bluuebunny/crossref_metadata_2025 huggingface dataset:
Driving effects of aridity on three dimensions of belowground components in grasslands change at aridity threshold
Authors: Li Changjia
Published: February 2023

The belowground component of the grassland has abrupt changes with increasing aridity. However, the effects and driving pathways of aridification on different dimensions of the belowground component (such as specific root length, belowground biomass and soil organic carbon) before and after the aridity threshold have not been fully elucidated. This research gap is addressed by evaluating changes in soil and plant attributes with aridity along a 2600 km aridity gradient in the arid and semiarid grasslands of Inner Mongolia. Results showed an overall aridity threshold for grassland ecosystems of 0.67, where abrupt changes in belowground components were observed. Structural equation models results showed that the effect of aridity on specific root length was negative (-0.18) before the threshold and positive (0.24) after the threshold, due to a shift of plant strategies from drought tolerance to avoidance. The effect of aridity on belowground biomass was always negative and increased from -0.24 to -0.55 after the threshold without grass regulation. The effect of aridity on soil organic carbon exhibited a subtle change, but the driving pathway changed from soil loss to aridity and vegetation cover at plot scale. These findings highlight the changes in effect and dominant pathways of aridity on belowground components in grassland ecosystems before and after the aridity threshold, which provides a basis for understanding the impact of plant drought resistance strategies, vegetation type and spatial scale when protecting grasslands at different aridity levels.
Root zone soil moisture in over 25 % of global land permanently beyond pre-industrial variability as early as 205
Authors: Lai En Ning , Wang-Erlandsson Lan , Virkki Vili , Porkka Miina , van der Ent Ruud
Published: February 2023

Root-zone soil moisture is a key variable representing water cycle dynamics that strongly interacts with ecohydrological, atmospheric, and biogeochemical processes. Recently, it was proposed as the control variable for the green water planetary boundary, suggesting that widespread and considerable deviations from baseline variability now predispose Earth System functions critical to an agriculture-based civilisation to destabilization. However, the global extent and severity of root-zone soil moisture changes under future scenarios remains to be scrutinized. Here, we analyzed root-zone soil moisture departures from the pre-industrial climate variability for a multi-model ensemble of 14 Earth System Models (ESMs) in the Coupled Model Intercomparison Project Phase 6 (CMIP6) in four climate scenarios as defined by the Shared Socioeconomic Pathways (SSP), SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5, between 2021 and 2100. The analyses were done for 43 ice-free climate reference regions used by the Intergovernmental Panel on Climate Change (IPCC).We defined ‘permanent departures’ when a region’s soil moisture exits the regional variability envelope of the pre-industrial climate and does not fall back into the range covered by the baseline envelope until 2100. Permanent dry departures (i.e. lower soil moisture than pre-industrial variability) were found to be most pronounced in Central America, southern Africa, the Mediterranean region, and most of South America, whereas permanent wet departures are most pronounced in southeastern South America, northern Africa, and southern Asia. In the Mediterranean region, dry permanent departure may have already happened according to some models. By 2100, there is dry permanent departures in theMediterranean in 70%of the ESMs in SSP1-2.6, the most mitigated situation, and more than 90% in SSP3-7.0 and SSP5-8.5, the medium-high and worst-case scenarios. Northeastern Africa is projected to experience wet permanent departures in 64% of the ESMs under SSP1-2.6, and 93% under SSP5-8.5. The percentage of ice-free land area with departures increases in all SSP scenarios as time goes by. Wet departures are more widespread than dry departures throughout the studied timeframe, except in SSP1-2.6. In most regions, the severity of the departures increases with the severity of global warming. In 2050, permanent departures (ensemble median) occur in about 10% of global ice-free land areas in SSP1-2.6, and in 25% in SSP3-7.0. By the end of the 21st century, the occurrence of permanent departures in SSP1-2.6 increases to 34 %, and in SSP3-7.0, 45 %. Our findings underscore the importance of mitigation to avoid further degrading the Earth System functions upheld by soil moisture. An asscociate paper is available as preprint on EGUsphere: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-971/
The 2022 Asian Summer Monsoon Transport and its Connection to the 2005-2021 Climatology as Illustrated by Carbon Monoxide
Authors: Liang Qing , Bian Huisheng , Chin Mian , Pan Laura , Newman Paul , Kinnison Doug
Published: February 2023

