TY - JOUR A1 - Engels, Stefan A1 - Medeiros, Andrew S. A1 - Axford, Yarrow A1 - Brooks, Steve A1 - Heiri, Oliver A1 - Luoto, Tomi P. A1 - Nazarova, Larisa B. A1 - Porinchu, David F. A1 - Quinlan, Roberto A1 - Self, Angela E. T1 - Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity JF - Global change biology N2 - Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a metadata analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric data sets overall consisting of 837 lakes. Our results indicate that in most of our data sets, summer temperature (T-jul) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing T-jul in regions with present-day T-jul between 2.5 and 14 degrees C. In some areas with T-jul > 14 degrees C, chironomid diversity stabilizes or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (similar to 15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites. KW - Arctic KW - biodiversity KW - climate warming KW - freshwater ecosystems KW - insects KW - palaeoecology KW - Quaternary Y1 - 2019 U6 - https://doi.org/10.1111/gcb.14862 SN - 1354-1013 SN - 1365-2486 VL - 26 IS - 3 SP - 1155 EP - 1169 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Runge, Alexandra A1 - Grosse, Guido T1 - Mosaicking Landsat and Sentinel-2 Data to Enhance LandTrendr Time Series Analysis in Northern High Latitude Permafrost Regions JF - Remote Sensing N2 - Permafrost is warming in the northern high latitudes, inducing highly dynamic thaw-related permafrost disturbances across the terrestrial Arctic. Monitoring and tracking of permafrost disturbances is important as they impact surrounding landscapes, ecosystems and infrastructure. Remote sensing provides the means to detect, map, and quantify these changes homogeneously across large regions and time scales. Existing Landsat-based algorithms assess different types of disturbances with similar spatiotemporal requirements. However, Landsat-based analyses are restricted in northern high latitudes due to the long repeat interval and frequent clouds, in particular at Arctic coastal sites. We therefore propose to combine Landsat and Sentinel-2 data for enhanced data coverage and present a combined annual mosaic workflow, expanding currently available algorithms, such as LandTrendr, to achieve more reliable time series analysis. We exemplary test the workflow for twelve sites across the northern high latitudes in Siberia. We assessed the number of images and cloud-free pixels, the spatial mosaic coverage and the mosaic quality with spectral comparisons. The number of available images increased steadily from 1999 to 2019 but especially from 2016 onward with the addition of Sentinel-2 images. Consequently, we have an increased number of cloud-free pixels even under challenging environmental conditions, which then serve as the input to the mosaicking process. In a comparison of annual mosaics, the Landsat+Sentinel-2 mosaics always fully covered the study areas (99.9–100 %), while Landsat-only mosaics contained data-gaps in the same years, only reaching coverage percentages of 27.2 %, 58.1 %, and 69.7 % for Sobo Sise, East Taymyr, and Kurungnakh in 2017, respectively. The spectral comparison of Landsat image, Sentinel-2 image, and Landsat+Sentinel-2 mosaic showed high correlation between the input images and mosaic bands (e.g., for Kurungnakh 0.91–0.97 between Landsat and Landsat+Sentinel-2 mosaic and 0.92–0.98 between Sentinel-2 and Landsat+Sentinel-2 mosaic) across all twelve study sites, testifying good quality mosaic results. Our results show that especially the results for northern, coastal areas was substantially improved with the Landsat+Sentinel-2 mosaics. By combining Landsat and Sentinel-2 data we accomplished to create reliably high spatial resolution input mosaics for time series analyses. Our approach allows to apply a high temporal continuous time series analysis to northern high latitude permafrost regions for the first time, overcoming substantial data gaps, and assess permafrost disturbance dynamics on an annual scale across large regions with algorithms such as LandTrendr by deriving the location, timing and progression of permafrost thaw disturbances KW - time series analysis KW - data fusion KW - disturbance tracking KW - permafrost KW - permafrost thaw Y1 - 2020 U6 - https://doi.org/10.3390/rs12152471 SN - 2072-4292 VL - 12 IS - 15 PB - MDPI CY - Basel ER - TY - JOUR A1 - Coesfeld, Jacqueline A1 - Kuester, Theres A1 - Kuechly, Helga U. A1 - Kyba, Christopher C. M. T1 - Reducing variability and removing natural light from nighttime satellite imagery: A case study using the VIIRS DNB JF - Sensors N2 - Temporal variation of natural light sources such as airglow limits the ability of night light sensors to detect changes in small sources of artificial light (such as villages). This study presents a method for correcting for this effect globally, using the satellite radiance detected from regions without artificial light emissions. We developed a routine to define an approximate grid of locations worldwide that do not have regular light emission. We apply this method with a 5 degree equally spaced global grid (total of 2016 individual locations), using data from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day-Night Band (DNB). This code could easily be adapted for other future global sensors. The correction reduces the standard deviation of data in the Earth Observation Group monthly DNB composites by almost a factor of two. The code and datasets presented here are available under an open license by GFZ Data Services, and are implemented in the Radiance Light Trends web application. KW - airglow KW - artificial light KW - calibration KW - VIIRS DNB KW - nightlights KW - remote sensing Y1 - 2020 VL - 20 PB - MDPI CY - Basel ER - TY - JOUR A1 - Zeeden, Christian A1 - Obreht, Igor A1 - Veres, Daniel A1 - Kaboth-Bahr, Stefanie A1 - Hošek, Jan A1 - Marković, Slobodan B. A1 - Bösken, Janina A1 - Lehmkuhl, Frank A1 - Rolf, Christian A1 - Hambach, Ulrich T1 - Smoothed millennial-scale palaeoclimatic reference data as unconventional comparison targets: Application to European loess records JF - Scientific Reports N2 - Millennial-scale palaeoclimate variability has been documented in various terrestrial and marine palaeoclimate proxy records throughout the Northern Hemisphere for the last glacial cycle. Its clear expression and rapid shifts between different states of climate (Greenland Interstadials and Stadials) represents a correlation tool beyond the resolution of e.g. luminescence dating, especially relevant for terrestrial deposits. Usually, comparison of terrestrial proxy datasets and the Greenland ice cores indicates a complex expression of millennial-scale climate variability as recorded in terrestrial geoarchives including loess. Loess is the most widespread terrestrial geoarchive of the Quaternary and especially widespread over Eurasia. However, loess often records a smoothed representation of millennial-scale variability without all fidelity when compared to the Greenland data, this being a relevant limiting feature in integrating loess with other palaeoclimate records. To better understand the loess proxy-response to millennial-scale climate variability, we simulate a proxy signal smoothing by natural processes through application of low-pass filters of delta O-18 data from Greenland, a high-resolution palaeoclimate reference record, alongside speleothem isotope records from the Black Sea-Mediterranean region. We show that low-pass filters represent rather simple models for better constraining the expression of millennial-scale climate variability in low sedimentation environments, and in sediments where proxy-response signals are most likely affected by natural smoothing (by e.g. bioturbation). Interestingly, smoothed datasets from Greenland and the Black Sea-Mediterranean region are most similar in the last similar to 15 ka and between similar to 50-30 ka. Between similar to 30-15 ka, roughly corresponding to the Last Glacial Maximum and the deglaciation, the records show dissimilarities, challenging the construction of robust correlative time-scales in this age range. From our analysis it becomes apparent that patterns of palaeoclimate signals in loess-palaeosol sequences often might be better explained by smoothed Greenland reference data than the original high-resolution Greenland dataset, or other reference data. This opens the possibility to better assess the temporal resolution and palaeoclimate potential of loess-palaeosol sequences in recording supra-regional climate patterns, as well as to securely integrate loess with other chronologically better-resolved palaeoclimate records. KW - last glacial period KW - Western Interior Basin KW - high-resolution record KW - Greenland ice cores KW - paleosol sequence KW - time-scale KW - Chinese loess KW - astronomical calibration KW - chronology (AICC2012) KW - Antarctic ice Y1 - 2020 VL - 10 IS - 1 PB - Springer Nature CY - Berlin ER - TY - JOUR A1 - Naliboff, John B. A1 - Glerum, Anne A1 - Brune, Sascha A1 - Péron-Pinvidic, G. A1 - Wrona, Thilo T1 - Development of 3-D rift heterogeneity through fault network evolution JF - Geophysical Research Letters N2 - Observations of rift and rifted margin architecture suggest that significant spatial and temporal structural heterogeneity develops during the multiphase evolution of continental rifting. Inheritance is often invoked to explain this heterogeneity, such as preexisting anisotropies in rock composition, rheology, and deformation. Here, we use high-resolution 3-D thermal-mechanical numerical models of continental extension to demonstrate that rift-parallel heterogeneity may develop solely through fault network evolution during the transition from distributed to localized deformation. In our models, the initial phase of distributed normal faulting is seeded through randomized initial strength perturbations in an otherwise laterally homogeneous lithosphere extending at a constant rate. Continued extension localizes deformation onto lithosphere-scale faults, which are laterally offset by tens of km and discontinuous along-strike. These results demonstrate that rift- and margin-parallel heterogeneity of large-scale fault patterns may in-part be a natural byproduct of fault network coalescence. KW - magma-poor KW - continental lithosphere KW - extension KW - insights KW - margins KW - architecture KW - systems KW - models KW - sea KW - reactivation Y1 - 2019 VL - 47 IS - 13 PB - John Wiley & Sons, Inc. CY - New Jersey ER - TY - JOUR A1 - Sharma, Shubham A1 - Hainzl, Sebastian A1 - Zöller, Gert A1 - Holschneider, Matthias T1 - Is Coulomb stress the best choice for aftershock forecasting? JF - Journal of geophysical research : Solid earth N2 - The Coulomb failure stress (CFS) criterion is the most commonly used method for predicting spatial distributions of aftershocks following large earthquakes. However, large uncertainties are always associated with the calculation of Coulomb stress change. The uncertainties mainly arise due to nonunique slip inversions and unknown receiver faults; especially for the latter, results are highly dependent on the choice of the assumed receiver mechanism. Based on binary tests (aftershocks yes/no), recent studies suggest that alternative stress quantities, a distance-slip probabilistic model as well as deep neural network (DNN) approaches, all are superior to CFS with predefined receiver mechanism. To challenge this conclusion, which might have large implications, we use 289 slip inversions from SRCMOD database to calculate more realistic CFS values for a layered half-space and variable receiver mechanisms. We also analyze the effect of the magnitude cutoff, grid size variation, and aftershock duration to verify the use of receiver operating characteristic (ROC) analysis for the ranking of stress metrics. The observations suggest that introducing a layered half-space does not improve the stress maps and ROC curves. However, results significantly improve for larger aftershocks and shorter time periods but without changing the ranking. We also go beyond binary testing and apply alternative statistics to test the ability to estimate aftershock numbers, which confirm that simple stress metrics perform better than the classic Coulomb failure stress calculations and are also better than the distance-slip probabilistic model. Y1 - 2020 U6 - https://doi.org/10.1029/2020JB019553 SN - 2169-9313 SN - 2169-9356 VL - 125 IS - 9 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Oberhänsli, Roland T1 - Deep-time Digital Earth (DDE) the first IUGS big science program JF - Journal of the Geological Society of India Y1 - 2020 U6 - https://doi.org/10.1007/s12594-020-1420-5 SN - 0016-7622 SN - 0974-6889 VL - 95 IS - 3 SP - 223 EP - 226 PB - Springer India CY - New Delhi ER - TY - JOUR A1 - León, Ena Mercedes Matienzo T1 - Observaciones sobre el clima de Lima y sus influencias en los seres organizados, en especial el hombre JF - Iberoamericana N2 - Una extraordinaria edición actualizada de Observaciones sobre el clima de Lima y sus influencias en los seres organizados, en especial el hombre de José Hipólito Unanue y Pavón ha sido publicado en el 2018 y merece ser anunciado a la comunidad académica peruana e internacional. Este libro incluye un exhaustivo estudio in troductorio del destacado historiador Lizardo Seiner Lizárraga. Esta introducción está conformada de tres partes encabezadas por los siguientes