Právě vyšlo - naše nejnovější studie
Dalton, A. S., Gowan, E. J., Mangerud, J., Möller, P., Lunkka, J. P., and Astakhov, V. (2022). Last interglacial sea-level proxies in the glaciated Northern Hemisphere, Earth Syst. Sci. Data, 14, 1447–1492
Because global sea level during the last interglacial (LIG; 130–115 ka) was higher than today, the LIG is a useful approximate analogue for improving predictions of future sea-level rise. Here, we synthesize sea-level proxies for the LIG in the glaciated Northern Hemisphere for inclusion in the World Atlas of Last Interglacial Shorelines (WALIS) database. We describe 82 sites from Russia, northern Europe, Greenland and North America from a variety of settings, including boreholes, riverbank exposures and along coastal cliffs. The database is available at https://doi.org/10.5281/zenodo.5602212.
April S. Dalton, Tamara Pico, Evan J. Gowan, John J. Clague, Steven L. Forman, Isabelle McMartin, Pertti Sarala, Karin F. Helmens (2022). The marine δ18O record overestimates continental ice volume during Marine Isotope Stage 3, Global and Planetary Change, 212, 103814.
There is disagreement in the Quaternary research community in how much of the marine δ18O signal is driven by change in ice volume. Here, we examine this topic by bringing together empirical and modelling work for Marine Isotope Stage 3 (MIS 3; 57 ka to 29 ka), a time when the marine δ18O record indicates moderate continental glaciation and a global mean sea level between −60 m and −90 m. We compile and interpret geological data dating to MIS 3 to constrain the extent of major Northern Hemisphere ice sheets (Eurasian, Laurentide, Cordilleran). Many key data, especially published in the past ~15 years, argue for an ice-free core of the formerly glaciated regions that is inconsistent with inferences from the marine δ18O record. We compile results from prior studies of glacial isostatic adjustment to show the volume of ice inferred from the marine δ18O record is unable to fit within the plausible footprint of Northern Hemisphere ice sheets during MIS 3. Instead, a global mean sea level between −30 m and − 50 m is inferred from geological constraints and glacial isostatic modelling. Our work urges caution regarding the reliance of the marine δ18O record as a de facto indicator of continental ice when few geological constraints are available, which underpins many Quaternary studies.
Helen E. Dulfer, Martin Margold, Christopher M. Darvill, Arjen P. Stroeven (2022). Reconstructing the advance and retreat dynamics of the central sector of the last Cordilleran Ice Sheet. Quaternary Science Reviews, 284, 107465
The Cordilleran Ice Sheet (CIS) formed part of the North American Ice Sheet Complex at the Last Glacial Maximum and contained an ice volume similar to the present-day Greenland Ice Sheet. Here we use the glacial landform record of northern British Columbia to unravel the advance and retreat dynamics of the central sector of the CIS, beneath the LGM ice divide. We use flowset classification to unravel complex changes in ice flow direction over time and the distribution of ice-marginal landforms to determine the relative deglaciation pattern. We also show that a Late Glacial cooling event resulted in the regional growth of independent mountain glaciers, ice caps, and ice fields at high elevations followed by the readvance of CIS outlet glaciers along its eastern margin. This allows us to establish the ice sheet configuration during the Late Glacial period for the first time.
Fraindová, K., Matoušková, M., Kliment, Z., Vlček, L., Vlach, V., Springerova, P., (2022). Headwaters biogeochemistry focused on different rainfall-runoff conditions, and the role of waterlogged areas: a comparative study of Czech mountains. Hydrological Sciences Journal, 67(4), 588–612.
This study focuses on changes of biogeochemical parameters related to variable rainfall-runoff conditions and to land cover types for eight headwater catchments in Central Europe. The presence of peatbogs and waterlogged spruce forests had a decisive influence on the biogeochemistry (higher concentration of organic matter, humins, iron, phosphorus and nitrogen compounds). The strongest positive correlation of organic matter and iron is represented in a catchment with the largest area of damaged forest (70%), but with a smaller proportion of waterlogged areas (8%). High flow rates influence greater release of organic matter and nitrate nitrogen. The catchment with the highest (80%) peatbog cover and the catchment that had undergone revitalization showed similar behaviour in terms of water biogeochemistry. The type of rainfall-runoff event affected the velocity of pH changes, whereas the variability in electric conductivity was also controlled by the catchment characteristics and hydrological preconditions.