The Asian Summer Monsoon (ASM) provides one of the most effective transport pathways to deliver surface pollution into the stratosphere and impact stratospheric composition and climate. To better understand the impact of ASM, the Asian summer monsoon Chemical and Climate Impact Project (ACCLIP) took place in South Korea from July 29 – Sep 2, 2022.  During ACCLIP, in situ measurements of a wide range of trace gas, including carbon monoxide (CO), and aerosol species in the Upper Troposphere and Lower Stratosphere (UT/LS) were collected.
CO is a key pollutant emitted from anthropogenic emissions, as well as biogenic and biomass emissions, along with many other precursors for ozone and aerosol. In addition, its > 30-day atmospheric lifetime and linear chemical loss rate make it a key marker tracer for atmospheric pollution transport and ozone photochemistry. In this study, we use CO simulated by the NASA GEOS model to (1) analyze the ACCLIP-2022 observations, (2) examine surface-to-stratosphere transport in the Asian Summer Monsoon region during the summer of 2022, (3) assess how transport in 2022 is similar to or different from the 2005-2021 Climatology.  In addition, we use idealized tagged CO tracers that are used track pollution transport from a suite of source regions, e.g., within East Asia, South Asia, and Southeast Asia, to quantify the contribution of these target regions to CO and air mass abundance in the lower stratosphere over Asia and downwind regions.
Access for free: How to get free-of-charge access to Dutch Earth scientific research labs through EPOS-NL
Authors: Wessels Richard , Pijnenburg Ronald
Published: February 2023

Access to top research equipment facilitates top research. However, the research equipment needed may not always be available within individual institutes, while access to external facilities may not in all cases be affordable. This restricts the research that any individual can do and hampers scientific breakthroughs, particularly across disciplines. To overcome this limitation, a collaborative infrastructure network was initiated: EPOS-NL (European Plate Observing System- Netherlands). EPOS-NL provides free-of-charge access to geophysical labs at Utrecht University and Delft University of Technology, both in the Netherlands, for research within rock physics, analogue modelling of tectonic processes, X-ray tomography and microscopy. These labs include capabilities for among others: A) Mechanical and transport testing at crustal stress, temperature and chemistry conditions; B) Analogue tectonic modelling, including dynamic model imaging in 2D and 3D; C) X-ray tomography at sub-µm resolution; and D) A correlative workflow for imaging and microchemical mapping, down to nm resolution. As such, these labs can provide you with the means and expertise for your research into the physical behavior of the Earth’s crust and upper mantle.Access to EPOS-NL can be requested by applying to a bi-annual call, posted on www.EPOS-NL.nl. This involves submitting a short (1-2 page) research proposal. Research proposals are reviewed on the basis of feasibility and excellence, but generally have a high chance of success (~80% in previous rounds). Interested? Have a look on the EPOS-NL website – and apply!
Development of a 3D-printed ion-electron plasma spectrometer with an hemispheric field of view for microsats and planetary missions
Authors: Hénaff Gwendal , Berthomier Matthieu , Frédéric Leblanc , Jean-Denis Techer , Gabriel Degret , Sylvain Pledel
Published: February 2023

One of the challenges in space instrumentation is to measure the energy and 3D angular distribution of charged particles within the limited resources available on planetary missions. Current electrostatic energy analyzers allow the measurement of the energy and angular distribution of charged particles around a 2D viewing plane.Since most planetary probes are three-axis stabilized, electrostatic scanning deflectors are needed to provide the 3D distribution of charged particles using a minimum of two sensors. However, deflections up to +/- 90° cannot be achieved at high energy (above 10-15 keV) while higher energy accelerated particles play a key role in the dynamics of planetary magnetospheres. In addition, electrons and positive ions have to be measured with dedicated sensors which increases the complexity of plasma payloads and of their accommodation on planetary platforms.We introduce a novel instrument design, that would allow measurement of the energy spectrum and 3D angular distribution of charged particles on three-axis stabilized platforms without using scanning deflectors. The design is possible using new electrostatic geometries and the capability of additive manufacturing technology. An innovative and compact ion/electron detection system is used to simultaneously observe both type of particles with a single sensor. We show that we reach the performance of current reference designs while having a true 3D field of view and significantly reducing the payload needs. With a mass budget of 2 kg, our combined electron/ion instrument fits the requirements to fly aboard small satellites. It would significantly reduce the size and cost of the platform and may open new perspectives for planetary exploration by a fleet of micro/nano-satellites.
Site characterization of META – the Marine Energy Test Area in Wales, UK
Authors: Neill Simon , Fairley Iain , Young Saul , Hill Tom , King Nicholas , Roberts Michael , Lewis Matthew , Austin Martin , Unsworth Chris , Reeve Dominic , Masters Ian
Published: February 2023

With lack of convergence on any single wave or tidal technology, test centres have a unique role in the marine renewable energy industry. Test centres facilitate real testing at sea for devices and components at various TRLs (Technology Readiness Level), reducing the time, cost, and risks faced by marine energy developers. META (Marine Energy Test Area) is a £2.7M project managed by Marine Energy Wales (MEW), consisting of eight test areas in the Milford Haven Waterway and surrounding waters (Pembrokeshire, Wales). Although various datasets have been collected from the META test areas over the last decade, and some aspects of these data have been published in various reports, the data has not been gathered together, systematically analyzed and critically assessed - the aim of this presentation. Here, the various META datasets are described and interpreted, including multibeam, ADCP (acoustic Doppler current profiler), and wave buoy data. We report the key parameters of relevance to testing at META, including bathymetry, the nature and magnitude of the tidal currents, turbulence, and wave climates. We make recommendations on future priorities for data collection at META, and discuss the future of the test areas, including expansion into floating wind and other evolving marine energy technologies.
Upper Crust structural evolution of the Alpine orogeny in an intracontinental belt: Western High Atlas (WHA) Mountains, Morocco
Authors: Amarir Salih , Amrouch Khalid , Belfoul Mhamed Alaeddine , Skikra Hamza
Published: February 2023

