Glacial Landscape Research Articles

Source-to-mainstream: Hydrochemical water changes in a channel head in the young glacial area (Pomeranian Lakeland, Poland)

A channel head is a zone where hydrological changes occur that shape the chemical features of water, during the final stage of underground flow and the beginning of the surface water cycle. The study aims were as follows: (i) to characterise spatial water chemistry patterns; (ii) to establish the role played by the hyporheic zone in the chemical transformations associated with the groundwater that supplies the first-order stream; and (iii) to identify the factors that control the chemical composition transformations that occur in headwater alcoves. The analysis was performed on three sets of samples taken at the Żarnowo channel head situated in the young glacial landscape of the Parsęta drainage basin (NW Poland).The performed hydrochemical measurements showed that the waters found in the alcoves displayed a mosaic pattern, with spatial variability in the levels of trace metals and nutrients. In turn, geogenic ions featured in the mineralogical-petrographic compositions of deposits found in headwater catchments, such as Ca2+, HCO3−, Mg2+, and Na+, showed low temporal variability and small differences among the various sampled headwater alcoves. These results indicated that the majority of spatial variance associated with the chemical composition of water is driven by the transformation of groundwater discharges in the hyporheic zone. The locations of hydrochemical transformation hotspots can be explained by the influences of critical physical variables, such as the intensity of seepage erosion, sediment texture, bottom microtopography, groundwater discharge characteristics, water temperatures, and the diversity of groundwater-fed vegetation. Hydrochemical studies performed in the ground- and surface-water contact zones within a channel head can identify the underlying causes of changes to water chemistry, which, in turn, can facilitate the protection of water resources against unfavourable changes that may affect the water quality at the headwater catchment.

Bed erosion during fast ice streaming regulated the retreat dynamics of the Irish Sea Ice Stream

Marine-terminating ice stream behaviour often defines the stability of ice sheets and is driven by a complex interplay of climatic, oceanic, topographic and glaciological factors. Here, we use new integrated high resolution, extensive (2100 km2) and continuous geophysical, sedimentological and geotechnical data to reconstruct past glacial environments during the Last Glacial Maximum from a well-preserved palaeo-landscape. The data is from the axial centre of the Irish Sea Ice Stream (ISIS), which drained > 17% of the former British-Irish Ice Sheet. Recent geochronological data of the palaeo-ISIS show a build-up and advance of ice to marine-terminating maximum limits in the southern Celtic Sea 27–25 ka BP, followed by rapid ice margin retreat into the northern Irish Sea Basin (ISB) by 20.8 ± 0.7 ka BP. However, the flow dynamics in the central and axial bed of the ISIS through this timeframe are not well understood. Here, we use our new glacial landscape reconstruction to identify the spatial and temporal patterns of flow re-organisation and re-activations for the marine-terminating ISIS. From this we infer how ice streaming was driven by a variety of factors through advance, deglaciation and towards a temporary lift-off of ice from its bed and an ultimate demise. Overprinted subglacial bedforms with differing ice flow directions indicate an on/off behaviour to the ice-streaming, an increasing topographical influence and substantial realignment of ice flows. Subsurface geophysical data reveal the erosive capability of the ice stream through time, with a first erosive component in the formation of mega-scale glacial lineations leaving bedrock exposed at the ice stream bed. The depositional component of MSGL crest building occurred in the same ice-flow phase. Whilst the ice stream was laterally constricted in two locations, likely contributing to changes in ice margin retreat rates, we also propose that changes in basal drag associated with exposed bedrock at the ice‒bed interface influenced the retreat dynamics, particularly when this exposure was near the grounding zone. The wider implications of this work are that episodic and highly erosive ice streaming during ice advance and early retreat can change ice‒bed conditions radically and in turn influence glacial dynamics during later retreat episode, thus constituting a feedback process to be considered in modelling the dynamics of marine-terminating ice streams.

