bluuebunny/crossref_metadata_2025 huggingface dataset:
Disentangling long-term and short-term temperature response of carbon fluxes in a subarctic grassland ecosystem exposed to long-term, geothermal warming 
Authors: Avila Linsey M. , Sigurdsson Bjarni D. , Riis Christiansen Jesper , Steenberg Larsen Klaus
Published: March 2022

The impact of rising global temperatures on carbon cycling in some of our most sensitive ecosystems, such as the Arctic, is critical yet challenging to quantify because short- and long-term effects of warming may be different. The observed short-term temperature response of soil organic carbon (SOC) decomposition may be altered in the long-term due to changes in substrate availability and possible acclimation of soil communities. 

Testing how the temperature response of soil decomposition changes over time with warming under open-air, field-scale conditions presents another obstacle for researchers, as warming experiments at different temperatures and over long measurement periods are expensive and rare. Fortunately, the ForHot grassland site in Iceland has provided us with a unique opportunity to explore soil warming effects by measuring along a naturally occurring geothermal gradient that resulted from an earthquake back in 2008.

As part of the FutureArctic project at the ForHot site, we collected five replicate soil cores to a soil depth of 5 cm (100cm3 per sample), from fourteen plots along the geothermal gradient spanning a soil warming gradient from 0°C to +80°C. The samples were incubated in the lab at 5, 15, 25, and 35°C, and flux rates of CO2 and CH4 were measured using a LGR-ICOS M-GGA-918 to produce observational Q10 temperature response relationships. 

Temperature response rates and curvature appeared to be driven primarily by substrate availability. Samples containing the greatest totals of carbon and nutrients produced the highest rates of CO2 emission and CH4 consumption at all temperatures. This likely being an effect of the 13 years of warming where organic content and spatial proximity to the hotspot are inversely correlated. From this, we can then present an analysis of the potential linearity or nonlinearity that temperature responses can have over a rather extensive temperature gradient and how these responses can change over time.

Samples collected from the hotspot, where previous in-situ chamber measurements have shown the highest emissions of CO2 and CH4, had significantly lower CO2 emissions and essentially no flux of CH4 during the laboratory incubations. This suggests a significant contribution of geogenic sourcing to in situ measurements. We present an analysis of the potential use for laboratory incubations at different temperatures to infer geogenic/biogenic flux contributions for in situ measurements where geogenic CO2 and CH4 emissions are present. This will allow us to construct a corrected biogenic carbon budget of the ForHot ecosystem and improve our fundamental understanding of the long-term effects that rising temperatures have on the carbon cycle in subarctic ecosystems. 
Variability of Atlantic Water on shelf of Northeast Greenland: Patterns and Drivers
Authors: McPherson Rebecca , Wekerle Claudia , Kanzow Torsten
Published: March 2022

During the last two decades, rising ocean temperatures have significantly contributed to accelerated mass loss of the Greenland Ice Sheet. The melting of the ice sheet is now the single largest contributor to global mean sea level rise. Warming subsurface Atlantic Intermediate Water (AIW) found on the wide continental shelf of Northeast Greenland and in the fjords interacts with marine-terminating glaciers, which until recently were considered stable, and causes their rapid melting and retreat. The main source of these waters is the westward recirculation of subducted Atlantic Water (AW) in Fram Strait, which has shown a warming of up to 1°C over the past few decades.

The variability of the AIW on the Northeast Greenland (NEG) shelf is investigated using historical hydrographic observations and high-resolution numerical simulations with the Finite-Element-Sea ice-Model (FESOM2). There is excellent agreement of both the mean and long-term distribution of AIW on the shelf between the model and observations. The two main circulation regimes of AW in Fram Strait are also well-replicated by the numerical simulations.

The dominant variability of the AIW temperature occurs at interannual timescales. A shelf-wide process drives this variability of AIW temperatures. EOF analysis shows that over 81% of the variance of maximum AIW temperatures is explained by the first mode, which features a monopol-like pattern across the whole NEG shelf. There is a strong co-variability between the maximum AIW temperature and the volume transport of AIW towards the glaciers, which moves through the deep trough system as a bottom intensified jet and recirculates on the shelf. A connection between the AIW temperatures on the shelf and the AW boundary current along the shelf edge suggests the East Greenland Current influences AIW properties. An increase in strength of the current corresponds to greater AIW volume transport through the trough system, and also warmer AIW and AW temperatures on both the shelf and off the continental slope. This suggests that the drivers of variability of AIW temperatures on the NEG shelf may be found further offshore, with a connection to AW circulation in Fram Strait.
Spatio-temporal variations of water sources and mixing in a riparian zone
Authors: Nogueira Guilherme , Schmidt Christian , Partington Daniel , Brunner Philip , Fleckenstein Jan
Published: March 2022

