bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of magnetic field fluctuations and their spectral properties within the heliosphere: Statistical approach
Authors: Safrankova Jana , Němeček Zdeněk , Němec František , Verscharen Daniel , Přech Lubomír , Horbury Timothy S. , Bale Stuart D.
Published: February 2023

The contribution presents the first comprehensive statistical study of the evolution of both compressive and non-compressive magnetic field fluctuations in the inner heliosphere. Based on Parker Solar Probe and Solar Orbiter data in various distances from the Sun, we address the general trends and compare them with Wind observations near 1 AU. We analyze solar wind power spectra of magnetic field fluctuations in the inertial and kinetic ranges of frequencies. We found a systematic steepening of the spectrum in the inertial range with the spectral index of around –3/2 at closest approach to the Sun toward –5/3 at larger distances (above 0.4 AU), the spectrum of the magnetic field component perpendicular to the background field being steeper at all distances. In the kinetic range, spectral indices increase from –4.5 at closest PSP approach to –3 at ≈0.4 AU and this value remains constant toward 1 AU. We show that the radial profiles of spectral slopes, fluctuation amplitudes, spectral breaks and their mutual relation rapidly change near 0.4 AU.
Storm Franz: Societal and energy impacts in northwest Europe on 11-12 January 2007
Authors: Kettle Anthony
Published: February 2023

January 2007 was a bad storm month for much of central and northern Europe with a series of extratropical cyclones bringing high winds and precipitation to highly populated areas between Ireland and Russia.  Although Storm Kyrill on 18-19 January 2007 was the most serious for its infrastructure damage and insurance costs, Storm Franz from the preceding week on 11-12 January 2007 was actually more serious for its maritime impacts in western Europe. This contribution takes a closer look at Storm Franz, presenting an overview of its impact to energy infrastructure as well as transportation networks and societal infrastructure damage.  Maritime casualties are reviewed with respect to met-ocean conditions.  An analysis is carried out on water level recorders around the North Sea to assess the storm surge and short period oscillations that may reveal harbour seiches or meteotsunamis.  The results are compared with wave recorders, which had a fairly good coverage across the North Sea in 2007.  The issue of wave damage to offshore infrastructure was highlighted in events associated with Storm Britta on 31 October - 1 November, 2006.  Offshore wind energy in northwest Europe was in a growth phase during this time, and there were questions about the extreme met-ocean conditions that could be expected in the 20 year lifetime of an offshore wind turbine.
Assessing North Atlantic climate variability since the early 1800s through historical New England whaling ship logbooks and reanalyses
Authors: Sander Neele , Ummenhofer Caroline C. , Münch Bastian , Walker Timothy D.
Published: February 2023

Historical wind patterns in the North Atlantic are assessed using U.S. whaling logbooks of voyages from the 19th century, a time when instrumental wind observations were not widely available. The recordings from whaling ship logbooks provide systematic daily to sub-daily information about wind force, wind direction, and other weather observations (e.g., precipitation, sea state) over a period from ca. 1785-1915 and are housed in the New England archives by the New Bedford Whaling Museum, Nantucket Historical Association, and Providence Public Library. The extracted data from the whaling logbooks is quality checked, and the qualitative wind descriptions transferred to the Beaufort wind force scale to better compare it to the 20th-Century-Reanalysis.  Specifically, the whaling ship logbook-sourced wind recordings are used in conjunction with several indices of North Atlantic climate variability, such as North Atlantic Oscillation, East Atlantic Pattern, and Atlantic Multidecadal Oscillation, to explore variations and change in predominant North Atlantic wind patterns in the past. Here we demonstrate that the wind data from the whaling ship logbooks agrees with mean wind patterns and climate variability reconstructed for the North Atlantic and therefore provides valuable insights into the past wind patterns in this area complementing existing reanalysis products. We further demonstrate how qualitative descriptive wind information can be turned into quantitative information that can be directly compared with numerical data from reanalysis models. Since the comparison of the historical logbook data with the 20th-Century-Reanalysis data shows overall good agreement, it can be used to gain a further understanding of the dominant climate patterns in the North Atlantic and might aid development of improved indices of North Atlantic climate variability, such as the North Atlantic Oscillation or Azores High index.
Joint inversion of Surface-wave Dispersions and Receiver Functions based on Deep Learning
Authors: Wang Feiyi , Song Xiaodong , Li Jiangtao
Published: February 2023

Joint inversion of surface-waves and receiver functions has been widely used to image Earth structures to reduce the ambiguity of inversion results. We propose a deep learning method (DL) based on multi-label Convolutional Neural Network (CNN) and Recurrent Neural Network (RNN) with a spatial attention module, named SrfNet, for deriving the Vs models from Rayleigh-wave phase and group velocity dispersions and receiver functions (RFs). We use a spline-based parameterization to generate velocity models instead of directly using the existing models from real data to build the training dataset, which improves the generalization of the method. Unlike the traditional methods, which usually set a fixed Vp/Vs ratio, our new method takes advantage of the powerful data mining ability of CNN to simultaneously constrain the Vp model. A loss function is specially designed that focuses on key features of the model space (such as the Moho and the surface sedimentary layer). Tests using synthetic data demonstrate that our proposed method is accurate and fast. Application to southeast of Tibet shows a consistent result and comparable misfits to observation data with the previous study, indicating the proposed method is reliable and robust.
The tidal proxy database: development, application, and a call for help
Authors: Perez Iael , Green J. A. Mattias , Bulawa Justyna , Ewing Amy , Fitzgerald Laura A. M. , Hewitt Jennifer M. , Pampaloni Olivia
Published: February 2023