Investigating lake sediments and peat deposits with geophysical methods - A case study from a kettle hole at the Late Palaeolithic site of Tyrsted, Denmark

Kettle holes are common ice decay features in formerly glacial landscapes like those in Southern Scandinavia and Northern Germany. Here the kettle holes are represented either as dry depressions, wetland areas or lakes. However, the majority of these features are silted and part of the present farmland. We investigated a small kettle hole at Tyrsted, near the township of Tyrsted, south of Horsens (Denmark) with the aim to determine the extension and depth of this feature using geophysical methods. A former excavation at Tyrsted carried out from the Horsens Museum in 2017 at a neighboring site revealed Late Palaeolithic flint of the Bromme type and worked reindeer antlers. This connection in a Late Glacial horizon is unique not only in a Danish context and it can help to improve and clarify the dating of the Bromme culture. We used ground penetrating radar (GPR), electromagnetic induction (EMI) and electrical resistivity tomography (ERT) to estimate the extension of the kettle hole (~16 m × 25 m). Shear wave reflection and refraction seismics (SH Seismics) were able to detect the bottom sediment of the former lake at about ~5 m depth. Furthermore, a seismic event at about 1.30 m depth is visible which can be associated to the transition between the Allerød and Younger Dryas sediment making the detection of the Bromme horizon possible. After the non-invasive investigation, a location for an open excavation has been chosen in a way to groundtruth the geophysical results allowing the direct comparison with the stratigraphy. These results allow the archaeologists to identify key excavation areas focused on the investigation of the Allerød and Younger Dryas layers in a way to improve the dating information about the Bromme horizon collected so far. Furthermore, geophysical investigations together with excavations will enable the archaeological and palaeoenvironmental research groups to search large scale palaeolandscapes for these very rare, but highly important finds.

3D Surface Modeling of Late Pleistocene Glaciers in the Munzur Mountains (Eastern Turkey) and its paleoclimatic implications

Located in the Eastern Anatolian Region in Turkey, the Munzur Mountains (Munzurs; 3463 m above sea level) are one of the most important glacial landscapes in Turkey, with evidence for extensive glaciations in the past and small-scale glaciation at present. As Turkey's second-largest glaciated region, these mountains include various glacial landforms, primarily glacial valleys, hanging valleys, cirques, and moraines. However, only limited data are available on the extent and chronology of former glaciations in the Munzur Mountains. This study produced data on the extent of paleoglaciers, calculated their equilibrium line altitudes (ELAs), revealed paleoclimate conditions, and modeled paleo temperatures during maximum ice extent using numerically derived reconstruction methods (GlaRe and ELA calculation tools) based on geomorphic evidence. The major glacial landforms were first mapped in detail before the reconstruction. Six hundred and eighty cirques and 30 glaciated valleys were identified. Paleoglaciers did not override the entire mountains, however, valley glaciers converged where topographic conditions were suitable.The maximum extent of glaciation covered an area of ca. 600 km2. The largest glacier was ca. 19 km in length. Moreover, 15 of the valley glaciers were over 10 km in length. Their average thickness was 75 m, and the maximum glacial thickness, in the Eastern Munzurs, was found to be ca. 300 m. The total volume of ice reached ca. 45 km3. The paleoglaciers reached as low as 1350 m above sea level. The average ELA was calculated approximately 2600 m above sea level, indicating an equilibrium line altitude depression of 1000-1100 m. The paleotemperatures, estimated based on different scenarios at the time of the maximum extent of Munzur glaciers, were 8-10 °C lower than today. The mountains experienced an increase in precipitation through this period with respect to the current precipitation scheme.

Tropical Paleoglacial Geoheritage Inventory for Geotourism Management of Chirripó National Park, Costa Rica

Globally, most active tropical glacial landscapes are found at elevations above 4000 m. Nonetheless, the presence of paleoglacial landforms in low latitudes, especially those formed during the Last Glacial Maximum (LGM), persists in different tropical regions. Chirripo National Park, in central-south Costa Rica, is one of these particular examples. The glacial and periglacial landscape in the park are located over 3000 m, with landforms such as aretes, glacial cirques, moraines, till deposits, and glacial lakes. We performed an integrated approach for the geoheritage inventory and geotourism management, crossing geomorphological and cultural information. A total of 14 geomorphosites were assessed and their management discussed. These geomorphosites achieved scientific scores between 0.5 (Valle Talari, Cerro Uran, and Cerro Terbi) and 0.88 (Cerro Chirripo and Los Crestones). The average scientific value of the geomorphosites is 0.75, since they are well preserved (0.75), rare (0.57) and representative (0.84) of the region’s geomorphology. They also play an important role in the geographical history (0.62), as well as the significant use and management characteristics (0.8). Chirripo National Park has key importance both naturally and culturally for Costa Rica. Its geomorphosites assessment is of critical value for the Costa Rican Conservation Areas System in order to promote improved geotourism. Geoheritage mapping can offer more opportunities of transferring geoscience knowledge to a larger public and policy makers. Our study aims to improve and further the state of the art of tropical glacial geoheritage.

