bluuebunny/crossref_metadata_2025 huggingface dataset:
Volcanically-triggered changes in glacier surface velocity 
Authors: Martin Michael , Barr Iestyn , Edwards Benjamin , Symeonakis Elias , Spagnolo Matteo
Published: March 2022

Many (~250) volcanoes worldwide are occupied by glaciers. This can be problematic for volcano monitoring, since glacier ice potentially masks evidence of volcanic activity. However, some of the most devastating and costly volcanic eruptions of the last 100 years involved volcano-glacier interactions (e.g. Nevado del Ruiz 1985, Eyjafjallajökull 2010). Therefore, improving methods for monitoring glacier-covered volcanoes is of clear societal benefit. Optical satellite remote sensing datasets and techniques are perhaps most promising, since they frequently have a relatively high temporal and spatial resolution and are often freely available. These sources often show the effects of volcanic activity on glaciers, including ice cauldron formation, ice fracturing, and glacier terminus changes. In this study, we use satellite sources to investigate possible links between volcanic activity and changes in glacier velocity. Despite some studies reporting periods of glacier acceleration triggered by volcanic unrest, the potential of using the former to monitor the latter has yet to be investigated. Our approach is to observe how glacier surface velocity responded to past volcanic events in Alaska and Chile by applying feature-tracking, mostly using optical satellite imagery. The overall aim is to systematically track changes in the glacier velocity, with hope of improving volcano monitoring and eruption prediction. 
Impact of hydrothermal activity on the Si cycle in Yellowstone Lake
Authors: Zahajská Petra , Fritz Sherilyn , Opfergelt Sophie , Stadmark Johanna , Cartier Rosine , Conley Daniel
Published: March 2022

Diatoms (unicellular algae forming siliceous tests) are a significant component of the linked carbon-silicon (Si) cycles in that they consume Si released from the weathering of silicate rocks and subsequently sequester carbon and silica when buried in sediments. Thus, regions of diatom-rich sediment yield a window into the conditions that favor high carbon export rates and burial. We studied the Si sources (tributaries, hydrothermal vents) and sinks (diatomaceous sediment) of Yellowstone Lake, which is situated on silicate rich volcanic rocks, to elucidate Si cycling dynamics in the present and during the Holocene. 

Recent lake water, tributaries, and hydrothermal vent fluids from Yellowstone Lake were analyzed for their dissolved Si (DSi) concentration and stable silicon isotopes (δ30Si) to aid in evaluating the sources of variability in the lake’s Si cycle. In addition, elemental composition (XRF), biogenic silica (BSi) content, and the diatom δ30Si were analyzed in two sedimentary core records spanning the Holocene from a hydrothermally influenced area and an undisturbed deep portion of the lake to identify whether past hydrothermal explosions and disturbance by Mazama ash deposition affected Si cycling.

Combinations of the Si and δ30Si mass balance, sedimentary BSi, diatom δ30Si with XRF, and lithology data revealed that Yellowstone Lake has a resilient biogeochemical system influenced by consistently high hydrothermal input throughout the Holocene. Several of the hydrothermal explosions identified in the lithology had no identifiable long-term impact on BSi accumulation or the diatom δ30Si signature. Both cores show similarities that suggest a stable and homogeneous DSi source across the entire lake. Thus, the diatom δ30Si values record changes in the relative proportion of DSi sources, diatom production connected with changes in climate, and hydrothermal inputs.
Seasonality of debris-flow events in the mining area of Călimani Mountains (Eastern Carpathians, Romania) inferred from tree rings
Authors: Pop Olimpiu , Rusu Andrei , Horvath Csaba
Published: March 2022

During the second half of 20th century, in the central part of the Călimani Mountains (Eastern Carpathians, Romania), the mining activities for sulfur-rich ore extraction and processing resulted in significant morphological changes. Hydrogeomorphic processes, i.e., debris flows originating in the spoil heap area produced in the last decades an increasing volume of sediments transferred along the stream channels. In this mining area, very limited information exist about the frequency and spatial extent of debris flow activity. To bridge the gap between the increasing need of information regarding debris flow patterns and the data provided by the costly field monitoring methods, dendrogeomorphic methods allow to document the spatial extent and temporal frequency of debris-flow activity in forested areas. Dendrogeomorphic approach rely on the identification of growth anomalies recorded by the annual rings of trees disturbed by debris flows. This method proven to be a viable tool for reconstruction of past natural debris flows occurring mountainous areas, but recently few dendrogeomorphic studies have focused also on reconstructing anthropogenically-induced debris flows. The main aim of this study is to apply dendrogeomorphic methods to reconstruct debris flow chronology in mining area of Cǎlimani Mts. Trees living along debris-flow channels below the spoil heaps, which exhibited clear external signs of disturbances (stem wounding) caused by the mechanical impact of past debris-flows were sampled. The growth anomalies, e.g., scars identified within the annual rings of the disturbed trees served to date the occurrence of debris-flows events with a seasonal resolution. In the study area, tree-ring analyses allowed the reconstruction of the past debris-flow events, spanning the period 1970–2021. Reconstructed debris flow frequencies and return periods indicate an increase of debris flow activity over the last two decades. Further studies will attempt to link the seasonality of reconstructed events and the analysis of meteorological patterns characterizing debris flow triggering rainfall events in the study area.
The influence of the 2018 Lombok earthquake sequence, Indonesia on the unrest Rinjani volcano inferred from InSAR time-series analysis 
Authors: Zhao Siyuan , McClusky Simon , Miller Meghan , Cummins Phil , Garthwaite Matt
Published: March 2022

