ocean and warming in Antarctica but may also have played a leading role in initializing these deglacial processes in the Southern Hemisphere.

Ice-buttressing-controlled rock slope failure on a cirque headwall, Lake District, UK

Abstract. Rock slope failures in the Lake District, UK, have been associated with deglacial processes after the Last Glacial Maximum, but the controls and timing of the failures remain poorly known. A cirque headwall failure was investigated to determine failure mechanisms and timing. The translated wedge of rock is thin and lies on a steep failure plane, yet the friable strata were not disrupted by downslope movement. Fault lines and a failure surface, defining the wedge, were used as input to a numerical model of rock wedge stability. Various failure scenarios indicated that the slope was unstable and would have failed catastrophically if not supported by glacial ice in the base of the cirque. The amount of ice required to buttress the slope is insubstantial, indicating likely failure during the thinning of the cirque glacier. We propose that, as the ice thinned, the wedge was lowered slowly down the cirque headwall, gradually exposing the failure plane. A cosmogenic 10Be surface exposure age of 18.0±1.2 ka from the outer surface of the wedge indicates Late Devensian de-icing of the backwall of the cirque, with a second exposure age from the upper portion of the failure plane yielding 12.0±0.8 ka. The 18.0±1.2 ka date is consistent with a small buttressing ice mass being present in the cirque at the time of regional deglaciation. The exposure age of 12.0±0.8 ka represents a minimum age, as the highly fractured surface of the failure plane has experienced post-failure mass-wasting. Considering the chronology, it appears unlikely that the cirque was reoccupied by a substantial ice mass during the Younger Dryas stadial.

Simulating Runoff Regime in a Glaciated High-Mountainous Basin: A Case Study of the Baksan River (Caucasus, Russia)

The water resources of the North Caucasus depend mostly on the state of glaciers, which have been intensely losing their mass in the recent decades against the background of climate changes. The deglaciation leads not only to a decrease in the glacier runoff of mountain rivers, but also to changes in the annual distribution of runoff. The focus of this study is the adaptation of ECOMAG software complex to simulating river runoff in the Baksan River basin based on data on the relief and underlying surface of the drainage basin (soil, vegetation) and daily data on the surface air temperature, air saturation deficit, and precipitation. The calibration and validation of the model and the statistical estimate of calculation efficiency were based on the data on water discharges in the Baksan River over 2000–2017. The developed model of runoff formation in the Baksan River basin was used to carry out numerical experiments for assessing the sensitivity of runoff characteristics to glacier area variations. Depending on the rate of deglaciation process, the runoff of the Baksan River can drop by 10–30% because of a decrease in its glacial component, and the maximal water discharges can drop by 10–15%.

Effects of deglaciation on the succession of methanotrophic communities in inland and tidewater glaciers in the high Arctic, Svalbard

The high Arctic region of Svalbard has undergone significant landscape transformations due to accelerated deglaciation driven by climate warming. The expansion of exposed soil surfaces during rapid deglaciation provides new habitats for plants and microorganisms and contributes to ecosystem succession. The primary succession process has the potential to impact methane flux by influencing the activities of methanotrophs and methanogens. While the primary succession of plant communities following glacier retreat has been extensively studied, microbial succession, in particular that of methanotrophs and methanogens, is still poorly understood. Moreover, previous investigations have focused on the forelands of inland or mountainous glaciers, neglecting those of tidewater glaciers that extend to the coastal line. In this study, we investigated the abundance of methanotrophs and methanogens, as well as methanotrophic communities along a 100-year soil chronosequence in the forelands of inland and tidewater glaciers in Svalbard. The abundance of methanotrophs showed a gradual increase with soil age in both glacier types, while the abundance of methanogens exhibited significant differences only in tidewater glaciers. Our results revealed clear trends in the structure of methanotrophic communities with an increase in their diversity during the deglaciation process in both glacier types. These trends were mediated by changes in soil physicochemical properties such as soil organic carbon and total nitrogen. Our findings indicate that methane oxidation may be enhanced by the increase in the abundance and diversity of methanotrophs in both glacier types throughout the successional stages, and that carbon and nitrogen contents play a crucial role in structuring the community at different stages of succession in the glacier forefield. These insights significantly contribute to our understanding of microbial dynamics during deglaciation and their implications for methane dynamics in the high Arctic.