The Atlas system is an intracontinental chain established upon a Paleozoic substratum by the inversion of Triassic basins starting in the late Mesozoic-early Cenozoic. The inversion of the chain is related to the Atlas rift system that was influenced by the opening of the Central Atlantic in the West and the Tethys in the north. This was coeval with a regional exhumation following the Alpine shortening responsible for the continuous uplifting of the chain since Late Cretaceous. The structural history and chronology of events are still matter of debates. To contribute to this, we focus on the Western High Atlas (WHA) aiming a retro enactment of the paleo-stresses states, by analyzing deformation structures at various scales. The geological data were collected at different stratigraphic levels: from the contact Paleozoic basement/Mesozoic cover interface to the Triassic detrital formations of the Argana corridor in the east, to the Jurassic-Cretaceous and Cenozoic plateaus in the west. Preliminary results highlight two major tectonic events: (1)- a first extensive event, with sub-horizontal minimal principal stress σ3 oriented NW-SE, that is linked to the Central Atlantic basin opening. This event is characterized by pull apart basins structured into horsts and grabens. (2)- a second compressive event, marked by NE-SW to NNE-SSW shortening. The later is subdivided into two episodes: i- an early post-rift episode (Middle-Late Jurassic to Early Cretaceous), marked by stylolites and meso-structures that occurred at the beginning of the main uplifting stage. ii- a late compression episode, characterized by a maximum principal stress σ1 mainly oriented NNE-SSW to NNW-SSE, starting at the late Cretaceous and accelerating during the Tertiary, simultaneously with the Africa-Europe collision.Keywords: Paleo-stress, Structural analysis, Atlas rift system, Tectonic inversion, Western High Atlas Morocco, Alpine orogeny.
Drought impact profiles: Analyzing multivariate socio-economic drought impacts using nonlinear dimensionality reduction
Authors: Sodoge Jan , Kuhlicke Christian , Mahecha Miguel , de Brito Mariana
Published: February 2023

Socio-economic drought impacts often occur concomitantly across multiple sectors, leading to more severe consequences than if they affected single sectors. Improved management of such disasters requires cross-sectoral impact assessments and analyses. As such, analyzing how regions are affected by multiple impacts can provide crucial information for mitigating their consequences. Here, we characterize the multivariate distributions of socio-economic drought impacts. Our aim is to understand patterns by which diverse drought impacts co-occur. We introduce the concept of drought impact profiles, which describe characteristic distributions of co-occurring impacts. To this end, we use a unique spatio-temporal dataset generated with text mining and machine learning applied to newspaper articles. This dataset describes reported socio-economic drought impacts along seven categories (agriculture, forestry, fires,  social, aquaculture, livestock, waterways) in Germany between 2000-2022. We combine several dimensionality reduction algorithms (PCA, ISOmap, self-organizing maps) to generate robust and interpretable representations of the drought impacts. Our results show characteristic patterns for both particular drought events and regions. Also, the applied methods provide a low-dimensional representation of the multivariate socio-economic drought impacts. This research provides a methodological contribution to the holistic, empirical investigation of co-occurring drought impacts. The proposed methods can inform risk models, and policy-makers on the urgency of cross-sectoral governance approaches. Also, the proposed method could apply to other hazards or compound events.
Modelling seabed shear stresses and sediment mobilization on the Scotian Shelf, eastern Canada
Authors: Li Michael , Wu Yongsheng , Ma Yongxing , Wang Yolanda
Published: February 2023

Ocean surface waves and currents can interact to produce strong seabed shear stress and mobilization of sediments that can significantly impact the seabed stability and benthic habitats on continental shelves. Modelled waves, near-bottom tidal current and circulation current data for a 3-year period were used in a widely applied sediment transport module to simulate the seabed shear stresses and the mobilization of observed sediment grain size on the Scotian Shelf of eastern Canada.The Scotian Shelf is affected by strong waves and tidal currents. These waves, currents and/or their interaction cause maximum mean bed shear velocities of 5 – 10 cm s−1. Observed sediments on the Scotian Shelf can be mobilized by tidal currents at least once during the modelled 3 year period over 28% of the shelf area while waves can mobilize sediments over 60% of the shelf area suggesting much stronger sediment mobilization by waves. Interaction between waves and currents can produce enhanced combined wave-current shear velocity that is capable to mobilize sediments over 74% of the shelf area. The spatial variation of the relative importance of sediment mobilization frequency by component processes was used to classify the Scotian Shelf into six disturbance types. In comparison with previous studies using depth-averaged tidal currents, the present study based on near-bottom tidal currents has resulted in reduced sediment mobilization frequency by tidal currents, smaller extent of high mobility areas and significant changes of the spatial pattern of disturbance type distribution on the Scotian Shelf. The universal Seabed Disturbance Index and Sediment Mobility Index have also been applied to quantify the seabed exposure to physical processes and sediment mobilization on the Scotian Shelf by accounting for both the magnitude and frequency of these processes. The results of this modelling study are important for environmental assessments and for the spatial planning and management of the Scotian Shelf bioregion. 
Cloud properties from airborne radar observations collected in field campaigns
Authors: Romatschke Ulrike
Published: February 2023

