TY - JOUR A1 - Tella, Timothy O. A1 - Winterleitner, Gerd A1 - Morsilli, Michele A1 - Mutti, Maria T1 - Testing sea-level and carbonate production effects on stratal architecture of a distally steepened carbonate ramp (Upper Miocene, Menorca) BT - a 3D forward modelling approach JF - Sedimentary geology : international journal of applied and regional sedimentology N2 - Although distally steepened carbonate ramps have been studied by numerous researchers, the processes that control the development of these carbonate systems, including tectonics, differential carbonate production along the ramp profile, or antecedent physiography of the slopes, are an ongoing discussion. We use a stratigraphic forward model to test different hypotheses to unravel controls over distally steepened ramp development, referenced to the well-known Upper Miocene Menorca carbonate ramp (Spain). Sensitivity tests show that distally steepened ramps develop under complex interaction among accommodation, carbonate production and sediment transport parameters. Ramp slope initiation is favoured by still stands and falls of sea-level, in a setting with high-frequency sea-level fluctuations with amplitude between 20 m and 40 m. Low-frequency and higher amplitude sea-level fluctuations of about 115 m tend to form models with no significant slope development. The impact of antecedent slope on the geometry of ramps is determined by the paleoslope inclination, with flat to subhorizontal paleosurfaces resulting in ramps that mirror the antecedent slope. In contrast, steeper paleosurfaces tend to result in ramps with well-defined slopes. Our models, therefore, show that the ramp profile becomes more influenced by the depth constraints on the carbonate sediment producers than by the geometry of the underlying topography as the inclination of the paleosurface increases. The presented models also show that seagrass-dominated shallow carbonate production tends to result in steep slopes due to the low-transport characteristic imposed by seagrass trapping. This steepness can, however, be altered by the introduction of high transport sediment grains from deeper carbonate producers, which fill the slopes and more distal sections of the ramp profile. KW - Forward model KW - Distally steepened ramp KW - Sea-level fluctuation; KW - Sensitivity analysis KW - Sediment transport KW - Carbonate production KW - Grain KW - association Y1 - 2022 U6 - https://doi.org/10.1016/j.sedgeo.2022.106267 SN - 0037-0738 SN - 1879-0968 VL - 441 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Knapp, Nikolai A1 - Attinger, Sabine A1 - Huth, Andreas T1 - A question of scale: modeling biomass, gain and mortality distributions of a tropical forest JF - Biogeosciences N2 - Describing the heterogeneous structure of forests is often challenging. One possibility is to analyze forest biomass in different plots and to derive plot-based frequency distributions. However, these frequency distributions depend on the plot size and thus are scale dependent. This study provides insights about transferring them between scales. Understanding the effects of scale on distributions of biomass is particularly important for comparing information from different sources such as inventories, remote sensing and modeling, all of which can operate at different spatial resolutions. Reliable methods to compare results of vegetation models at a grid scale with field data collected at smaller scales are still missing. The scaling of biomass and variables, which determine the forest biomass, was investigated for a tropical forest in Panama. Based on field inventory data from Barro Colorado Island, spanning 50 ha over 30 years, the distributions of aboveground biomass, biomass gain and mortality were derived at different spatial resolutions, ranging from 10 to 100 m. Methods for fitting parametric distribution functions were compared. Further, it was tested under which assumptions about the distributions a simple stochastic simulation forest model could best reproduce observed biomass distributions at all scales. Also, an analytical forest model for calculating biomass distributions at equilibrium and assuming mortality as a white shot noise process was tested. Scaling exponents of about 0.47 were found for the standard deviations of the biomass and gain distributions, while mortality showed a different scaling relationship with an exponent of 0.3. Lognormal and gamma distribution functions fitted with the moment matching estimation method allowed for consistent parameter transfers between scales. Both forest models (stochastic simulation and analytical solution) were able to reproduce observed biomass distributions across scales, when combined with the derived scaling relationships. The study demonstrates a way of how to approach the scaling problem in model-data comparisons by providing a transfer relationship. Further research is needed for a better understanding of the mechanisms that shape the frequency distributions at the different scales. Y1 - 2022 U6 - https://doi.org/10.5194/bg-19-4929-2022 SN - 1726-4170 SN - 1726-4189 VL - 19 IS - 20 SP - 4929 EP - 4944 PB - Copernicus CY - Katlenburg-Lindau [u.a.] ER - TY - THES A1 - Fernandez Palomino, Carlos Antonio T1 - Understanding hydrological dynamics in the tropical Andes of Peru and Ecuador and their responses to climate change T1 - Verständnis der