julilili42/papers huggingface dataset:
Comparing the effects of large scale solar farms on climate and regional surface energy budget in different climate models
2023-02-26

Solar panels of utility scale are a rapidly growing contribution to the renewable energy supply with increasing efficiency and steeply reducing costs of photovoltaics (PV). Although there is consensus on long term reduction of greenhouse gas emissions and advantages of avoided emissions by using PV systems, there is need to understand the climatic effects of land surface modifications of such systems.We first review studies focusing on effects of utility-scale solar farms and compare their results in accordance to their characterization of a photovoltaic and the type of model used to evaluate effects. Then, we perform simulations of larger than current utility-scale solar farms but also comparatively small localized farms which are both characterized by modified land surface properties. These regions are either identified on the basis of solar insolation and desert-like criteria (low precipitation) or are proposed in existing studies for potential deployment of solar farms. The solar farm deployments are characterized by static or gradual changes in respective boundary conditions of albedo, soil roughness and outgoing longwave thermal properties. Separate experiments are conducted with non-dynamic and dynamic vegetation components to investigate potential feedbacks originating from the interplay of vegetation and precipitation. To this end, we use a comprehensive model (MPI-ESM-LR; Mauritsen et al., 2019), and the Earth System Model of Intermediate Complexity PlaSim (Fraedrich et al., 2005) to understand, and cross-validate, the effects in two models of different complexity model.We examine the results considering changes in radiative forces and surface energy budget and, therefore, the surface temperatures which can likely lead to atmospheric circulation patterns, precipitation and vegetation feedbacks. If lower complexity models provide results in an acceptable ballpark of comprehensive ESMs, then they could be further used for future quick compute simulations with various deployment scenarios and experimentation with variable technical aspects. Spatially explicit deployment of PV with focus on parameterized thermal properties dependent on the simulated climate would also allows us to look at the complementary effect of climate on panels and could help constrain the effect of different pathways on PV technology in the future.
Drivers of eastern Andean Plateau incision from integrated thermochronology and thermo-kinematic modelling
2023-02-26

Proposed drivers of eastern Andean Plateau river incision in the Pliocene include climate change, dynamically driven plateau uplift, and long-wavelength surface uplift above deep basement structures. However, the evaluation of each mechanism has been hampered in previous studies due to the lack of along-strike data on the timing and extent of canyon incision. In addition, the magnitude of exhumation, permissible structural geometries, and integration of the long-term deformation, erosion, exhumation, and sedimentation histories remain poorly understood.This presentation focuses on two balanced geologic cross-sections and thermochronologic bedrock sample transects across the Andean Plateau, Eastern Cordillera, and Subandes in southern Peru. Based on (i) age-distance and age-elevation patterns of &gt;80 new thermochronologic dates (apatite and zircon (U-Th)/He and fission-track) from plateau, interfluve, and canyon sample locations; (ii) inverse thermal history model results; and (iii) flexural and thermo-kinematic modeling, we highlight similarities and differences in thermochronometric age patterns, exhumation magnitude, structural geometries, and shortening rates between each section.Results show that the first-order thermochronometric age pattern is a function of rocks' vertical and lateral movement over basement ramps and resulting exhumational erosion. This pattern is superimposed with a regional and synchronous incision-related exhumation signal since the Pliocene. While this incision occurred independent of structural deformation, the exhumation magnitude and difference in interfluve and canyon thermochronometric ages require the presence of a tectonic contribution to exhumation. We conclude that uplift over a basement ramp in the Eastern Cordillera and a decrease in shortening rates since ~10 Ma set the stage for climate-enhanced incision to occur in southern Peru.
The signature of heavy halogens across the evolution of a Sn-W-Cu mineralized system: a fluid inclusion study
2023-02-26