Recent numerical tidal modelling efforts strongly suggest that present day tides are anomalously large in comparison to the tides over the past 1.5 Gyr. Whilst these results can be qualitatively explained from dynamical principles, there are only a few quantitative validations of deep-time tidal simulations done using tidal proxies. One reason for this is a lack of easily accessible proxies for tides and something we are proposing to rectify here. Through extensive literature searches, we have identified over 600 publications containing potential tidal proxies and processed around 300 of them to date.From the literature, we have identified proxies for three tidal properties. Under favourable circumstances, the geological record can provide direct estimates of the tidal range. These situations are rare (~10 papers have this information to date), but it is the best proxy for validation purposes. Tidal currents can be constrained by indirect methods. The presence of black shales indicates a poorly ventilated water column, which in turn is a sign of weak tides. By plotting the location of tidal mixing fronts and ensuring that they are located so black shales end on the stratified side of the front, we have a potential proxy for large-scale tidal current speeds. Tidal currents can also be constrained locally by investigating the dimensions of current ripples in the sediments. Finally, day-length, which is directly linked to global tidal dissipation rates, can often be inferred from the variation and cyclicity in layer composition and thickness in tidalites. These are vertically accreted laminated facies of a succession of couplets composed of sand and clay or silt and clay, with thicknesses of millimeters to centimeters, and they are at the heart of our inventory. Further potential proxies involve using paleobiology to track ranges of intertidal species (to obtain tidal ranges) and use microfossil assemblages as another mean of tracking tidal mixing from (and hence constrain current speed). As a proof-of-concept application, we revisit tidal model simulations from five deep-time slices showing that the methods we propose are viable as tidal proxies. The model simulations and proxies usually agree within the uncertainties of both methods.The database will be made available to the community once the information currently in it has been quality controlled and used in our initial publications. Furthermore, any information that may be of use is welcome and we would love to hear about any potential tidal proxies you may have.
Monte Carlo modelling of a pulsed neutron capture tool for CO2 saturation estimation in sandstone reservoirs
Authors: Szucs Jozsef Gabor , Galsa Attila , Balazs Laszlo
Published: February 2023

One of the key factors for a successful carbon capture and storage (CCS) project, is the ongoing monitoring of the carbon-dioxide injected into the reservoir rocks. Borehole geophysics measurements are invaluable for this process. Due to the evident presence of borehole casing, the number of effective well logging methods is limited.  This means, that nuclear measurements play a highly important role owing to their relatively great depth of penetration. We present a method for PNC (Pulsed Neutron Capture) tools to estimate CO2 saturation in sandstone reservoirs independently of the water salinity. To achieve this, we utilize a carefully selected energy window in the inelastic part of the gamma spectra. The ratio created from the number of counts in this window for different detector spacings is sensitive to hydrogen content of the reservoir rock, thus indirectly to CO2 saturation as well. We estimate the energy deposited by gamma photons in the scintillation detectors of the PNC tool for different model parameters such as rock properties (e.g. porosity) and CO2 saturations. A systematic modelling of the measurement was carried out using Monte Carlo N-Particle (MCNP), a general-purpose particle transport code. These results demonstrate the potential of this method for CO2 monitoring in sandstone reservoirs.
Dating fossil lower-crustal earthquakes by in-situ apatite U-Pb geochronology
Authors: Zertani Sascha , Menegon Luca , Whitehouse Martin , Jamtveit Bjørn
Published: February 2023

The only accepted evidence in the rock record for fossil earthquakes are pseudotachylytes, quenched frictional melts produced during seismic slip. Specifically, earthquakes in the lower continental crust recently have received increased attention, because they occur at depths where the lower continental crust is expected to flow rather than fracture. Nevertheless, lower crustal seismicity is also reported from active settings, for example, below the Himalaya. In order to properly address how and why they occur, pseudotachylytes exhumed from lower-crustal terranes are used as analogues. However, in order to fully understand lower-crustal seismicity, it is important to constrain the tectonic setting in which pseudotachylytes formed, which requires determining their age. Rapid melting and quenching, re-crystallization, and extremely fine grain sizes make age dating difficult. In this context, apatite may provide useful information, as it is known to quickly reset U-Pb ages during recrystallization.We present the first reported in-situ U-Pb ages from lower crustal pseudotachylytes. The analyses were performed on samples from the Lofoten archipelago (Northern Norway) that exposes a block of lower continental crust with only minor overprint from the Caledonian orogeny. Field observations indicate that some of the exposed amphibolite-facies pseudotachylytes in the area have been overprinted by amphibolite-facies ductile shear zones. We couple in-situ U-Pb analysis (SIMS) with cathodoluminescence (CL) and electron backscatter diffraction (EBSD) to ensure full microstructural control of the ages. Analysis was conducted on variably mylonitized pseudotachylytes. All apatites originated from the Paleoproterozoic host rock and are either preserved in the immediate damage zone within the host rock or as survivor clast within the pseudotachylytes. Our analysis reveal that apatite in pristine pseudotachylytes deformed only by fragmentation and was subsequently annealed. Apatite in mylonitized pseudotachylytes displays evidence that deformation occurred dominantly by grain-boundary sliding after fragmentation, while grains in the host rock show evidence of crystal-plasticity and recrystallization. SIMS analyses yield a bimodal age distribution at ~450 and ~350 Ma. Combination of the ages with the microstructural evidence shows that the former captures the age of the earthquake, while the latter is related to late fluid infiltration, which was localized in the pseudotachylyte-bearing faults embedded in an otherwise dry and impermeable lower-crustal block.
Synchronization theory for Pleistocene glacial-interglacial cycles
Authors: Mitsui Takahito , Willeit Matteo , Boers Niklas
Published: February 2023