Detrital Thermochronometry Reveals That the Topography Along the Antarctic Peninsula is Not a Pleistocene Landscape

AbstractUsing offshore detrital apatite (U‐Th)/He thermochronometry and 3D thermo‐kinematic modeling of the catchment topography, we constrain the timing of major topographic change at Bourgeois Fjord, Antarctic Peninsula (AP). While many mid‐latitude glacial landscapes developed primarily in response to global cooling over the last ~2.6 Ma, we find that kilometer‐scale landscape evolution at Bourgeois Fjord began ~30–12 Ma ago and <2 km of valley incision has occurred since ~16 Ma. This early onset of major topographic change occurred following the initiation of alpine glaciation at this location and prior to the development of a regional polythermal ice sheet inferred from sedimentary evidence offshore of the AP. We hypothesize that topographic change relates to (i) feedbacks between an evolving topography and glacial erosion processes, (ii) effects of glacial‐interglacial variability, and (iii) the prevalence of subglacial meltwater. The timing and inferred spatial patterns of long‐term exhumation at Bourgeois Fjord are consistent with a hypothesis that glacial erosion processes were suppressed at the AP during global Plio‐Pleistocene cooling, rather than enhanced. Our study examines the long‐term consequences of glacial processes on catchment‐wide erosion as the local climate cooled. Our findings support the hypothesis that landscapes at different latitudes had different responses to global cooling. Our results also suggest that erosion is enhanced along the plateau flanks of Bourgeois Fjord today, which may be due to periglacial processes or mantling via subglacial till. If regional warming persists and meltwater becomes more pronounced, we predict that enhanced erosion along the plateau flank will accelerate topographic change.

A glacial buzzsaw effect generated by efficient erosion of temperate glaciers in a steady state model

Studies on relief and hypsometry in glaciated mountain ranges have recognized the equilibrium line altitude of glaciers as a major control on mountain height. This has led to the belief that, in contrast to fluvial topography, glacial topography is limited by climate, with tectonics playing a secondary role. This concept is known as the glacial buzzsaw. However, the understanding of controls on glacial relief has remained mainly qualitative, in part because a reference scenario for glacial landscape evolution — a glacial topographic steady state linked to the base level by a fluvial topographic steady-state downstream of the glacier terminus - and its dependencies have not yet been defined. Here we define such a reference and compare steady state longitudinal profiles in a coupled system of glacial and fluvial erosion that involves both tectonics and climate. Our model is based on the stream power law for fluvial erosion, the shallow ice approximation in combination with a glacial erosion rule, and an empirically determined drainage area-flow length relationship for both rivers and glaciers. Further, we introduce a new approach to incorporate dendritic glacier network structures into the one-dimensional model. Modeling of coupled glacial-fluvial steady-state profiles with empirical glacial and fluvial erosion parameters shows that the difference between glacial and fluvial relief depends on climate, tectonics and the applied erosion laws. Our results imply that glacial erosion can typically balance tectonic uplift rates at lower relief and topographic slopes than fluvial erosion. This steady state equivalent of the glacial buzzsaw effect suggests that glaciers may indeed be more efficient erosional agents than rivers increasing erosion in a cooling climate.