hydrologischen Dynamik in den tropischen Anden von Peru und Ecuador und ihrer Reaktionen auf den Klimawandel N2 - Human-induced climate change is impacting the global water cycle by, e.g., causing changes in precipitation patterns, evapotranspiration dynamics, cryosphere shrinkage, and complex streamflow trends. These changes, coupled with the increased frequency and severity of extreme hydrometeorological events like floods, droughts, and heatwaves, contribute to hydroclimatic disasters, posing significant implications for local and global infrastructure, human health, and overall productivity. In the tropical Andes, climate change is evident through warming trends, glacier retreats, and shifts in precipitation patterns, leading to altered risks of floods and droughts, e.g., in the upper Amazon River basin. Projections for the region indicate rising temperatures, potential glacier disappearance or substantial shrinkage, and altered streamflow patterns, highlighting challenges in water availability due to these expected changes and growing human water demand. The evolving trends in hydroclimatic conditions in the tropical Andes present significant challenges to socioeconomic and environmental systems, emphasizing the need for a comprehensive understanding to guide effective adaptation policies and strategies in response to the impacts of climate change in the region. The main objective of this thesis is to investigate current hydrological dynamics in the tropical Andes of Peru and Ecuador and their responses to climate change. Given the scarcity of hydrometeorological data in the region, this objective was accomplished through a comprehensive data preparation and analysis in combination with hydrological modeling using the Soil and Water Assessment Tool (SWAT) eco-hydrological model. In this context, the initial steps involved assessing, identifying, and/or generating more reliable climate input data to address data limitations. The thesis introduces RAIN4PE, a high-resolution precipitation dataset for Peru and Ecuador, developed by merging satellite, reanalysis, and ground-based data with surface elevation through the random forest method. Further adjustments of precipitation estimates were made for catchments influenced by fog/cloud water input on the eastern side of the Andes using streamflow data and applying the method of reverse hydrology. RAIN4PE surpasses other global and local precipitation datasets, showcasing superior reliability and accuracy in representing precipitation patterns and simulating hydrological processes across the tropical Andes. This establishes it as the optimal precipitation product for hydrometeorological applications in the region. Due to the significant biases and limitations of global climate models (GCMs) in representing key atmospheric variables over the tropical Andes, this study developed regionally adapted GCM simulations specifically tailored for Peru and Ecuador. These simulations are known as the BASD-CMIP6-PE dataset, and they were derived using reliable, high-resolution datasets like RAIN4PE as reference data. The BASD-CMIP6-PE dataset shows notable improvements over raw GCM simulations, reflecting enhanced representations of observed climate properties and accurate simulation of streamflow, including high and low flow indices. This renders it suitable for assessing regional climate change impacts on agriculture, water resources, and hydrological extremes. In addition to generating more accurate climatic input data, a reliable hydrological model is essential for simulating watershed hydrological processes. To tackle this challenge, the thesis presents an innovative multiobjective calibration framework integrating remote sensing vegetation data, baseflow index, discharge goodness-of-fit metrics, and flow duration curve signatures. In contrast to traditional calibration strategies relying solely on discharge goodness-of-fit metrics, this approach enhances the simulation of vegetation, streamflow, and the partitioning of flow into surface runoff and baseflow in a typical Andean catchment. The refined hydrological model calibration strategy was applied to conduct reliable simulations and understand current and future hydrological trajectories in the tropical Andes. By establishing a region-suitable and thoroughly tested hydrological model with high-resolution and reliable precipitation input data from RAIN4PE, this study provides new insights into the spatiotemporal distribution of water balance components in Peru and transboundary catchments. Key findings underscore the estimation of Peru's total renewable freshwater resource (total river runoff of 62,399 m3/s), with the Peruvian Amazon basin contributing 97.7%. Within this basin, the Amazon-Andes transition region emerges as a pivotal hotspot for water yield (precipitation minus evapotranspiration), characterized by abundant rainfall and lower atmospheric water demand/evapotranspiration. This finding underlines its paramount role in influencing the hydrological variability of the entire Amazon basin. Subsurface hydrological pathways, particularly baseflow from aquifers, strongly influence water yield in lowland and Andean catchments, sustaining streamflow, especially during the extended dry season. Water yield demonstrates an elevation- and latitude-dependent increase in the Pacific Basin (catchments draining into the