Rinjani volcano is a highly active volcano located on Lombok Island in eastern Indonesia which has experienced ten eruptions in the last 100 years. Between 2014 and 2020, this stratovolcano has erupted twice, on 25th October 2015; and on 1st August 2016. Both eruptions lasted approximately two months, with activity concentrated in the volcanoes central Barujari Crater region. In 2018, four deadly (Mw 6.2 to 6.9) earthquakes struck the north coast of Lombok Island on 28th July, 5th August, and 19th August, causing hundreds of fatalities and extensive damage. These earthquakes also resulted in the remobilization of ash deposits on the flanks of Rinjani volcano located on the north island as landslides. Our InSAR-based finite fault rupture modelling suggests the estimated maximum fault slip of 1.4 m, 2.3 m, and 2.5 m for the three mainshocks located on southward dipping fault planes to the northwest-northeast of the Rinjani volcano occurred at depths of ~15 km, 12 km, and 32 km, respectively. Coulomb stress change modelling based on the these rupture models indicates about 1 MPa of extensional stress change at 10 to 20 km of depth around the crater region was observed, which may promote opening of the magma conduit. The short distance between the peak slip region and the volcano, as well as the stress change, raises the question of whether the earthquake sequence may have influenced the spatio-temporal deformation pattern of the Rinjani volcano.We use an InSAR time-series, consisting of 658 descending and 370 ascending Sentinal-1 interferograms to investigate the time-dependent inflation and deflation signals around the crater region generated by the 2015, 2016 eruptions and the 2018 earthquakes. We analyse the average inflation/deflation rate and the cumulative displacements in different periods between 2014 and 2020 to quantify the volcano deformation before and after the 2018 earthquake sequence. Our preliminary results reveal that the crater region has undergone rapid inflation of up to 20 mm/yr through the 2014 to 2017 period, before significantly slowing to ~10 mm/yr over the 2017 to 2018 period. During the first three months following the 2018 earthquake sequence, a noticeable deflation of the edifice was detected, followed by gentle inflation lasting until late 2020. These results imply that the influence of the 2018 earthquakes acted to reduce the pressure in the reservoir, at least temporarily. We will present results from modelling the volume change and the location of the volcano pressure source for better understanding how changes in the magma body and magma movement may have been influenced by the 2018 Lombok earthquake sequence.
Effects of load and repeated wheeling from lightweight autonomous field robots on soil structure
Authors: Calleja Huerta Alvaro , Lamandé Mathieu , Green Ole , Munkholm Lars Juhl
Published: March 2022

Lightweight agricultural robots are expected to be widely used in the future and will use the same tracks for many operations within a season (i.e. repeated wheeling) and perhaps across seasons. The objectives of this study were to characterize the effects of repeated wheeling and wheel load from the traffic of a lightweight autonomous field robot on soil structural properties and the potential risk of soil compaction.

The experiment was conducted on sandy loam soil at water content close to field capacity. The field had not been tilled for approx. a year and stubbles were remaining from the previous crop. The robot used for the experiment was the AGROINTELLI ROBOTTI 150D. In total, three wheeling scenarios with one, five and ten passes were conducted both with the robot alone (3.3 Mg, inflation pressures 60-80 kPa) and at its maximum load with an implement (3.8 Mg, inflation pressures 70-90 kPa). For each treatment, rut depth and apparent cohesion were measured in the field and soil cores were taken at 10 cm depth for measuring air permeability (ka) and effective air-filled porosity (εpyc) in the laboratory.

The results show that both wheel load and repeated wheeling had a significant effect on rut depth and apparent cohesion. Rut depth seemed to increase linearly with the number of wheel passes. However, apparent cohesion decreased after one pass, then increased linearly with the consecutive passes. Thus, a single pass weakened the soil structure and made it more sensitive to compaction for the following passes. Both ka and εpyc, decreased significantly with repeated wheeling but not with wheel load. The average value of ka at the tenth wheel pass was 7 µm2, being five times lower than the first pass for both loads. The values of εpyc for the fifth and tenth passes were similar for both loads (approx. 0.15 cm3∙cm-3). This was not the case for the value of the first pass, which was higher for the robot alone compared to loaded (0.21 and 0.17 cm3∙cm-3 respectively), although not significantly. 