Tectonic controls on rates and spatial patterns of glacial erosion through geothermal heat flux

Glacial erosion has shaped many mountain belts during the cold periods of the Late Cenozoic. The rate of glacial erosion is sensitive to the subglacial environment, including both the subglacial hydrology and the basal thermal regime. Geothermal heat from underlying bedrock is a major contributor to glacier energy budgets, controlling ice dynamics at the ice-bed interface by changing the basal temperature and the supply of meltwater. Despite the known influence of geothermal heat on the subglacial environment, its impact on glacial erosion has received little study. The geothermal heat flux in glaciated mountain ranges varies widely as a function of the tectonic setting. Therefore, if glacial erosion is sensitive to geothermal heat flux, the evolution of glaciated landscapes may depend upon tectonically-controlled geothermal gradients. We explore the impact of geothermal heat flux on the rates and spatial patterns of glacial erosion in mountain ranges using numerical models. We couple a sliding-dependent glacial erosion model with the Parallel Ice Sheet Model (PISM) to simulate the evolution of a synthetic glacial landscape. We find a robust tendency for increasing glacial erosion with increasing geothermal heat flux. The spatial pattern of erosion also varies with the magnitude of geothermal heat flux. At low geothermal heat flux, glacial erosion is consistently focused in major valleys. As geothermal heat flux increases, the area of significant glacial erosion expands into higher elevations and the rate of erosion increases. The location of maximum erosion migrates up-valley as geothermal heat flux increases, suggesting that glacial erosion tends to produce distinct landscapes as a function of geothermal heat flux. Our finding suggests that active mountain belts with high geothermal heat flux will express the glacial buzzsaw effect, in which high elevation topography is preferentially removed by glacial erosion. Glaciers at passive margins with low geothermal heat flux, in contrast, will tend to incise deep valleys at relatively low elevations. Previous work on the interaction between tectonics and landscape evolution has focused on relief generation and fracturing of rocks. Our results introduce a novel potential linkage between tectonics and erosion based on the sensitivity of glacial erosion to geothermal heat.

Palaeosols and their cover sediments of a glacial landscape in northern central Europe: Spatial distribution, pedostratigraphy and evidence on landscape evolution

Knowledge of the distribution, types and properties of buried soils, i.e. palaeosols, is essential in understanding how lowlands in northern central Europe have changed over past millennia. This is an indispensable requirement for evaluating long-term human impact including soil erosion and land-cover dynamics. In the Serrahn area (62 km2), a young glacial landscape representative for northeastern Germany and part of the Müritz National Park, 26 pedosedimentary sections were documented and analysed. To this end, a multiproxy-approach was applied using pedology, micromorphology, geochronology, and palaeoecology. Statistical and spatial analyses of c. 5200 soil profiles, of which 10% contain palaeosols, show that buried soils cover an area of 5.7 km2, i.e. 9% of the area studied. Most palaeosols are Cambisols, Arenosols and Gleysols. Palaeosols are mainly covered by aeolian and colluvial sands, as well as by lacustrine sands and peat. Radiocarbon and luminescence dating together with palynological and anthracological data reveal that former land surfaces were dominantly buried through erosion triggered by human activity in the late Holocene. In addition, but to a clearly smaller extent, Lateglacial/early Holocene palaeosols and cover sediments occur. Following Medieval clear-cutting and intensive land use, the study area is today again widely forested. The high share of buried land surfaces detected here is expected to be representative for the hilly glacial landscapes even in the wider region, i.e. in northern central Europe, and should be considered in soil mapping, soil carbon budgeting and assessments of past human impact.

The Give and Take of Mercury in Glacial Landscapes

As glacial ice melts, toxic mercury is released into the environment. But a new study shows vegetation may be an effective cleanup crew.

Exceptional hydrological stability of a Sphagnum-dominated peatland over the late Holocene

Lowering of the water table and substantial drying are observed in peatlands worldwide. A significant drying of European peatlands in the last 200–300 years influenced the vegetation, lowered carbon storage potential in peatlands, and modified microbial diversity. Here, we reconstructed in high resolution hydrological changes, local and extra-local vegetation composition, and fire activity based on a peat core from a Sphagnum-dominated peatland located in a young glacial landscape in Central Eastern Europe, NE Poland. The last ca. 1500 years of history of the Jaczno bog has been supported by a dense accelerator mass spectrometry (AMS) radiocarbon (14C) dating resolution: 20 dates per 400 cm of the peat profile. We also investigated changes in the functional and morphological traits of testate amoebae as well as the functional diversity of testate amoeba communities over time. Our reconstruction showed a rare case of hydrological stability in the peatland over the late Holocene, and no dry shifts were recorded during the study period. Relatively stable hydrological conditions and undisturbed Sphagnum growth enabled the bog to maintain notably high peat accumulation rates. Although increasing human impact has been recorded in the last ca. 400 years, we did not reconstruct strong disturbances (e.g., vast deforestations, intensive grazing or farming, fires) influencing the site. Compared with other hydrological records from Europe, the Jaczno bog was one of the few bogs in Central and Eastern Europe that did not experience drying during the Little Ice Age. Moreover, the traits and functional diversity of testate amoebae did not show any critical turnover. In the last 70 years, human impact on the site decreased, and the area became afforested. Unlike most of the European peatlands, the Jaczno bog possesses high water tables up to the present time. Therefore, our data suggest that nature conservation practices, which target high water tables, are essential to maintain peatlands as a sink and not as a source of carbon in the future.

