bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub-seasonal temporal clustering of extreme precipitation: Spatio-temporal distribution, physical drivers and impacts
Authors: Tuel Alexandre , Schaefli Bettina , Zscheischler Jakob , Romppainen-Martius Olivia
Published: March 2022

The successive occurrence of extreme precipitation events on sub-seasonal (weekly to monthly) timescales can lead to large precipitation accumulations and severe impacts for humans and ecosystems. We take here a global perspective to explore the spatio-temporal distribution of sub-seasonal temporal clustering of extreme precipitation (TCEP) and the physical mechanisms that are responsible for it. We first discuss the seasonal distribution of TCEP and its statistical significance, assessed with Ripley’s K function. Though TCEP is mainly confined to the tropical oceans, it is also significant regionally in the Northern Hemisphere extra-tropics, especially along the eastern margins of ocean basins. We then examine thanks to Generalized Linear Models how large-scale modes of variability and regional dynamics affect the occurrence of temporal clustering across the world. In the tropics, ENSO, the Indian Ocean Dipole and the MJO all modulate TCEP frequency, while the effect of the North Atlantic Oscillation and Pacific North American pattern dominate in the Northern Hemisphere. We conclude with an impacts-focused discussion of how TCEP affects river discharge across Europe. TCEP leads to a higher and more prolonged discharge response, especially in pluvial-dominated catchments, and thus to higher flooding risk.
Investigating δ13C values in stalagmites from tropical South America
Authors: Novello Valdir F. , Rehfeld Kira ,   South American Speleothem Group
Published: March 2022

Multiple factors control δ13C values in speleothems and complicate their paleoclimatic and paleoenvironmental interpretation. Therefore, most studies avoid the presentation of δ13C values, and instead, focus only on δ18O. This development can be observed with regard to most recent cave studies from tropical South America, in which stalagmite δ18O were preferentially published without the consideration of δ13C data. Here we present a large δ13C dataset of 98 speleothem records covering multiple time scales from South America, of which 42 remained unpublished or were not available until now. Our main objective is concentrating on the support of existing and emerging databases, such as SISAL, and providing new data for the speleothem community and climate modelling.

As a first approach, we review the δ13C values for the last two millennia and evaluate the environmental influencing factors on this proxy, e.g., local hydroclimate, altitude, temperature, and abundant vegetation types. Our results indicate that the main factors controlling variations in δ13C values are due to changes in the local hydroclimate and, to a minor extent, in temperature. For this time period, most of the isotope records show a significant correlation between the δ13C and δ18O values, indicating a close relationship between local hydroclimate and large-scale atmospheric processes related to shifts of the South American Monsoon System (SAMS). Furthermore, in most of the karst systems studied here, the predominant occurrence of C3 plants growing on soils above the caves is responsible for a considerable lowering of δ13C values (≤6‰) in most of the speleothems.
Cobalt and REE distribution at the Zinkgruvan Zn-Pb-Ag and Cu deposit, Bergslagen, Sweden
Authors: Jansson Nils , Hjorth Ingeborg , Ivarsson Filip , Aiglsperger Thomas , M. Azim Zadeh Amir , Kooijman Ellen , Kielman-Schmitt Melanie , Drakou Foteini , Kozub-Budzyń Gabriela
Published: March 2022

The metamorphosed, stratiform, c. 1.9 Ga Zinkgruvan Zn-Pb-Ag deposit is one of Europe’s largest producers of Zn. Since 2010, disseminated Cu mineralization is also mined from dolomite marble in a hydrothermal vent-proximal position in the stratigraphic footwall. Local enrichments of Co and REE exist in the vent-proximal mineralization types, albeit their distribution is poorly known. This contribution provides new data on the distribution of Co and REE within the Zinkgruvan deposit.