Repeated wheeling from lightweight autonomous field robots can cause significant compaction even for a soil that has not been tilled recently. Even though soil properties were not critical for crop growth, the compacted wheel tracks may serve as hotspot areas e.g. water erosion. Thus, attention should be drawn towards avoiding traffic and limiting the number of wheel passes.
Climate of the last 125 kyr at Skytrain Ice Rise, Antarctica
Authors: Wolff Eric , Hoffmann Helene ,   WACSWAIN science team plus collaborating scientists
Published: March 2022

There is intense interest in the future stability of the West Antarctic Ice Sheet (WAIS).  Models range widely in their predictions and in the physics they include.  Because the timescales for ice sheets are long, our best hope of constraining the solutions is to look at the past behaviour of WAIS. The last interglacial (LIG) is a particularly important time because Antarctic temperature was higher than present and some models predict the complete loss of WAIS and of the large ice shelves adjacent to it.

Within the WACSWAIN (WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial) project, in 2019 we retrieved a 651 metre ice core to the bed of Skytrain Ice Rise. This ice rise is adjacent to the Ronne Ice shelf and the WAIS, but is expected to have maintained an independent ice flow because of the protection afforded by the Ellsworth Mountains.  The ice core has been processed and analysed continuously for a range of analytes, including water isotopes, methane and major chemistry.

In this presentation we will first describe the dating of the ice core achieved in the top half of the ice column by annual layer counting supplemented by fixed horizons, and deeper down by ice flow modelling supplemented by tie points from chemistry, 10Be, as well as atmospheric CH4 and δ18O. The core is continuous through the last glacial period, and most of the last interglacial. Discontinuities occur near the base, in the ice at the older end of the LIG, so that although older ice may be  present, we can only interpret the core to 125 ka.

Overall, the ice core record shows the clearly recognisable pattern of all the Antarctic Isotopic Maxima seen in East Antarctic ice cores over the last glacial cycles. In the early part of the Holocene, we see a very interesting pattern representing thinning of the ice rise and retreat of the Ronne Ice shelf.  This allows us to add reliable dates to the history of ice retreat in the early Holocene.

In the LIG, the record of marine ions in the ice suggest that the Ronne Ice Shelf was present at least from 125 ka onwards. This rules out occurrence of some of the more extreme retreats of WAIS that would have led to seaways between the Weddell, Amundsen and Ross Seas.  We see somewhat higher water isotope ratios in the LIG than the Holocene, possibly consistent with some drawdown of WAIS in sectors other than the Weddell region.
Assessing the impact of Aeolus wind data assimilation on the Saharan dust simulations in the framework of the JATAC campaign
Authors: Gkikas Antonis ,   NEWTON team
Published: March 2022

Throughout the year, the Tropical Atlantic Ocean receives constantly enormous amounts of mineral particles emitted over the western Sahara. Despite the numerous efforts, the current state-of-the-art atmospheric-dust models are not yet able to represent adequately the Saharan dust outflows towards the Atlantic Ocean. Several drawbacks in the relevant parameterization schemes can explain this deficiency, which subsequently hampers an optimal assessment of the dust-induced impacts. One of these aspects is the wind acting as the driving force of dust emission and transport. Thanks to the deployment of the ALADIN (Atmospheric Laser Doppler Lidar) lidar, onboard the European Space Agency (ESA) Aeolus satellite, profiles of HLOS (Horizontal Line-Of-Sight) winds are acquired globally up to a maximum of 30 km altitude. This unique global dataset is filling an existing observational gap in the Tropics, among other regions of the planet. In addition, the assimilation of Aeolus HLOS winds has revealed an improvement in numerical weather predictions (NWP), particularly in the Tropics where the major portion of the global dust budget resides.

The improvements of NWP are expected to also advance dust numerical simulations. Such hypothesis is under investigation in the NEWTON (ImproviNg dust monitoring and forEcasting through Aeolus Wind daTa assimilatiON) project funded by ESA under the Aeolus+Innovation framework. To address the NEWTON scientific objective, short-term regional dust forecasts, relying on the WRF model operating at the National Observatory of Athens (NOA), are conducted. More specifically, two WRF runs are performed using boundary and initial conditions from the ECMWF IFS (Integrated Forecasting System) outputs, produced with (hel4) and without (hel1) the assimilation of Aeolus quality screened Rayleigh-clear and Mie-cloudy wind profiles. Our simulation domain encompasses most part of the Sahara Desert and the Atlantic Ocean, bounded between the Equator and mid-latitudes. Focus is given on September 2021, when the JATAC (Joint Aeolus Tropical Atlantic Campaign) campaign took place in Cape Verde providing reference observations (ground-based, airborne) valuable for a comprehensive evaluation of WRF dust-related outputs. The assessment analysis is further extended by utilizing the satellite dust datasets MIDAS (ModIs Dust AeroSol) and LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies), both developed at NOA, providing columnar dust optical depth and vertical profiles of dust extinction, respectively. Finally, all the NEWTON related activities are disseminated via the official website (https://newton.space.noa.gr) and the EO4Society portal (https://eo4society.esa.int/).
(Un)predictability of sediment pathways in the transport sections of Source to Sink systems
Authors: Gailleton Boris , Malatesta Luca , Braun Jean , Cordonnier Guillaume , Bovy Benoit
Published: March 2022

Source to sink systems involve processes happening at very large timescales and the current state of the earth only represents a brief snapshot of it through space and time. These processes encompass any of those involved in the removal, transport and deposition of material from sources to sinks. The relatively stable incising valleys of the upland source landscapes allow for very efficient mathematical expressions to model their evolution over geological timescales. The transport part of the system is more challenging to study and resists radical simplification. Softer and lower-relief compared to their upstream counterparts, they are much more dynamics and undergo convoluted cycles of erosion/deposition/remobilisation only leaving sparse clues. The presence (or absence) of materials from identified provenance in the transport zone is commonly used to interpret landscapes connectivity through time. However, recent studies suggest that the dynamic nature of the transport section can make apparent provenance data ambiguous and misleading.