Riparian zones are known for their role in regulating water quality in stream corridors. Specifically, riparian zones can act as buffers for high-concentration nutrient inputs into the stream, which can be harmful for the aquatic ecosystem. This natural attenuation capacity is controlled by variable water and solute exchanges bringing together different reactants via the mixing of stream water (SW) and local groundwater (GW). The degree and the extent of this mixing can regulate the potential for turnover processes for certain solutes. Here, we couple a previously calibrated transient and fully-integrated 3D numerical flow model with a Hydraulic Mixing Cell (HMC) method to map the different water sources in the stream corridor of the 4th-order Selke stream and track their spatio-temporal evolution. This allows us to identify areas where waters from different sources mix enhancing the potential for turnover of groundwater-borne solutes such as nitrate. We evaluate HMC results with hydrochemical field data, and outline mixing hot-spots defined by high degrees of mixing (i.e. balanced volume fractions of the mixing endmembers in a model cell) expressed in terms of a threshold mixing degree (d=dh) within the stream corridor. Our results show that around 50% of the water in the aquifer originates from infiltrating SW. Especially around the stream (within 250m from the stream), aquifer water is almost exclusively made up of infiltrating SW with minimal amount of water from other sources being mixed in. On average, 9% of the floodplain aquifer are characterized by high degrees of mixing (d=dh), but this value can be nearly 1.5 time higher following big discharge events. Our modeling results further suggest that peak intensity of events is more significant for the increase of mixing degrees than event duration. We also found that discharge events mainly facilitate high mixing degrees at greater distances from the stream; while near the stream growing SW influxes dominate water composition in the aquifer and decreasing water transit times reduce exposure-times of water and solutes to the conditions in mixing hot-spots. With this easy-to-transfer modeling framework we seek to show the applicability of the HMC method as a complementary tool for the identification of SW-GW mixing hot-spots at the floodplain-scale, when simulating the spatio-temporal patterns of SW-GW exchange in stream corridors.
Application of a dense network cross-correlation event detector to seismicity induced by hydraulic stimulations in Espoo/Helsinki, Finland
Authors: Vuorinen Tommi , Hillers Gregor , Veikkolainen Toni , Heikkilä Taavi
Published: March 2022

We have developed a cross-correlation based event detector with the primary application focus on dense, surface-installed temporary seismic networks monitoring the seismicity from a set target area. The event detector is capable of handling a terabytes-sized, noisy multi-channel dataset with hundreds of stations on a regular desktop PC. The detector works in 4 steps: 1. Generate templates from known events in a database. 2. Run cross-correlation for templates on continuous data. 3. Filter initial detections based on the surface network geometry. 4. Relocate the events in the filtered dataset applying correlation time delays and amplitude based magnitude corrections. The detector is accompanied with an event viewer designed to rapidly browse the resulting catalogue. We apply the detector on the induced seismicity of a planned Enhanced Geothermal System (EGS) doublet in Espoo, Finland. The company St1 Oy performed two hydraulic stimulations at around 6 kilometer depth beneath the Aalto University campus in Otaniemi, Espoo, Finland, in June-July 2018 and in May 2020. For both stimulations, the Institute of Seismology, University of Helsinki, installed a temporary ~100 geophone network to monitor the stimulation and post-stimulation stages. The network consisted of three-component 4.5 Hz geophones, mostly DATA-CUBE3s recording at 400 Hz. The geophone stations were organized into large arrays consisting of up to 25 stations, smaller 3-4 station arrays, and additional single stations for better azimuthal coverage. We present here the results from applying the detector on the datasets collected from the Otaniemi-EGS. The anatomy, such as magnitude of completeness, of the resulting event catalogue consisting of thousands of induced events will be discussed with the goal of publishing the finalized catalogue in near future. We also briefly discuss the impact of adding sub-surface borehole stations, and applying the detector to a sparser surface station network to broaden the scope of usefulness. 
Hourly sea-level change with long-term trends for impact attribution: the HLT Dataset
Authors: Mengel Matthias , Treu Simon , Muis Sanne , Dangendorf Sönke , Wahl Thomas , Heinicke Stefanie , Frieler Katja
Published: March 2022

Rising seas are a threat for human and natural systems along coastlines. The relation between global warming and sea-level rise is established, but impacts due to historical sea-level rise are not well quantified on a global scale. To foster the attribution of observed coastal impacts to sea-level rise, we here present HLT, a sea-level forcing dataset encompassing factual and counterfactual sea-level evolution along global coastlines from 1979 to 2015. HLT combines observation-based long-term changes with reanalysis-based hourly water level variation. Comparison to tide gauge records shows improved performance of HLT, mainly due to the inclusion of density-driven sea-level change. We produce a counterfactual by removing the trend in relative sea level since 1900. The detrending preserves the timing of historical extreme sea-level events. Hence, the data can be used in event-based impact attribution to sea-level rise with tuples of impact simulations driven with the factual and counterfactual dataset. The dataset is made available openly through the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP).
Quantitative relationships between insect herbivory severity and BVOC emissions in a Subarctic mountain birch forest
Authors: Rieksta Jolanta , Li Tao , Lauge Borchmann Rikke , Rinnan Riikka
Published: March 2022

