julilili42/papers huggingface dataset:
Using multi-temporal Sentinel-2 data to predict chemical properties of the organic surface layer of forest soils
2020-03-10

&amp;lt;p&amp;gt;Area-wide high resolution information of organic layer properties is required for assessing the current nutrient availability in forest stands. Together with climate, location, parent material and terrain predictors, vegetation is known to have a direct impact on the characteristics of the organic surface layer of forest soils and therefore plays an important role in predicting its chemical properties.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Here, we use multi-temporal Sentinel-2 (S2) Earth Observation (EO) data as a proxy for various vegetation characteristics to spatially predict forest organic layer properties at 10 m spatial resolution in Saxony/Germany. To ensure full data coverage of the study area, we used multi-temporal statistical measures of S2 data generated by the FORCE algorithm. Complementary to ancillary predictors (climate, location, parent material, terrain), we compared three different sets of vegetation related data as predictors: (1) categorical tree species groups from a field survey, (2) multi-temporal statistical measures derived from S2 data and (3) S2 multi-temporal statistical measures and additional S2 multi-temporal spectral indices.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We used random forest regression models to estimate pH value, base saturation, C/N ratio and effective cation exchange capacity of the organic surface layer and the upper 0-5 cm of the first mineral soil horizon. For model evaluation 5-times 10-fold cross-validation was applied. For predictor evaluation and selection, we used recursive feature elimination.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The results indicate that S2 data can serve as a vegetation proxy when predicting forest organic layer properties. For example, the cross-validation estimate of the prediction error in scenario (3) for C/N ratio (organic surface layer) is about 7.3 % lower than in scenario (1). In some cases the explanatory power is higher compared to the field survey data of the tree species groups, probably due to the high local variability of EO based data. This may help to reveal short range variability of chemical properties. We conclude that the three scenarios show comparable results and thus multi-temporal S2 data can be used as a vegetation proxy to spatially predict chemical properties of the organic surface layer of forest soils.&amp;lt;/p&amp;gt;
Issues with fracturing ice during an ice drilling project in Greenland (EastGRIP)
2020-03-10

&amp;lt;p&amp;gt;Drilling an ice core through an ice sheet (typically 2000 to 3000 m thick) is a technical challenge that nonetheless generates valuable and unique information on palaeo-climate and ice dynamics. As technically the drilling cannot be done in one run, the core has to be fractured approximately every 3 m to retrieve core sections from the bore hole. This fracture process is initiated by breaking the core with core-catchers which also clamp the engaged core in the drill head while the whole drill is then pulled up with the winch motor.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;This standard procedure is known to become difficult and requires extremely high pulling forces (Wilhelms et al. 2007), in the very deep part of the drill procedure, close to the bedrock of the ice sheet, especially when the ice material becomes warm (approximately -2&amp;amp;#176;C) due to the geothermal heat released from the bedrock. Recently, during the EastGRIP (East Greenland Ice coring Project) drilling we observed a similar issue with breaking off cored sections only with extremely high pulling forces, but started from approximately 1800 m of depth, where the temperature is still very cold (approximately -20&amp;amp;#176;C). This has not been observed at other ice drilling sites. As dependencies of fracture behaviour on crystal orientation and grain size are known (Schulson &amp;amp; Duval 2009) for ice, we thus examined the microstructure in the ice samples close to and at the core breaks.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;First preliminary results suggest that these so far unexperienced difficulties are due to the profoundly different c-axes orientation distribution (CPO) in the EastGRIP ice core. In contrast to other deep ice cores which have been drilled on ice domes or ice divides, EastGRIP is located in an ice stream. This location means that the deformation geometry (kinematics) is completely different, resulting in a different CPO (girdle pattern instead of single maximum pattern). Evidence regarding additional grain-size dependence will hopefully help to refine the fracturing procedure, which is possible due to a rather strong grain size layering observed in natural ice formed by snow precipitation.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;---------------------&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Wilhelms, F.; Sheldon, S. G.; Hamann, I. &amp;amp; Kipfstuhl, S. Implications for and findings from deep ice core drillings - An example: The ultimate tensile strength of ice at high strain rates.&amp;amp;#160;Physics and Chemistry of Ice (The proceedings of the International Conference on the Physics and Chemistry of Ice held at Bremerhaven, Germany on 23-28 July 2006), &amp;lt;strong&amp;gt;2007&amp;lt;/strong&amp;gt;, 635-639&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Schulson, E. M. &amp;amp; Duval, P. Creep and Fracture of Ice. Cambridge University Press, &amp;lt;strong&amp;gt;2009&amp;lt;/strong&amp;gt;, 401&amp;lt;/p&amp;gt;
Detection of High-Organic-Carbon Features in Sediments by Direct-Push Color Logging
2020-03-10