In this contribution, we leverage the ability of a newly developed cellular automata landscape evolution modelling framework, CHONK, to investigate the transport zone. CHONK is a landscape evolution modelling framework combining advantages of cellular-automata methods with common eulerian ones. Equations are implemented in a cell referential and cells are processed in a lake-aware multiple flow topological order. Because everything happens within a cell before communicating with downstream landscape, this framework allows fine tracking of sediment provenance through space and time, unconditionally to which law is implemented, or how complex the landscape structure.

We set up a basic mountain range with its foreland, exhume a discrete pluton of different rock type and track the pathways of the sediments through time, including in a stratigraphy allowing remobilisation. We show how, even in this simplistic setting, complex and stochastic patterns of sediment pathways arise.  We explore at which degree these patterns are predictable and at extents they are stochastic – in other word we track the variability of the proportion of sediment coming from the pluton at given locations through time. Finally, adding more complexity to the settings with variable tectonic and climatic cycles, intermediate sink (lakes) and heterogeneous lithologies, we offer a perspective on the framework’s potential to study the role of sediment flux in shaping the landscape and its record in novel ways.
Winter Euro-Atlantic Climate Modes: Future Scenarios From a CMIP6 Multi-Model Ensemble
Authors: Cusinato Eleonora , Rubino Angelo , Zanchettin Davide
Published: March 2022

Dominant Euro-Atlantic climate modes such as the North Atlantic Oscillation (NAO), the Eastern Atlantic pattern (EA), the Eastern Atlantic Western Russian pattern (EAWR), and the Scandinavian pattern (SCA) significantly affect interannual-to-decadal Euro-Mediterranean climate fluctuations, especially in winter.

In this contribution, we will present and discuss results from a CMIP6 multi-model analysis performed to investigate the robustness of historical and projected state and variability of such modes under the historical and ssp585 future scenario of anthropogenic forcing (fossil-fueled development with 8.5W/m2 forcing level) simulations, focusing on the winter season.

Toward this goal, we first search for a reliable box-based index definition for each of the abovementioned observed climate modes and, then, we perform a comparative assessment of the temporal, spectral and distributional properties of the so-defined indices during the historical (1850-2014) and ssp585 future scenario (2015-2099) time periods, with a special focus on the two interdecadal periods 1960-1999 and 2060-2099.

Results show overall good skills of the historical ensemble to reproduce the observed temporal, spectral and distributional properties of all considered modes. At the end of the 21st Century the ssp585 ensemble yields non-significant distributional changes for NAO, EAWR, and SCA indices and a transition to a stronger baroclinic structure for EA, with persistent positive anomalies in the mid-troposphere enhancing globally-driven warming over the Euro-Mediterranean region. The hemispheric spatial correlation patterns with temperature and precipitation significantly change for all modes, that is, we observe a significant modulation of the teleconnections associated with each index.

 
Glacial/Interglacial temperature signal in 2 km deep borehole Litoměřice, Czechia
Authors: Šafanda Jan , Dědeček Petr , Uxa Tomáš , Čermák Vladimír
Published: March 2022

Litoměřice borehole located in the Lowland of the Northern Czechia was drilled in 2007 to the depth of 2 km and repeatedly logged in the period 2007−2020. The analysis of the obtained data enabled us to reconstruct the temperature-depth record undisturbed by the drilling and to recognize a robust past climate signal. Whereas this signal is hidden by the temperature gradient variations caused by heterogeneous thermal properties of the sedimentary/volcanic rock strata in the uppermost 950 m, below this depth the temperature-depth profile clearly indicates a warming at the end of the last glacial. Numerical solution of the transient heat conduction equation shows that the temperature gradient increase by about 3 K/km observed in the homogenous mica schist section between 1000−1500 m depth is consistent with the ground surface temperature warming of about 10 K. The numerical simulations also suggest that the permafrost occurrence, at least in the coldest periods of the last glacial, was highly probable in the Central European lowlands.
The Land surface Carbon Constellation (LCC) project: Overview and first results
Authors: Scholze Marko ,   The LCC project team
Published: March 2022

In the context of climate change it is of paramount importance to quantify CO2 sources and sinks, estimate their spatio-temporal distribution, and advance our understanding of the underlying processes. This information is needed to improve the projections of future trends in carbon sinks and sources, and thus the potential magnitude of climate change. However, there are large uncertainties in the quantification of the terrestrial carbon sinks arising mainly from uncertainties in the underlying models used for the quantification of these sinks. A major source for these model uncertainties are uncertainties in their parameterisations and parameter values. Reducing these uncertainties is critical for reducing the spread in simulations of the global carbon cycle, and hence in climate change projections.