The dominant periodicity of glacial cycles changed from 41 kyr to roughly 100 kyr across the Mid-Pleistocene Transition (MPT) around 1 Myr ago. The mechanisms leading to these dominant periodicities and their changes during the MPT remain debated. We propose a synchronization theory explaining these features of glacial cycles and confirm it using an Earth system model that reproduces the MPT under gradual changes in volcanic CO2 outgassing rate and regolith cover. We show that the model exhibits self-sustained oscillations without astronomical forcing. Before the MPT, glacial cycles synchronize to the 41-kyr obliquity cycles because the self-sustained oscillations have periodicity relatively close to 41 kyr. After the MPT the time scale of internal oscillations becomes too long to follow every 41-kyr obliquity cycle, and the Earth's climate system synchronizes to the 100-kyr eccentricity cycles that modulate the amplitude of climatic precession. The latter synchronization is only possible with the help of the 41-kyr obliquity forcing through a mechanism that we term vibration-enhanced synchronization.
Emulating radiative transfer in a numerical weather prediction model
Authors: Chantry Matthew , Ukkonen Peter , Hogan Robin , Dueben Peter
Published: February 2023

Machine learning, and particularly neural networks, have been touted as a valuable accelerator for physical processes. By training on data generated from an existing algorithm a network may theoretically learn a more efficient representation and accelerate the computations via emulation. For many parameterized physical processes in weather and climate models this being actively pursued. Here, we examine the value of this approach for radiative transfer within the IFS, an operational numerical weather prediction model where both accuracy and speed are vital. By designing custom, physics-informed, neural networks we achieve outstanding offline accuracy for both longwave and shortwave processes. In coupled testing we find minimal changes to forecast scores at near operational resolutions. We carry out coupled inference on GPUs to maximise the speed benefits from the emulator approach.
Gravity Waves in the Tropical UTLS: New Insights from Aeolus Wind Profiling Data
Authors: Ratynski Mathieu , Khaykin Sergey , Hauchecorne Alain , Alexander Joan
Published: February 2023

The European Space Agency's Aeolus satellite mission, launched in 2018, provides global wind profiling using a Doppler lidar instrument ALADIN. In this study, we examined ALADIN’s ability to capture and resolve internal gravity waves (IGWs) in the upper troposphere and lower stratosphere (UTLS). To derive the IGW-induced perturbations in the vertical profiles of ALADIN’s horizontal line-of-sight (HLOS) quasi-zonal wind velocity at ~1 km vertical resolution, we subtract the Aeolus-derived "background" wind profiles from the individual measurements. Through a spectral analysis of these data, we then derive the IGW kinetic energy and dominant vertical wavelength in the UTLS over the entire Aeolus mission lifespan.   This study represents the first attempt to reconstruct the global distribution of IGW activity using the global wind information exclusively provided by the Aeolus mission. The analysis reveals the well-known IGW sources such as orography, polar vortex dynamics and tropical convection. Here we focus on the tropical UTLS region, where ALADIN has an extended stratospheric coverage. The analysis reveals a previously undocumented spot of enhanced IGW activity in the UTLS, recurring above the Indian Ocean during Boreal Summer. The IGW activity spot is shown to slowly migrate from eastern Africa to the Pacific maritime continent during the June-December period.   The Aeolus-derived distribution and seasonal variation of IGW activity were cross-validated using the global temperature profiling by EUMETSAT radio-occultation (RO) satellites. The RO data were resampled to ALADIN resolution and spectrally analyzed in the same way as it was done for ALADIN wind data. The derived IGW potential energy data confirm the seasonal/zonal variation of IGW activity observed by ALADIN, in particular the eastward migration of the IGW activity hotspot, presumably linked to convection within the MJO (Madden-Julian Oscillation). The results suggest that the interannual variation of the IGW kinetic and potential energies in the UTLS is modulated by the Quasi-Biennial Oscillation, whereas the MJO-related waves can be characterized by shorter vertical wavelengths.   Another important finding enabled by the joint analysis of the Aeolus wind and RO temperature data is the evidence for a strong IGW generation by the Smoke-Charged Vortex (SCV) produced by the 2019/20 Australian megafires. Overall, with this study we point out the potential of Aeolus wind profiling to improve our understanding of atmospheric dynamics, particularly in the UTLS region.
Library of simulated gamma-ray glows and application to previous airborne observations
Authors: Sarria David , Østgaard Nikolai , Marisaldi Martino , Lehtinen Nikolai , Mezentsev Andrey
Published: February 2023