&amp;lt;p&amp;gt;A biogeochemical site characterization aims at delineating zones of reducing and oxidizing conditions in the subsurface to infer their influence on solute and contaminant turnover processes along groundwater flow paths. Hereby, large values of the total organic carbon (TOC) content mark reducing conditions in soils and sediments. Dark sediment colors are good predictors for high-TOC zones and thus indicate hotspots of biogeochemical turnover and microbial activity. Traditionally, obtaining the sediment color requires costly sampling, resulting in poor horizontal resolution and related uncertainty caused by interpolation. We suggest using a direct-push soil color optical screening tool to acquire multiple high-resolution vertical color profiles and demonstrate its applicability in floodplain sediments down to 12 m depth. We use Gaussian mixture models for a cluster analysis of the color logs in the CIE L*a*b* color space to identify color-facies, determine facies-specific relationships between the L*a*b* color-values and the TOC content of the sediments, and to construct the 3-D distributions of three distinct facies and organic matter. Direct-push color-logging may also be used for in-situ mapping of redox-zonation, iron content, or sedimentary structures.&amp;lt;/p&amp;gt;
How alternating gaining and losing conditions along a low order agricultural stream govern the behavior of nitrogen species
2020-03-10

&amp;lt;p&amp;gt;Perennial low order streams are normally well connected to shallow groundwater and therefore, they are among the first receptors of agricultural effluents. Understanding the processes governing the water quality in agricultural areas requires identifying sources of potential pollutants (such as nitrate), hotspots of biogeochemical reactivity and defining the different hydrologic flowpaths connecting groundwater and surface water. To this end, we have equipped an agricultural drainage system (Sch&amp;amp;#246;nbrunnen) in south-western Germany with 3 stream gauging stations along a test segment of approximately 550 m and 33 piezometers in the adjacent shallow aquifer. Hydrological, hydrochemical, isotopic and microbiological variables have been monitored between August 2017 and December 2019 to spatially and temporally identify the controls of nitrogen cycling dynamics in our stream.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The Sch&amp;amp;#246;nbrunnen generally loses water in its mid-segment and it gains in the lower part of the catchment, although this behavior showed strong seasonal variations, considering winter and summer as the two main annual seasons. The groundwater-streamwater (GW-SW) exchange flux, and the replacement of streamwater lost to the aquifer over a reach by shallow groundwater, defined as hydrologic turnover, was found to influence streamwater chemistry. The main groundwater flow directions were determined based on hydraulic head contour maps. We used them to characterize the nitrogen (N) species&amp;amp;#8217; behavior along the flowpaths under two different hydrologic conditions: losing and gaining. Even though the losing condition at the midstream provides more favorable condition for N-species reduction at the GW-SW interface, reduction occurred also along gaining reaches. The isotope analyses of nitrate yielded data points plotting along the denitrification trend (slope of 0.5) in a dual isotope plot (&amp;lt;sup&amp;gt;15&amp;lt;/sup&amp;gt;N-NO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;&amp;lt;sup&amp;gt;-&amp;lt;/sup&amp;gt; versus &amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O-NO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;&amp;lt;sup&amp;gt;-&amp;lt;/sup&amp;gt;) for some of the sampling locations within the losing area. Comprehensive molecular approaches suggested a hotspot for denitrifying microbial communities in sediments of the losing stream reach. Along the GW flow path to the gaining area a depletion of nitrate was identified in concert with increasing sulfate and declining sulfide (H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;S) concentrations. Sulfide-driven nitrate reduction was likely to occur under anoxic conditions in this part of the aquifer. In summary, the findings demonstrate, that hydrologic turnover does not only mean hydrological exchanges, but also triggers variations in water composition along the transition zone between groundwater and streamwater by linking both, mixing and reactive processes.&amp;lt;/p&amp;gt;
3D Structure of NEGIS shear margins from radar stratigraphy
2020-03-10