The Land surface Carbon Constellation project, as part of ESA’s Carbon Science Cluster, is designed to achieve such understanding and reduce these uncertainties in an integrated approach exploiting both observations (satellite and in situ) and modelling. The project demonstrates the synergistic exploitation of satellite observations from active and passive microwave sensors together with optical data for an improved understanding of the terrestrial carbon and water cycles. As such, the community terrestrial ecosystem model D&B based on the well-established DALEC (Williams et al.2004) and BETHY (Knorr, 2000) models together with appropriate observation operators is applied in a data assimilation framework at two contrasting field sites (Sodankylä, Finland, representing a boreal forest biome, and Majadas de Tietar, Spain, representing a temperate savanna biome) and their surrounding regions. The model development as well as the satellite data interpretation is supported by dedicated field campaigns at the two sites plus an additional agricultural field site (Reusel, The Netherlands).

In this contribution, we will report on the overall project design and lay out a roadmap for the synergistic use of remotely sensed observations of solar induced fluorescence and high resolution above-ground biomass and illustrate their use in combination with the assembled campaign data base including data from on ground radiometers as well as FloX Boxes.
Impact of Offsets on Assessing the Low-Frequency Stochastic Properties of Geodetic Time Series
Authors: Gobron Kevin , Rebischung Paul , de Viron Olivier , Demoulin Alain , Van Camp Michel
Published: March 2022

Understanding and modelling the properties of the stochastic variability -- often referred to as noise -- in geodetic time series is crucial to obtain realistic uncertainties for deterministic parameters, e.g., long-term velocities, and helpful in characterizing non-modelled processes. With the ever-increasing span of geodetic time series, it is expected that additional observations would help better understanding the low-frequency properties of the stochastic variability. In the meantime, recent studies evidenced that the choice of the functional model for the time series may bias the assessment of these low-frequency stochastic properties. In particular, the presence of frequent offsets, or step discontinuities, in position time series tends to systematically flatten the periodogram of position residuals at low frequencies and prevents the detection of possible random-walk-type variability.

 

In this study, we investigate the ability of frequently-used statistical tools, namely the Lomb-Scargle periodogram and Maximum Likelihood Estimation (MLE) method, to correctly retrieve low-frequency stochastic properties of geodetic time series in the presence of frequent offsets. By evaluating the biases of each method for several functional models, we demonstrate that neither of these tools is reliable for low-frequency investigation. By assessing alternative approaches, we show that using  Least-Squares Harmonic Estimation and Restricted Maximum Likelihood Estimation (RMLE) solves part of the problems reported by previous works. However, we evidence that, even when using those optimal methods, the presence of frequent offsets inevitably blurs the estimated low-frequency properties of geodetic time series by increasing low-frequency stochastic parameter uncertainties more than that of other stochastic parameters.

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Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion
Authors: Giuliani Andrea , Drysdale Russell N. , Woodhead Jon D. , Planavsky Noah J. , Phillips David , Hergt Janet , Griffin William L. , Oesch Senan , Dalton Hayden , Davies Gareth R.
Published: March 2022

Earth’s carbon cycle is strongly influenced by subduction of sedimentary material into the mantle. The composition of the sedimentary subduction flux has changed considerably over Earth’s history, but the impact of these changes on the mantle carbon cycle is unclear. Here we show that the carbon isotopes of kimberlite magmas record a fundamental change in their deep-mantle source compositions during the Phanerozoic Eon. The 13C/12C of kimberlites prior to ~250 Myr preserves typical mantle values, whereas younger kimberlites exhibit lower and more variable ratios – a switch coincident with a recognised surge in kimberlite magmatism. We attribute these changes to increased deep subduction of organic carbon with low 13C/12C following the Cambrian Explosion when organic carbon deposition in marine sediments increased significantly. These observations demonstrate that biogeochemical processes at Earth’s surface have a profound influence on the deep mantle, revealing an integral link between the deep and shallow carbon cycles.
Ice rise and ice rumple dynamics, and the consequences for ice sheet evolution
Authors: Henry Clara , Schannwell Clemens , Višnjević Vjeran , Drews Reinhard
Published: March 2022

The Antarctic contribution to sea level projections remains poorly constrained, particularly due to the complex dynamical response of the ice sheet to changes in external forcing in coastal regions. In our study we investigate ice rises and ice rumples, features which form in ice shelves where ice is locally grounded due to elevated bed topography. As a consequence, upstream ice is buttressed, regulating the flow of ice. Ice rises and ice rumples differ from one another in their characteristic flow regimes, with ice rises having a local, radial flow regime and ice rumples having a flow regime predominantly aligned with that of the surrounding ice shelf. Ice rises cause the surrounding ice shelf to flow either side of the feature and thereby cause a greater degree of buttressing.