Geoheritage of Postglacial Areas in Northern Poland\u2014Prospects for Geotourism

This study aims to identify potential geosites and show existing geosites in a young glacial landscape in northern Poland through a qualitative assessment of the local geoheritage. Three areas of diversified morphology and geology located within the extent of the last Scandinavian Ice Sheet have been selected as the research polygons: the north-eastern part of the Dobrzyń Lake District, the Lower Vistula Valley and the Kashubian Lake District. Three basic abiotic components of the environment have been analysed: geology, terrain relief and hydrology. This research is based on some specific materials including maps and photographs. Methodology of this research includes the inventory, characterization and assessment of selected areas. The final results are proposals for geosites of high educational value in each of the three investigated regions. For the north-eastern part of the Dobrzyń Lake District, the creation of a geopark has been proposed, and the geosites of the Lower Vistula Valley provide the potential for a geotourist footpath to be designed. The Kashubian Lake District is characterised by the occurrence of numerous glacial landforms and sediments as well as high denivelations and a concentration of erratic boulders. Therefore, this region also has the potential to be selected for valuable geosites and the designing of a geotourist footpath.

Late glacial and Holocene climate variability, southernmost Patagonia

A Late glacial – Holocene palaeoecological record, constrained by a robust chronology, from a peat bog near Punta Burslem (54°54′S, 67°57′W) on Isla Navarino, southernmost Patagonia documents the shifts in intensity and focus of the Southern Westerly Winds (SWWs) at these high latitudes. Such long-term records are required to reconstruct and better understand the likely regional impacts of a poleward shift and intensification of the SWWs predicted under global warming scenarios. Deglaciation at Punta Burslem occurs sometime before c. 17,000 cal a BP, and the post glacial landscape is dominated by cold tolerant pioneer species. Nothofagus woodland is established by c. 12,250 cal a BP, this moisture sensitive vegetation type retreats in the early to mid-Holocene from c. 9700 to 7050 cal a BP reflecting an intense and sustained drier phase associated with a prolonged poleward contraction of the SWWs. After c. 6000 cal a BP there is a regional trend to cooler and wetter climate. However, we identify at least five periods of rapid climate change (RCC) leading to drier conditions at this southern extreme of Patagonia: c. 5350-4750 cal a BP, c.4300-3300 cal a BP, c. 2600-1850 cal a BP, c. 1350-1100 cal a BP and c. 550-350 cal a BP. From a synthesis of our Isla Navarino records and a latitudinal spread (34°-64°S) of multiproxy records it is proposed that these periods of RCC and relatively drier conditions indicate latitudinal shifts in the location and intensity of the SWWs in response to climatic warming leading to reduced precipitation at the southern margins of Patagonia.

Glacial landscape and paleoglaciation in Terra Sabaea: Evidence for a 3.6 Ga polythermal plateau ice cap