Pacific Ocean), while it follows an unimodal curve in the Peruvian Amazon Basin, peaking in the Amazon-Andes transition region. This observation indicates an intricate relationship between water yield and elevation. In Amazon lowlands rivers, particularly in the Ucayali River, floodplains play a significant role in shaping streamflow seasonality by attenuating and delaying peak flows for up to two months during periods of high discharge. This observation underscores the critical importance of incorporating floodplain dynamics into hydrological simulations and river management strategies for accurate modeling and effective water resource management. Hydrological responses vary across different land use types in high Andean catchments. Pasture areas exhibit the highest water yield, while agricultural areas and mountain forests show lower yields, emphasizing the importance of puna (high-altitude) ecosystems, such as pastures, páramos, and bofedales, in regulating natural storage. Projected future hydrological trajectories were analyzed by driving the hydrological model with regionalized GCM simulations provided by the BASD-CMIP6-PE dataset. The analysis considered sustainable (low warming, SSP1-2.6) and fossil fuel-based development (high-end warming, SSP5-8.5) scenarios for the mid (2035-2065) and end (2065-2095) of the century. The projected changes in water yield and streamflow across the tropical Andes exhibit distinct regional and seasonal variations, particularly amplified under a high-end warming scenario towards the end of the century. Projections suggest year-round increases in water yield and streamflow in the Andean regions and decreases in the Amazon lowlands, with exceptions such as the northern Amazon expecting increases during wet seasons. Despite these regional differences, the upper Amazon River's streamflow is projected to remain relatively stable throughout the 21st century. Additionally, projections anticipate a decrease in low flows in the Amazon lowlands and an increased risk of high flows (floods) in the Andean and northern Amazon catchments. This thesis significantly contributes to enhancing climatic data generation, overcoming regional limitations that previously impeded hydrometeorological research, and creating new opportunities. It plays a crucial role in advancing hydrological model calibration, improving the representation of internal hydrological processes, and achieving accurate results for the right reasons. Novel insights into current hydrological dynamics in the tropical Andes are fundamental for improving water resource management. The anticipated intensified changes in water flows and hydrological extreme patterns under a high-end warming scenario highlight the urgency of implementing emissions mitigation and adaptation measures to address the heightened impacts on water resources. In fact, the new datasets (RAIN4PE and BASD-CMIP6-PE) have already been utilized by researchers and experts in regional and local-scale projects and catchments in Peru and Ecuador. For instance, they have been applied in river catchments such as Mantaro, Piura, and San Pedro to analyze local historical and future developments in climate and water resources. N2 - Menschgemachter Klimawandel beeinflusst den globalen Wasserkreislauf durch Veränderungen in Niederschlagsmustern, Verdunstungsdynamiken, dem Rückgang der Gletscher und komplexen Trends in den Abflussraten in den Flüssen. Diese Veränderungen, gepaart mit der zunehmenden Häufigkeit und Schwere von extremen hydrometeorologischen Ereignissen wie Überschwemmungen, Dürren und Hitzewellen, tragen zu hydroklimatischen Katastrophen bei und haben erhebliche Auswirkungen auf lokale und globale Infrastruktur, die menschliche Gesundheit und die Gesamtproduktivität. In den tropischen Anden zeigt sich der Klimawandel durch Erwärmungstrends, Gletscherschmelzen und Verschiebungen in den Niederschlagsmustern, was zu erhöhten Risiken von Überschwemmungen und Dürren führt, beispielsweise im oberen Amazonas-Einzugsgebiet. Projektionen für die Region deuten auf steigende Temperaturen, potenzielles Verschwinden oder erhebliche Schrumpfung von Gletschern und veränderte Abflussmuster hin, was die Herausforderungen bei der Wasserverfügbarkeit aufgrund dieser erwarteten Veränderungen und des wachsenden menschlichen Wasserbedarfs zeigt. Die Trends in den hydroklimatischen Bedingungen in den tropischen Anden stellen erhebliche Herausforderungen für sozioökonomische und Umweltsysteme dar und unterstreichen die Notwendigkeit eines umfassenden Verständnisses, um effektive Anpassungspolitiken und -strategien im Hinblick auf die Auswirkungen des Klimawandels in der Region zu steuern. Das Hauptziel dieser Dissertation ist es, die aktuellen hydrologischen Dynamiken in den tropischen Anden von Peru und Ecuador und ihre Reaktionen auf den Klimawandel zu untersuchen. Aufgrund der Knappheit von hydrometeorologischen Daten in der Region wurde dieses Ziel durch eine umfassende Datenvorbereitung und -analyse in Kombination mit hydrologische Modellierung mithilfe des ökohydrologischen Modells Soil and Water Assessment Tool (SWAT) erreicht. Die ersten Schritte umfassten die Bewertung, Identifizierung und/oder Generierung zuverlässigerer Klimadaten, um Datenbeschränkungen zu bewältigen. Die Arbeit beginnt mit der Vorstellung von RAIN4PE, einen hochauflösenden Niederschlagsdatensatz