Gamma-Ray Glows (GRGs) are bursts of high-energy radiation that are emitted by thunderclouds and have a duration of seconds to minutes. These radiation sources are extended over several to tens of square kilometers. GRGs have been observed from detectors on the ground, in aircraft, and on balloons. In this paper, we present a Monte-Carlo model that can be used to study the production and propagation of GRGs. We compare our model to one developed by Zhou et al. (2016) and find small differences between the two. We have also created a library of simulations that is available to the community. Using this library, we were able to reproduce five previous GRG observations from five airborne campaigns: balloons from Eack et al. (1996) and Eack et al. (2000), and aircraft from the ADELE (Kelley et al. 2015), ILDAS (Kochking et al. 2016), and ALOFT campaigns (Østgaard et al. 2019).Our simulation results confirm that the flux of cosmic-ray secondary particles at a given altitude can be enhanced by several percent or even several orders of magnitude due to the effect of thunderstorms' electric fields. These results explain the five observations we studied and will be useful for the upcoming ALOFT-2023 campaign. While some GRGs can be explained solely by the MOS process, the strongest GRGs observed require electric fields significantly larger than the RREA threshold value (E_th). Some of the observations also came with in-situ electric field measurements that were always lower than E_th, but these measurements may not have been taken from the regions where the glows were produced. This study supports the idea that some thunderstorms must have electric fields with magnitudes of at least E_th on a kilometer scale. References :-Effect of near-earth thunderstorms electric field on the intensity of ground cosmic ray positrons/electrons in tibet. Zhou et al. (2016). https://doi.org/10.1016/j.astropartphys.2016.08.004-Balloon-borne x-ray spectrometer for detection of x-rays produced by thunderstorms. Eack et al. 1996. https://doi.org/10.1063/1.1146959-Gamma-ray emissions observed in a thunderstorm anvil. Eack et al. 2000. https://doi.org/10.1029/1999GL010849-Relativistic electron avalanches as a thunderstorm discharge competing with lightning. Kelley et al. 2015. https://doi.org/10.1038/ncomms8845-In-Flight Observation of Gamma Ray Glows by ILDAS. Kochkin et al. 2017. https://doi.org/10.1002/2017JD027405 -Gamma Ray Glow Observations at 20-km Altitude. Østgaard et al. 2019. https://doi.org/10.1029/2019JD030312
Effects of grain size and seawater salinity on brucite dissolution and secondary calcium carbonate precipitation kinetics: implications for Ocean Alkalinity Enhancement
Authors: Moras Charly , Bach Lennart , Cyronak Tyler , Joannes-Boyau Renaud , Schulz Kai
Published: February 2023

Ocean Alkalinity Enhancement (OAE) is a carbon dioxide (CO2) removal technology with one of the largest potentials, which simultaneously decreases the pressure of ocean acidification. Most of the current understanding of OAE stems from numerical models. However, two recent studies have shown that secondary calcium carbonate (CaCO3) precipitation can occur at unexpectedly low saturation state, when using particle based OAE feedstocks. This is undesirable as it reduces OAE efficiency and can lead to “runaway CaCO3 precipitation”.Both mineral dissolution kinetics and secondary CaCO3 precipitation are influenced by the physical and environmental properties of mineral feedstock and seawater. For example, the surface area of particles in suspension is an important factor for dissolution kinetics of minerals, as well as secondary CaCO3 precipitation kinetics. Furthermore, CaCO3 precipitation depends directly on the concentrations of calcium (Ca2+) and carbonate ions (CO32-) in seawater. The higher their concentrations, the more likely CaCO3 will precipitate. Since Ca2+ concentration have a positive correlation with salinity in the open ocean, variations in seawater salinity could be an important modifier.Here, we present experimental data on the effects of grain size and salinity on the kinetics of brucite (magnesium hydroxide) dissolution and secondary CaCO3 precipitation. Preliminary results on the effect of grain size suggest that CaCO3 precipitation for medium sized particles (63-180 µm) is slower. At larger grain size, the slower dissolution rate, as of the smaller surface area, leads to more quickly measurable CaCO3 precipitation. At smaller grain size, it is the greater surface area that seems to increase the CaCO3 precipitation rate.For salinity, first results suggest that dissolution rates increase towards lower salinities, while CaCO3 precipitates quicker. The former finding is most likely related to higher brucite dissolution at lower ambient magnesium concentrations, due to lower salinity. The quicker CaCO3 precipitation is also likely due to the lower magnesium concentration in lower salinity seawater. Magnesium ions are known to inhibit CaCO3 precipitation, hence CaCO3 precipitation is less likely inhibited at lower rather than higher salinities. Therefore, both feedstock grain size and seawater salinity are two key parameters for real-world OAE applications.
Simulating the West Pacific Heatwave of 2021 with Analog Importance Samping
Authors: Pons Flavio , Yiou Pascal , Jezequel Aglae
Published: February 2023