The HIAPER Cloud Radar (HCR) is a 94 GHz W-band radar deployed in an underwing pod on the NCAR HIAPER aircraft. We use dual polarized Doppler observations collected in three major field campaigns:The Cloud Systems Evolution in the Trades (CSET) study focused on the characterization of the cloud fields in the stratocumulus and the fair-weather cumulus regimes within the subtropical easterlies over the northern Pacific.
Motivated by challenges in their modeling, Southern Ocean clouds were observed south of Tasmania during the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES).
Deep convective clouds in a tropical environment were the focus in the Organization of Tropical East Pacific Convection (OTREC) field campaign.
In this study we classify clouds sampled by HCR in these very different environments into twelve categories, based on the clouds’ convective and stratiform characteristics. We calculate dimensional and convective properties of the clouds in the different categories and contrast and compare derived statistics. We analyze updraft regions observed in all cloud categories, their dimensions and velocities. Characteristics of precipitation shafts from the precipitating clouds, such as precipitation fraction or strength are also provided.
Local variability of internal wave driven upwelling at four remote Pacific Reefs
Authors: O'Hara Megan , Robins Peter , Williams Gareth , Green Mattias
Published: February 2023

Internal wave driven upwelling has been shown to deliver cool, nutrient-rich water (‘cold pulses’) to the shallow shores of remote reefs, providing potential thermal refugia and nutrient enrichment. However, the spatial variability within nearby islands is yet to be explored. Two methods were used to quantify the distribution of cold pulse events between two sets of remote tropical Pacific Islands: Kingman Reef and Palmyra Atoll (66 km apart), and Howland and Baker Islands (70 km apart); the two groups of islands are ~1700 km apart.Using data from subsurface temperature loggers (STR’s) from 2008 to 2018, moored on the forereefs of our four Islands, we show that there were clear differences in upwelling behaviour. Around Palmyra Atoll, the northwest and west logger sites are <1 km apart and have a difference in degree cooling hours (DCH – hours in a day during which cold pulses were present) of up to 0.6 per day. The temperature drop at these sites differs by up to 1°C per cold pulse. Kingman Reef showed up to 0.5 DCH difference between sites (~4 km apart) per day, with temperature drop differences of up to 2°C per pulse. In contrast, Howland and Baker Islands showed up to 3 DCH difference per day between islands, whereas the temperature drop around Baker Island differed by up to 2°C per pulse. During the very strong 2015/2016 El Niño, Palmyra showed an increase of up to 1.3 DCH in a day, whereas Kingman reached <0.2 DCH per day. Howland and Baker Islands showed a similar response during this El Niño event but differed during normal ENSO phases. For example, during 2013/2014, Baker Island showed a maximum of up to 2.75 DCH per day, whereas Howland Island did not reach past 0.5 DCH per day.We conclude that cold pulse behaviour varies between geographically close reefs and so one reef’s data cannot be used as a proxy for other islands and reefs. Subsequently, we hypothesise that the slope angle of the reef may be correlated to the presence of cold pulse activity, and that increased cold pulses may be able to mitigate the effects of a global warming on reefs with specific characteristics.
Volcanos – the gift that keeps on giving
Authors: Grasby Stephen , Percival Jeanne , Smith Rod , Galloway Jennifer , Bringué Manuel
Published: February 2023

The Smoking Hills Formation of Arctic Canada represents a Cretaceous metalliferous black shale named after auto-combusting exposures in Ingniryuat, Northwest Territories. This area was also named The Smoking Hills by the Franklin Expedition after the ever-present clouds of sulphuric acid smoke produced. Similar burning Cretaceous mudstones occur in Yukon, and northern Alberta, as well as western Greenland (as recorded in the Viking Sagas). These burning shales reflect deposition during OAE 2 and 3 events across the Arctic region. Metal in the Smoking Hills Formation are enriched over 1000x average shale values. The metal concentrations strongly correlate with heulandite content, an alteration product of volcanic glass, suggesting an origin related to volcanic loading. Abundant bentonite beds in the Smoking Hills Formation support deposition during active volcanism. This is further consistent with the eruption history of the High Arctic Large Igneous Province to the north, or Cretaceous arc related volcanics to the west. These metals are now being recycled into the otherwise modern pristine Arctic environment, generating hyper acidic waters (recording negative pH values) with extremely high metal concentrations orders of magnitude higher than safe drinking levels. Cretaceous eruptions are still driving widespread deleterious environmental impact today.
Estimating and Understanding the Energy Decay of Coherent Eddies from In situ Observations and Satellite Altimetry.
Authors: Meunier Thomas , Bower Amy , Perez Brunius Paula
Published: February 2023