Insect herbivory amplifies the biogenic volatile organic compound (BVOCs) emissions into the atmosphere, where BVOCs participate in atmospheric chemistry processes. In the high latitudes, herbivory induced BVOCs are considered as a major contribution to the total plant BVOC emissions during periods of active insect herbivore feeding. However, current BVOC models do not quantify BVOC emissions upon insect herbivory. Including effects of herbivory in models would be especially relevant in order to model BVOC emissions in the Arctic, where insect herbivore pressure is expected to increase with climate change.

We gathered data from enclosure-based field studies conducted in the Subarctic, that assessed the effects of outbreak-causing geometrid moth larvae (Operophtera brumata and Epirrita autumnata) feeding on the BVOC emissions of the dominant tree species, mountain birch (Betula pubescens var. pumila (L.)). The feeding damage ranged from background herbivory to up to 100% defoliation, thus mimicking local insect outbreak conditions.

The leaf area based BVOC emissions from mountain birch increased linearly with increasing feeding damage up to a maximum of 15 %, depending on the BVOC group. After this maximum, BVOC emissions declined as the leaf area decreased.

These results provide quantitative relationships between leaf area eaten and the emission rate of atmospherically important BVOC groups in the Subarctic mountain birch forest. Our results have practical implications for incorporating the modelling of herbivory induced BVOC emissions into the mainstream VOC models such as MEGAN (Model of Emissions of Gases and Aerosols from Nature) or LPJ-GUESS (Lund-Potsdam-Jena General Ecosystem Simulator).
Crustal structure beneath northern Myanmar: preliminary results from ambient noise tomography
Authors: Liang Yanling , Yuan Xiaohui , Schurr Bernd , Tilmann Frederik , Li Wei , Than Oo
Published: March 2022

Adjoining the Eastern Himalayan Syntaxis, linking to the Indian slab indentation northward and Andaman slab subduction eastward, Myanmar is one of the most complicated and active tectonic regions in the world, and exposed to a high seismic hazard. The Burmese arc consists of the Indo-Burman Ranges (IBR), an accretionary wedge in the west and the Central Myanmar Basin in the east. It is bounded in the east by the seismically active Sagaing Fault to the Shan Plateau which is part of the Asian plate. Intermediate-depth seismicity below Myanmar occurs at depths up to ~150 km, generally understood to be related to the subducting Burma slab.  An important open question concerns the transition from oceanic subduction to continental subduction/collision along the Burmense arc. The transition is also thought to affect the upper plate crust. In this study, we collected ambient noise data set based on a temporary seismic array in Myanmar in order to constrain the variation of crustal structure. The station array includes 30 broadband stations from a temporary network (code 6C 2019-2021) at GEOFON data center. They were deployed by the German Research Centre for Geosciences (GFZ) and the Department of Meteorology and Hydrology of Myanmar (DMH) across the eastern IBR and Central Myanmar Basin in early 2019  with an average interstation distance of ~60 km and data are available to 2020 for most stations. We calculated the cross-correlations daily for all available station pairs through the NoisePy code and stacked further into yearly time-series. We measured Rayleigh wave group and phase velocity dispersions from cross-correlations by using the frequency-time analysis (FTAN) and calculated maps of phase dispersion. As a next step, we will construct a detailed crustal and upper mantle structure beneath Myanmar.
Assessment of the soil-water dynamics in an intensively used agricultural lowland area of Lombary, Italy
Authors: Bernini Alice , Becker Rike , Maerker Michael
Published: March 2022

The use of hydrological models can be a suitable basis for the development of sustainable land use and respective water management policies, according to the sustainable development goals (SDGs) of EU. In this study, a process-based numerical model was developed, to determine the hydrological dynamics of a micro-scale basin in a flat and intensely used agricultural area that is partly irrigated, in the Lombardy Region, Italy. In this area, agriculture has a fundamental role in the local hydrological cycle, indeed, landuse and land management practices date back to medieval times with the construction of irrigation channels and reuse of water along the fluvial terrace cascade of the Ticino River. From a hydrological point of view the study area is very complex: there is almost no natural surface runoff, but prevailing vertical soil water dynamics. The water infiltrates on the highest and oldest fluvial terrace level and reemerges in form of springs (risorgive) at the base of the terrace escarpments and is further used for irrigation on the next terrace level.