Holocene sedimentary sequences from Nachvak and Saglek Fjords (Northern Labrador) as a record of deglaciation of the Torngat Mountains and Hudson Bay

Constraining the final retreat of the Laurentide Ice Sheet offers the best opportunities to understand the impacts of glacial retreat on landscapes and sedimentary processes, and their relation to oceanography and climate variations in Eastern North America. In Northern Labrador, an area that lacks chronological constraints on terrestrial data, investigating deglacial dynamics is also important as meltwater pulses may affect the deepwater formation that takes place in the Labrador Sea. In this paper, we investigate the deglacial sedimentary sequences from Nachvak and Saglek Fjords located in the Torngat Mountains of Northern Labrador. Sub-bottom profiles reveal that both fjords contain a deglacial sequence thicker than 100 m, including important mass-movement deposits reaching thicknesses of 40 m. These events were possibly triggered by glacio-isostatically induced earthquakes during the Younger Dryas and the Early Holocene. Estimations based on well-dated gravity cores sampled in both fjords suggest a deglaciation before the Younger Dryas for the Nachvak Outer Basin, but only 2000 yr later for the equivalent basin in Saglek Fjord. Such asynchronous retreat is explained by the presence of Saglek Bay acting as a buffer zone against oceanic forcing at the entrance of Saglek Fjord. In the sediment cores, high concentrations of detrital carbonates and an equivalent of the Hudson-Strait red bed are correlated with major deglacial events occurring between 9.2 and 8.1 cal ka BP in the Hudson Bay area. A progressive postglacial transition began around 8.0 cal ka BP with a decrease of detrital carbonate inputs and an increasing influence of North Atlantic waters. This transition ended abruptly with a regional major environmental change around 6.3 cal ka BP after the end of the Laurentide Ice Sheet melting. Magnetic properties reflecting enhanced bottom oxygen consumption reveal a high primary productivity from 6.3 to 3.8 cal ka BP in Saglek and Nachvak main basins, and probably a stronger water stratification. Overall, these results indicate that the deglacial and postglacial sedimentary dynamics of Nachvak and Saglek Fjords was influenced by (1) massive mass-movement deposits possibly generated by earthquakes, (2) sediment export by deglacial processes from both the local and the Hudson Bay areas and (3) the influence of Labrador Sea waters.

Holocene glacial oscillations in the Tyroler Valley (NE Greenland)

AbstractAlthough the spatiotemporal oscillations of the Greenland Ice Sheet (GrIS) during the last millennia have played a prominent role in global environmental changes, its glacial response to the natural variability still needs to be better constrained. Here, we focused on the reconstruction of the glacial behavior and deglaciation process along the Tyroler Valley (74° N, 22° E), within the Northeast Greenland National Park. This NW‐SE valley connects with the GrIS via the Pasterze Glacier and divides two ice caps (A.P. Olsen Land and Payer Land), this last one feeding two piedmont glaciers (Copeland and Kløft glaciers). For this study, we combined the interpretation of the spatial pattern of geomorphological features and the chronological framework defined by a new dataset of 15 10Be cosmic‐ray exposure (CRE) ages from glacially polished bedrock surfaces and moraine boulders together with one optically stimulated luminescence (OSL) age of a glaciolacustrine deposit. CRE ages indicate that the deglaciation of the lowest parts of the valley and the exposure of the highest slopes took place during the Early Holocene, at ca. 10–8.5 ka (ka = thousand year [BP]). Furthermore, this ice thinning also favored the disconnection of the valley tributary glaciers. Samples from the moraines of the two tributary glaciers indicate that the deglaciation was not continuous, but it was interrupted by at least three phases of glacial advance during the Neoglacial cooling (before ca. 5.9 ka), and the Little Ice Age (LIA, 0.6, and 0.3 ka). The larger piedmont glacier (Copeland Glacier) occupied the valley floor during these major advances, damming the river and allowing the formation of a proglacial glacial lake upvalley, as confirmed by the OSL date of lacustrine sediments that yielded an age of 0.53 ± 0.06 ka. In short, our study provides new evidence of the relative stability of GrIS and the regional ice caps in the area, in which glacial fronts have been rather stable since their advances during the Neoglacial and the LIA.