LA-ICP-MS analysis suggest that lattice-bound cobalt in sphalerite range between 44 ppm and 1372 ppm, with the lowest and highest values occurring in distal and proximal mineralization, respectively. Proximal Co-rich sphalerite is always Fe-rich. Lattice-bound Co also occur in pyrrhotite; ranging from 52 ppm in distal ore to 1608 ppm in proximal ore. There is a concurrent increase in lattice-bound Ni from 3 ppm to 529 ppm. In proximal ore, Co is also hosted by cobalt minerals such as costibite (27.37 wt.% Co), safflorite (16.21 wt.% Co), nickeline (7.54 wt.% Co), cobaltite (32.74 wt.% Co) and cobaltpentlandite (25.49 wt.% Co). Automated quantitative mineralogy suggest that these minerals are highly subordinate to sphalerite (<70.11%) and pyrrhotite (<14.69%), amounting to <2.88% cobalt minerals with safflorite being most common (up to 2.67%). Cobalt deportment calculations suggest that the proportion of whole-rock Co that is lattice-bound to sphalerite and pyrrhotite ranges from 7.80% to 100%, with sphalerite being the main host. Whole-rock As and Ni contents pose a strong control on whether Co occurs lattice-bound or as Co minerals.

LA-ICP-MS analysis show that accessory apatite in proximal, marble-hosted Cu mineralization carries a few thousand ppm ∑REE, but locally up to c. 1.6 wt.% ∑REE. The apatite can be subdivided into two types. Type 1 apatite is characterized by dumbbell-shaped chondrite-normalized REE profiles with relative enrichment of in particular Sm-Tb, depletion of Yb-Lu relative to La-Pr, local positive Gd anomalies, and weak positive to negative Eu anomalies. Type 2 apatite is characterized by flat to negatively sloping REE profiles from La to Gd and relative HREE depletion. Additional REE is hosted by monazite. Type 1 apatite was only found as a gangue to Cu mineralization. The Type 1 apatite REE signature is characteristic of hydrothermal apatite, and a direct genetic association with vent-proximal Cu mineralization can be inferred.

Comparison with published REE contents in apatite suggest that vent-proximal Zinkgruvan apatite is locally as REE-rich as apatite from Kiruna-type apatite iron oxide deposits, and more REE-rich than apatite in other metamorphosed sediment-hosted sulphide deposits in the world, such as the Gamsberg deposit (RSA).
Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamics of transform margins
Authors: Jourdon Anthony , Kergaravat Charlie , Duclaux Guillaume , Huguen Caroline
Published: March 2022

Transform margins represent ~30% of nonconvergent margins worldwide. Their formation and evolution have traditionally been addressed through kinematic models that do not account for the mechanical behaviour of the lithosphere. In this study, we use high-resolution 3D numerical thermo-mechanical modelling to simulate and investigate the evolution of intra-continental strain localization under oblique extension. The obliquity is set through velocity boundary conditions that range from 15 (high obliquity) to 75 (low obliquity) every 15 for rheologies of strong and weak lower continental crust. Numerical models show that the formation of localized strike-slip shear zones leading to transform continental margins always follows a thinning phase during which the lithosphere is thermally and mechanically weakened. For low- (75) to intermediate-obliquity (45) cases, the strike-slip faults are not parallel to the extension direction but form an angle of 20 to 40 with the plate motion vector, while for higher obliquities (30 to 15) the strike-slip faults develop parallel to the extension direction. Numerical models also show that during the thinning of the lithosphere, the stress and strain re-orient while boundary conditions are kept constant. This evolution, due to the weakening of the lithosphere, leads to a strain localization process in three major phases: (1) initiation of strain in a rigid plate where structures are sub-perpendicular to the extension direction; (2) distributed deformation with local stress field variations and formation of transtensional and strikeslip structures; (3) formation of highly localized plate boundaries stopping the intra-continental deformation. Our results call for a thorough re-evaluation of the kinematic approach to studying transform margins.
Are European forests currently experiencing a shift in climate-related mortality? A retrospective analysis across the last 25 years.
Authors: George Jan-Peter , Lang Mait , Neumann Mathias , Sanders Tanja , Cammalleri Carmelo , Vogt Jürgen
Published: March 2022

European forests are an important source for timber production, human welfare, income, protection and biodiversity. During the last two decades, Europe has experienced a number of droughts which were exceptionally within the last 500 years both in terms of duration and intensity and these droughts seem to left remarkable imprints in the mortality dynamics of European forests. However, systematic observations on tree decline with emphasis on single species together with high-resolution drought data has been scarce so far so that deeper insights into mortality dynamics and drought occurrence is still limiting our understanding at continental scale.

Here we make use of the ICP Forest crown defoliation dataset, permitting us to retrospectively monitor tree mortality for four major conifers, two major broadleaves as well as a pooled dataset of nearly all minor tree species in Europe. In total, we analysed more than 3 million observations gathered during the last 25 years and employed a high-resolution drought index which is able to assess soil moisture anomaly based on a hydrological water-balance and runoff model every ten days across the continent.