Quantifying and understanding the mixing and decay properties of oceanic mesoscale coherent eddies is crucial, as coupled climate models become eddy-permitting. Measuring experimentally the decay of coherent eddies is a difficult and expensive task. As of now, only a very limited number of repeated field surveys across the same eddy have been achieved. On the other hand, satellite altimetry offers a nearly synoptic two-dimensional view of the evolution of ocean vortices, and the record is now 30 years-long, allowing for the computation of solid statistics. But most coherent eddies are essentially baroclinic and knowledge of their vertical structure is crucial to understand the decay of their energy, or heat and salt contents. Here, we take advantage of the dense array of ARGO float profiles in the Gulf of Mexico (GoM) to reconstruct the three-dimensional structure of all Loop Current Rings (LCR) detached since 1993, using the Gravest Empirical Modes (GEM) method and a gridded altimetry product. The 3D reconstruction method was validated using independent glider observations and exhibits a striking accuracy in estimating the kinetic and available potential energy of LCRs, as well as their heat and salt contents. The decay of LCRs in terms of energy and thermohaline properties is then studied in details and it is shown that, despite their longevity of 6 to 15 months, they decay continuously with time at an inverse exponential rate, and have lost 80 % of their total energy as they reach the western GoM’s continental slope, where they were previously suspected to decay. We studied the impact of the wind and the feed back of the current on the wind on the energy decay of LCRs, and found that wind stress work (using relative wind stress), is responsible for half of the total energy loss during the eddy’s life time, while available potential energy decay is entirely driven by Ekman buoyancy fluxes and the barotropic vorticity decay is driven by wind stress curl. This suggests that wind forcing (when considering the feed-back of ocean currents on wind stress) is the leading-order mechanism in the decay of these coherent eddies.
How will the Surface Urban Heat Island respond to changes in climate?
Authors: Berk Sarah , Joshi Manoj , Nowack Peer , Goodess Clare
Published: February 2023

The Surface Urban Heat Island (SUHI), known as the difference in land surface temperature (LST) created by the presence of a city, is impacted by both the climate and morphology of the city in question. Subsequently, a changing climate would be expected to result in consequences for characteristics of the SUHI. Modelling the future climate of cities remains a challenge as resolution of global climate models is too coarse to capture the scale of a city, and regional climate models are computationally expensive. In order to address these issues, statistical models can be used. Using a dataset of cities selected based on similar characteristics such as population, variation of elevation within the city and surrounding area, and proximity to water bodies, satellite data is used to quantify the SUHI magnitude. A statistical model is fitted to current observations using predictive variables based on climate. The model shows promising performance for the majority of cities in the dataset and results are discussed.  
Implications of zircon Th/U for global continental crustal evolution and geodynamics
Authors: Wu Yujing , Fang Xianjun , Ji Jianqing
Published: February 2023

The continental crust is formed by the mantle’s successive crystallization differentiation and then aggregation, which is the result of the continuous energy acquisition and evolution of the mantle. This process has been objectively recorded in the growth of zircons which are widely present in the continental crust, owing to the close relationship between the zircon Th/U ratio and the crystallization temperature of zircons. As shown by theoretical calculations, phenomenon statistics, and/or crystallization simulations, higher zircon Th/U generally indicates higher zircon (re)crystallization temperature in metamorphic and magmatic systems. Here, we compiled ~600,000 zircon Th/U data from the global continental crust and obtained the time series of zircon Th/U ratios. The average level of the Th/U ratio in global zircons has a slow growth trend from old to new and fluctuates quasi-periodically around 0.5. There are two significant cycles of zircon Th/U ratios, ca. 600 and 120 Myr, which are associated with the supercontinent cycle and whole-mantle convection, respectively. It is inferred that the zircon Th/U periodicity is related to the periodic thermal state changes in the mantle, which might be regulated by tidal energy dissipation.
D-Vine Copula based Postprocessing of Wind Speed Ensemble Forecasts
Authors: Jobst David , Möller Annette , Groß Jürgen
Published: February 2023