The objective of this study is to assess the hydrological dynamics of this complex area that is getting under increasing pressure related to climate changes and socioeconomic transformations.  In order to achieve the study goals, we applied the Soil Water Assessment Tool (SWAT), a complex hydrological model that works at the basin scale and generates variable spatio-temporal outputs and is being applied successfully worldwide for soil and water management studies. We present the methodological approach for deriving the model input and boundary conditions. Moreover, we show the effects of selecting different model entity configurations as well as calibration and validation procedures. First preliminary results show that SWAT is able to simulate the general hydrological dynamics of the area according to the use of satellite soil moisture and evapotranspiration data. In addition, through local soil moisture measurements carried out in the field, qualitative evaluation of infiltration capacities have been made and with these measurements it will be possible to validate the model. Hence, the model results obtained, provide information on the soil water dynamics that can be used as a basis for studying future scenarios (i.e., impacts of climate change or different management such as different irrigation schemes).
An efficient polarimetric radar forward operator for NWP model validation and data assimilation
Authors: Mendrok Jana , Carlin Jacob , Snyder Jeffrey , Trömel Silke , Shrestha Prabhakar , Blahak Ulrich
Published: March 2022

Radar observations play a crucial role in detecting and measuring precipitation (QPE, nowcasting) and are useful in various ways to improve numerical weather prediction (NWP) models. Accurate quantitative precipitation estimation remains a challenge as relationships between radar reflectivity and precipitation rate are inheritly ambiguous.Polarimetric observations have the potential to constrain hydrometeor microphysics (size, shape, orientation, etc.) better than conventional ones. Beside improving precipitation measurements, polarimetric observations can be used to evaluate, validate, and improve the representation of hydrometeors in NWP models.Calculating radar observables from prognostic NWP state variables, forward operators (FOs) are a crucial link in comparing radar measurements to NWP output. This requires that the FOs can accurately simulate corresponding observations and that they are consistent with the model(s), e.g. regarding hydrometeor microphysics. However, a wide range of parameters that affect FO output, are not constrained well by the NWP models. This includes, e.g. the melting state, the shape and microstructure, and the orientation of the hydrometeors. Characterization of the uncertainties of an FO, hence, is fundamental to allow its optimal exploitation. Here, we present the revised and polarimetry-extended version of EMVORADO (Efficient Modular VOlume RADar forward Operator) that is coupled to the ICON and COSMO NWP models and applied by DWD in operational weather forecast/data assimilation. Recent developments have focused on enabling polarimetric simulations with computational speed comparable to the Mie-based simulations so far applied in the operational data assimilation as well as to transferability of the code and intermediate calculation results (lookup tables, namely) between different computer architectures. The ability of the FO to reproduce observed polarimetric signatures is evaluated. Uncertainties resulting from weakly or unconstrained assumptions as well as effects of certain techniques and approximations to enhance efficiency are discussed, regarding their impact on analysis of observations and evaluation of NWP models.
Performance of dynamic vegetation in land-surface models - a multi-site comparison
Authors: Westermann Sven , Hildebrandt Anke , Boussetta Souhail , Thober Stephan
Published: March 2022

Land-surface models aim to represent exchange processes between soil and atmosphere via the surface by coupling hydrological and carbon fluxes. Vegetation directly links between hydrological and carbon cycle and, thus essentially, is included in land-surface models. But its dynamics are challenging to capture in models, which is not least because of difficulties in data acquisition. Nevertheless, some land-surface models are available that come with modules for dynamic vegetation. Here, we conducted a model-data comparison to evaluate the representation of dynamic vegetation and related surface fluxes of the two models ECLand and Noah-MP by using the FLUXNET 2015 dataset, data from the TERENO site “Hohes Holz” and a MODIS leaf area product. With the current implementation, using dynamic vegetation modules did not enhance representativeness of the vegetation in ECLand. Dynamic vegetation in Noah-MP improved vegetation representations at least for some sites. For the exchange fluxes, using prescribed leaf-area climatology from remote sensing products appeared with the best model performance. The representation of hydrological fluxes and soil moisture remained almost untouched for both models. Additionally, the performance of the models in vegetation- and hydrology-related variables did not depend on each other. The current implemented modules for dynamic vegetation in these two models yielded no better model performance compared to runs with prescribed leaf-area climatology. Hence, they provide an example that additional model complexity does not lead to improved model performance.
On modeling the fate of microplastics along river networks
Authors: Portillo De Arbeloa Nerea , Marzadri Alessandra , Bellin Alberto
Published: March 2022