In a previous study, we demonstrated with a comparative morphometrical analysis the first morphometric evidence of a glacial landscape composed of glacial cirques and glacial valleys in the south of Terra Sabaea at an elevation > 1000m in two impact craters and one mountain. The purpose of this study is to use the same method to seek other geomorphologic evidence of glacial landscapes elsewhere in Terra Sabaea. Based on a comparison between current and old glacial landscapes on Earth and Mars, we identified 81 glacial valleys and possible evidence for a former plateau ice cap dated at 3.6 Ga at the highest elevation in Terra Sabaea. The identified glacial valleys have the same morphometric properties as terrestrial and martian glacial valleys with U-shaped cross-sectional profiles, a V-index >0.2, a length to with ratio >1 and a cross-sectional area to drainage area ratio four times higher than the fluvial ones. Moreover, these properties are different from terrestrial and martian fluvial valleys. We did not find well preserved glacial cirques in this area, this absence questions the origin of glacial valleys. However, the presence of an extensive flat plateau, from which the long valleys radiate, could have hosted an ancient plateau ice cap which was the source of these glacial valleys. A comparison with the Cantal and the Shaluli Shan in the southeastern Tibetan plateau on Earth reveals morphometrical similarities with our study area. In fact, long glacial valleys, originating radially from a plateau at higher elevation are characteristics of an ancient plateau ice cap. This analysis allowed us to propose a polythermal regime for martian glacial landscape, namely a cold-based ice cap except at the margin where the regime is warmed-based due to the steeper topography. This topography created shear stress which increased the heat at the base of the ice and created the outlet glacial valleys. Near the plateau, the radial valleys are U-shaped with a V-index >0.2 but downstream, to the low elevation area, these valleys become more V-shaped with a V-index around 0.1. This hypothesis is supported by the presence of an open-basin paleolake making the transition between inlet glacial valleys upstream and an outlet V-shaped valley downstream. So the morphometry of the radiating valleys suggests that liquid water played a role in the formation of this landscape.

Concepts of geoparks establishment in Bulgaria and their geothermal resources

Bulgaria is the third country in the world by number of mineral springs after Japan and Iceland. The Bulgarian-Russian collaboration in geological, environmental and landscape conservation provided a new development of the methodology for identification, evaluation and characterization of geodiversity including their geotermal resources. Individual approach to the concepts of the national geoparks stressed on their scientific and geodiversity features, environmental conditions and economic premises by defining one major geopark theme and many minor topics. Regardless of their radically different themes, the geothermal activity in geoparks is the common feature, which provides them with a great balneological potential. The concept of Geopark “Iskar Canyon” is based on the remarkable geodiversity of the Iskar River Canyon with a number of wonderful landscapes and scenic outcrops of various rock types ranging from Precambrian to Quaternary. The concept of Geopark “Belogradchik Rocks” lies on the famous Lower Triassic sandstone pinnacles. Geopark “Rila” is based on its remarkable glacial landscapes - glacier valleys, cirques, moraines, arêtes and horns. The major theme of Geopark “Burgas Lakes” is related with the ancient sea-level changes and balneo-healing properties of their humus mud. The unifying theme of these geoparks is the high spa potential of their thermal springs that have been used since the Roman Age.

Participatory Planning Under Scenarios of Glacier Retreat and Tourism Growth in Southeast Iceland

Glacial mountain environments are changing rapidly as a result of climate change and the expansion of nature-based recreation. Anticipatory planning to adapt to such changes is a key management challenge. The aim of this study was to explore how adaptation planning for recreation sites in these areas can be supported using participatory scenario planning (PSP). For this purpose, a study area in southeast Iceland was chosen where management is likely to be heavily impacted in the near future. PSP involves local stakeholder workshops in which participants generate maps reflecting plausible glacial land cover and land use in the near future. This process takes place in stages, including the identification of potential drivers of land-use change, development of multiple land-use scenarios, and examination of the potential consequences of these scenarios and options for adapting to them. The study demonstrates that PSP can be a valuable tool to support recreational land-use planning in glacial landscapes, and to improve anticipatory adaptation to potentially undesirable future changes. PSP also has the potential to provide salient and usable knowledge for local stakeholders, stimulate stakeholders to elaborate on long-term changes and associated uncertainties through scenario construction and visualization, provide insight into the adaptive capacity of current recreational planning systems, and reframe stakeholders' guiding assumptions to encourage a more future-oriented mentality. This approach could be valuable in other glaciated mountain areas and in recreation areas where there are multiple significant future changes in landscape attributes, processes, and uses at play simultaneously.