Statistical postprocessing of ensemble forecasts has become a common practice in research to correct biases and errors in calibration. Meanwhile, machine learning methods such as quantile regression forests or neural networks are often suggested as promising candidates in literature. However, interpretation of these methods is not always straightforward. Therefore, we propose the D-vine (drawable-vine) copula based postprocessing, where for the construction of a multivariate conditional copula the graphical D-vine model serves as building plan. The conditional copula is based on this tracetable model using bivariate copulas, which allow to describe linear as well as non-linear relationships between the response variable and its covariates. Additionally, our highly data-driven model selects the covariates based on their predictive strength and thus provides a natural variable selection mechanism, facilitating interpretability of the model. Finally, (non-crossing) quantiles from the obtained conditional distribution can be utilized as postprocessed ensemble forecasts. In a case study for the postprocessing of 10 m surface wind speed ensemble forecasts with 24 hour lead time we compare local and global D-vine copula based models to the zero-truncated ensemble model output statistics (tEMOS) for different sets of predictor variables at 60 surface weather stations in Germany. Furthermore, we investigate different types of training periods for both methods. We observe that the D-vine based postprocessing yields a comparable performance with respect to tEMOS models if wind speed ensemble variables are included only and a significant improvement if additional meteorological and station specific weather variables are integrated. The case study indicates that training periods capturing seasonal patterns are performing best for both models. Additionally, we provide a criterion for calculating the variable importance in D-vine copulas and utilize it to outline which predictor variables are the most important for the correction of 10 m surface wind speed ensemble forecasts.
Mega-Disturbances and forest decline in the Sierra Nevada of California, USA: Insights for managing disturbance dynamics
Authors: Steel Zack , Jones Gavin , Collins Brandon , Green Rebecca , Koltunov Alex , Purcell Kathryn , Sawyer Sarah , Slaton Michele , Stephens Scott , Stine Peter , Thompson Craig
Published: February 2023

Mature forests characterized by high cover of tall trees and complex understories are important habitat for native plant and wildlife species and support critical ecosystem functions globally. In California’s Sierra Nevada a combination of a century of fire exclusion and worsening climate change has led to increasingly severe wildfires and extreme drought that threaten habitats of sensitive species. Using spatially explicit datasets of forest structure and the Ecosystem Disturbance and Recovery Tracker, we quantified the loss of conifer forest cover in the southern Sierra Nevada between 2011 and 2020, a decade and region characterized by unprecedented mega-disturbances. Due to the combination of wildfires, drought, and drought-associated beetle kill, 30% of conifer forest extent was lost (fell below 25% canopy cover) during this period. Of the spatially limited mature forest habitats, 56% of moderate density (40-60% canopy cover) and 84% of high density (>60% canopy cover) forests were degraded. Drought and beetle-kill caused greater cumulative degradation than areas where wildfire mortality overlapped with the other disturbances. However, burned areas resulted in larger patches of forest loss and greater forest fragmentation on average. These results highlight that current conservation approaches are failing to protect mature forest habitats within disturbance-prone ecosystems like the conifer forests of California. We emphasize the need to switch from a static approach to conservation toward one focused on managing healthy disturbance dynamics, especially using frequent low-severity fire to increase forest resilience to future mega-disturbances. Without rapid management interventions, remaining mature forest habitat in the Sierra Nevada may be susceptible to complete loss in the coming decades.
Stationary Waves Weaken and Delay the Near-Surface Response to Stratospheric Ozone Depletion
Authors: Garfinkel Chaim , Gerber Ed , White Ian , Son Seok-Woo , Jucker Martin
Published: February 2023

An intermediate-complexity moist general circulation model is used to investigate the factors controlling the magnitude of the surface impact from Southern Hemisphere springtime ozone depletion. In contrast to previous idealized studies, a model with full radiation is used; furthermore, the model can be run with a varied representation of the surface, from a zonally uniform aquaplanet to a configuration with realistic stationary waves. The model captures the observed summertime positive Southern Annular Mode response to stratospheric ozone depletion. While synoptic waves dominate the long-term poleward jet shift, the initial response includes changes in planetary waves that simultaneously moderate the polar cap cooling (i.e., a negative feedback) and also constitute nearly one-half of the initial momentum flux response that shifts the jet poleward. The net effect is that stationary waves weaken the circulation response to ozone depletion in both the stratosphere and troposphere and also delay the response until summer rather than spring when ozone depletion peaks. It is also found that Antarctic surface cooling in response to ozone depletion helps to strengthen the poleward shift; however, shortwave surface effects of ozone are not critical. These surface temperature and stationary wave feedbacks are strong enough to overwhelm the previously recognized jet latitude/persistence feedback, potentially explaining why some recent comprehensive models do not exhibit a clear relationship between jet latitude/persistence and the magnitude of the response to ozone. The jet response is shown to be linear with respect to the magnitude of the imposed stratospheric perturbation, demonstrating the usefulness of interannual variability in ozone depletion for subseasonal forecasting. Garfinkel, C. I., White, I., Gerber, E. P., Son, S., & Jucker, M. (2023). Stationary Waves Weaken and Delay the Near-Surface Response to Stratospheric Ozone Depletion, Journal of Climate, 36(2), 565-583. 
Evidence of Mediterranean water in the Atlantic margin during the Messinian
Authors: Bulian Francesca , Jiménez-Espejo Francisco J. , Andersen Nils , Larrasoaña Juan C. , Sierro Francisco J.
Published: February 2023