títulos: a) Unanue: una historiografía de amplio espectro b) Textos, registros y referencias: una indagación en la biblioteca de Unanue y c) Observaciones sobre el clima de Lima: una obra en dos tiempos. Y1 - 2020 U6 - https://doi.org/10.18441/ibam.20.2020.74.279-394 SN - 1577-3388 SN - 2255-520X VL - 20 IS - 74 SP - 305 EP - 308 PB - Vervuert CY - Frankfurt, Main ER - TY - JOUR A1 - Marcisz, Katarzyna A1 - Jassey, Vincent E. J. A1 - Kosakyan, Anush A1 - Krashevska, Valentyna A1 - Lahr, Daniel J. G. A1 - Lara, Enrique A1 - Lamentowicz, Lukasz A1 - Lamentowicz, Mariusz A1 - Macumber, Andrew A1 - Mazei, Yuri A1 - Mitchell, Edward A. D. A1 - Nasser, Nawaf A. A1 - Patterson, R. Timothy A1 - Roe, Helen M. A1 - Singer, David A1 - Tsyganov, Andrey N. A1 - Fournier, Bertrand T1 - Testate amoeba functional traits and their use in paleoecology JF - Frontiers in Ecology and Evolution N2 - This review provides a synthesis of current knowledge on the morphological and functional traits of testate amoebae, a polyphyletic group of protists commonly used as proxies of past hydrological changes in paleoecological investigations from peatland, lake sediment and soil archives. A trait-based approach to understanding testate amoebae ecology and paleoecology has gained in popularity in recent years, with research showing that morphological characteristics provide complementary information to the commonly used environmental inferences based on testate amoeba (morpho-)species data. We provide a broad overview of testate amoeba morphological and functional traits and trait-environment relationships in the context of ecology, evolution, genetics, biogeography, and paleoecology. As examples we report upon previous ecological and paleoecological studies that used trait-based approaches, and describe key testate amoebae traits that can be used to improve the interpretation of environmental studies. We also highlight knowledge gaps and speculate on potential future directions for the application of trait-based approaches in testate amoeba research. KW - protists KW - functional traits KW - morphological traits KW - ecology KW - peatlands KW - lakes KW - soils KW - trait-based approaches Y1 - 2020 U6 - https://doi.org/10.3389/fevo.2020.575966 SN - 2296-701X VL - 8 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Soares, Gabriel Brando A1 - Yamazaki, Yosuke A1 - Cnossen, Ingrid A1 - Matzka, Jürgen A1 - Pinheiro, Katia J. A1 - Morschhauser, Achim A1 - Alken, Patrick A1 - Stolle, Claudia T1 - Evolution of the geomagnetic daily variation at Tatuoca, Brazil, From 1957 to 2019 BT - a transition from Sq to EEJ JF - Journal of geophysical research : Space physics N2 - The magnetic equator in the Brazilian region has moved over 1,100 km northward since 1957, passing the geomagnetic observatory Tatuoca (TTB), in northern Brazil, around 2013. We recovered and processed TTB hourly mean values of the geomagnetic field horizontal (H) component from 1957 until 2019, allowing the investigation of long-term changes in the daily variation due to the influence of secular variation, solar activity, season, and lunar phase. The H day-to-day variability and the occurrence of the counter electrojet at TTB were also investigated. Until the 1990s, ionospheric solar quiet currents dominated the quiet-time daily variation at TTB. After 2000, the magnitude of the daily variation became appreciably greater due to the equatorial electrojet (EEJ) contribution. The H seasonal and day-to-day variability increased as the magnetic equator approached, but their amplitudes normalized to the average daily variation remained at similar levels. Meanwhile, the amplitude of the lunar variation, normalized in the same way, increased from 5% to 12%. Within the EEJ region, the occurrence rate of the morning counter electrojet (MCEJ) increased with proximity to the magnetic equator, while the afternoon counter electrojet (ACEJ) did not. EEJ currents derived from CHAMP and Swarm satellite data revealed that the MCEJ rate varies with magnetic latitude within the EEJ region while the ACEJ rate is largely constant. Simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model based on different geomagnetic main field configurations suggest that long-term changes in the geomagnetic daily variation at TTB can be attributed to the main field secular variation. Y1 - 2020 U6 - https://doi.org/10.1029/2020JA028109 SN - 2169-9380 SN - 2169-9402 VL - 125 IS - 9 PB - American Geophysical Union CY - Washington ER -