The increasing amount of microplastics (hereafter MPs) in freshwater ecosystems appears as a highly relevant environmental issue as MPs represent a group of contaminants of emerging concern responsible for water pollution worldwide. Within MPs are included particles with the potential to enter the environment, persist in it and be easily ingested by aquatic organisms with important adverse effects on both the ecosystems and human health. Research has revealed that the presence of MPs in organisms can cause negative effects and the risk associated with their long-term exposure is still under debate. Within freshwater ecosystems, streams and rivers represent one of the most important delivery vectors responsible for the transfer of MPs from terrestrial to marine environments. Therefore, understanding their transport dynamics became crucial to propose mitigation strategies and to manage and possibly reduce adverse health effects. Here, we present a simple model able to predict the fate of MPs along the different reaches that compose a river network. The model solves the general advection-dispersion-reaction equation (ADRE) along each reach of the river network considering the release of MPs from the Waste Water Treatment Plants (WWTPs). Using a combination of free access databases (MERIT, ReachHydro) and computational algorithms we estimate MPs concentrations at different locations in the river network. The model capability to capture MPs transport was tested by using available literature data where MPs samples were collected upstream and downstream of WWTPs. Our proposed method was able to satisfactorily reproduce the measured values proving a useful tool to understand the role of river networks in controlling the fate of MPs and to provide the basis for introducing suitable mitigation strategies.
Groundwater induced sediment diagenesis in LakeCadagno, Switzerland
Authors: Wille Martin , Vogel Hendrik , Berg Jasmine , Pellaton Jonathan
Published: March 2022

Lake Cadagno, a meromictic, redox stratified lake located in Val Piora in Switzerland has extensively been studied serving as a modern analogue of the Archean/Proterozoic ocean. Euxinic conditions were established after a short transition interval immediately following lake formation ~10’000 years ago. Overall elevated but very variable Mn concentration during this transition period have been thought to reflect fluctuating bottom water redox condition with authigenic accumulation of sedimentary Mn from the water column in line with observation from deep basins of the Baltic Sea.

To test this hypothesis we measured the Mo isotopic composition of Lake Cadagno sediments with a focus on the transition interval following lake formation between 7.4 and 7.8 m depth. With a δ98/95MoNIST+0.25 composition ranging from -1.72 to +3.77‰ the Mo isotopic variability of the transition interval sediments is significantly larger compared to Cadagno sapropels deposited under euxinic conditions and significant larger compared to the entire Mo isotopic variability observed in marine reservoirs. Aside this large variability in δ98/95MoNIST+0.25 a gradual change from isotopically very light to very heavy Mo isotopic composition upcore is observed. This transient sedimentary Mo isotope pattern cannot be explained by fluctuating bottom water redox conditions at the beginning of the lake and cannot be a primary signature caused by changes in the depositional environment. Likely, the inflow of oxic groundwater from subsurface karst aquifers present in Cadagno into organic-matter-rich lake sediments, a likely active and currently ongoing process, causes the formation of a chemocline at depth in the sediment column. Here the reduction of sulphate and the precipitation of isotopically light Mo from the dissolved oxic groundwater reservoir causes progressively higher δ98/95MoNIST+0.25 upwards in the sediment column.  
Chaotic variability of the North Atlantic Subtropical Mode Water
Authors: Narinc Olivier , Thierry Penduff , Guillaume Maze , Stéphanie Leroux
Published: March 2022

Following the recommendations of CMIP6, some climate models have for the first time started using a resolution of 1/4° for their oceanic component. This is significant, as it means that large eddies are resolved (so-called eddy-permitting models), introducing chaotic variability in oceanic models. Observational studies of the North Atlantic Subtropical Mode Water (STMW) have found that not all of its variability can be explained by atmospheric variability. The STMW is a water mass formed by ventilation over the winter and is the most abundant T,S class of water in the surface North Atlantic. Consequently it plays a key role in air-sea exchanges over the basin. These elements have motivated the present model investigation of the STMW's ocean-driven (intrinsic) chaotic variability using a NEMO-based, 1/4°, 50-member ensemble simulation of the Northern Atlantic ocean. Using this dataset, six STMW-wide integrated variables are defined and analysed: total volume, and averaged potential vorticity, depth, temperature, salinity and density. The model solution is assessed against the ARMOR3D ocean reanalysis, based on in situ data collected from ARGO floats and satellite observations. The water mass' chaotic variability is estimated from the time-averaged ensemble standard deviation, and is compared to the total variability estimated from the ensemble mean of the temporal standard deviations of all members. Initial results show that chaotic variability is significant for STMW properties at interannual timescales, representing almost half of the total variability of its average temperature. A spectral analysis indicates that chaotic variability remains significant at longer timescales. This suggests that as climate models move towards finer spatial resolution in the ocean, oceanic chaos can be expected to introduce more variability at interannual and longer timescales. This study also highlights the necessity of a good parametrisation of this oceanic chaos in non-eddying ocean models.
Variability of the Atlantic Meridional Overturning Circulation (AMOC) at 26°N and the design of the RAPID observing array
Authors: Smeed David , Moat Ben , Frajka-Williams Eleanor , Rayner Darren , Volkov Denis , Johns William
Published: March 2022