At present, the Mediterranean is connected to the Atlantic Ocean through the narrow Strait of Gibraltar (only 13 km wide). The latter, in the late Miocene, most probably did not exist, and the Mediterranean – Atlantic water exchange took place through the Betic (Southern Spain) and Rifian (Northern Morocco) corridors. Studying the evolution of such gateways is fundamental when investigating the extraordinary event known as the Messinian Salinity Crisis (5.96 – 5.33 Ma), when the connection between the Mediterranean Sea and Atlantic Ocean significantly diminished or even ceased. In this work we present a new high resolution geochemical (XRF and stable isotope) record of the Tortonian – Messinian interval of the Montemayor-1 and Huelva-1 cores located in the Betic corridor, current Guadalquivir Basin. Our new data enabled in the first place the high-resolution tuning of the 7.4 – 5.8 Ma time interval, and consequently to precisely date environmental changes and relate them to Mediterranean and global events.Our results indicate that, at 7.17 Ma and in concomitance with a shallowing of the basin, the bottom water residence time, temperature and salinity increased. These changes have been associated with a reduction of the Mediterranean Outflow Water reaching the Guadalquivir Basin as a consequence of the restriction of the last strand of the Betic corridor connecting the Mediterranean and the Atlantic. This hypothesis is in line with the analogous changes observed in several Mediterranean Sea locations, where from 7.17 Ma a reduced Mediterranean – Atlantic connection is visible. Nonetheless, even if such reduction of the connection was feasible, the same changes in isotope record and analogous cyclicity observed both in the Guadalquivir and Alboran Basin record imply that the Mediterranean signal was still reaching the Betic gateway to some degree. In addition, the significant offset present between our and North Atlantic oxygen stable isotope records entails how the signal in the Guadalquivir basin could not have been purely Atlantic. Consequently, we conclude that a significant Mediterranean signal was still present in the Betic corridor during the Messinian.
Phases of enhanced exhumation during the Cretaceous and Tertiary orogenies in the Eastern European Alps: new insights from thermochronological data and thermokinematic modeling
Authors: Wölfler Andreas , Hampel Andrea , Wolff Reinhard , Hetzel Ralf , Dunkl István
Published: February 2023

The Austroalpine nappes in the Eastern European Alps have preserved the record of two orogenic phases in the Cretaceous and Tertiary but their cooling and exhumation history remains poorly constrained. Here we use new low-temperature thermochronological data and thermokinematic modeling to unravel the exhumation history of the Austroalpine nappes in the Nock Mountains east of the Tauern Window (Wölfler et al., submitted). Our data show that the central Nock Mountains (Ötztal-Bundschuh and Drauzug-Gurktal nappes) cooled through the zircon fission track closure temperature (~240 °C) already in the Late Cretaceous. Apatite fission track ages cluster around 35-30 Ma, indicating that the rocks have been at depths of ≤5-6 km since the Eocene-Oligocene boundary. In contrast, the Radenthein and Millstatt Complexes, which are located south of the Hochstuhl Fault, cooled below 240 °C during the Eocene and show apatite fission track ages of ~15 Ma. Thermokinematic modeling of an age-elevation profile in the central Nock Mountains (near Innerkrems) revealed a phase of enhanced exhumation (~0.62 km/Ma) between ~100 and ~85 Ma, which we relate to syn- to late-orogenic Late Cretaceous extension. After a period of slow exhumation (~0.03 km/Ma), the exhumation rate increased to ~0.16 km/Ma at ~32 Ma. In contrast, thermokinematic modeling of an age-elevation profile near Millstatt shows that rocks of the Radenthein and Millstatt Complexes were rapidly exhumed (~0.78 km/Ma) from ~44 Ma to ~38 Ma during the initial Europe-Adria collision. After a phase of slow exhumation (~0.07 km/Ma) between ~38 and ~19 Ma, the exhumation rate increased to ~0.3 km/Ma with the onset of Miocene lateral extrusion in the Eastern Alps. Altogether, ~16 km of rock have been removed since ~100 Ma in the Innerkrems region, whereas ~11 km of rock have been removed in the last ~44 Ma in the Millstatt area. These findings are consistent with pressure-temperature estimates for the Ötztal-Bundschuh nappe and the Radenthein/Millstatt Complexes, respectively (Koroknai et al., 1999; Schuster, 2003; Krenn et al., 2003, 2011). The distinct differences in the cooling histories north and south of the Hochstuhl Fault further suggest that this fault, which has hitherto been considered as a dextral strike-slip fault during Miocene lateral extrusion (Polinski & Eisbacher, 1992; Linzer et al., 2002), also accommodated a considerable amount of thrust movement. The difference between the amount of exhumation north and south of the Hochstuhl Fault indicates ca. 5 km of vertical offset between ~44 and ~38 Ma.
Defining spatial uncertainty in main field magnetic models
Authors: Beggan Ciaran , Brown William
Published: February 2023