&amp;lt;p&amp;gt;The North East Greenland Ice Stream (NEGIS) is delineated by well-defined shear margins, which are evident in the gradient of surface velocity field as well as in the surface topography, where they form troughs up to ten meters deep. In the upper part of the ice stream the margins appear not to be linked to bedrock topography. To understand this efficient system of mass transport towards the ocean it is essential to investigate the nature of the shear margins, as here very localized deformation decouples the inner ice stream from the slower flowing surrounding ice sheet. This process is influenced by several factors and feedback mechanisms, including the crystal fabric orientation, strain heating and localization of meltwater. In summary, the shear margins are area-wise a small part of the ice stream itself, but the processes leading to the localization of deformation are of similar importance for ice discharge as the processes enabling fast flow of the main trunk over the bed.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We present results from an airborne radar survey with the AWI Ultra-Wide Band Radar system, covering an area 150 km upstream and 100 km downstream of the deep drilling site on the ice stream (EGRIP). Over the survey area the ice stream accelerates from 12 m/a to 75 m/a. We focus on the signatures of the shear margins in the radar data. In the regions of localized shear, the internal reflections in the radargrams show disturbances in the form of steep undulations, or chevron folds, which are intensified with ongoing shear. As the ice stream has been covered with 36 flow-perpendicular radar sections we are able to show the evolution of these characteristic signatures over the survey area, and thus, as an analog, over time. 3D-representations of the folded stratigraphic layers reveal how new folds are formed when the ice stream widens and how older structures are preserved in the outer part of the main trunk, where they are no longer subject to shear. Furthermore, we link the change of the shape of the internal reflections in the shear zones to a strain rate field calculated from high resolution flow velocities derived by TerraSAR-X data.&amp;lt;/p&amp;gt;
Dynamics of redox potential and nutrient turnover in dry floodplain soils during a simulated rain fall event
2020-03-10

&amp;lt;p&amp;gt;Floodplain soils experience highly dynamic wet and dry cycles that trigger changes in redox conditions and as such play a crucial role for environmental nutrient cycling and pollutant fate.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;To elucidate the effects of varying water saturation on the predominant biogeochemical processes and their dynamics we simulated a heavy rain fall event with subsequent steady rain over ten consecutive days at a plot of arable soil in a floodplain near T&amp;amp;#252;bingen, southwest Germany. We monitored how soil redox conditions, redox sensitive soil constituents and microbial communities responded to changing water saturation.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The experiment design was fully randomized comprising irrigated plots mimicking rain events and dry controls.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Multi-level redox probes recorded in situ redox potentials at 10 cm intervals down to 90 cm depth on irrigated and dry plots. The initially dry soil showed redox potentials of +600 mV. The simulated heavy rain fall provoked a drop in redox potentials within hours in depths down to 40 cm and within a delay of 1 to 2 days in depths down to 60 cm. Subsequent steady rain lead to a decrease of the redox potentials to a minimum of -200 mV to -300 mV in depths of 20 to 30 cm and -100 mV in depths of 40 to 50 cm.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Soil cores were retrieved throughout the experiment to identify microbial communities and to determine depth profiles of nitrate, ammonium, adsorbed and poorly crystalline iron as well as total iron, and sulfide and sulfate in the pore water and the solid phase.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The high resolution temporal data on changes in redox potential, soil chemistry and soil microbial communities will be presented and discussed in terms of the predominant biogeochemical processes in the soil profile.&amp;lt;/p&amp;gt;
How vegetation drives initial soil development together with soil organic matter accrual in maritime Antarctica
2020-03-10