Detection of Crustal Uplift Deformation in Response to Glacier Wastage in Southern Patagonia

The Southern Patagonian Icefield (SPI) is the largest continuous ice mass in the Southern Hemisphere outside Antarctica. It has been shrinking since the Little Ice Age (LIA) period, with increasing rates in recent years. An uplift of crustal deformation in response to this deglaciation process has been expected. The goal of this investigation is to analyze the crustal deformation caused by ice retreat using time-series data from continuous GPS stations (2015–2020) in the northern area of the SPI. For this purpose, we installed two continuous GPS stations on rocky nunataks of the SPI (the GRCS near Greve glacier and the GBCS close by Cerro Gorra Blanca). In addition, ice elevation changes (2000–2019) were analyzed by the co-registration of the SRTM digital elevation model and ICESat elevation data points. The results of the vertical components are positive (36.55 ± 2.58 mm a−1), with a maximum at GBCS, indicating the highest rate of crustal uplift ever continuously recorded in Patagonia; in addition, the mean horizontal velocities reached 11.7 mm a−1 with an azimuth of 43°. The negative ice elevation changes detected in the region have also accelerated in the recent two decades, with a median Δh (elevation change) of −3.36 ± 0.01 m a−1 in the ablation zone. The seasonality of the GPS signals was contrasted with the water levels of the main Patagonian lakes around the SPI, detecting a complex interplay between them. Hence, the study sheds light on the knowledge of the crustal uplift as evidence of the wastage experienced by the SPI glaciers.

The timing of the deglaciation in the Atlantic Iberian mountains: Insights from the stratigraphic analysis of a lake sequence in Serra da Estrela (Portugal)

AbstractUnderstanding the environmental response to the last glacial termination in regions located in transitional climate zones such as the Atlantic Iberian mountains is crucial to estimate potential changes in regions affected by current glacial melting. We present an 8.5 m‐long, solid last deglaciation and Holocene chronostratigraphic record including detailed sediment analysis from Lake Peixão, a pro‐glacial lake in the Serra da Estrela (Central Portugal). The age–depth model relies on a Bayesian approach that includes 16 AMS 14C dates and 210Pb–137CS measurements, robustly dating the lake formation at 14.7 ± 0.32 cal. ka BP. This chronological reconstruction shows an average sedimentation rate of ca. 0.07 cm yr−1 (15 yr cm−1), enabling proxy analyses at decadal timescales. The sediment sequence is composed of five lithological units: (U1) coarse and unsorted fluvioglacial lacustrine deposits; (U2) massive fluvioglacial lacustrine deposits (863–790 cm below surface [bsf]; 14.7 ± 0.32–13.8 ± 0.12 cal. ka BP); (U3) water current fluvioglacial lacustrine deposits (790–766 cm bsf; 13.8 ± 0.12–12.9 ± 0.29 cal. ka BP); (U4) laminated/banded lacustrine deposits characterized by terrigenous deposits from ice‐covered lake periods and episodic events of ice and snow melting (766–752 cm bsf; 12.9 ± 0.29–11.7 ± 0.15 cal. ka BP); and (U5) massive muddy lacustrine deposits (752–0 cm bsf; 11.7 ± 0.15 cal. ka BP–present). The occurrence of U2 to U4 deposits defines the transition from glacial cold (U1) to net warm postglacial conditions (U5). These climate transitions are marked by changes in sediments and the presence of very low sedimentation rate periods, possibly related to the Intra‐Allerød Cold Period and the coldest phase of the Younger Dryas. Our results support the previously proposed timing of the retreat of the Serra da Estrela glaciers ca. 13.8 ± 0.12 cal. ka BP. The robust chronology of Lake Peixão highlights the potential of Iberian pro‐glacial lakes for dating deglaciation processes and will lead to unprecedented decadal‐to‐centennial timescale palaeoclimate reconstructions in this region since the last glacial–interglacial transition.

History of Anvers-Hugo Trough, western Antarctic Peninsula shelf, since the Last Glacial Maximum. Part II: Palaeo-productivity and palaeoceanographic changes during the Last Glacial Transition

