Just published: our recent studies
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: 10.1080/17445647.2021.1937729
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.
Vlach, V., Matoušková, M., & Ledvinka, O. (2021). Impacts of regional climate change on hydrological drought characteristics in headwaters of the Ore Mountains. River Research and Applications, 1–12.
Recent years suggested an increasing risk of drought occurrence and restricted water supply even in usually humid mountain regions. This study was focused on the effects of regional climate change on hydrological drought characteristics in headwaters of the Ore Mountains along the Czech/German border. Results pointed to significant, continuous warming in the region which is accompanied by decreasing trends in snow cover depths in the colder half of the year. The seasonality of hydrological droughts changed markedly after 1992, when most severe drought events started to concentrate between August and October within the study area. Increasing trends in deficit volumes were found in two catchments along with a significant decrease in average and minimum flows in spring and summer months between 1967 and 2018.
Dulfer, H., Margold, M., Engel, Z., Braucher, R., & Team, A. (2021): Using 10Be dating to determine when the Cordilleran Ice Sheet stopped flowing over the Canadian Rocky Mountains. Quaternary Research, 1-12.
The Cordilleran Ice Sheet (CIS) repeatedly covered the mountainous regions of western North America during the Pleistocene and formed part of the North American Ice Sheet Complex during the last glacial maximum (LGM). This paper confirms the eastward flow of the CIS over the Rocky Mountains during the LGM and uses in situ produced cosmogenic 10Be dating at two high elevation sites to determine when the Cordilleran Ice Sheet retreated from the central Canadian Rocky Mountains. Deglaciation at the eastern site (Mt Spieker) occurred around 15.6 ka while the western site (Mt Morfee) was inundated with ice from the west until the Younger Dryas stadial (around 12.2 ka). Our results represent the first application of 10Be dating on the deglaciation history in the Canadian Rocky Mountains and provide valuable new data on the timing of deglaciation of the central sector of the CIS.
Uxa, T., Křížek, M., and Hrbáček, F. (2021): PERICLIMv1.0: a model deriving palaeo-air temperatures from thaw depth in past permafrost regions, Geosci. Model Dev., 14, 1865–1884.
This study presents and evaluates a simple new inverse modelling scheme called PERICLIMv1.0 (PERIglacial CLIMate) that derives palaeo-air temperature characteristics related to the palaeo-active-layer thickness, which can be recognized using many relict periglacial features found in past permafrost regions. The evaluation against modern temperature records showed that the model reproduces air temperature characteristics with average errors ≤1.3 ∘C. The past mean annual air temperature modelled experimentally for two sites in the Czech Republic hosting relict cryoturbation structures was between -7.0 ±1.9 and -3.2±1.5 ∘C, which is well in line with earlier reconstructions utilizing various palaeo-archives. These initial results are promising and suggest that the model could become a useful tool for reconstructing Quaternary palaeo-environments across vast areas of mid-latitudes and low latitudes where relict periglacial assemblages frequently occur, but their full potential remains to be exploited.
Hartvich, F., Tábořík, P., Šobr, M., Janský, B., Kliment, Z., and Langhammer, J. (2020): Landslide‐dammed lake sediment volume calculation using waterborne ERT and SONAR profiling. Earth Surf. Process. Landforms, 45: 3463– 3474.
Experimental stationary ERT profiling across a landslide‐dammed lake using custom‐made flotation devices was performed. Combining with the SONAR sounding proved very suitable and yielded very good results allowing to reconstruct original lake floor. Sediment volume accumulated during 145 years long history of the lake was calculated. Sedimentation velocity was assessed to predict the future development of the lake.
Tumajer J, Kašpar J, Kuželová H, Shishov VV, Tychkov II, Popkova MI, Vaganov EA and Treml V (2021): Forward Modeling Reveals Multidecadal Trends in Cambial Kinetics and Phenology at Treeline. Front. Plant Sci. 12:613643.
Woody plants experience prominent variability in their annual growth rates due to climate change. Increasing temperature stimulates formation of wider tree-rings mainly in cold environments but associated higher drought stress can reduce the tree-ring formation at dry locations. However, it is not known whether this alteration of growth is due to shifting phenology (changing growing season duration) or trends in growth kinetics (the production of cells is faster/slower). We seek the answer for this question at the treeline of the Krkonoše Mts. We employed the Vaganov-Shashkin process-based model of tree-ring formation to ‘slice’ the tree-ring width into daily growth segments. By the analysing specific model outputs, we were able to identify two main drivers of increased tree-ring widths of treeline trees since 1960 – (i) higher summer rate of cell production due to temperature increase and (ii) earlier spring onset of cambial activity. By contrast, autumn growth rates and phenology do not show significant trends. Surprisingly, we observed a clear pattern of drought stress on trees during warm and dry summer days controlling the formation of around 22 % of tree ring. The increasing drought stress might slow-down the future positive response of a cold treeline ecosystems to increasing temperature.