A paraglacial rock-slope failure origin for cirques: a case study from Northern Iceland

The contribution of paraglacial rock-slope failure (RSF) to the excavation of cirques in glacial landscapes is explored in the Tindastóll Mountain, Skagi peninsula, northern Iceland. We analyze 8 cirques that developed during the Quaternary and 13 paraglacial RSF cavities that developed during the Holocene in this paleo-plateau. From a reconstruction of the pre-Quaternary surface of the plateau, we calculate the excavated volumes of the cirques and RSF cavities and quantify the contribution of Holocene RSF to cirque growth. By extrapolating this contribution to the whole Quaternary, we find that paraglacial RSF is a first-order contributor to the development of cirques. This contribution is twofold: first, paraglacial RSF creates cavities along valley slopes, in which cirque glaciers can develop during subsequent glaciations; second, paraglacial RSF along pre-existing cirque walls promotes cirque widening and deepening. Our results also reveal that Quaternary glacial/paraglacial erosion rates range from 0.02 to 0.17 mm yr‑¹ in the studied cirques. We infer that glaciers are (i) efficient preparatory factors for the destabilization of slopes by paraglacial RSF, (ii) efficient conveyors to evacuate deposits produced by paraglacial RSF in cirques, but (iii) not necessarily predominant agents in the excavation of cirque bedrocks.

The Role of Management of Stream–Riparian Zones on Subsurface–Surface Flow Components

A managed riparian lowland in a glacial landscape (Holtum catchment, Denmark) was studied to quantify the relative importance of subsurface and surface flow to the recipient stream. The hydrogeological characterization combined geoelectrical methods, lithological logs, and piezometric heads with monthly flow measurements of springs, a ditch, and a drain, to determine seasonality and thereby infer flow paths. In addition, groundwater discharge through the streambed was estimated using temperature and water-stable isotopes as tracers. The lowland received large groundwater inputs with minimal seasonal variations from adjacent upland aquifers. This resulted in significant amounts of groundwater-fed surface flow to the stream, via man-made preferential flow paths comprising ditches, drainage systems, and a pond, and via two natural springs. Roughly, two thirds of the stream gain was due to surface flow to the stream, mainly via anthropogenic alterations. In contrast, direct groundwater discharge through the streambed accounted for only 4% of the stream flow gain, although bank seepage (not measured) to the straightened and deepened stream potentially accounted for an additional 17%. Comparison to analogous natural flow systems in the catchment substantiate the impact of anthropogenic alterations of riparian lowlands for the subsurface and surface flow components to their streams.

Searching for Viking Age Fortresses with Automatic Landscape Classification and Feature Detection

Across the world, cultural heritage is eradicated at an unprecedented rate by development, agriculture, and natural erosion. Remote sensing using airborne and satellite sensors is an essential tool for rapidly investigating human traces over large surfaces of our planet, but even large monumental structures may be visible as only faint indications on the surface. In this paper, we demonstrate the utility of a machine learning approach using airborne laser scanning data to address a “needle-in-a-haystack” problem, which involves the search for remnants of Viking ring fortresses throughout Denmark. First ring detection was applied using the Hough circle transformations and template matching, which detected 202,048 circular features in Denmark. This was reduced to 199 candidate sites by using their geometric properties and the application of machine learning techniques to classify the cultural and topographic context of the features. Two of these near perfectly circular features are convincing candidates for Viking Age fortresses, and two are candidates for either glacial landscape features or simple meteor craters. Ground-truthing revealed the latter sites as ice age features, while the cultural heritage sites Borgø and Trælbanke urge renewed archaeological investigation in the light of our findings. The fact that machine learning identifies compelling new candidate sites for ring fortresses demonstrates the power of the approach. Our automatic approach is applicable worldwide where digital terrain models are available to search for cultural heritage sites, geomorphological features, and meteor impact craters.

Glacial geomorphology of the Chirripó National Park, Costa Rica

ABSTRACT Several regions of tropical America show imprints of past glacial activity. These relict landforms can support the understanding of past climate conditions, such as during the Last Glacial Maximum (LGM), and the implications that these paleoclimatic conditions could have had on landscape change. Here, we present and analyze glacial morphologies for the Chirripó National Park in Costa Rica based on aerial imagery (1:25,000), detailed Digital Elevation Models, geomorphic mapping, as well as geomorphic assessments in the field to determine and validate landforms. This study adds valuable insights into the reconstruction of the maximum expansion of tropical glaciation during the LGM in Costa Rica and into tropical America glacial landscapes in general.