Following the Last Glacial Maximum (LGM; ca. 23-19 calibrated [cal.] kyr before present [BP]), atmospheric and oceanic warming, together with global sea-level rise, drove widespread deglaciation of the Antarctic Ice Sheet, increasing the flux of freshwater to the ocean and leading to substantial changes in marine biological productivity. On the Antarctic continental shelf, periods of elevated biological productivity, often preserved in the sediment record as laminated (and sometimes varved) diatomaceous oozes (LDO), have been reported from several locations and are typically associated with the formation of calving bay re-entrants during ice sheet retreat. Understanding what drives the formation and deposition of LDOs, and the impact of deglacial processes on biogenic productivity more generally, can help inform how Antarctic coastal environments will respond to current and future ice sheet melting. In this study we utilise a suite of sediment cores recovered from Anvers-Hugo Trough (AHT), western Antarctic Peninsula shelf, which documents the transition from subglacial to glacimarine conditions following retreat of an expanded ice stream after the LGM. We present quantitative absolute diatom abundance (ADA) and species assemblage data, to investigate changes in biological productivity during the Last Glacial Transition (19-11 cal kyr BP). In combination with radiocarbon dating, we show that seasonally open marine conditions were established on the mid-shelf by 13.6 cal kyr BP, but LDOs did not start to accumulate until ∼11.5 cal kyr BP. The ∼1.4 kyr delay between the onset of seasonally open marine conditions and LDO deposition indicates that physiographic changes, and specifically the establishment of a calving bay in AHT, is insufficient to explain LDO deposition alone. LDO deposition in AHT coincides with the early Holocene climatic optimum (∼11.5 – 9.0 kyr) and is therefore explained in terms of increased atmospheric/ocean temperatures, high rates of sea and glacial ice melt and the formation of a well-stratified water column in the austral spring. An implication of our study is that extensive bathymetric mapping in conjunction with detailed core analyses is required to reliably infer environmental controls on LDO deposition.

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.

Lakes of Eurasian interior, which significantly raised their levels in the recent past

Abstract. The paper presents geomorphological evidences of former appearances of huge lakes in Mongolia and in the south of Siberia visible on satellite images. Most of lakes in Mongolia and transboundary Russia are terminal basins collecting waters from catchments of large rivers draining the Altai, Khangai and Khentey Mountains, while in the south of Siberia such lakes had no sizeable sources for water input. The discussing reasons for these rises are obviously climatic with possible high influence of deglaciation processes in the surrounding mountains.

Tracing the Long-Term Evolution of Land Cover in an Alpine Valley 1820–2015 in the Light of Climate, Glacier and Land Use Changes

Alpine glacial environments and their fluvial systems are among those landscapes most comprehensively affected by climate change. Typically, studies on the consequences of climate change in such environments, e.g., glacier retreat, cover a maximum of 70 years, reflecting the availability of orthophotos or satellite images. This study addresses the long-term transformation processes in a glaciated catchment and highlights the role of human agency in a changing Alpine environment. In order to identify land cover changes between 1820 and 2015 in the Long-Term Ecosystem Research (LTER) site “Jamtal” (Tyrol, Austria) we apply a “regressive-iterative GIS reconstruction method” combining both historical maps and optical remote sensing data. Below 2,100 m a.s.l. the Jamtal experienced a massive 62% decline of unvegetated debris areas and bedrock outcrops (so-called “wasteland”) that was mainly transformed to grassland and sparsely wooded areas. Forests increased by an outstanding 323% and grassland was replaced by sparsely or densely wooded areas. This primarily reflects the abandonment of agricultural uses at unfavourable remote sites. In the higher (formerly) glaciated subbasin, ice-covered areas declined by 55%, which was associated with a major (82%) growth of exposed wasteland. Concurrently, Alpine grassland expanded by 196% and krumholz even by 304%. Approximately half of the new fluvial system that evolved in deglaciated areas between 1870 and 1921 still existed in 2015. Unconsolidated debris buried almost one fifth of the new channels, and almost one third was colonized by vegetation. Recent data show that the deglaciation process is much faster than the colonization process by Alpine vegetation. Accordingly, the extent of wasteland has expanded and potentially amplifies the sediment supply to the fluvial system. Alterations in high Alpine hydrological and sediment/debris regimes significantly affect human use in lower, more favourable areas of the Alpine region. The long-term investigation of the Alpine landscape reveals that the transformation processes have accelerated in recent decades.

From deglaciation to postglacial filling: post-LGM evolution of an isolated glacier system at the northern fringe of the Eastern Alps (Austria)