During the summer of 2021, the North American Pacific Northwest was affected by an extreme heatwave that broke previous temperature records by several degrees and lasted almost two months after the initial peak. The event caused severe impacts on human life and ecosystems, and was associated with the superposition of concurrent extreme drivers, whose effects were amplified by climate change. We evaluate whether this record-breaking heatwave could be anticipated prior to 2021, and how climate change affects North American Pacific Northwest worst case heatwave scenarios. We use a stochastic weather generator  with empirical importance sampling. The generator simulates temperature sequences with realistic statistics using circulation analogues, chosen with an importance sampling based on the daily maximum temperature over the region that recorded the most extreme impacts. We show how some of the large-scale drivers of the event can be obtained form the circulation analogues, even if such information is not directly given to the stochastic weather generator.
Anthropogenic activities significantly increase annual greenhouse gas (GHG) fluxes from temperate streams, rivers, and drainage ditches in Germany
Authors: Mwanake Ricky , Gettel Gretchen , Wangari Elizabeth , Glaser Clarissa , Houska Tobias , Breuer Lutz , Butterbach-bahl Klaus , Kiese Ralf
Published: February 2023

Anthropogenic activities increase the contributions of inland waters to global greenhouse gas (GHG; CO2, CH4, and N2O) budgets, yet the mechanisms driving these increases are still not well constrained. In this study, we quantified year-long GHG concentrations and fluxes, as well as water physico-chemical variables from 23 streams, three ditches, and two wastewater inflow sites across five catchments in Germany contrasted by land use. Using mixed-effects models, we determined the overall impact of land use and seasonality on the intra-annual variabilities of these parameters. We found that land use was more significant than seasonality in controlling the intra-annual variability of GHG concentrations and fluxes. Agricultural land use and wastewater inflows in settlement areas resulted in elevated riverine CO2, CH4, and N2O emissions, as substrate inputs by these sources appeared to favor in situ GHG production processes. Dissolved GHG inputs directly from agricultural runoff and waste-water inputs also contributed substantially to the annual emissions from these sites. Drainage ditches were hotspots for CO2 and CH4 fluxes due to high dissolved organic matter concentrations, which appeared to favor in situ production via respiration and methanogensis. Overall, the annual emission from anthropogenic-influenced streams and rivers in CO2-equivalents was up to 20 times higher (~71 kg CO2 m-2 yr-1) than from natural streams (~3 kg CO2 m-2 yr-1). Future studies aiming to estimate the contribution of riverine systems to GHG emissions should therefore focus on anthropogenically perturbed streams, as their GHG emission are much more variable in space and time.
The dry-to-wet transition of summer precipitation over the Three-River Headwaters’ region: the role played by three interdecadal oceanic modes
Authors: Liu Xuan , Yang Mingxiang , Chen Deliang , Wang Hao
Published: February 2023

AbstractSummer (June to August) precipitation over the Three-River Headwaters’ (TRH) region has experienced a significant dry-to-wet transition during 1979-2020. The transition could have been caused by changed atmospheric circulations, which was modulated by oceanic forcings. This study intends to improve our understanding of the summer precipitation variability over the TRH region under the influence of oceanic modes. The combined effect of three interdecadal oceanic modes [Pacific decadal oscillation (PDO), Atlantic multidecadal oscillation (AMO), and Indian Ocean Basin mode (IOBM)] on the interdecadal dry-to-wet transition was examined, using composite analysis on HadISST and the fifth generation ECMWF reanalysis (ERA5) datasets. The results show that in positive AMO and negative PDO phases, a zonally oriented teleconnection wave train is generated across the Eurasian mid-to-high latitudes, propagating from the North Atlantic to northern East Asia along the westerly jet. This results in a weakened and northward-shifted westerly jet. Furthermore, the enhanced and northward-shifted Western Pacific Subtropical High (WPSH) brings water vapor from the Pacific Ocean, and cyclonic circulation over the Arabian Sea increases the amount of water vapor entering the TRH region. In positive IBOM phases, the warm Indian Ocean induces an anomalous anticyclone over the Bay of Bengal, and anomalous southwesterly delivers abundant water vapor from the Indian Ocean to the TRH region, which overlaps with the vapor transport caused by a positive AMO and PDO. As the Atlantic and Northern Pacific Oceans warm, the enhanced Walker circulation suppresses the ascending motion in the central Pacific and enhances the equatorial easterly, which in turn strengthens the anomalous anticyclone over the Bay of Bengal. As a result, the summer precipitation over the TRH is further increased. The analysis shows that the combined effect of the three oceanic modes played an important role in the dry-to-wet transition.
Improving the Contribution of Forests to CarbonNeutrality under Different Policies—A Case Study fromthe Hamburg Metropolitan Area
Authors: Martes Leam , Köhl Michael
Published: February 2023