&amp;lt;p&amp;gt;Antarctica with its unique conditions for soil development offers the opportunity to disclose basic soil biogeochemical processes in an environment with a low degree of ecosystem interactions. The region&amp;amp;#8217;s climate is divided by the mountain ridge of the Antarctic Peninsula: on the South Shetland Islands (King George Island (KGI)) in the west a maritime cold climate prevails, while James Ross Island (JRI) in the east faces the continental cold climate of a polar desert with less precipitation and distinctly more pronounced temperature variations throughout the year. In addition, the autochthonous vegetation differs; while it solely consists of cryptogams on JRI, on KGI two vascular plants (Dechampsia antarctica, Colobanthus quitensis) are endemic. This scarce vegetation patterns together with land surfaces ice-free for several millenia allows studying the complex interaction between soil organic matter (SOM) sequestration and soil structure development with respect to the varying presence and growth of vegetation. &amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The main aim of our study is to decode the mechanisms determining the fate of SOM in maritime Antarctica and to understand how the scarce vegetation drives the chemical composition and distribution of SOM within specific physical SOM fractions. Therefore, we sampled transects ranging from vegetated patches to plant-free soil surfaces. The distance to these vegetation patches was reflected in clear variations in the distribution of carbon and nitrogen and in a decrease in labile SOM constituents as revealed by &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C-CPMAS NMR spectroscopy, while clay-sized mineral-associated SOM dominated the carbon storage throughout all sites. The ongoing climate change is assumed to significantly alter the vegetation distribution and thus drive the storage and composition of SOM. In the future, this will also strongly affect soil microbial activity and land-ocean transitions in Antarctica.&amp;lt;/p&amp;gt;
Middle Miocene rise of the High Himalaya and the disruption of transverse drainage due to basal accretion
2020-03-10

&amp;lt;p&amp;gt;The Himalaya is the highest and steepest mountain range on Earth and an efficient north-south barrier for moisture-bearing winds. The close coupling of changes in topography, erosion rates, and uplift has previously been interpreted as an expression of a climatic control on tectonic deformation. Here, we present 17 new zircon U/Th-He (ZHe) bedrock-cooling ages from the Sutlej Valley that &amp;amp;#8211; together with &amp;gt;100 previously published mica &amp;lt;sup&amp;gt;40&amp;lt;/sup&amp;gt;Ar/&amp;lt;sup&amp;gt;39&amp;lt;/sup&amp;gt;Ar, zircon and apatite fission track ages &amp;amp;#8211; allow us to constrain the crustal cooling and exhumation history over the last ~20 Myr. Using 1D-thermal modeling, we observe a rapid decrease in exhumation rates from &amp;gt;1 km/Myr to &amp;lt;0.4 km/Myr that initiated at 15-13 Ma across the entire Greater Himalaya and the north-Himalayan Leo Pargil gneiss dome, both in the hanging and footwall of major Miocene shear zones, suggesting that cooling is associated to surface erosion and not due to tectonic unroofing. We explain the middle Miocene deceleration of exhumation by the onset of the growth of the Lesser Himalayan duplex, which resulted in accelerated uplift of the Greater Himalaya above a mid-crustal ramp and the establishment of an efficient orographic barrier. The period of slow exhumation in the upper Sutlej Valley coincides with a period of internal drainage in the south-Tibetan Zada Basin farther upstream, which we interpret to be a consequence of tectonic damming of the upper Sutlej River. External drainage of the Zada Basin was re-established at ~1 Ma, when we observe exhumation rates in the upper Sutlej Valley to accelerate again.&amp;lt;/p&amp;gt;
Changes in water balance of the Qaidam Basin from Pliocene to present day
2020-03-10