für Peru und Ecuador, der durch die Zusammenführung von Satelliten-, Reanalysen- und bodengestützten Daten mit der Geländeoberfläche durch die Methode des Random Forest entwickelt wurde. Weitere Anpassungen der Niederschlagsschätzungen erfolgen unter Verwendung von Abflussdaten für Einzugsgebiete, die durch den Einfluss von Nebel-/Wolkenwasser auf der östlichen Seite der Anden beeinflusst werden, und mit Hilfe der Methode der Reverse-Hydrologie. RAIN4PE übertrifft andere globale und lokale Niederschlagsdatensätze und zeigt eine überlegene Zuverlässigkeit und Genauigkeit bei der Darstellung von Niederschlagsmustern und der Simulation hydrologischer Prozesse in den tropischen Anden. Dies etabliert ihn als das optimale Niederschlagsprodukt für hydrometeorologische Anwendungen in der Region. Aufgrund der signifikanten Ungenauigkeiten und Beschränkungen globaler Klimamodelle (GCMs) bei der Darstellung wichtiger atmosphärischer Variablen über den tropischen Anden entwickelte diese Studie regional angepasste GCM-Simulationen, die speziell für Peru und Ecuador maßgeschneidert wurden. Diese Simulationen sind als der BASD-CMIP6-PE-Datensatz bekannt und wurden unter Verwendung zuverlässiger, hochauflösender Datensätze wie RAIN4PE als Referenzdaten abgeleitet. Der BASD-CMIP6-PE-Datensatz weist gegenüber rohen GCM-Ergebnissen bedeutende Verbesserungen auf, zeigt eine verbesserte Darstellung beobachteter Klimaeigenschaften und eine genaue Simulation des Wasserabflusses einschließlich seiner Hoch- und Niedrigflussindizes. Dies macht ihn geeignet, regionale Auswirkungen des Klimawandels auf Landwirtschaft, Wasserressourcen und hydrologische Extremereignisse zu bewerten. Zusätzlich zur Generierung genauerer klimatischer Eingabedaten ist ein zuverlässiges hydrologisches Modell für die Simulation hydrologischer Dynamiken im Einzugsgebiet unerlässlich. Um diese Herausforderung zu bewältigen, stellt die Arbeit einen innovativen multiobjektiven Kalibrierungsrahmen vor, der fernerkundungsbasierte Vegetationsdaten, Basisabfluss-Index, Abflussgütemaße und Kennzeichen der Abflussdauerkurve integriert. Im Gegensatz zu traditionellen Kalibrierungsstrategien, die ausschließlich auf Abflussgütemaße beruhen, verbessert dieser Ansatz die Simulation von Vegetation, Wasserabfluss und Aufteilung des Abflusses in Oberflächen- und Basisabfluss in einem typischen Anden-Einzugsgebiet. Die verfeinerte Kalibrierungsstrategie des hydrologischen Modells wurde angewendet, um zuverlässigere Simulationen zu erzielen und aktuelle und zukünftige hydrologische Entwicklungen in den tropischen Anden zu verstehen. Aufbauend auf einer der Region angepassten hydrologischen Modell mit hochauflösenden und zuverlässigen Niederschlagsdaten von RAIN4PE liefert diese Studie neue Einblicke in die räumlich-zeitliche Verteilung von Wasserbilanzkomponenten in Peru und grenzüberschreitenden Einzugsgebieten. Die wichtigsten Erkenntnisse betonen die Schätzung der Gesamtmenge an erneuerbarem Süßwasser in Peru (Gesamtwasserabfluss von 62.399 m3/s), wobei das peruanische Amazonasbecken 97,7% dazu beiträgt. Innerhalb dieses Beckens wird die Übergangsregion Amazonas-Anden als zentraler Hotspot für Wasserertrag (Niederschlag minus Evapotranspiration) hervorgehoben, geprägt durch reichlichen Niederschlag und eine geringere atmosphärische Wassernachfrage/Evapotranspiration. Diese Erkenntnis unterstreicht ihre herausragende Rolle bei der Beeinflussung der hydrologischen Variabilität des gesamten Amazonasbeckens. Unterirdische hydrologische Komponenten, insbesondere der Grundwasserabfluss, beeinflussen deutlich die Abflussbildung in Tiefland- und Anden-Einzugsgebieten und unterstützen den Abfluss in den Flüssen, insbesondere während der verlängerten Trockenzeit. Wasserertrag zeigt einen höhen- und breitengradabhängigen Anstieg im Pazifikbecken (Einzugsgebiete, die in den Pazifik münden), während er im peruanischen Amazonasbecken einer unimodalen Kurve folgt und im Übergangsgebiet Amazonas-Anden seinen Höhepunkt erreicht. Dieses Ergebnis verdeutlicht den Zusammenhang zwischen Abflussbildung und Geländehöhe. In Flüssen der Tiefebenen des Amazonas, insbesondere im Ucayali-Fluss, spielen Überschwemmungsgebiete eine bedeutende Rolle bei der saisonalen Wasserflussdynamik, indem sie Spitzenflüsse für bis zu zwei Monate während Perioden hoher Abflüsse abschwächen und verzögern. Dieses Ergebnis unterstreicht die Wichtigkeit der Einbeziehung von Überschwemmungsdynamiken in hydrologische Simulationen und Flussmanagementstrategien für eine präzise Modellierung und effektive Wasserressourcenbewirtschaftung. Hydrologische Reaktionen variieren je nach Landnutzungstypen in hohen Anden-Einzugsgebieten. Weideflächen zeigen den höchsten Wasserertrag, während landwirtschaftliche Flächen und Bergwälder geringere Wasserertrag aufweisen, was die Bedeutung von Puna (hochgelegenen) Ökosystemen wie Weiden, Páramos und Bofedales bei der Regulierung natürlicher Speicher betont. Projektierte zukünftige hydrologische Entwicklungen wurden analysiert, indem das hydrologische Modell mit regionalisierten GCM-Simulationen des BASD-CMIP6-PE-Datensatzes angetrieben wurde. Diese Analyse berücksichtigte nachhaltige (geringe Erwärmung, SSP1-2.6) und auf starker Nutzung fossiler Brennstoffe basierende (hochgradige Erwärmung, SSP5-8.5) Szenarien für die Mitte (2035-2065) und das Ende (2065-2095) des 21. Jahrhunderts. Die