Fraindová, K., Matoušková, M., Kliment, Z., Vlach, V., (2022). Changes and dynamics of headwaters chemistry on the boundary of nature protected areas: Example of upper Blanice River catchment, Czechia. Geografie,127.
Changes of biogeochemical parameters in the context of long-term trends and different rainfall-runoff conditions were examined with a special focus on various catchment characteristics. The study area is situated in the upper part of the Blanice River catchment, where more than 77% of the area belongs to a Protected Landscape Area and is unique for the most abundant population of the critically endangered freshwater pearl mussel (Margaritifera margaritifera) in Central Europe. A decrease of nitrogen and phosphorus compounds has been proven at the catchment outlet since 2003. The nine study catchments were divided into three main groups according to biogeochemical composition (natural, partly anthropogenically influenced, subsurface drainage). Changes of biogeochemical parameters during different runoff conditions revealed a higher release of aluminium, organic matter, dissolved organic carbon and total phosphorus during heavy precipitation event, which could have a negative effect on the vulnerable ecosystem including freshwater pearl mussel.
Nedelcev O., Jenicek, M. (2021). Trends in seasonal snowpack and their relation to climate variables in mountain catchments in Czechia. Hydrological Sciences Journal, 66(16), 2340-2356.
This study investigated trends in snowpack for the period 1965–2014 in 40 catchments located in five mountain regions in Czechia. We analysed daily series of air temperature, precipitation, and snow water equivalent (SWE) that were simulated with a conceptual model. The Mann-Kendall test showed strong increasing trends in air temperature at all elevations, mostly at the end of the cold season. This increase caused a decrease in snowfall fraction and SWE. Maximum SWE decreased mainly in western parts of Czechia (by up to −45 mm/decade). The length of the snow-covered period decreased by up to −6.8 days/decade, mainly due to earlier melt-out. Snowpack was more sensitive to changes in air temperature at elevations below 900 m a.s.l., while precipitation had a larger impact on snowpack at elevations above 1200 m a.s.l. The relative importance of air temperature for snow variability increased at all elevations in the last few decades.
Dalton, A.S., Stokes, C.R., Batchelor, C.L. (2022). Evolution of the Laurentide and Innuitian ice sheets prior to the Last Glacial Maximum (115 ka to 25 ka). Earth-Science Reviews, 224. 103875.
The Laurentide Ice Sheet was the largest global ice mass to grow and decay during the last glacial cycle (~115 ka to ~10 ka). Despite its importance for driving major changes in global mean sea level, long-term landscape evolution, and atmospheric circulation patterns, the history of the Laurentide (and neighbouring Innuitian) Ice Sheet is poorly constrained owing to sporadic preservation of stratigraphic records prior to the Last Glacial Maximum (~25 ka) and a case-study approach to the dating of available evidence. Here, we synthesize available geochronological data from the glaciated region, together with published stratigraphic and geomorphological data, as well as numerical modelling output, to derive 19 hypothesised reconstructions of the Laurentide and Innuitian ice sheets from 115 ka to 25 ka at 5-kyr intervals, with uncertainties quantified to include best, minimum, and maximum ice extent estimates at each time-step.
Juras, R., Blöcher, J.R., Jenicek, M., Hotovy, O., Markonis, Y. (2021). What affects the hydrological response of rain-on-snow events in low-altitude mountain ranges in Central Europe? Journal of Hydrology, 603(C), 127002.
Rain-on-snow (ROS) events influence the hydrological regime of rivers in regions with seasonal snow cover. We analysed eleven years of hourly meteorological, snow water equivalent and streamflow data from 15 catchments located in two mountain ranges in Czechia. We identified 611 ROS events which were further analysed and classified using selected meteorological, snow and runoff indices. The analysis of the runoff response of all ROS events revealed that only 5% of them resulted in high runoff exceeding the 1-year return period, but most of the events (82%) did not cause any significant runoff increase. High volumes of rain together with low snow cover were identified as important factors in the generation of high runoffs. In contrast, a deep and extended snowpack affected by rain under low air temperatures usually caused lower runoffs. The results of this study showed the importance of the snowpack, which can often prevent extreme runoff even when a large amount of rainfall occurs.