ABSTRACT During the last glacial maximum (LGM), large parts of the European Alps were occupied by an extensive interconnected system of valley glaciers. At lower elevations on the eastern fringe of the Alps, only a patchy pattern of isolated glaciers developed. Erosion by many of these smaller glaciers was however sufficient to excavate subglacial basins (‘overdeepening’) large enough to act as sedimentary archives of deglaciation processes. To constrain the deglaciation history and the post-LGM evolution of an isolated glacial system, we analyzed the geomorphology and the sedimentary record of a local overdeepening at the northern fringe of the Northern Calcareous Alps. We focus on the heavily silted lake system Taferlklaussee (TKS) (Höllengebirge massif, Austria) confined by a succession of terminal moraines and a steep headwall. Field techniques (mapping, Direct Current Resistivity, and core drilling), lab techniques (lithostratigraphic analyses and radiocarbon dating) and Geographic Information System (GIS) analyses are employed to document dynamics of erosion and sedimentation after deglaciation. We discuss drivers and controls of paraglacial landscape evolution. The almost complete postglacial (lake) record indicates abundant sediment input during the lateglacial and early Holocene, but strongly reduced dynamics since the Mid-Holocene. Sediment storage volumes range between 3.83 Mm³ and 5.75 Mm³ and lithology-specific mechanical denudation rates range between 0.8 mm/a and 1.7 mm/a depending on the scenario used. The study provides a well-constrained reference for the depositional dynamics of isolated LGM glacier systems of the Eastern Alps. It highlights the potential of using related sedimentary records to constrain the local variability in postglacial landscape evolution.

Glacier Geometry Changes in the Western Shore of Admiralty Bay, King George Island over the Last Decades.

This paper presents changes in the range and thickness of glaciers in Antarctic Specially Protected Area (ASPA) No. 128 on King George Island in the period 1956–2015. The research indicates an intensification of the glacial retreat process over the last two decades, with the rate depending on the type of glacier front. In the period 2001–2015, the average recession rate of the ice cliffs of the Ecology Glacier and the northern part of the Baranowski Glacier was estimated to be approximately 15–25 m a−1 and 10–20 m a−1, respectively. Fronts of Sphinx Glacier and the southern part of the Baranowski Glacier, characterized by a gentle descent onto land, show a significantly lower rate of retreat (up to 5–10 m a−1 1). From 2001 to 2013, the glacier thickness in these areas decreased at an average rate of 1.7–2.5 m a−1 for the Ecology Glacier and the northern part of the Baranowski Glacier and 0.8–2.5 m a−1 for the southern part of the Baranowski Glacier and Sphinx Glacier. The presented deglaciation processes are related to changes of mass balance caused by the rapid temperature increase (1.0 °C since 1948). The work also contains considerations related to the important role of the longitudinal slope of the glacier surface in the connection of the glacier thickness changes and the front recession.

Paraglacial rock-slope deformations: sudden or delayed response? Insights from an integrated numerical modelling approach

Glacial and paraglacial processes have a major influence on rock slope stability in alpine environments. Slope deglaciation causes debuttressing, stress and hydro-mechanical perturbations that promote progressive slope failure and the development of slow rock slope deformation possibly evolving until catastrophic failure. Paraglacial rock slope failures can develop soon after or thousands of years after deglaciation, and can creep slowly accelerating until catastrophic failure or nucleate sudden rockslides. The roles of topography, rock properties and deglaciation processes in promoting the different styles of paraglacial rock slope failure are still elusive. Nevertheless, their comprehensive understanding is crucial to manage future geohazards in modern paraglacial settings affected by ongoing climate change. We simulate the different modes and timing of paraglacial slope failures in an integrated numerical modelling approach that couples realistic deglaciation histories derived by modelling of ice dynamics to 2D time-dependent simulations of progressive failure processes. We performed a parametric study to assess the effects of initial ice thickness, deglaciation rate, rock-slope strength and valley shape on the mechanisms and timing of slope response to deglaciation. Our results allow constraining the range of conditions in which rapid failures or delayed slow deformations occur, which we compare to natural Alpine case studies. The melting of thicker glaciers is linked to shallower rockslides daylighting at higher elevation, with a shorter response time. More pronounced glacial morphologies influences slope lifecycle and favour the development of shallower, suspended rockslides. Weaker slopes and faster deglaciations produce to faster slope responses. In a risk-reduction perspective, we expect rockslide differentiation in valleys showing a strong glacial imprint, buried below thick ice sheets during glaciation.

Deglaciation Rate of Selected Nunataks in Spitsbergen, Svalbard—Potential for Permafrost Expansion above the Glacial Environment

Spitsbergen has recently experienced a continuous deglaciation process, linked to both glacier front retreat and lowering of the glacier surface. This process is accompanied by permafrost aggradation from the top of the slopes down to the glacier. Here, the authors determine the rate of permafrost expansion in this type of vertical profile. To this end, seven nunataks across the island were analysed using Landsat satellite imagery, a high-resolution digital elevation model (ArcticDEM), and geoinformation software. Over the last 24–31 years, new nunataks gradually emerged from the ice cover at an average linear rate of 0.06 m a−1 per degree of increment of the slope of the terrain at an average altitude of approximately 640 m a.s.l. The analysis showed that the maximum rate of permafrost expansion down the slope was positively correlated with the average nunatak elevation, reaching a value of approximately 10,000 m2 a−1. In cold climates, with a mean annual air temperature (MAAT) below 0 °C, newly exposed land is occupied by active periglacial environments, causing permafrost aggradation. Therefore, both glacial and periglacial environments are changing over time concomitantly, with permafrost aggradation occurring along and around the glacier, wherever the MAAT is negative.