The time series of the Atlantic Meridional Overturning Circulation at 26°N has been extended to March 2020 and is now almost 16 years long.    During the period from 2004 to 2008 the AMOC was c. 2.5 Sv stronger than in the following years.   Since then, there has been significant interannual variability, but the AMOC has remained relatively weak compared with the first four years of observations. The design of the array was changed in 2020 so that continuous measurements are no longer made over the mid-Atlantic Ridge.  In this presentation we examine the impact of this change on the accuracy of the RAPID timeseries. We find that, although the mid-Atlantic ridge measurements have been important in determining the mean structure of the overturning streamfunction, the impact upon the variability of the streamfunction maximum is very small.   
Theory and empirical evidence for the irregularity of self-organized vegetation patterns
Authors: Kästner Karl , Caviedes Voullieme Daniel , Frechen Nanu , Hinz Christoph
Published: March 2022

In arid environments, vegetation tends to self-organize into patches separated by bare soil. This is necessitated by the lack of water for sustaining a continuous vegetation cover and facilitated by the attraction of water from barren interpatch areas by the vegetation. This process is a positive feedback which introduces spatially heterogeneity into otherwise homogeneous environments, characterised by regular patterns. These patterns are typically considered to be periodic and distinguished on hand of their wavelength. Such patterns have so far been studied with numerical models which generate periodic patterns in homogeneous environments. However, environments are rarely homogeneous, as topography and soil-hydraulic properties vary in space. This raises the questions to which degree heterogeneity of vegetation is self-organized or imposed by the environment, and how environmental heterogeneity interacts with the self-organization process. In contrast to the persisting conceptual model of periodic patterns, natural vegetation exhibit a high degree of irregularity. Several studies have linked this irregularity to heterogeneity in the environment, but a comprehensive theory for analysing the irregularity has not yet been established. Furthermore remains the extend of irregularity unexplored on a global scale. To fill this gap, we, demonstrate empirically the global prevalence of irregularity in vegetation patterns and find that natural vegetation patterns are stochastic, rather than periodic. We then propose a stochastic framework to conceptually describe and measure the regularity, based on the spectral density of the patterns. In addition to the dominant wavelength, measuring the spatial scale, it reveals a novel parameter, measuring the regularity. The parameter is determined by the correlation structure and discriminates gradually between the limit cases of periodicity and white noise. Applied to natural and computer-generated patterns, we find that the former are highly irregular, while the latter are close to periodic. We reproduce the stochasticity of patterns with numerical models by introducing spatial heterogeneity of the model coefficients. We provide a fresh look at the nature of vegetations patterns and present a comprehensive theory for a more holistic understanding of self-organized systems.

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Weather circulation patterns associated with extreme precipitation events in Italy
Authors: Scott Wazita , Gaetani Marco , Fosser Giorgia
Published: March 2022

In the last years, many countries in Europe have been experiencing an increased frequency of extreme precipitation leading to natural disasters like floods and landslides. In Italy, the majority of the country’s natural disasters have been related to extreme precipitation. Floods and landslides have led to the country experiencing great loss in its social and economic structure. Early warning systems are important to stakeholders such as Disaster Risk Managers to make informed decisions in relation to a forecasted disaster.

Extreme precipitation is often associated with specific circulation patterns. Precursor information about atmospheric circulation patterns can therefore act as an indicator of an oncoming extreme precipitation event. The objective of this work is to identify the weather circulation patterns associated with extreme precipitation events over Italy.

E-OBS precipitation datasets were used to identify the most intense extreme precipitation events for each season for the period 1990-2020 across Italy. Mean sea level pressure and 500 hPa geopotential height from the ERA5 dataset were used to identify circulation anomalies associated with the extreme events. The analysis is performed by clustering extreme precipitation events into three homogeneous climatic zones in Italy defined following the Köppen-Geiger classification.

Results show that extreme precipitation events are always associated with an intense low pressure system located within the Euro-Mediterranean region. Depending on the location of precipitation extremes across different climatic zones, low pressure location changes, also modifying the atmospheric circulation and the associated moisture transport. Namely, for precipitation extremes occurring in the Italian peninsula, the low pressure is located in central-western Europe, while for extremes in Sardinia and Sicily, low pressure is in the Mediterranean. 
Hydrological changes in high alpine environments detected with relative gravimetry
Authors: Scandroglio Riccardo , Heinze Markus , Rehm Till , Pail Roland , Krautblatter Michael
Published: March 2022

Here we present the first long-time mass monitoring in periglacial environment with spring gravimetry and correlate it with external weather conditions (rainfall, snow melt) and cleft water discharge to understand water dynamics inside the bedrock.

Water is widely recognized as a preparing and triggering factor in unstable slopes. Pressurized water is documented coincident to alpine rock slope failures, but the quantification of water and of effective destabilizing pressures inside the slope remains unresolved. Gravimetry allows to monitor water mass changes at different resolutions: satellite based gravimetry can detect hydrological changes with kilometer scale, while ground based absolute and relative superconducting gravimeters provide promising results at sub-basins scale. However, only relative spring gravimeters are light and handy enough for extended measurements in high-alpine environments, but example of this use are missing in the literature.