As various political initiatives have set goals to reach net-zero emissions bythe mid-21st century, forests will play an important role as a carbon sink for sequesteringunavoidable emissions. Forest management can take two approachesby either decreasing harvest and enlarging the forest carbon stock or increasingharvest to increase carbon uptake of the remaining forest stock and create harvestedwood products (HWPs). Currently, these two management options seemat odds with seemingly conflicting policy directives being written. We used theBEKLIFUH model to assess six management scenarios based on carbon offsetpotential taking into consideration forest carbon, HWPs and the material andenergetic substitution effects. The results show that while conservation leadsto a higher above-ground carbon pool, including HWPs, material and energeticsubstitution leads to more overall carbon offsets for management scenarios withmore timber harvesting. With compromise being possible by selectively conservingold growth forests with a high biodiversity value. In conclusion, if theforest sector decouples GHG reporting from forest management and includesall the secondary effects of timber harvest, this new approach can lead to adifferent cost–benefit analysis for the choice between harvest vs. conservation.This could result in a paradigm shift to a future where biodiversity and carbonneutrality can coexist.
Insensitivity of global temperature response to the magnitude of volcanic eruptions
Authors: Enger Eirik , Theodorsen Audun , Rugenstein Maria , Graversen Rune
Published: February 2023

We investigate how the global mean temperature responds to single volcanic events of different magnitudes and to multiple events occurring close in time. We are using the Community Earth System Model version 2 (CESM2) to simulate the Earth system forced only with stratospheric aerosols from explosive volcanoes, with the rest of the climate system fixed at 1850 conditions. The model is run with a dynamical ocean component, and the Whole Atmosphere Community Climate Model version 6 (WACCM6) atmosphere component using middle atmosphere chemistry.Previous efforts of estimating a response function assume a linear relationship between the forcing and the deterministic temperature response to the forcing [1], defined as Tdet(t)=L[F(t)]. Studies also show that the forcing is similar across forcing agents [2] (although this is not a settled debate [3]), in which case volcanoes could provide a valuable means of estimating global temperature response to radiative forcing due to their short-lived and large temperature responses.We present simulations of single volcano events with ejected sulphate aerosol loadings differing in orders of magnitude and simulations where two volcanic eruptions are close enough in time that the second eruption occurs as the temperature is still recovering from the first event.We show that the functional form of the temperature response is similar for volcanic events of different magnitudes and that non-linearities are not important as a second eruption occurs when the temperature is well below equilibrium in a perturbed state. The results further suggest the global mean temperature time series may be reduced to a simple superposition of individual pulses, and thus that it may be described by a convolution between a linear response function and some forcing, analogous to the model used by [1].[1] K. Rypdal and M. Rypdal, ‘Comment on “Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcing” by S. Lovejoy and C. Varotsos (2016)’, Earth System Dynamics, 2016, vol. 7, no. 3, pp. 597–609.[2] T. B. Richardson et al., ‘Efficacy of Climate Forcings in PDRMIP Models’, Journal of Geophysical Research: Atmospheres, 2019, vol. 124, no. 23, pp. 12824–12844.[3] P. Salvi, P. Ceppi, and J. M. Gregory, ‘Interpreting differences in radiative feedbacks from aerosols versus greenhouse gases’, Geophysical Research Letters, 2022, vol. 49, no. 8, p. e2022GL097766.
Unexpected new compounds and their states in the interior of giant planets predicted from first-principles calculations
Authors: Sun Jian
Published: February 2023

ABSTRACTIn this talk, I will introduce the methods developed in my group, especially the machine learning and graph theory aided crystal structure prediction method (MAGUS) [1]. In addition, I will show some applications of these methods combined with first-principles calculations, for instance, the predictions of new possible compounds (helium-water, helium-ammonia, helium-methane, helium-silica, silica-water, etc) in the interior of giant planets or exoplanets, and their exotic new states under planetary high-pressure and high-temperature conditions (superionic state, plastic state, and their coexistence) [2-6]. These new compounds and their states may have some important implications for giant planets, including demixing, magnetic field, erosion of the rocky core, etc. REFERENCEKang Xia et al., “A novel superhard tungsten nitride predicted by machine-learning accelerated crystal structure search”, Sci. Bull. 63, 817 (2018).
Cong Liu et al., “Mixed coordination silica at megabar pressure”, Phys. Rev. Lett. 126, 035701 (2021).
Cong Liu et al., “Multiple superionic states in helium-water compounds”, Nature Physics 15, 1065 (2019).
Cong Liu et al., “Plastic and Superionic Helium Ammonia Compounds under High Pressure and High Temperature”, Phys. Rev. X 10, 021007 (2020).
Hao Gao et al., “Coexistence of plastic and partially diffusive phases in a helium-methane compound”, Natl. Sci. Rev. 7, 1540 (2020).
Hao Gao et al., “Superionic Silica-Water and Silica-Hydrogen Compounds in the Deep Interiors of Uranus and Neptune”, Phys. Rev. Lett. 128, 035702 (2022).
Insights into biology’s role in future ocean carbon storage from CMIP6 models
Authors: Baker Chelsey , Painter Stuart , Tagliabue Alessandro , Halloran Paul , Planchat Alban , McQuatters-Gollop Abigail , Henson Stephanie
Published: February 2023