projektierten Veränderungen in Wasserertrag und Wasserabfluss in den tropischen Anden zeigen deutliche regionale und saisonale Variationen, insbesondere unter einem Szenario mit hoher Erwärmung gegen Ende des Jahrhunderts. Diese Projektionen deuten auf ganzjährige Zunahmen im Wasserertrag und Wasserabfluss in den Andenregionen und Rückgänge in den Tiefebenen des Amazonas hin, mit Ausnahmen wie im nördlichen Amazonasgebiet, wo Zunahmen während der Regenzeiten projektiert werden. Trotz dieser regionalen Unterschiede wird der jährliche Wasserabfluss des oberen Amazonas voraussichtlich im gesamten 21. Jahrhundert relativ stabil bleiben. Darüber hinaus deuten die Projektionen auf eine Abnahme der Niedrigabflüsse in den Tiefebenen des Amazonas und ein erhöhtes Risiko von Hochwasserabflüssen (Überschwemmungen) in den Anden- und nördlichen Amazonas-Einzugsgebieten hin. Diese Arbeit trägt erheblich zur Verbesserung der Datenlage bzgl. des Klimas in dieser Region bei, überwindet regionale Datenbegrenzungen, die zuvor hydrometeorologische Forschung behinderten, und schafft neue Möglichkeiten. Sie trägt zur Fortentwicklung der Kalibrierung hydrologischer Modelle bei, der Verbesserung der Darstellung interner hydrologischer Prozesse und damit der Erzielung hydrologisch konsistenter Simulationsergebnisse. Diese neuen Erkenntnisse zu den hydrologischen Dynamiken in den tropischen Anden sind grundlegend für eine verbesserte Bewirtschaftung der regionalen Wasserressourcen. Die erwartete Intensivierung des regionalen Wasserkreislaufs unter einem Szenario mit hoher Erwärmung unterstreichen die Dringlichkeit der Umsetzung von Maßnahmen zur Emissionsminderung und Anpassung, um den verstärkten Auswirkungen auf Wasserressourcen zu begegnen. Tatsächlich wurden die neuen Datensätze (RAIN4PE und BASD-CMIP6-PE) bereits von Forschern und Experten in regionalen und lokalen Projekten und Einzugsgebieten in Peru und Ecuador genutzt. Zum Beispiel wurden sie in Flusseinzugsgebieten wie Mantaro, Piura und San Pedro angewendet, um lokale historische und zukünftige Entwicklungen in Klima und Wasserressourcen zu analysieren. KW - hydrology KW - Hydrologie KW - tropical Andes KW - tropische Anden KW - climate change KW - Klimawandel KW - water resources KW - Wasserressourcen KW - RAIN4PE KW - RAIN4PE KW - BASD-CMIP6-PE KW - BASD-CMIP6-PE Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-656534 ER - TY - JOUR A1 - Vyse, Stuart A. A1 - Herzschuh, Ulrike A1 - Pfalz, Gregor A1 - Pestryakova, Lyudmila A. A1 - Diekmann, Bernhard A1 - Nowaczyk, Norbert A1 - Biskaborn, Boris K. T1 - Sediment and carbon accumulation in a glacial lake in Chukotka (Arctic Siberia) during the Late Pleistocene and Holocene BT - combining hydroacoustic profiling and down-core analyses JF - Biogeosciences N2 - Lakes act as important sinks for inorganic and organic sediment components. However, investigations of sedimentary carbon budgets within glacial lakes are currently absent from Arctic Siberia. The aim of this paper is to provide the first reconstruction of accumulation rates, sediment and carbon budgets from a lacustrine sediment core from Lake Rauchuagytgyn, Chukotka (Arctic Siberia). We combined multiple sediment biogeochemical and sedimentological parameters from a radiocarbon-dated 6.5m sediment core with lake basin hydroacoustic data to derive sediment stratigraphy, sediment volumes and infill budgets. Our results distinguished three principal sediment and carbon accumulation regimes that could be identified across all measured environmental proxies including early Marine Isotope Stage 2 (MIS2) (ca. 29-23.4 ka cal BP), mid-MIS2-early MIS1 (ca. 23.4-11.69 ka cal BP) and the Holocene (ca. 11.69-present). Estimated organic carbon accumulation rates (OCARs) were higher within Holocene sediments (average 3.53 gOCm(-2) a(-1)) than Pleistocene sediments (average 1.08 gOCm(-2) a(-1)) and are similar to those calculated for boreal lakes from Quebec and Finland and Lake Baikal but significantly lower than Siberian thermokarst lakes and Alberta glacial lakes. Using a bootstrapping approach, we estimated the total organic carbon pool to be 0.26 +/- 0.02 Mt and a total sediment pool of 25.7 +/- 1.71 Mt within a hydroacoustically derived sediment volume of ca. 32 990 557m(3). The total organic carbon pool is substantially smaller than Alaskan yedoma, thermokarst lake sediments and Alberta glacial lakes but shares similarities with Finnish boreal lakes. Temporal variability in sediment and carbon accumulation dynamics at Lake Rauchuagytgyn is controlled predominantly by palaeoclimate variation that regulates lake ice-cover dynamics and catchment glacial, fluvial and permafrost processes through time. These processes, in turn, affect catchment and within-lake primary productivity as well as catchment soil development. Spatial differences compared to other lake systems at a trans-regional scale likely relate to the high-latitude, mountainous location of Lake Rauchuagytgyn. Y1 - 2021 U6 - https://doi.org/10.5194/bg-18-4791-2021 SN - 1726-4170 SN - 1726-4189 VL - 18 IS - 16 SP - 4791 EP - 4816 PB - Copernicus CY - Katlenburg-Lindau ER - TY - JOUR A1 - Mohr, Christian H. A1 - Manga, Michael A1 - Helle, Gerhard A1 - Heinrich, Ingo A1 - Giese, Laura A1 - Korup, Oliver T1 - Trees talk tremor-wood anatomy and δ13C content reveal contrasting tree-growth responses to earthquakes JF - JGR / AGU, American Geophysical Union. Biogeosciences N2 - Large earthquakes can increase the amount of water feeding stream flows, raise groundwater levels, and thus grant plant roots more access to water in water-limited environments. We examine growth and photosynthetic responses of Pine plantations to the Maule M-w 8.8 earthquake in headwater catchments of Chile's Coastal Range. We combine high-resolution wood anatomic (lumen area) and biogeochemical (delta 13C of wood cellulose) proxies of daily to weekly tree growth sampled from trees on floodplains and close to ridge lines. We find that, immediately after the earthquake, at least two out of six tree trees on valley floors had increased lumen area and decreased delta 13C, while trees on hillslopes had a reverse trend. Our results indicate a control of soil water on this response, largely consistent with models that predict how enhanced postseismic vertical soil permeability causes groundwater levels to rise on valley floors, but fall along the ridges. Statistical analysis with boosted regression trees indicates that streamflow discharge gained predictive importance for photosynthetic activity on the ridges, but lost importance on the valley floor after the earthquake. We infer that earthquakes may stimulate ecohydrological conditions favoring tree growth over days to weeks by triggering stomatal opening. The weak and short-lived signals that we identified, however, show that such responses are only valid under water-limited, rather than energy-limited tree, growth. Hence, dendrochronological studies targeted at annual resolution may overlook some earthquake effects on tree vitality. KW - tree rings KW - isotope KW - wood anatomy KW - earthquake KW - Chile KW - vegetation Y1 - 2021 U6 - https://doi.org/10.1029/2021JG006385 SN - 2169-8953 SN - 2169-8961 VL - 126 IS - 10 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Cannone, Nicoletta A1 - Guglielmin, Mauro A1 - Malfasi, Francesco A1 - Hubberten, Hans Wolfgang A1 - Wagner, Dirk T1 - Rapid soil and vegetation changes at regional scale in continental Antarctica JF - Geoderma : an international journal of soil science N2 - Antarctica is the last pristine environment on Earth, its biota being adapted to the harsh and extreme polar climate. Until now, soil formation and vegetation development in continental Antarctica were considered very slow due to the extreme conditions of this polar desert. Since the austral summer 2002/2003, a long-term monitoring network of the terrestrial ecosystems (soils, vegetation, active layer thickness) has been established at Victoria Land (VL) across a > 500 km latitudinal gradient of coastal sites (73 degrees -77 degrees S). In only one decade large ecosystem changes were detected. Climate was characterized by a significant increase of thawing degree days in northern VL and of autumn air temperature. No extreme climatic events (such as hot spells) where detected in the study period. Soil chemistry suffered large quantitative changes, clearly indicating rapid pedogenetic processes. In most soils the upper layers exhibited a strong alkalinization (pH increases up to 3 units) and increases in conductivity, anions and cations (in particular of SO4 and Na). The largest changes were observed in soils with low vegetation cover. Statistically significant differences in soil chemistry were detected between soils with high and low vegetation cover, the former showing lower pH, conductivity, Na and Cl. Most plots exhibited changes of total cover, species richness and floristic composition, with vegetation expansion in soils with low vegetation cover and the largest increase recorded at Apostrophe Island (northern VL). Principal Component Analysis (PCA) identified the main trend of vegetation change, with a shift from lower to higher cover and a secondary trend of change associated with a gradient of water availability, consistent with an increase in water instead of snow. Redundancy analysis (RDA) identified the trend of change in soil chemistry with increases in pH, conductivity, anions and cations associated with the concomitant decrease in C, N, NO3, PO4. The RDA confirmed that soil changes were associated with a gradient of vegetation change (from low to high cover) as well as of water availability, as already indirectly outlined by the PCA. Field manipulation experiments carried out at five locations of the network between 73 degrees S and 77 degrees S, simulating increases of precipitation from snow or water additions didn't induce changes in soil pH, indicating that pulse events of snow accumulation or melting could not trigger persistent soil pH changes. These data allow hypothesize the occurrence of a main ecosystem change occurring at regional scale at Victoria Land. The slight air warming and its consequences on soil chemistry and vegetation, further highlight the sensitivity of the fragile Antarctic ecosystems to the consequences of even small changes in climate. KW - Soil chemistry KW - Alkalinization KW - Vegetation changes KW - Manipulation KW - experiment Y1 - 2021 U6 - https://doi.org/10.1016/j.geoderma.2021.115017 SN - 0016-7061 SN - 1872-6259 VL - 394 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Döpper, Veronika A1 - Jagdhuber, Thomas A1 - Holtgrave, Ann-Kathrin A1 - Heistermann, Maik A1 - Francke, Till A1 - Kleinschmit, Birgit A1 - Förster, Michael T1 - Following the cosmic-ray-neutron-sensing-based soil moisture under grassland and forest BT - exploring the potential of optical and SAR remote sensing JF - Science of remote Sensing N2 - Deriving soil moisture content (SMC) at the regional scale with different spatial and temporal land cover changes is still a challenge for active and passive remote sensing systems, often coped with machine learning methods. So far, the reference measurements of the data-driven approaches are usually based on point data, which entails a scale gap to the resolution of the remote sensing data. Cosmic Ray Neutron Sensing (CRNS) indirectly provides SMC estimates of a soil volume covering more than 1 ha and vertical depth up to 80 cm and is thus able to narrow this scale gap. So far, the CRNS-based SMC has only been used as validation source of remote sensing based SMC products. Its beneficial large sensing volume, especially in depth, has not been exploited yet. However, the sensing volume of the CRNS, which is changing with hydrological conditions, bears challenges for the comparison with remote sensing observations. This study, for the fist time, aims to understand the direct linkage of optical (Sentinel 2) and SAR (Sentinel 1) data with CRNS-based SMC. Thereby, the CRNS-based SMC is obtained by an experimental CRNS cluster that covers the high temporal and spatial SMC variability of an entire pre-alpine subcatchment. Using different Random Forest regressions, we analyze the potentials and limitations of both remote sensing sensors to follow the CRNS-based SMC signal. Our results show that it is possible to link the CRNS-based SMC signal with SAR and optical remote sensing observations via Random Forest modelling. We found that Sentinel 2 data is able to separate wet from dry periods with a R2 of 0.68. It is less affected by the changing soil volume that contributes to the CRNS-based SMC signal and it is able to assign a land cover specific SMC distribution. However, Sentinel 2 regression models are not accurate (R2 < 0.21) in mapping the CRNSbased SMC for the frequently mowed grassland areas of the study site. It requires soil type and topographical information to accurately follow the CRNS-based SMC signal with Random Forest regression. Sentinel 1 data instead is affected by the changing soil volume that contributes to the CRNS-based SMC signal. It has reasonable model performance (R2 = 0.34) when the CRNS data correspond to surface SMC. Also for Sentinel 1 the retrieval is impacted by the mowing activities at the test site. When separating the CRNS data set into dry and wet periods, soil properties and topography are the main drivers of SMC estimation. Sentinel 1 or Sentinel 2 data add the existing temporal variability to the regression models. The analysis underlines the need of combining optical and SAR observations (Sentinel 1, Sentinel 2) as well as soil property and topographical information to understand and follow the CRNS-based SMC signal for different hydrological conditions and land cover types. KW - Sentinel 1 KW - Sentinel 2 KW - soil texture KW - topography KW - sensing volume KW - Random Forest regression KW - CRNS Y1 - 2022 U6 - https://doi.org/10.1016/j.srs.2022.100056 SN - 2666-0172 VL - 5 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ben-Zion, Yehuda A1 - Dresen, Georg T1 - A synthesis of fracture, friction and damage processes in earthquake rupture zones JF - Pure and applied geophysics N2 - We review properties and processes of earthquake rupture zones based on field studies, laboratory observations, theoretical models and simulations, with the goal of assessing the possible dominance of different processes in different parts of the rupture and validity of commonly used models. Rupture zones may be divided into front, intermediate, and tail regions that interact to different extents. The rupture front is dominated by fracturing and granulation processes and strong dilatation, producing faulting products that are reworked by subsequent sliding behind. The intermediate region sustains primarily frictional sliding with relatively high slip rates that produce appreciable stress transfer to the propagating front. The tail region further behind is characterized by low slip rates that effectively do not influence the propagating front, although it (and the intermediate region) can spawn small offspring rupture fronts. Wave-mediated stress transfer can also trigger failures ahead of the rupture front. Earthquake ruptures are often spatially discontinuous and intermittent with a hierarchy of asperity and segment sizes that radiate waves with different tensorial compositions and frequency bands. While different deformation processes dominating parts of the rupture zones can be treated effectively with existing constitutive relations, a more appropriate analysis of earthquake processes would require a model that combines aspects of fracture, damage-breakage, and frictional frameworks. KW - Earthquake rupture zones KW - fracture KW - friction KW - rock damage KW - shear; KW - dilatancy Y1 - 2022 U6 - https://doi.org/10.1007/s00024-022-03168-9 SN - 0033-4553 SN - 1420-9136 VL - 179 SP - 4323 EP - 4339 PB - Birkhäuser CY - Basel ER - TY - JOUR A1 - Zhou, Xiangqian A1 - Jomaa, Seifeddine A1 - Yang, Xiaoqiang A1 - Merz, Ralf A1 - Wang, Yanping A1 - Rode, Michael T1 - Exploring the relations between sequential droughts