Minařík, R., Langhammer, J., Lendzioch, T., 2021. Detection of Bark Beetle Disturbance at Tree Level Using UAS Multispectral Imagery and Deep Learning. Remote Sensing 13, 4768.
This study aimed to examine the potential of convolutional neural networks (CNNs) for the detection of individual trees infested by bark beetles in a multispectral high-resolution dataset acquired by an unmanned aerial system (UAS). We compared the performance of three CNN architectures and the Random Forest model to classify the trees into four categories: pines, healthy spruce, longer infested spruce trees when needles turn yellow, and spruce trees under green attack. Based on our findings, we conclude that the CNN models are superior to the RF models and enable building learning models for the identification of infested trees and for distinguishing between different infestation stages. We see the potential application of the tested workflow in combination with multitemporal analysis for monitoring bark beetle disturbance, detecting hotspots, and predicting infestation spreading.
Tumajer, J., Buras, A., Camarero, J. J., Carrer, M., Shetti, R., Wilmking, M., Altman, J., Sangüesa-Barreda, G., & Lehejček, J. (2021). Growing faster, longer or both? Modelling plastic response of Juniperus communis growth phenology to climate change. Global Ecology and Biogeography, 30, 2229– 2244.
Common juniper (Juniperus communis) is the most widely distributed woody plant. Its range spreads across most of the northern hemisphere including Eurasia, North America, and Arctics. Juniper is a resistant shrub that survives in both extremely dry and cold environments. We tested whether intraannual growth patterns (i.e., timing and intensity of wood formation during the year) and their responses to climate change vary between contrasting environments. We used a process-based model to simulate the variability of wood formation at 16 sites and over 70 years of climate change. Geographically, there are three distinct intraannual growth patterns typical for cold (Arctic + Northern Ural), dry (Mediterranean + Southern Ural), and wet (Alps) environments. Recently, dry regions showed an extension of the growing season, but declining growth rates due to climate change (growing for longer, but not faster). By contrast, growth rates increased, but the duration of the growing season remained stable in cold environments (growing faster, but not longer). High intraannual growth plasticity enabled junipers to couple their intraannual growth dynamics with the local pattern of climate change. This might constitute an important advantage that facilitated the expansion of junipers to their large geographical range.
Jenicek, M., Hnilica, J., Nedelcev, O., Sipek, V. (2021). Future changes in snowpack will impact seasonal runoff and low flows in Czechia. Journal of Hydrology: Regional Studies, 37, 100899.
Mountains are referred to as “water towers” because they substantially affect the hydrology of downstream areas. Main objectives of this study were 1) to simulate the future changes in snow for a large set of mountain catchments in Czechia, reflecting a wide range of climate projections and 2) to analyse how the snow changes will affect groundwater recharge, streamflow seasonality and low flows in the future. The future hydrological projections showed a decrease in annual maximum SWE by 30 %–70 % in the study area until the end of the 21st century. Additionally, snowmelt was found to occur on average 3–4 weeks earlier. Changes in snowpack will cause the highest streamflow during melting season to occur one month earlier, in addition to lower spring runoff volumes due to lower snowmelt inputs. The future climate projections leading to overall dry conditions in summer are associated with both the lowest summer precipitation and seasonal snowpack. The expected lower snow storages might therefore contribute to more extreme low flow periods.
Kropáček, J., Vilímek, V. & Mehrishi, P. A preliminary assessment of the Chamoli rock and ice avalanche in the Indian Himalayas by remote sensing. Landslides (2021).