Biotic processes in the ocean play a crucial role in driving and mediating natural long-term ocean carbon storage. IPCC assessment exercises find high uncertainty, and therefore low confidence, around the magnitude and sign of change in future ocean carbon storage. This uncertainty is due to a lack of mechanistic understanding of relevant biological processes and/ or a paucity of observational data which limits robust parameterisations in global ocean biogeochemical models. Our study aims to identify and prioritise the processes that have a strong impact on future ocean carbon storage, with tractability from both a modelling and observational perspective. These processes could be the focus of future studies that aim to improve parameterisations in global biogeochemical models used in Earth System Models. We undertook a gap analysis to identify key processes and highlight future research priorities around three areas: net primary production (NPP), interior remineralisation and alkalinity. Here we evaluate CMIP6 model projections to 2100 under the high emissions SSP5-8.5 scenario to determine both the spread and uncertainty in NPP, particulate organic carbon transfer efficiency through the ocean interior and surface salinity-normalised alkalinity. We undertook a model interrogation of which processes are represented, their level of parameterised complexity and the variability in the parameterisation approach. Our analysis shows that CMIP6 models generally agree on the sign of change for transfer efficiency, but display a wide spread for NPP and salinity-normalised alkalinity by the end of the 21st century. Combining our analysis of CMIP6 models and gaps in knowledge allows the potential key processes and uncertainties driving future changes in key biological components of the ocean carbon cycle to be identified. By highlighting the potential gaps that require attention, the representation of biological processes in global ocean biogeochemical models can be improved in future modelling efforts. 
GIS-Based Rockfall modelling and risk-assessment in the low mountain ranges of Rhineland Palatinate, Germany
Authors: Süßer Philip , Hagge-Kubat Teemu , Enzmann Frieder , Wehinger Ansgar
Published: February 2023

Geographic information systems are a valuable tool to assess the vulnerability of infrastructure posed by mass movements. Since 2014, the State-Geological Survey of Rhineland-Palatinate, Germany (LGB) recorded over 130 cases of rockfall and rockslides. Since only cases near vital infrastructure are recorded, the actual number is estimated to be much higher. The research presented here, makes use of the free to use algorithms of Q-, SAGA- and GRASS-GIS to create semi-automated workflows to identify endangered zones and infrastructure.  Based on high-definition LiDar-Digital Elevation Models Source Areas for the processes are calculated and used as start cells for Gravitational Path Models.  The start cells are calculated by looking for erosion contributing parameters such as exposure, insulation, surface runoff but also rock specific parameters like rock loosening and lithology. Through the precise identification of the rockfall source areas and further input data like vegetation and relief energy numerous cases exemplary in the area were modeled. Validation using the Mass-Movement Database of the Rhineland-Palatine Geological Survey and numerous ground checks show, that concrete rockfall events were simulated. By intersecting with real infrastructure data, it is possible to carry out risk assessments of specific sections of roads and railway lines. These coincide with the actual cases of damage and safety measures and can therefore be assessed as plausible and used for hazard zoning.
Underestimation of potassium in forest dry deposition? – A simulation experiment in rural Germany
Authors: Schmitz Andreas , Ahrends Bernd , Herrmann Hartmut , Moravek Alexander , Poulain Laurent , Sanders Tanja , Wiedensohler Alfred , Bolte Andreas
Published: February 2023

Measurements of throughfall (TF) and wet deposition (WD) are a common method to assess nitrogen (N) and base cation (BC) deposition to forests. Using TF and WD, dry deposition (DD) is usually calculated with a canopy budget model (CBM) assuming similar BC to Na+ ratios in WD and DD. This assumption is especially uncertain for K+, since K+ is often bound to smaller particles compared to Na+. Here we asses this assumption by comparing the DD of K+ estimated with the CBM (DDKCBM) to the DD of K+ simulated with a process oriented DD model (“inferential model”, DDKINF). Simulation experiments were performed at two indicator forest stands (“virtual” broadleaved (BL) and coniferous (CF) forest) based on six years of daily PM2.5 and PM10 concentrations and weekly WD observations measured at the rural background research station Melpitz, Germany. On average, the K+:Na+ ratio in WD was 0.24 while the K+:Na+ ratio in DDINF was 0.43 (CF) and 0.40 (BL), respectively. Accordingly, DDKCBM would need to be multiplied by a correction factor of 1.77 (CF) and 1.66 (BL) to match DDKINF, with substantial variation between years (lowest correction factor: 0.98, highest correction factor: 3.89). However, applying the correction factors in CBM calculations at nearby ICP Forests monitoring sites had only little effect on total (WD+DD) deposition rates of N and BC. The results were robust against changes in the meteorological data used for the inferential model. Uncertainty arises from periods affected by presence of particles larger than 10 µm diameter, not covered by local measurements. A corresponding lower boundary estimate for the average underestimation of DDKCBM is a correction factor of 1.37 (CF) and 1.29 (BL). More work is required to assess to what extend the observed underestimation of DDKCBM is confirmed by other methods and at sites with different atmospheric conditions.
Experimental observation of antigorite dehydration triggered by shear stress at subduction zone pressure and temperature conditions
Authors: Eberhard Lisa , Plümper Oliver , Stünitz Holger
Published: February 2023