Lendzioch T, Langhammer J, Vlček L, Minařík R., 2021. Mapping the Groundwater Level and Soil Moisture of a Montane Peat Bog Using UAV Monitoring and Machine Learning. Remote Sensing. 13(5):907.
This paper presents a novel approach for using UAV thermal and multispectral imagery to enhance the spatio-temporal predictions of groundwater level and top-layer soil moisture of montane peat bogs using a machine learning model. Our research aimed to obtain information and predict the dynamic properties of groundwater level (GWL) and top-layer soil moisture (SM) in 2 dimensions and time based on data from digital surface models (DSMs), RGB, multispectral, and thermal data from drone imagery. We used a CAST spatiotemporal Machine Learning (ML) prediction model using the Random Forest algorithm. For two seasons, we have launched recurrent UAV monitoring campaigns and field sampling of GWL and SM ground truth data at the Rokytka Peat bog within the Sumava Mountains, Czechia. We used 34 predictors, derived from UAV imaging datasets to feed the random forest model. Results showed that the ML model, using the UAV-derived datasets, delivers accurate predictions of GWL and SM spatial distribution. The method is well suited and unique for planning and decision-making about the best sampling strategy, most notably with limited data.
Engel, Z., Braucher, R., Aster Team (2020): Origin and 10Be surface exposure dating of a coarse debris accumulation in the Hrubý Jeseník Mountains, Central Europe. Geomorphology, 365, 1˗12.
The paper deals with age and development oo block-field and tor in the Hrubý Jeseník Mts. and presents the first chronological evidence for planation surfaces and slopes in the East Sudetes Mts., on which mountain patterned ground formed. In addition, the paper provides broader paleoenvironmental interpretations and provides the first chronological evidence for the occurrence of permafrost and periglacial conditions in the High Sudetes during the penultimate (Saalian) cold period.
Engel, Z., Křížek, M., Braucher, R., Uxa, T., Krause, D., Aster Team (2021): 10Be exposure age for sorted polygons in the Sudetes Mountains. Permafrost and Periglacial Processes, 32, 1, 154-158.
This paper presents the first chronological evidence for sorted patterned ground using terrestrial in situ-produced cosmogenic nuclides (10Be) in the world. It provides age thresholds for relict sorted polygons sampled at four sites in the High Sudetes. (Mt. Luční hora and Mt. Vysoké Kolo in the Krkonoše Mts. and Mt. Břidličná and Větrná louka site in the Hrubý Jeseník, the highest part the central European uplands. The results indicate that these landforms started to form at the end of Marine Isotope Stage 3, and the main phase of their formation occurred between 30 and 20 ka. This research confirms the hypothesis of sorted-polygons formation within the last (Weichselian) glacial stage (110.6–11.7 ka) and suggests that earlier-sorted features are not preserved in the Sudetes. The recognized period of enhanced periglacial activity coincides with a prominent cold interval identified earlier in both regional and northern-hemispheric proxy records.
Kalovoda, J. (2020): The Dynamics of Geomorphic Evolution in the Makalu Barun Area of the Nepal Himalaya. P3K, 387 p. ISBN 978-80-7667-011-2.
Research into the dynamics of landform evolution in the East Nepal Himalaya is intended to provide knowledge of the long-term integrity of climate-driven morphogenetic and tectonic processes as an essential phenomenon of active collisional orogeny. Landform patterns of the Makalu – Barun region in the Himalaya are the result of orogenetic processes, as well as the denudation and erosional efficiency under very variable palaeoclimatic conditions during the late Cenozoic. Geomorphic processes and landforms in the region between the Chomolongma and Makalu Massifs and the Sapt Kosi lowland with an elevational gradient of over 8,000 m are explored in relation to morphostructural patterns and in the framework of extreme glacial, glacial and periglacial zones and the seasonally cold/warm humid zone. The observed landform changes in the Nepal Himalaya on a decadal scale indicate the high intensity of climate-driven morphogenetic processes, especially very effective erosion and transport of weathered material by a combination of diverse exogenic factors, integrated with active orogenetic processes. The dynamic evolution of landforms in the Himalaya is also essential evidence of the present-day severe natural hazards.