Evidence of strong small‐scale population structure in the Antarctic freshwater copepod Boeckella poppei in lakes on Signy Island, South Orkney Islands

AbstractEnvironmental conditions were particularly severe during the Last Glacial Maximum, altering the distribution of the Southern Hemisphere biota, particularly at higher latitudes. The copepod Boeckella poppei is the only macroscopic continental invertebrate species known to be distributed today across the three main biogeographic regions in Antarctica as well as in southern South America. Signy Island (South Orkney Islands) is a unique location for the study of Antarctic freshwater ecosystems due to its location and geographic isolation; it contains 17 lakes in several low altitude catchments. We conducted phylogeographic and demographic analyses using the cox1 gene on 84 individuals of B. poppei from seven lakes across Signy Island. We recorded low levels of genetic diversity and a strong genetic differentiation signal between the eastern and western valleys within the island. Phylogeographic structure and demographic inference analyses suggested at least one asymmetrical dispersal event from west to east. Demographic inference detected a strong signal of population growth during the deglaciation process, which may have followed either (1) a strong genetic bottleneck due to a reduction in population size during the last glacial period, or (2) a founder effect associated with postglacial recolonization of Signy Island from elsewhere. The genetic architecture of this island's populations of B. poppei shows that historical events, rather than continuous dispersal events, likely played a major role in the species' current distribution. Finally, our study considers possible mechanisms for dispersal and colonization success of the most dominant species in the Antarctic freshwater community.

Black carbon as a factor in deglaciation in polar and mountain ecosystems: A Review

Black carbon is considered a product of the incomplete combustion of fossil fuels and materials that originated from volcanic eruptions or were emitted during wildfires. It is a strong light-absorbing component that has many atmospheric and surface effects in terrestrial and glacial ecosystems. Normally, black carbon is presented as a solid particle, consisting mainly of pure carbon, which absorbs solar radiation at all wavelengths. Some black carbon particles are amended by a mineral compound, though black carbon substances are normally dark or greyish dark. Black carbon is the most active part of suspended particles in the atmosphere and on glacial surfaces, absorbing solar radiation, the main component of ash, which consists of carbon particles with impurities in the form of mineral particles and also contains carbon of biogenic origin. In this paper, we have analyzed the literature on black carbon and its effect on deglaciation processes in the Earth’s polar and mountainous regions. The physical, chemical, and microbiological composition of black carbon accumulations were studied using the examples of the Arctic, the Antarctic, and the Central Caucasus. Potential sources and conditions of the transportation of black carbon into the polar zone and their effect on ice and snow have also been discussed.

Genesis of the pleistocene hummocky moraines in the Moracke Planine Mountains (Montenegro)

The Moracke Planine Mountains, situated in the central part of Montenegro, were the center of intensive Pleistocene glaciation. Specific type of moraines - hummocky ones, which have not been recorded in the southeastern Dinarides up to now, were recently identified and investigated in western part of the Moracke Planine Mts. Moraine material accumulated on limestone basement, where several tens of irregularly distributed hummocks and similar number of bowl-shaped dolines have been carved already. The hummocky moraines formed in the glaciokarst landscape where the well-developed karst morphology has been shaped before glaciation. Pre-glacial karst morphology determined the direction of glacier movement as well as its main morphological characteristics (thickness and width). During the most intensive glaciation phase (?IS 12) the Lukavicko-lukovski Glacier, spread out from the central part of mountain towards west, reaching a length of 16.5 km. Due to uneven glacier thickness, the deglaciation process led to its breaking and separation of the lower and shorter part from the rest of the icy mass. Stagnant state of the icy mass led to specific accumulation of moraine material in a form of numerous hummocks, whose melting produced a bowl-shaped dolinas in-between. The paleogeographic significance of hummocky moraines lies in the possibilities of more detailed studies of the Pleistocene glaciers specifics that arise from their evolution in glacio-karst conditions.