On 7 February 2021, a process chain disaster hit tributaries of the upper Alaknanda river in the Indian Himalayas referred to as the Chamoli disaster in the media. A large rock and ice avalanche was released from an elevation of approximately 5,100 m a.s.l. The avalanche turned into a debris flow and further downstream into a flood, leaving behind four damaged hydropower projects and dozens of casualties. The initially dry flow, as indicated by dust observed on a satellite image, turned into a moist flow by entrainment of water from water courses, snow and sediment. Using satellite images from Sentinel-2 and PlanetScope, we were able to map the geometry of the event. Furthermore, satellite data allowed us to reveal a drop in the snow line elevation of approximately 1,500 m, which indicated a snow fall three days before the event. We were also able to track the flood front propagation four days after the slope collapse. The analysis of temperature data from a near weather station indicated below zero temperatures in the detachment zone one month before the event and a temperature increase in the morning of the event. We suggest that the weather conditions may have been the final trigger, whereas a heavy predisposition was given mainly by the structural and morphological aspects of the slope.
Šípek, V., Jenicek, M., Hnilica, J., Zelíková, N. (2021). Catchment storage and its influence on summer low flows in central European mountainous catchments. Water Resources Management. 35, 2829–2843.
The objective of this study was to determine the role of spring catchment water storage on the evolution of low flows in central European mountainous catchments. The study analysed 58 catchments for which catchment storage, represented by snow, soil water and groundwater storages, was determined by the HBV hydrological model over a 35-year period. The mean runoff in the summer and autumn periods was mostly related to rainfall sums from the respective season. The median relative contribution of rainfall to the total mutual information value was 48.4% in summer, and 44.2% in autumn period, respectively. The relative contribution of soil water and groundwater storages was approximately 25% for each of the components. In contrast, the minimum runoff, its duration and deficit runoff volume, were equally related to both catchment storage and seasonal rainfall, especially in the autumn period.
Ben J. Stoker, Stephen J. Livingstone, Iestyn D. Barr, Alastair Ruffell, Robert D. Storrar, Sam Roberson (2021). Variations in esker morphology and internal architecture record time-transgressive deposition during ice margin retreat in Northern Ireland. Proceedings of the Geologists' Association, 132, (4), 409-425.
The subglacial hydrological system has a strong influence on variations in ice flow velocity. Eskers are sinuous ridges formed as water beneath a glacier deposits sediment within a subglacial channel. We used ground penetrating radar to investigate the internal architecture of a large esker system. We identified that the eskers were formed by two styles of deposition. Subglacial deposition of poorly-sorted sediment forms the esker core. Then, the deposition of more well-sorted, delta sediments which are superimposed on the esker in certain locations. This sequence of deposition occurred repeatedly during ice margin retreat. Despite variations in esker morphology, the internal structure remained consistent. Therefore, the variations in esker morphology cannot be explained by past subglacial flow processes alone. Instead, topography seems to be a strong control on esker morphology in this region.
Norris, S. L., Garcia-Castellanos, D., Jansen, J. D., Carling, P. A., Margold, M., Woywitka, R. J., & Froese, D. G. (2021). Catastrophic drainage from the northwestern outlet of glacial Lake Agassiz during the Younger Dryas. Geophysical Research Letters, 48, e2021GL093919.
The Younger Dryas was a short-lived interval of cooling that interrupted warming during the last deglaciation. The cause of this rapid change in climate is debated. One suggestion is the drainage of meltwater from glacial Lake Agassiz, a large ice-dammed lake in central North America, into the surrounding oceans may have affected ocean circulation, contributing to this climatic event. Here we model the discharge of water from the northwestern outlet of this lake. We estimate the discharge and demonstrate the connection between Lake Agassiz and the Arctic Ocean during the Younger Dryas.
Helen E. Dulfer & Martin Margold (2021). Glacial geomorphology of the central
sector of the Cordilleran Ice Sheet, Northern British Columbia, Canada. Journal of Maps, DOI:
Northern British Columbia was repeatedly covered by the Cordilleran Ice Sheet (CIS) during the glacial periods. However, its mountainous terrain and remote location have thus far impeded our understanding of the central sector of the ice sheet. In this study we use high resolution remotely sensed data to map glacial landforms across this inaccessible region and thousands of previously unrecognised glacial landforms have been mapped including eskers, moraines, meltwater channels, kame terraces and subglacial ribs. Our glacial geomorphological map can now be used to unravel the complex glacial history beneath the LGM ice divide region of the CIS and help us to better understand the advance and retreat dynamics of this ephemeral Pleistocene ice sheet.