We conducted monthly relative measurements with a spring gravimeter Scintrex CG-5 at 20 stations located at different altitude and slope expositions inside the permafrost affected Kammstollen tunnel (Mount Zugspitze, 2962 m asl, Germany) from 2015 to 2021. Additionally, monitoring with temperature loggers and electrical resistivity detected permafrost degradation, geological mapping provided cleft structure and snowpack simulations quantified water from snowmelt. Due to the low porosity of the local lithology (Wetterstein Limestone with 4-5% effective porosity), we expect perched water to accumulate in single fractures, especially when they are sealed by permafrost.

A clear seasonal trend results from gravimetry, resistivity and temperature measurements, mainly attributable to the hydrological summer-winter cycle. Correlation with the water flow in clefts is also evident, as well with the snowmelt from the models. Uncertainties due to internal drifts of the instrument can be corrected but also show the limitations of this highly sensitive instrument.

Although measuring hydrostatic pressures in single clefts remains an open challenge, this feasibility study is a benchmark showing that relative gravimetry can provide quantitative data on fluid flow and hydrostatic pressure in fractures even in periglacial and mountainous environments.
Development of persistent Southern Ocean biases in HadGEM-GC3.1-MM and implications for modelled ocean-ice interaction in West Antarctica
Authors: Lekakou Kyriaki M. , Webber Ben G.M. , Heywood Karen J. , Stevens David P. , Hyder Patrick , Hewitt Helene
Published: March 2022

The ice shelves of the Amundsen Sea are rapidly thinning, and this can be largely explained by basal melting driven by the ocean. However, sparse observational data and poorly known bathymetry contribute to the difficulty of quantifying the key ocean mechanisms that transport warm water onto the Amundsen Sea continental shelf and their variability. These processes should be represented in coupled climate models such as those used for CMIP6. Previously, we leveraged recent observational campaigns and gains in process understanding to assess how well four models, UKESM1 and the HadGEM-GC3.1 family of models, represent the ocean processes forcing warm water onto the Amundsen Sea continental shelf. We identified the medium resolution (1/4°) HadGEM-GC3.1-MM model’s inability to represent warm water intrusion on the continental shelf, revealing substantial biases in sea ice, SST, salinity and circulation in the Southern Ocean. It is important to understand the processes that are driving these biases, to guide the improvement of this and similar models. Here, we study model behaviour during the spin-up, control and historical runs, to identify what is causing this unrealistic behaviour. A key result is the rapid development of biases in temperature and salinity on the Amundsen’s Sea continental shelf, after only 15 years in the spin-up run, entering a state which persists throughout the following runs. By calculating the differences in sea ice concentration between years 0-5 and 10-15 of the spin up-run, we found significant changes across multiple regions of the Southern Ocean and continental shelf, with most of the East Antarctic sector and Bellingshausen Sea showing a considerable decline that exceeds 20% in some places. The differences between years 0-5 and 10-15 Notable freshening takes place in the whole West Antarctic sector and a strong westward slope current appears, which encircles Antarctica. While strong biases in sea ice and salinity develop later in the Weddell Sea, during the first 15 years the largest biases occur in Drake Passage and the west Antarctic sector. We analyse tendencies and the freshwater budget from the spin-up run to quantify the key processes that drive the development of these biases in selected regions.
Integrating geophysical, geochemical, petrological and geological data for the thermal and rheological characterization of unconventional geothermal fields: the case study of Long Valley Caldera
Authors: Gola Gianluca , Barone Andrea , Castaldo Raffaele , Chiodini Giovanni , D'Auria Luca , García-Hernández Rubén , Pepe Susi , Solaro Giuseppe , Tizzani Pietro
Published: March 2022

We propose a novel multidisciplinary approach to image the thermo-rheological stratification beneath active volcanic areas, such as Long Valley Caldera (LVC), which hosts a magmatic-hydrothermal system. Geothermal facilities near the Casa Diablo locality supply 40 MWe from three binary power plants, exploiting about 850 kg s−1 of 160–180 °C water that circulates within the volcanic sediments 200 to 350 meters deep. We performed a thermal fluid dynamic model via optimization procedure of the thermal conditions of the crust. We characterize the topology of the hot magmatic bodies and the hot fluid circulation (the permeable fault-zones), using both a novel imaging of the a and b parameters of the Gutenberg-Richter law and an innovative procedure analysis of P-wave tomographic models. The optimization procedure provides the permeability of a reservoir (5.0 × 10−14 m2) and of the fault-zone (5.0 · 10−14 – 1.0 × 10−13 m2), as well as the temperature of the magma body (750–800°C). The imaging of the rheological properties of the crust indicates that the brittle/ductile transition occurs about 5 km b.s.l. depth, beneath the resurgent dome. There are again deeper brittle conditions about 15 km b.s.l., agreeing with the previous observations. The comparison between the conductive and the conductive-convective heat transfer models highlights that the deeper fluid circulation efficiently cools the volumes above the magmatic body, transferring the heat to the shallow geothermal system. This process has a significant impact on the rheological properties of the upper crust as the migration of the B/D transition. Our findings show an active magmatic system (6–10 km deep) and confirm that LVC is a long-life silicic caldera system. Furthermore, the occurrence of deep-seated, super-hot geothermal resources 4.5 – 5.0 km deep, possibly in supercritical conditions, cannot be ruled out.
Modelling the stratification and circulation in a shallow embayment off Peru: the case of Paracas bay
Authors: Arellano Cinthia , Echevin Vincent , Colas Francois , Chamorro Adolfo , Merma Lander
Published: March 2022