&amp;lt;p&amp;gt;In the Pliocene, the Qaidam Basin in the northeastern Tibetan Plateau contained a freshwater mega-lake system. The lake system disappeared and the lower parts of the basin now feature hyperarid conditions. What led to the collapse of the lake system and could it appear again in the future? Understanding the sensitivity of the basin&amp;amp;#8217;s water balance to changes in atmospheric conditions is crucial for answering this question. We employed the Weather Research and Forecasting model for the dynamical downscaling of two time slices. These were simulated by ECHAM5-wiso atmospheric general circulation model under different boundary conditions, representing present day and Pliocene climate. We present a comparison study analyzing how the basin&amp;amp;#8216;s water balance changes, when we put the Qaidam basin catchment area with its modern geographical features into the Pliocene climate environment. Furthermore, we investigate large scale controls of the basin&amp;amp;#8217;s water balance. We find that (1) the Basin&amp;amp;#8217;s water balance is more positive or less negative under Pliocene climate; (2) the atmospheric water transport from the west into the basin to be stronger under Pliocene than under present day conditions except for the summer months, while at the same time the influence of the Indian Summer Monsoon is weaker. The analysis suggests that minor changes in atmospheric boundary conditions can have substantial effects on the basin&amp;amp;#8217;s water balance.&amp;lt;/p&amp;gt;
How can natural hazard scientists enhance their contribution to building sustainable and resilient societies?
2020-03-10

&amp;lt;p&amp;gt;Reducing disaster risk is critical to securing the ambitions of the Sustainable Development Goals (SDGs), and natural hazard scientists can help to do this. Their understanding of Earth dynamics underpins hazard analysis, which (alongside analysis of other disaster risk drivers) in turn informs the actions needed to manage and reduce disaster risk. Here we outline how natural hazard research scientists can contribute to the planning and development of sustainable and resilient communities through improved engagement in disaster risk reduction (DRR). Building on existing good practice, this talk therefore aims to provoke discussion in the natural hazard science community about how we strengthen our engagement in DRR. We first set out seven reflections on improving the integration of natural hazard science into DRR: (i) characterise multi-hazard environments, (ii) prioritise effective, long-term partnerships, (iii) understand and listen to stakeholder, (iv) embed cultural understanding into natural hazards research, (v) ensure improved and equitable access to hazards information, (vi) champion people-centred DRR (leave no one behind), and (vii) improve links between DRR and sustainable development. We then proceed to synthesise key actions that natural hazards scientists and research funders can take to improve education, training, and research design, and to strengthen institutional, financial and policy actions. We suggest that these actions support the translation, adoption and effective application of natural hazards science, and will enable the natural hazard science community to contribute more effectively to the integrated work needed to improve DRR activities.&amp;lt;/p&amp;gt;
Paleo-drip rates from trace metal concentrations in stalagmites: An inverse modeling problem with data uncertainties
2020-03-10

&amp;lt;p&amp;gt;The concentration of trace elements such as Ni, Co, and Cu in a stalagmite is determined by (i) the amount of these elements present in so-called organic-metal complexes (OMCs) that trap the ionic forms of such elements in the dripwater, and (ii) the amount that is able to decay from the OMCs into the aqueous phase, from where the elements can adsorb to the growing stalagmite surface (and remain captured within the stalagmite crystal structure). A statistical treatment of the decay of a population of trace element ions from OMCs allow us to model the rates at which the dripwater dropped from the roof of the cave on to the stalagmite&amp;amp;#8217;s surface. The problem is however made challenging due to: (i) the lack of reliable monitoring data that quantifies the relationship between OMC trace metal ion concentration and stalagmite trace metal ion concentration, and (ii) the presence of chronological uncertainties in our estimates of trace element concentrations at past time points from the depth-based measurements along the stalagmite. We present here a semi-heuristic, semi-theoretical approach that estimates dripwater rates using a theoretical model based on the population-level chemical kinetics of trace element decay from OMCs, and a heuristic choice of calibration data sets based on precipitation and temperature from nearby weather station data. Our approach is applied to trace metal data from the Heshang Cave in southeastern China, and we are able to reconstruct a driprate proxy time series &amp;amp;#8212; a first quantitative hydrological proxy record presented along with well-defined estimates of uncertainty.&amp;lt;/p&amp;gt;