The recent need of a green-energy transition has sparked even more interest on critical elements such as tungsten and tin, whose genesis in ore deposits is linked to fluids exsolving from granitic plutons, but some mechanisms of formation remain unclear. Most authors in the past have proposed the mixing with meteoric, metamorphic or basinal fluids to be critical, while others believe that these deposits can form by simple cooling of magmatic fluids.Given the modern advances in analytical techniques, it is nowadays possible to characterize fluid inclusions in-situ also for trace elements such as bromine and especially iodine with the LA-ICP-MS. This study aims to apply a novel technique of measuring Br/Cl and I/Cl in individual fluid inclusions and bring some new insights on the Sn-W ore deposits genesis from a different perspective. In fact, halogens are well known to be highly incompatible in most minerals, retaining the fluid source reservoir signature, and to behave conservatively in fluid-rock interaction, therefore they can be regarded as suitable tracers for fluid evolution. These characteristics make heavy halogen studies particularly suitable for tackling the open question on the formation of Sn-W mineralized systems.The study area is the well-studied Cornubian batholith, in south-west England, which has been extensively mined in the past mostly for tin, copper and tungsten. It consists of 5 types of granites, divided into two main fractionation series, and cross-cut by mineralized veins rich in cassiterite, Cu-sulphides and W-oxides (among others), outcropping mainly in proximity of the contacts with the country rock.Despite significant mineralogical variation across the samples, representing different stages of the transition from magmatic to hydrothermal environments, halogen ratios are relatively homogeneous, especially under the hydrothermal regime, with magmatic fractionation as the only candidate process for a shift to higher Br/Cl and I/Cl values. On the other hand, alkalis and metals in fluid inclusions display variations of several orders of magnitude, with Li and B peaking in pegmatites and base metals being particularly abundant in the magmatic stage.These results suggest that even moderate changes in P-T conditions (from granitic stage to low-T mineralisation) do not affect significantly the halogen signature of the evolving fluids in the Cornubian batholith. Additionally, given the linear relation between fluid salinity and alkali/metal content, it can be postulated that meteoric water is the main diluting agent throughout the evolution of the system, as mixing with metamorphic fluids or basinal brines would also significantly change the halogen signatures.&amp;#160;
Mapping the ratio of meteoric and continental ice in Antarctic Ice Shelves as a metric for susceptibility to future climate change
2023-02-26

Ice shelves encircling the Antarctic perimeter buttress ice flow from the continent towards the ocean, and their evolution and integrity are governed by surface accumulation, basal melting, and ice dynamics. The disintegration of ice shelves, caused by future changes in the climate, leads to an increase in ice discharge towards the ocean and a consequent increase in global sea level &amp;#8211; making their future stability important.In this study we focus on the structure and composition of ice shelves. We model ice shelf stratigraphy for all ice shelves around Antarctica using a simplistic and observationally driven ice-dynamic forward model (validated on the Roi Baudouin Ice Shelf, Visnjevic et al., 2022), and map spatial variations in the percentage of locally accumulated ice on the ice shelf (local meteoric ice - LMI) compared to the ice inflowing from the continental ice sheet (continental meteoric ice - CMI). We investigate differences between LMI and CMI dominated ice shelves in the context of ice shelf stability, and discuss their susceptibility to future atmospheric and oceanic changes in climate. Expanding the analysis to the continental scale allows us to identify zones where future changes in climate might strongly impact ice shelf geometry and composition.
At the bottom of ice streams: unraveling the physics of sliding onset through a glacier-scale field experiment
2023-02-26

Fast ice stream flow at speeds of hundreds to thousands of meters per year is sustained by sliding at the ice sheet base, whereas slow flow outside of ice streams is characterized by limited-to-no basal sliding. In this sense, the transition from no sliding to significant sliding exerts a key control on ice stream flow. The detailed physical processes that enable the onset of basal sliding are somewhat debated, but laboratory experiments, recent theoretical work, and a handful of direct observations support the notion of sliding initiating below the melting point as a result of regelation and premelting.&amp;#160;In this contribution we describe a recently funded glacier-scale field experiment that has been designed to advance the understanding of sliding onset physics by testing the hypothesis that sliding starts below the melting point. The experiment will take place at the Grenzgletscher (Swiss Alps), which is known to have a cold-based accumulation region and a temperate-based ablation region. Our work will involve extensive surface geophysics (radio echo sounding, terrestrial radar interferometry, radar thermal tomography) aimed at identifying the sliding onset region. This work will guide the site selection for a subsequent borehole study of englacial deformation that is meant illuminate the relation between sliding velocity and basal temperature. The borehole work will allow us to test systematically the hypothesis that sliding starts below the melting point through an extended region of temperature-dependent sliding, and possibly to advance the formulation of temperature-dependent friction laws that are used to describe the onset of sliding in ice flow models.The focus of this contribution will be specifically on the experimental design - how it is informed by existing theory and observations, and how it will support theoretical and ice flow modeling advances, at the glacier scale and beyond.
Thermodynamic assessment of simulations of the last deglaciation with an Earth system model of intermediate complexity
2023-02-26