We found significant overall and species-specific increasing trends in mortality rates accompanied by decreasing soil moisture. In particular, previous-year soil moisture anomaly had a stronger influence on mortality rates than current-year soil moisture, suggesting that legacy effects (either physiological or caused by secondary biotic agents) play a keyrole in actual forest decline. Remarkable peaks in mortality occurred simultaneously in Norway spruce and Scots pine (2004, 2018, 2019), but were largely asynchronous in broadleaves. Mortality rates in Norway spruce and Scots pine have increased by 60% and 40%, respectively (period 2010-2020 compared to 1995-2009). Oak (Quercus robur and petraea) as well as Silver-fir (Abies alba) showed much lower mortality and only a weak upward trend.

We conclude that mortality patterns in European forests are currently reaching a concerning upward trend which could be further accelerated by future global change-type droughts.
Storm-resolving simulations with IFS-NEMO/FESOM in the NextGEMS project
Authors: Rackow Thomas , Becker Tobias , Pedruzo Bagazgoitia Xabier , Sandu Irina , Zampieri Lorenzo , Ziemen Florian ,   ECMWF-AWI Team
Published: March 2022

We give an overview of the global coupled storm-resolving simulations performed so far with IFS-NEMO and IFS-FESOM2 for the H2020 Next Generation Earth Modelling Systems (NextGEMS) project. The project aims to build a new generation of eddy- and storm-resolving global coupled Earth System Models. Such models will constitute the substrate for prototype digital twins of Earth as envisioned in the EU’s ambitious Destination Earth project.

NextGEMS relies on several model development cycles, in which the models are run and improved based on feedback from the analysis of successive runs. In an initial set of storm-resolving coupled simulations, the models were integrated for 75 days, starting in January 2020. ECMWF’s Integrated Forecasting System (IFS) has been run at 9km and 4km global spatial resolution. The runs at 9km were performed with the deep convection parametrization, while at 4km, the IFS was run with and without the deep convection parametrization. So far, the underlying ocean models NEMO and FESOM2 were run on an eddy-permitting 0.25° resolution grid in a single-executable configuration with IFS. Based on the analysis by project partners during a Hackathon organised in October, several key issues were identified both in the runs with IFS, and in those run with the second storm-resolving coupled model developed in NextGEMS, ICON.

We will describe the model improvements made to IFS-NEMO/FESOM based on the lessons learned from the first runs, which will be included for the second round of simulations. These mainly consist in vastly improved conservation properties of the coupled model systems in terms of water and energy balance, which are crucial for longer climate integrations, and in a much more realistic representation of the snow and surface drag. The second round of NextGEMS simulations will also target eddy-resolving resolution in large parts of the global ocean (better than 8km) to resolve mesoscale eddies and leads in sea ice. This is thanks to a refactored FESOM2 ocean model code that allows for efficient coupled simulations in the single-executable context with IFS via hybrid parallelization with MPI and OpenMP.
Structure of a new submarine volcano and magmatic phases to the East of Mayotte, in the Comoros Archipelago, Indian Ocean.
Authors: Masquelet Charles , Leroy Sylvie , Delescluse Matthias , Chamot-Rooke Nicolas , Thinon Isabelle , Lemoine Anne , Franke Dieter , Watremez Louise , Werner Philippe , Sauter Daniel ,   SISMAORE team
Published: March 2022

50 km East of Mayotte Island (North Mozambique Channel; Comoros Archipelago), a submarine volcanic edifice formed during the first year of a seismo-volcanic crisis, between May 2018 and May 2019. Thanks to the French ANR Project COYOTES and the SISMAORE oceanographic cruise (2021), a multichannel seismic profile gives the first in-depth image of the new East-Mayotte volcano and its surrounding volcanic area. The seismic interpretation reveals that several distinct magmatic phases affected the area. The new volcano is built on a ~150 m thick sedimentary layer. Beneath this sedimentary layer, we found a major volcanic layer, ~2.5 km thick, which extends ~91 km to the south and ~33 km to the north of the newly formed submarine volcano. This volcanic unit is composed of multiple seismic facies that may indicate distinct successive volcanic phases. We interpret this major volcanic layer as part of the Mayotte volcanic edifice, with the presence of a complex magmatic feeder system underneath. We observe a ~2.2-2.5 km thick sedimentary cover between the main volcanic layer, below the new volcano, and the top of the crust. We tentatively identified the top-Oligocene seismic horizon (~23 Ma) well above the main volcanic layer, and assuming a constant sedimentation rate we estimate the onset of the volcanism at Mayotte Island at 28 Ma.
On the shortwave instability of the stratified Kolmogorov flow
Authors: Kurgansky Michael
Published: March 2022