Understanding the circulation in the narrow (5-10 km) and shallow (15 m depth) Paracas bay in the Peruvian Upwelling System and the mechanisms that set up stratification are key steps for the forecast of extreme events affecting the highly exploited coastal ecosystem of the bay. Using a CROCO offline dynamical downscaling from 10 km to 500 m resolution in the bay, sensitivity experiments were carried out to investigate the impact of local forcing (diurnal wind variability, solar heat flux, river discharge, tides) and of parameterizations of the solar radiation absorption. According to observations, the bay stratification is strongest in summer, with a temperature vertical difference of ∼ 4-5 °C. Results show that stratification increases slightly (<0.5 °C) when diurnal wind variability was introduced. Parameterization of shortwave absorption using chlorophyll-dependent water type affects mainly the bottom temperature in the bay. Furthermore, the freshwater flow associated with the Pisco River discharge only affects the salinity (and stratification) in the bay during periods of weak winds, when low salinity water is transported southward and then mixed in the bay. It is also shown that the shape of the wind forcing, which is difficult to obtain in small bay surrounded by orographical obstacles,  has a major impact on the stratification.
Oxygen in the trapped air: identifying primary atmospheric signals and secondary bubble close-off fractionation
Authors: Yan Yuzhen , Bender Michael , Higgins John
Published: March 2022

Ice cores offer a unique opportunity to study past atmospheric composition because the trapped gases are ultimately derived from ancient atmosphere. This distinctive ability has motivated some pioneering efforts in the late 1980s to measure the elemental composition of the trapped air. The goal at that time was to reconstruct past atmospheric O2 concentration variations (PO2), the primary (atmospheric) signal. However, these measurements quickly revealed that oxygen, argon, and nitrogen concentrations in the ice (expressed as δO2/N2 and δAr/N2) are altered by gas-trapping processes. This is the secondary (and confounding) signal formation process.

Such alterations have long thwarted the application of ice core δO2/N2 to reconstruct true PO2. Empirically though, δO2/N2 in the trapped air has a high coherency with local summer insolation, but the cause is not well understood. Presumably, the intensity of sunlight on the surface of the ice sheet determines the extent and nature of snow metamorphism, which in turn modulates the magnitude of O2 and Ar losses relative to N2 at the “bubble close-off depth” (typically 70-120 m in polar regions).

Here, we discuss recent efforts to identify the secondary signals in δO2/N2 and extract the primary, atmospheric PO2 signals. First, using δAr/N2 as a proxy for insolation, we show that PO2 remained stable prior to the Mid-Pleistocene Transition (MPT), the shift from 40- to 100-kyr glacial cycles. After the MPT, however, PO2 began to decline, possibly linked to enhanced to weathering as a result of glacier expansion and, to a lesser degree, more exposed areas of the continental shelves.

Next, we proceed to exploit the secondary signal itself. That is, δO2/N2 and δAr/N2 could be used as a direct proxy of local insolation. By examining the relationship between elemental ratios and temperature proxies, we explore the relationship between high-latitude southern hemisphere insolation and Antarctic temperature in three time slices in the Pleistocene. The implications for the nature of 40-kyr glacial cycles will be discussed.
Modeling the run-out behavior of the July 23rd, 2015 Cancia debris-flow event using two numerical models
Authors: Qiao Zhitian , Shen Wei , Berti Matteo , Li Tonglu
Published: March 2022

Numerical models have become a useful tool for predicting the potential risk caused by debris flows. Although a variety of numerical models have been proposed for the runout simulation of debris flows, the differences and performances of these models are unknown. To this end, in this paper, two typical depth-averaged models have been selected to analyze the debris-flow event that occurred in the Cancia basin on July 23rd, 2015. The simulations with and without entrainment are conducted to analyze the influence of entrainment on the runout behavior of the debris flow. The simulated results are compared and discussed in detail. In the scenario without entrainment, a part of the debris mass deviates from the main path during propagation, while the debris mass propagates along the channel if entrainment is considered. This conclusion illustrates that entrainment cannot be ignored in this case. Additionally, the comparison between measured and simulated results shows that both models perform generally well in the terms of simulating the erosion-deposition distribution, but the DAN3D model will present a greater lateral spreading and a thinner depositional thickness than Shen’s model.