As we observe and expect severe changes in the Earth&amp;#8217; climate, the analyses of past climate state transitions is of major value for improving our Earth system understanding. Under this objective, the last deglaciation (~ 21 ka to 9 ka before present), the transition from the Last Glacial Maximum (LGM) to the Holocene, is an ideal case study. During this transition, the orbital configuration gradually changed and greenhouse gases have risen, which caused a sharp decline in northern hemisphere ice sheets and an increase in the global mean surface temperature.We create an ensemble of deglaciation simulations with a modified version of the Planet Simulator, an Earth system model of intermediate complexity (EMIC). We produce single and combined forcing simulations for further investigation from a thermodynamic perspective. The response to the transiently changing radiative forcing is investigated in terms of energy and entropy budgets of the atmosphere. Here, we focus on the deglacial evolution of the material entropy production (MEP). Its contributions represent the strength of major climate features such as the kinetic energy generation rate, vertical and horizontal heat transport and the hydrological cycle. Preliminary results show an increase of the global mean MEP from the LGM to the Holocene because of a strengthening of the hydrological contribution. In contrast, the relative importance of kinetic energy dissipation and turbulent heat diffusion in the boundary layer decrease. Our work can provide the basis for investigating the MEP as a diagnostic quantity with other models and for other climate state transitions.
Radar forward modelling as a precursor for statistical inference
2023-02-26

Projections of the future development of the Antarctic Ice Sheet still exhibit a large degree of uncertainty due to difficulties in constraining parameters of ice-flow models such as basal boundary conditions. Deriving better estimates of these parameters from radargrams could greatly improve model accuracy, but integration of inferred radar attributes into ice-flow models is not yet widespread.Here, we develop a radar forward modeling framework that is geared to train a machine learning workflow (likely simulation-based inference) to extract radar attributes such as the internal stratigraphy and basal boundary conditions (e.g., frozen vs. wet) from radar data. The workflow starts with ice-dynamic forward models predicting physically sound stratigraphies and internal/basal temperatures for synthetic flow settings using shallow ice, shallow shelf and higher order ice-flow models. This is then used as input to the radar simulator (here gprMax), which calculates the radar image produced by such a stratigraphy. To do so, we match the synthetic permittivities of the modeled stratigraphy with statistical properties known from ice-core logging data and prescribe temperature dependent attenuation via an Arrhenius relation. gprMax is optimized for acceleration using GPUs which can be efficiently employed when solving the FDTD discretized Maxwell equations. Currently, 200 m wide and 500 m deep sections can be simulated on a single NVIDIA GeForce RTX 2070 Super graphics card within 390 minutes. The runtime can be substantially improved in a HPC environment. In order to obtain radar simulations comparable with observations, we also add system specific noise and contributions from volume scattering with variable surface roughness. Here, we focus on 50 MHz pulse radar for which we have many observational counterparts. However, the workflow is designed to encompass multiple ice-dynamic settings and different radar frequencies.The application of physical forward models will result in physically meaningful radargrams which are indistinguishable from observations. This provides a tool to create datasets for training machine learning workflows for inference without the limitations of hand-labeled data.
Characterisation of multi-scale deformation in NEGIS from microstructure analysis of the EastGRIP ice core
2023-02-26

We present the results from a microstructural analysis of more than 1000 thin section samples from the East Greenland Ice Core Project (EastGRIP) ice core that is being drilled at the onset of the fast-flowing North East Greenland Ice Stream (NEGIS) since 2017, focusing on the grain boundary network and bubbles.The data were recorded directly at the drilling site with a Large Area Scanning Macroscope from the polished and sublimated surface of samples from between 0 and 2121 m ice depth. Most samples are cut vertically, along the core axis, but a selected number of perpendicular vertical and horizontal sections from volume samples are included, providing the opportunity to deduce the three-dimensional microstructure in these depths. Processing of the image data was done with the open source software Ice Microstructure Analyser, extracting a fully digitalized grain boundary network by applying machine learning for the classification of grain boundaries and air inclusions.We analysed the shape-preferred orientation (SPO) of grains and bubbles based on statistically computed parameters from the data set under consideration of available azimuthal core-orientation data reconstructed from visual stratigraphy data. These SPO parameters include grain size distribution, grain shape and derived measures like perimeter ratio and aspect ratio, and grain boundary orientation angle.The data show varying trends throughout the core and on different length scales, supporting and complementing earlier observations in the crystallographic-preferred orientation data from the same set of samples. We provide microstructural evidence for dynamic recrystallisation driven by deformation throughout the core. Specifically, we will discuss our findings of heterogeneities that point to internal deformation due to the occurrence of high strain localisation and link them to the observed complex pattern of anisotropy in the ice column.
Empirical Distortions in Climate Networks
2023-02-26