Using a three-dimensional, isothermal,  full Stokes, idealised model setup (Elmer/Ice), we investigate the response of ice rises and ice rumples to sea level change, mimicking a glacial cycle. During sea level increase, a transition from ice rise to ice rumple occurs, and with a subsequent decrease in sea level, hysteretic behaviour is observed, i.e. the current grounded area, dome position and flow regime are dependent on the past state of the system. The hysteretic behaviour seen in the ice rise-rumple system is reflected in the upstream ice shelf and is likely to have an effect on continental grounding line dynamics. These findings have important implications for the initialisation and transient simulation of ice rises and ice rumples within continental-scale ice sheet models given that the evolution of these features is important for the timing and magnitude of sea level projections.
The Antarctic Circumpolar Current’s Southern Boundary at the Greenwich Meridian
Authors: Oelerich Ria , Heywood Karen J. , Damerell Gillian M. , Swart Sebastiaan , du Plessis Marcel
Published: March 2022

The southern boundary of the Antarctic Circumpolar Current (ACC) is often associated with the southern limit of Upper Circumpolar Deep Water, and so forms the boundary between warm ACC waters and colder waters within the marginal seas of Antarctica. Strong density gradients across the southern boundary constitute the frontal jet and are thought to modulate the heat transport across the southern boundary. It is well known that eddies cross the fronts of the ACC and are advected downstream, but how does an eddy interact with the southern boundary of the ACC? Does it change its frontal structure? Does it impact the intensity of the frontal jet? Can changes of the southern boundary’s frontal structure impact mixing? These are questions that we aim to discuss.

As part of the Robotic Observations And Modelling in the Marginal Ice Zone (ROAM-MIZ) project, profiling ocean glider observations at the Greenwich Meridian between 54-57 °S from the 20th of October 2019 to the 18th of February 2020 provide a unique data set of 5 highly resolved hydrographic transects that cross the southern boundary repeatedly. Θ/S diagrams from the hydrographic transects, maps of absolute dynamic topography and dive average currents are used to identify the location, properties and rotational direction of eddies crossing the meridional transects in close proximity to the southern boundary and the frontal jet. We demonstrate that a cyclonic eddy crossing the meridional transect significantly impacts the southern boundary's frontal structure. While the eddy is crossing the meridional transect, density gradients are strengthened and geostrophic velocities show a narrow and strong frontal jet (~50 km wide with velocities of ~80 cm/s). Shortly after the eddy has crossed the meridional transect, density gradients are weakened and geostrophic velocities show a broadened and weakened frontal jet (~75 km wide with velocities of ~60 cm/s). Mixing length scales (the length at which a water parcel can move before mixing laterally) are calculated for all transects with L_mix=Θ_rms/(∇_n Θ_m)  (Θ_rms a measure of temperature fluctuations , ∇_n the gradient along density surfaces  and Θ_m mean temperature field). Values of L_mix are near zero across the frontal jet while the eddy is crossing and near 40 km after the eddy has crossed the meridional transect. The increased mixing length scales indicate that the exchange of water parcels between ACC waters and waters further south is increased after the eddy has crossed the meridional transect.
Moho depth evaluation using GOCE gradient data and Least Square Collocation over Iran
Authors: De Gaetani Carlo Iapige , Heydarizadeh Shali Hadi , Ramouz Sabah , Safari Abdolreza , Barzaghi Riccardo
Published: March 2022

Investigating the crustal architecture, specifically the discontinuity interface between the upper mantle and lower crust of the Earth, so-called Moho, can be done in three prevailing techniques, namely lithology, seismicity, and gravity. In contrast to using the information from analyzing the characteristics of rocks and seismic waves, which are sparsed and expensive, inverting gravity data of satellite missions such as GOCE and GRACE is a suitable alternative for such purposes.

The present paper attempts to map the Moho surface using the gravity data as we considered a simplified Earth model based on three shells including the core, mantle and crust with a potential T on a given sphere outside this body. In this notation, by subtracting the topographic effects, compensating for density anomalies in the crust, and other known constants from the observation that are given on and outside the mean Earth radius, one is left with the potential of a single layer on the mean Moho sphere by taking into consideration the Helmert condensation approach. In planar approximation, this is to say that the topography is formally referred to an xy plane and also the condensation surface which is a plane, situated at a depth D below the previous one. Therefore, relating the topographic load of a mass column with height h over the same elementary area element at depth d, the measure of how deep the crust is sinking into the mantle material as a consequence of the load, we can interpret the Moho variations with respect to some mean crustal thickness.

To do this inversion, we applied the Least Square Collocation (LSC) approach which uses the functional relationships between the quantities, the auto-covariance and cross-covariance matrices based on a covariance function between observations and the unknowns. Practically, after constructing the required residual data, an empirical covariance is estimated, then fitted to analytical one to define the required covariance models.