Models of the Earth’s main magnetic field, such as the International Geomagnetic Reference Field (IGRF), are described by spherical harmonic (Gauss) coefficients to degree and order 13, which allows the continuous evaluation of the field at any location and time on or above the surface. They are created from satellite and ground-based magnetometer data and describe the large-scale variation (spatial scale of 3000 km) of the magnetic field in space and time under quiet conditions.In its technical form, the model is a spectral representation and thus its formal uncertainty (as a wavelength) is of limited advantage to the spatial value expected by the average user.  To address this, we estimated the large-scale time-invariant spatial uncertainty of the IGRF based on the globally averaged misfit of the model to ground-based measurements at repeat stations and observatories between 1980 and 2021. As an example, we find the 68.3% confidence interval is 87 nT in the North (X) component, 73 nT in the East (Y) component and 114 nT in vertical (Z) component. These values represent an uncertainty of around 1 part in 500 for the total component which, for the (average) compass user is well below instrumental detectability.For advanced users, in applications such as directional drilling, higher resolution models (<30 km) are required and the associated uncertainties are thus further divided into random and global as well as correlated and uncorrelated parts. However, the distribution of errors is Laplacian not Gaussian and communicating the subtleties of long-tailed distributions to end-users is often a difficult task. We describe the different types of uncertainties for magnetic field models and how these are used (or not) in industrial applications.
Quantifying nitrogen oxide emissions in the Eastern Mediterranean - Middle East region using TROPOMI observations
Authors: Rey-Pommier Anthony , Chevallier Frédéric , Ciais Philippe , Kushta Jonilda , Christoudias Theodoros , Sciare Jean
Published: February 2023

Urban areas and industrial facilities are major sources of air pollutants, as they concentrate a large part of human activity and industrial production. For most of these pollutants, emission inventories are highly uncertain, especially in developing countries. In this context, satellite observations can be used to observe column densities of chemical species to reduce uncertainties in inventories. Here, we use three years of TROPOMI daily nitrogen dioxide (NO2) retrievals to map nitrogen oxide (NOx) emissions at high resolution in Egypt, Qatar and Cyprus. We use a flux-divergence scheme, which expresses NOx emissions as the sum of a wind transport term and a chemical sink term representing the reaction between NO2 and hydroxyl radical (OH). The model allows to identify major NOx hotspots. Among these, heavy industrial facilities, such as cement plants and fossil-fuel fired power plants, are characterized by a predominance of the transport term over the sink term. Heavily populated urban centers can also be identified, with a predominance of the sink term. In Egypt, our model is able to detect a weekly cycle in NOx emissions, reflecting Egyptian social norms, and to quantify the drop of emissions in 2020 due to the Covid-19 pandemic. In Qatar, it is able to infer the emission factor of isolated power plants, which is consistent with reported values. In Cyprus, it is able to quantify the emissions from different power plants, with higher emissions on the north side of the island due to the use of different technologies and fuels. These results demonstrate a high potential for satellite-based emission mapping at the scale of large urbanised areas well observed by TROPOMI.
Borehole Heat Exchangers: a potential trigger for aquifer cross-contamination?
Authors: Casasso Alessandro , Ferrantello Natalia , Pescarmona Simone , Sethi Rajandrea
Published: February 2023

The number of Ground Source Heat Pumps (GSHPs) has been growing steadily in the last 20 years, and so has the number of Borehole Heat Exchangers (BHEs), which perform the heat exchange between the ground and the heat pump. BHEs are generally about 100 m deep and, hence, they can cross different aquifers. Concerns have been raised about the possible preferential flow of contaminants that can occur through boreholes, also known as cross-contamination. The strength of such phenomenon depends on the vertical hydraulic gradient between the aquifers and the hydraulic conductivity of the grout filling. Therefore, we developed a numerical flow and solute transport model in severe conditions to assess to which extent a BHE can induce cross-contamination between a shallow contaminated aquifer and a deep uncontaminated one, separated by an aquiclude. The results show that the leakage flow and the contaminant spatial distribution in the deep aquifer are well reproduced with analytical formulae, which can therefore be used to assess the potential impact of cross-contamination. Results also confirm that the geothermal grouts available in the market, with hydraulic conductivities well below 10-6 m/s, guarantee a sufficient protection from preferential flow through borehole heat exchangers.
Global and regional trends of atmospheric carbon monoxide – a background ozone precursor
Authors: Worden Helen , Buchholz Rebecca
Published: February 2023

Carbon monoxide (CO) plays an important role in both air quality and climate. Photochemical oxidation of CO produces ozone (O3) and carbon dioxide (CO2) while also affecting the lifetime of methane (CH4) through reactions with the hydroxyl radical (OH). Because CO2, CH4 and O3 are greenhouse gases, emissions of CO have an indirect radiative forcing, estimated at 0.22 W/m2. Ground-level O3 and CO are also air pollutants that affect human and ecosystem health. Quantifying trends in carbon monoxide is essential for understanding trends in tropospheric ozone, especially in background regions. Using the 22-year data record from MOPITT (Measurements of Pollution In The Troposphere), we show global and regional trends from satellite observations of atmospheric CO. We also examine trends in CO emissions based on model inversions for CO emitted by biomass burning (BB) and fossil fuels (FF) and from chemical production from emissions of biogenic (BG) VOCs (volatile organic compounds). We find that CO concentrations and CO emissions from BB and FF have been mostly decreasing globally, with some notable regional exceptions.