Climate networks have become a popular tool for detecting complex structures in spatio-temporal data. However, they require to estimate correlation values on many edges based on limited and noisy time series. Consequently any constructed network likely contains false and missing edges. To measure how severely and in which ways estimated networks are distorted by statistical errors, we simulate time-dependent isotropic random fields on the sphere. We comprehensively present several patterns of distortion in local as well as global network characteristics and demonstrate which network construction methods enhance statistical robustness. When the data has a locally coherent correlation structure, spurious link bundle teleconnections and spurious high-degree clusters have to be expected. Anisotropic estimation variance can also induce severe biases into empirical networks. We validate all our findings with ERA5 reanalysis data. Finally, we explain why commonly applied resampling procedures &amp;#160;are insufficient for evaluating statistical significance of network structures, and introduce a new ensemble construction framework that aims to alleviate most of the discussed shortcomings.
Modelling the three-dimensional stratigraphy of an ice rise
2023-02-26

The geometry of englacial isochrones is a product of the past and present ice velocity field and is useful for our understanding of steady-state ice flow dynamics, flow regime re-organisation, and calibration of models. Ice rises contain various flow regimes (divide flow, flank flow, and grounding zones) on small spatial scales, meaning they are ideal locations to study ice-flow dynamics and stratigraphy to constrain model parameters. We run full Stokes, thermo-mechanically coupled simulations of Derwael Ice Rise in East Antarctica and simulate the three-dimensional stratigraphy of the ice rise and the surrounding ice shelf using the finite element model Elmer/Ice. Over the ice rise, we derive the accumulation rate from internal reflection horizons and use RACMO2.3 surface mass balance data over the surrounding ice shelf. Simulations are run for Glen's flow law exponents of n=3 and n=4 with appropriate values derived for the Arrhenius law. To calibrate the model, comparisons are made with the BedMachine surface elevation and density-adjusted internal reflection horizons observed in many transects recorded by AWI&amp;#8217;s ultra-wide band radar covering the divide, the flanks, and the grounding zones. To understand ice flow dynamics where the velocity field of the ice rise and the ice shelf converge in the compressive and shear zones, we analyse the modelled englacial stress and strain rate fields. Our results allow us to investigate isochronal structures where observed internal reflection horizons are too steep or obscured to be adequately picked up by radar. A comparison between the model and observed fracturing can be used to infer threshold stress and strain rates for fracture initiation. These simulations are a blueprint for the full Stokes, three-dimensional modelling of ice rises and have further relevance in the study of three-dimensional influences on Raymond arch evolution, the constrained coupling of the anisotropy equations, comparisons with ice core data and the automated inference of ice flow parameters from internal reflection horizons.
Quantifying Ireland’s Dust Bowl: An interdisciplinary assessment of loess genesis, deposition, and dynamics in the Burren
2023-02-26

The west coast of Ireland is currently one of the wettest environments in Europe, with year-round precipitation, high humidity, and minimal thermal seasonality maintained by a strongly North Atlantic climate. While such conditions are not conducive to dust entrainment, transport, and deposition today, we report geologic evidence from the limestone Burren uplands for a period of sustained aeolian sedimentation during the last glacial termination. Contrasting with Ireland&amp;#8217;s till- and glacial-outwash-dominated lowlands, the Burren&amp;#8217;s extant sediment cover comprises a homogenous mineral silt preserved in lee-side zones and karst depressions, the outer reaches of caves, and amongst drumlins. Compositionally, our sedimentologic-geochemical data confirm the quartz minerology of these silts, which are consistent in composition and morphology to similar deposits reported from the England and France previously identified as loess. We used U-Pb age profiling of zircons to establish the primary source of the loess, providing a robust test of whether Irish deposits are locally sourced or instead derived from more distal regions (e.g., central Europe-Asia); both scenarios have ramifications for atmospheric circulation patterns during glacial-interglacial transitions and abrupt climate shifts. While OSL dating of the Burren silts is ongoing, the sedimentary stratigraphy is consistent with deposition during or immediately following ice sheet retreat, which our 10Be-dating of glacial surfaces places during early Heinrich Stadial 1 (HS1). In Ireland, HS1 was also characterised by winter sea ice, extreme thermal seasonality, and relatively low sea level. At multiple Burren sites, a bi-fold stratigraphy suggests the in situ (i.e., airfall) loess is overlain by a subsequently reworked unit of silt that was remobilised during the mid-Holocene, potentially reflecting a combination of climatic and anthropogenic drivers. Thus far, the Burren loess is providing a new aeolian vantage on Europe&amp;#8217;s Atlantic margin during the close of the last ice age and has considerable potential for exploring environmental conditions during climatic transitions.