Finally, the Moho variations has been estimated in an active tectonic zone created by the continental collision of the Arabian plate from South-West and Turan shield from North-East with respect to a mean Moho depth equal to 45 km. Results of this study are comparable and much the same with other studies so that different rheological zones of Iranian plateau can be seen in this estimated map of Moho. For instance, a maximum depth is estimated for Sanandaj-Sirjan zones in South-East and minimum depth for Caspian Sea in North.
A design of the optimal setup for a coupled data assimilation for decadal climate predictions
Authors: Polkova Iuliia , Lyu Guokun , Stammer Detlef , Schubert Silke , Lunkeit Frank , Köhl Armin
Published: March 2022

The need for reliable climate predictions is growing in demand for various socio-economic sectors. The predictability studies though show that Earth System Models (ESMs) can predict important climate variables, the predictions suffer from model errors and initialization shocks that limit predictability. The magnitude of this effect is difficult to quantify unless one could perform experiments in dynamically- and model-consistent settings to contrast against each other various sources of initialization shocks. This is the idea of our study, which concerns quantifying and understanding the impact of deriving dynamically balanced initial conditions on the decadal prediction skill.

Among a variety of coupled data assimilation (CDA) methods, the adjoint method is one of the promising because its result is dynamically consistent with the ESM equations; however, the method might also be one of the most demanding to design and maintain. Here, we use the coupled adjoint model developed for the ESM of intermediate complexity CESAM (Centrum für Erdsystemforschung und Nachhaltigkeit Erdsystem Assimilations-Modell) to produce a coupled ocean-atmosphere reanalysis. So far, we prepared and tested the forward and adjoint CESAM for upcoming decadal climate prediction experiments. We present the performance of the forward CESAM in terms of the 20th-century historical simulations, which are typically used as the benchmark for comparing initialized versus uninitiated climate simulations. We also present the setup for the adjoint CESAM as well as the initial CDA experiments. In the following, these CDA experiments will serve as a source of initial conditions for ensembles of retrospective decadal predictions. In a model-consistent approach, the study will compare initialization based on the coupled ocean-atmosphere reanalysis and based on the widespread strategy in decadal prediction studies of nudging toward ocean and atmosphere reanalyses, which are usually external to a prediction system as well as they are un-coupled. Results of this study aim to guideline future initialization developments for comprehensive ESMs.
Evidence of frictional melting observed in the fault rock drill cuttings from Pohang enhanced geothermal system (EGS) site
Authors: Jung Sejin , Kang Ji-Hoon , Kil Youngwoo , Jung Haemyeong
Published: March 2022

The 2017 Mw 5.5 Pohang earthquake in South Korea has been reported as one of the largest triggered earthquakes at an enhanced geothermal system (EGS) site. A fault that was ruptured in Pohang was not identified by geological investigations or geophysical surveys before the Mw 5.5 Pohang earthquake. “Mud balls” showing a fault gouge structure were reported in the Pohang EGS site only at the depth range of 3,790 – 3,816 m. In this study, we present new observation on the fault rocks retrieved from the Pohang EGS site as drill cuttings. The drill cuttings from 3,256 – 3,911 m interval contained mud balls similar to those observed at the depth of 3,790 – 3,816 m. Mud balls contained fine grains and showed foliated clay matrix with well-rounded clasts of quartz or feldspar, which are a typical fault gouge structure. In addition, mud balls retrieved from the depth of 3,256 and 3,260 m contained black fragments. SEM and TEM observation revealed that these black fragments consist of glassy matrix with sub-micrometer size clasts. Abundant vesicles were observed inside the black fragments, and some of the black fragments preserved foliation defined by compositional layering. TEM observation confirmed that the glassy matrix in the black fragments is amorphous material with a chemical composition similar to illite-smectite. These observations indicate that black fragments are resulted from the frictional melting during the coseismic slip.
A multi-year drought can alter the nitrate retention capacity of a catchment
Authors: Winter Carolin , V. Nguyen Tam , Musolff Andreas , Lutz Stefanie R. , Rode Michael , Kumar Rohini , Fleckenstein Jan H.
Published: March 2022

From 2018 to 2020, large parts of Central Europe experienced an unprecedented multi-year summer drought with severe impacts on society and ecosystems. While strong reductions of water quantity were reported, our study is one of the first to analyze its impacts on water quality by looking at nitrate export dynamics in a nested mesoscale catchment in Germany with heterogeneous landscape settings. We used concentration-discharge (CQ) relationships to analyze catchment functioning in terms of nitrate retention and release, and the mechanistic process based mHM-SAS model (Nguyen et al., 2021) to simulate the underlying belowground nitrogen (N) fluxes and associated hydrologic transit times. For the three drought years, we found an amplification of the seasonality in nitrate export with lower concentrations in summer and higher concentration in winter, compared to normal conditions. Compared to the long-term average behavior, the catchment exhibited a disproportionally high annual load export relative to the discharge available for its transport. We argue that this loss in nitrate retention capacity was driven by a complex mixture of changes in N cycling and heterogeneous transit times among different contributing areas. During dry periods, long transit times and sufficient subsurface denitrification likely caused the low in-stream nitrate concentrations in the upper, more mountainous catchment, while reduced soil denitrification and plant uptake resulted in an accumulation of N in the soils. During the following wet periods, this accumulated N was rapidly exported to the stream (median transit times < 2 month) causing a steep increase in nitrate concentrations and load export. In the downstream (lower) sub-catchment, long median transit times (> 20 years) prevent such an immediate export of the accumulated soil-N to the stream. Our modeling analysis, however, suggests that the build-up of soil N-stores and the lack of fast, shallow flow path may exacerbate N legacies in the downstream part of the catchment, which might become visible as higher N export to the stream decades later. Hence, the more immediate concentration response to drought observed at the catchment outlet was dominated by the flushier upstream catchment. Overall, this increased temporal variability of nitrate export and intensified within-catchment differences caused by a multi-year drought call for a higher spatiotemporal resolution of monitoring and more site-specific management plans for site-specific problems.