and stream nitrogen dynamics in central Germany through catchment-scale mechanistic modelling JF - Journal of hydrology N2 - Like many other regions in central Europe, Germany experienced sequential summer droughts from 2015 to 2018. As one of the environmental consequences, river nitrate concentrations have exhibited significant changes in many catchments. However, catchment nitrate responses to the changing weather conditions have not yet been mechanistically explored. Thus, a fully distributed, process-based catchment Nitrate model (mHM-Nitrate) was used to reveal the causal relations in the Bode catchment, of which river nitrate concentrations have experienced contrasting trends from upstream to downstream reaches. The model was evaluated using data from six gauging stations, reflecting different levels of runoff components and their associated nitrate-mixing from upstream to downstream. Results indicated that the mHM-Nitrate model reproduced dynamics of daily discharge and nitrate concentration well, with Nash-Sutcliffe Efficiency >= 0.73 for discharge and Kling-Gupta Efficiency >= 0.50 for nitrate concentration at most stations. Particularly, the spatially contrasting trends of nitrate con-centration were successfully captured by the model. The decrease of nitrate concentration in the lowland area in drought years (2015-2018) was presumably due to (1) limited terrestrial export loading (ca. 40 % lower than that of normal years 2004-2014), and (2) increased in-stream retention efficiency (20 % higher in summer within the whole river network). From a mechanistic modelling perspective, this study provided insights into spatially heterogeneous flow and nitrate dynamics and effects of sequential droughts, which shed light on water -quality responses to future climate change, as droughts are projected to be more frequent. KW - drought KW - nitrate mixing KW - catchment hydrology KW - water quality model Y1 - 2022 U6 - https://doi.org/10.1016/j.jhydrol.2022.128615 SN - 0022-1694 SN - 1879-2707 VL - 614 IS - Part B PB - Elsevier CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Jiang, Feng A1 - Song, Junwei A1 - Bauer, Jonas A1 - Gao, Linyu A1 - Vallon, Magdalena A1 - Gebhardt, Reiner A1 - Leisner, Thomas A1 - Norra, Stefan A1 - Saathoff, Harald T1 - Chromophores and chemical composition of brown carbon characterized at anurban kerbside by excitation-emission spectroscopy and mass spectrometry JF - Atmospheric chemistry and physics N2 - The optical properties, chemical composition, and potential chromophores of brown carbon (BrC) aerosol particles were studied during typical summertime and wintertime at a kerbside in downtown Karl-sruhe, a city in central Europe. The average absorption coefficient and mass absorption efficiency at 365 nm (Abs(365) and MAE(365)) of methanol-soluble BrC (MS-BrC) were lower in the summer period (1.6 +/- 0.5 Mm(-1), 0.5 +/- 0.2 m(2) g(-1)) than in the winter period (2.8 +/- 1.9 Mm(-1), 1.1 +/- 0.3 m(2) g(-1)). Using a parallel factor (PARAFAC) analysis to identify chromophores, two different groups of highly oxygenated humic-like substances (HO-HULIS) dominated in summer and contributed 96 +/- 6 % of the total fluorescence intensity. In contrast, less-oxygenated HULIS (LO-HULIS) dominated the total fluorescence intensity in winter with 57 +/- 12 %, followed by HO-HULIS with 31 +/- 18 %. Positive matrix factorization (PMF) analysis of organic compounds detected in real time by an online aerosol mass spectrometer (AMS) led to five characteristic organic compound classes. The statistical analysis of PARAFAC components and PMF factors showed that LO-HULIS chromophores were most likely emitted from biomass burning in winter. HO-HULIS chromophores could be low-volatility oxy-genated organic aerosol from regional transport and oxidation of biogenic volatile organic compounds (VOCs) in summer. Five nitro-aromatic compounds (NACs) were identified by a chemical ionization mass spectrometer (C7H7O3N, C7H7O4N, C6H5O5N, C6H5O4N, and C6H5O3N), which contributed 0.03 +/- 0.01 % to the total organic mass but can explain 0.3 +/- 0.1 % of the total absorption of MS-BrC at 365 nm in winter. Furthermore, we identified 316 potential brown carbon molecules which accounted for 2.5 +/- 0.6 % of the organic aerosol mass. Using an average mass absorption efficiency (MAE(365)) of 9.5 m(2)g(-1) for these compounds, we can es-timate their mean light absorption to be 1.2 +/- 0.2 Mm(-1), accounting for 32 +/- 15 % of the total absorption of MS-BrC at 365 nm. This indicates that a small fraction of brown carbon molecules dominates the overall ab-sorption. The potential BrC molecules assigned to the LO-HULIS component had a higher average molecular weight (265 +/- 2 Da) and more nitrogen-containing molecules (62 +/- 1 %) than the molecules assigned to the HOHULIS components. Our analysis shows that the LO-HULIS, with a high contribution of nitrogen-containing molecules originating from biomass burning, dominates aerosol fluorescence in winter, and HO-HULIS, with fewer nitrogen-containing molecules as low-volatility oxygenated organic aerosol from regional transport and oxidation of biogenic volatile organic compounds (VOC), dominates in summer. Y1 - 2022 U6 - https://doi.org/10.5194/acp-22-14971-2022 SN - 1680-7316 SN - 1680-7324 VL - 22 IS - 22 SP - 14971 EP - 14986 PB - EGU CY - Katlenburg-Lindau ER -