The trigger mechanism of intermediate depth earthquakes (30 - 300 km) is a long-standing debate. Many studies showed that these seismic events nucleate along a double-seismic zone within the subducting slab. The seismic events of the lower plane coincide with the depth of major dehydration reactions in the lithospheric mantle. Consequently, it is thought that these events are related to the release of fluids. Several scenarios are currently discussed that might lead to brittle deformation. Among these are dehydration embrittlement and dehydration-driven stress transfer.Antigorite is one of the most important candidates for fluid release due to its high H2O content and stability limits within the lower Wadati-Benioff zone. The release of water through antigorite dehydration can be calculated by equilibrium thermodynamics and is mainly a function of temperature. This does, however, not account for deformation (e.g., stored internal strain energy) leading to local variations in the free energy of minerals. In this study we aim to explore the effect of shear stress on the stability of antigorite.We performed high-pressure and high-temperature experiments in a Griggs rig. We used intact drill cores of two different starting materials for our experiments: a foliated and an isotropic antigorite-serpentinite. Both starting materials did not contain relict olivine and/or orthopyroxene. We run our experiments at 620 to 650 °C with a confining pressure of 1.5 GPa and a strain rate of 10-6 s-2. Subsequent analyses of the experimental runs revealed no dehydration products within the bulk sample. However, we observed the formation of ultra-fine grained (< 100 nm) olivine and orthopyroxene along narrow zones, which are orientated 30 to 40 ° with respect to the compression axis. These zones are similar in all runs and independent of the starting material microstructure. We thus propose that shear stress localization within our cylindrical sample triggered the dehydration. Within subduction zones local variations in stress field due to mineralogical or textural heterogeneities could promote dehydration, eventually leading to seismic events through stress transfer.
Simulating forest drought legacy-effects from tree hydraulic damage: An integrated modelling approach
Authors: Grote Rüdiger , Nadal-Sala Daniel , Petrík Peter , Ruehr Nadine
Published: February 2023

The inclusion of tree hydraulic processes into ecosystem models provides opportunities to better capture instantaneous tree drought responses as well as drought legacy effects. Here we are presenting a simple tree hydrologic approach implemented into a process-oriented ecosystem model that simulates instantaneous tree water potential dynamics based on soil water availability and transpiration demand. Reductions in tree water potential are then calculated into a loss of hydraulic functioning leading to sap wood and leaf area losses. This affects within-tree allocation as tissue becomes damaged, and finally may result in tree death if either hydraulic function is impaired beyond repair or tissues for resource acquisition cannot be sufficiently recovered anymore. This approach further provides potential explanations for various medium- and long-term legacy effects of drought, as well as mortality rates in dependence on environmental conditions.Here we describe the model and evaluate the approach at a number of different sites over several decades, illustrating the species-specific sensitivity to drought stress and the dependency on precipitation pattern, potential soil water storage, and specific tree physiological traits such as xylem vulnerability. The importance of considering stem water storage and depletion as well as the possibility to link this water pool to micro-dendrometer measurements for evaluation is emphasized. Also, we indicate a possible way to integrate the hydraulic failure hypothesis with the theory of carbon starvation and discuss which process may be dominating under specific environmental conditions.
New high-resolution relocation of the seismicity in the Southwestern Alps (France, Italy) to improve active faults imaging: Preliminary results
Authors: Godano Maxime , Jacquemond Laeticia , Cappa Frederic , Larroque Christophe
Published: February 2023

The geodynamic complexity of the Southwestern Alps (France, Italy) comes from its strong tectonic inheritage due to the European-African plates convergence. The motion being currently mainly accommodated along the Maghrebides, this region of the Alps only registers small to moderate seismicity linked to low-deformation rates (convergence rates of 0.3-0.9 mm/yr). Hence until now, the geometry of the active faults in the Southwestern Alps remains unclear and imprecise. Yet, a better knowledge of these faults is a prerequisite for the establishment of a regional deformation model and the improvement of the seismic hazard assessment.Taking advantages of a nine-year seismicity catalog (7659 earthquakes of local magnitudes ranging between -0.73 and 5.03), recorded by the French and Italian permanent national networks presenting no major evolution since 2014, a high-resolution relocation is currently ongoing. The purposes are to (1) understand how the seismic events are linked to the mapped faults, (2) highlight unknown deep seismogenic structures and (3) finally improve the overall picture of the 3D geometry of active faults in the Southwestern Alps.We present here the preliminary analysis of the relocated catalog. The seismicity is relocated using the double-difference relative method HYPODD with both cross-correlation and catalog times. As a result, the relocation is achieved for 5828 earthquakes. The uncertainties are reduced to less than 120m in horizontal and less than 600m in vertical compared to the initial average uncertainties of less than 2 kilometers for both values, referred by previous papers.We assess the reliability of our results by comparing, at regional scale, our new relocations with those obtained by similar methods in Ubaye region. We illustrate how the double-difference relocation refines active zones imaging at multiple scales, particularly in the swarms. In Isola region located around 60 kilometers from Nice, a swarm, active since summer 2021, initially detected by the national network as a 3-kilometerlong/1-kilometer-large shape, has been precised into a 1-kilometer-long/100-meterlarge spatial activity. This relocation improvement enabled us to detect progressive activation of fault segments. On larger scale, relation between faults that may play a key role in the present-day general dynamics of the Alpine chain and deep seismogenic structures is clarified. It is the case for the High-Durance valley (France), where the precise geometry at depth of the Crustal penninic Front and High-Durance fault is determined.