Nguyen, T. V., Kumar, R., Musolff, A., Lutz, S. R., Sarrazin, F., Attinger, S., & Fleckenstein, J. (2021, July 13). Disparate Seasonal Nitrate Export from Nested Heterogeneous Subcatchments Revealed with StorAge Selection Functions [preprint]. https://doi.org/10.1002/essoar.10507516.1
Accelerating simulations of convective clouds by reducing the spectral resolution of radiative transfer
Authors: veerman menno , Pincus Robert , van Heerwaarden Chiel
Published: March 2022

The energy transfer by electromagnetic radiation drives atmospheric processes on a wide range of scales: Solar irradiance drives heat and moisture fluxes from the surface and the net radiative cooling of the upper troposphere enables deep convection. However, computing accurate radiative fluxes in atmospheric models is expensive because of the integration over the non-linear absorption spectra of the atmosphere. This integration is typically approximated using so-called correlated k-distribution or similar methods and requires a large number (~102) of spectral quadrature points. In this study, we aim to find the lowest spectral resolution that still allows for accurate cloud field properties in large-eddy simulations of convective clouds. First, we reduce the spectral resolution of the radiation parametrization RRTMGP with an optimization algorithm that repeatedly combines adjacent quadrature points while maintaining the highest possible accuracy on a set of radiative metrics. Reduced sets of quadrature points are then tested further using three distinct sets of large-eddy simulations of convective clouds: deep convection in radiative-convective equilibrium (RCEMIP), shallow convection with precipitation shallow cumulus over the ocean (RICO), and shallow convection over land with a tight connection to the surface energy balance. We find that the spectral resolution of the radiation model, and thereby its computational costs, can be reduced by a factor three to four while retaining statistically similar cloud field properties. While this could reduce the total computational costs of an atmospheric simulation, or allow for a smaller radiation time step, it may also be a crucial step in increasing the feasibility of using 3D radiative transfer in large-eddy simulations.
Simulating long term climate variation with a planetary evolution model
Authors: Vandemeulebrouck Romain , Forget Francois , Lange Lucas , Millour Ehouarn , Delavois Antony , Bierjon Antoine , Naar Joseph , Spiga Aymeric
Published: March 2022

To accurately simulate the climate and the fate of volatiles for thousands to millions of years we must couple physical processes with very different timescale, ranging from  clouds microphysics and atmospheric dynamics (represented in the GCM) to the evolution of lakes, glacier accumulation, and subsurface ice evolution.

Given the diversity and the complexity of the Martian paleoclimates, we choose to use use an ambitious “asynchronous coupling” between the slow ice and water reservoirs models and the GCM.

In practice our innovative Mars evolution model will use a horizontal grid identical to that of the GCM, and include the same representation of the micro-climate on slopes. In our case, we will run the Mars Evolution Model with a timestep of 50 to ~500 years, depending upon the dynamics of the modeled system (smaller timesteps must first be used so that the different volatile reservoirs reach a quasi-equilibrium, then the timestep will depends on the evolution of the forcing, which is slow in the case of obliquity, for instance)  . At each timestep, the inputs from the atmosphere (e.g. mean precipitation, sublimation and evaporation, temperatures, dust deposition) will be obtained through a multi-annual run of the Global Climate model using the outcome of the Mars Evolution Model as initial state.

First results about evolution of water ice and CO2 ice glacier will be presented.
How will climate change impact Australian drylands and what is the role of plant species in modulating these responses
Authors: stewart jana , Kingsford Richard , Munoz-Rojas Miriam
Published: March 2022

A recent global study showed that there was a large discrepancy between air temperature and soil temperature with variances of up to 10 degrees depending on ground cover and soil moisture. Vegetation cover increases soil moisture and decreases soil temperature, and vegetation types have shown significant differences in their impact on soil respiration. Australian vegetation has evolved closely with the soil biota and the influence of these organisms likely has a strong role in dictating vegetation type. Exploring the correlation of vegetation and soil microbes under climate change would have two-way benefits. Identifying microbes which improve soil functionality under climate change could improve revegetation strategies. Understanding how vegetation cover might buffer the impacts of climate change on soil functionality could enable targeted management for facilitating ecosystem resilience and resistance to climate change.  