Vlach, V., Ledvinka, O., Matoušková, M. (2020): Changing Low Flow and Streamflow Drought Seasonality in Central European Headwaters. Water, 12 (12), 3575.
In the context of the ongoing climate warming in Central Europe, the seasonality and magnitudes summer streamflow droughts are expected to worsen in the future.nThis study analyzed the long-term variability and seasonality of low flows and streamflow droughts in 15 headwater catchments of 3 border regions within Central Europe during the 1968–2019 period. Our results showed a substantial increase in the proportion of summer streamflow droughts during the last 52 years, accompanied with an apparent shift in the average date of drought occurrence towards the start of the year. The most pronounced seasonality shifts were found mostly in catchments with the mean altitude 800–1000 metres above sea level. In contrast, the regime of low flows in catchments with terrain above 1000 metres remained nearly stable throughout the 1968–2019 period.
Hotovy, O., Jenicek, M. (2020): The impact of changing subcanopy radiation on snowmelt in a disturbed coniferous forest. Hydrological Processes, 34 (26), 5298-5314.
Understanding the role of forest on snowmelt processes enables better estimates of snow storages at a catchment scale and contributes to a higher accuracy of spring flood forecasting. Forests modify the snowpack energy balance by reducing solar shortwave radiation and enhancing the role of longwave radiation. Measurements of radiation fluxes were performed at three sites with different canopy structure, including one site affected by the bark beetle. The results showed that the forest decay causes significant changes in individual energy balance components, mainly shortwave radiation increase and longwave radiation decrease. These changes further lead to increase in snowmelt rates by 50% after forest disturbance. Our findings have important implications for runoff from areas affected by land cover changes due to either human activity or climate change.
Minařík, R.; Langhammer, J.; Lendzioch, T. (2020): Automatic Tree Crown Extraction from UAS Multispectral Imagery for the Detection of Bark Beetle Disturbance in Mixed Forests. Remote Sensing, 12, 4081.
Multispectral imaging using unmanned aerial systems (UAS) enables rapid and accurate detection of pest insect infestations, which are an increasing threat to midlatitude natural forests. Pest detection at the level of an individual tree is of particular importance in mixed forests, where it enables a sensible forest management approach. In this study, we propose a method for individual tree crown delineation and feature extraction to detect a bark beetle disturbance in a mixed urban forest using a photogrammetric point cloud and a multispectral orthomosaic. An excess green index threshold mask was applied to separate targeted coniferous trees from deciduous trees and backgrounds and different algorithms for automated delineation of tree crowns were tested and statistically compared. We found that for the accuracy of delineation, the density of the photogrammetric point cloud is more significant than the algorithm used. We conclude that the proposed automatic delineation workflow can substitute the time-consuming manual tree crown delineation, used for the detection and sanitation of individual infested trees in forests undergoing bark-beetle disturbance.
Vilímek, V., Klimeš, J., Ttito Mamani, R.V. et al. (2020): Contribution of the collaborative effort of the Czech WCoE to landslide risk reduction at the Machupicchu, Peru. Landslides 17, 2683–2688.
The paper presents results from monitoring of potentially dangerous slope movements at the archaeological site in the Machupicchu, Peru. This was achieved with the installation of an environmentally friendly network of dilatometric instruments. The 17-year-long monitoring identified no major hazard to the archaeological site which used to support decision of site managers to limit the entrance of tourists to the Intiwatana hill since 2019. Historical photographs of Czech travellers (from 1949, 1950, 1954, and 1961) were shared with Peruvian experts, who compared them with the oldest photos from the explorer Hiram Bingham and the most recent situation. The photographs were used to document the historical development of selected structures inside Machupicchu as well as landslide occurrences on the surrounding slopes.
Girons Lopez M., Vis, M.J.P., Jenicek, M., Griessinger, N., Seibert, J. (2020). Assessing the degree of detail of temperature-based snow routines for runoff modelling in mountainous areas in central Europe. Hydrology and Earth System Sciences, 24, 4441–4461.
Snow processes are a key component of the water cycle in mountainous areas. The complexity of these processes, coupled with the limited data available on them, has led to the development of different modelling approaches aimed at improving our understanding of these processes and supporting management practices. We assessed the suitability of a number of formulations of different components of the simple temperature-index method for rainfall-runoff modelling using the HBV model. We analysed a total of 64 alternative snow routine structures over 54 catchments. Overall, the most valuable modifications were (a) using an exponential snowmelt function coupled with no refreezing and (b) computing melt rates with a seasonally variable degree-day factor. Our results also demonstrated that increasing the degree of detail of the temperature-based snow routines in rainfall-runoff models did not necessarily lead to an improved model performance per se.