In relation to internal gravity waves (IGW) propagating at a small angle to the vertical, the linear stability problem of the stratified Kolmogorov flow in a viscous and diffusive Boussinesq fluid, driven by a sinusoidal force in space is re-analyzed using Floquet theory, Galerkin approximations and the method of (generalized) continued fractions. Numerical and analytical arguments are provided in favor of the conjecture that an ideal Kolmogorov flow is prone to shortwave instability for Richardson numbers markedly greater than the critical Richardson number Ri = ¼ appearing in the Miles–Howard theorem, although the stratified Kolmogorov flow is in no way distinguished within the fairly general arguments of this theorem. The shortwave instability of the stratified Kolmogorov flow is conjectured to be due to resonant amplification of the Doppler-shifted IGW modes, but it is emphasized that complete resolution of the above paradox is the task of future research.

This work was supported by the Russian Science Foundation (grant no. 22-27-00039).
Development of a cost efficient observation operator for GNSS tropospheric gradients
Authors: Zus Florian , Galina Dick , Wickert Jens
Published: March 2022

GNSS data collected at a single station allow the estimation of the Zenith Total Delay (ZTD) and tropospheric gradients. In order to make use of such data in numerical weather prediction the observation operators must be developed. The development of a cost efficient observation operator for ZTDs is a straightforward task. On the other hand the development of a cost efficient observation operator for tropospheric gradients is not an easy task. It is also important to bear in mind that for variational data assimilation the corresponding tangent-linear and adjoint operators must be coded.

Our current observation operator for tropospheric gradients is based on dozens of tropospheric delays (Zus et al., 2019). Thereby each tropospheric delay is computed with high precision utilizing a technique called ray-tracing. Clearly, this makes the current observation operator for tropospheric gradients for practical applications too expensive. In this contribution we show how to reduce the computational cost. For example, as expected the high precision with which the tropospheric delays are computed is not too crucial. In addition, the number of tropospheric delays that are involved in the computation of the tropospheric gradients can be reduced. The tropospheric gradients can be understood as a specific linear combination of tropospheric delays. Hence, the difficulty in the derivation of the tangent-linear (adjoint) code for tropospheric gradients lies in the difficulty in the derivation of the tangent-linear (adjoint) code for tropospheric delays. However, this does actually not pose a problem as these codes are available from our previous work.

The output of this study is a cost efficient observation operator (a piece of Fortran code), which, together with its tangent-linear and adjoint operator, is ready to be implemented into existing assimilation systems. One of them is our experimental assimilation system (Zus et al., 2019). Another one will be the assimilation system of the Weather Research and Forecasting (WRF) model in support of the research project EGMAP (Exploitation of GNSS tropospheric gradients for severe weather Monitoring And Prediction) funded by the German Research Foundation (DFG).

Zus, F.; Douša, J.; Kačmařík, M.; Václavovic, P.; Dick, G.; Wickert, J. Estimating the Impact of Global Navigation Satellite System Horizontal Delay Gradients in Variational Data Assimilation. Remote Sens. 2019, 11, 41. https://doi.org/10.3390/rs11010041
Projected Future Changes in Equatorial Wave Spectrum in CMIP6
Authors: Bartana Hagar , Garfinkel Chaim , Shamir Ofer , Rao Jian
Published: March 2022

The simulation of the Madden-Julian Oscillation (MJO) and convectively coupled equatorial waves (CCEWs) is considered in 13 state-of-the-art models from phase 6 of the Coupled Model Intercomparison Project (CMIP6). We use frequency-wavenumber power spectra of the models and observations for Outgoing Longwave Radiation (OLR) and zonal velocity at 250 hPa (U250), and consider the historical and end-of-century projections for the SSP245 and SSP585 scenarios. The models simulate a spectrum quantitatively resembling that observed, though systematic biases exist. MJO and Kelvin waves (KW) are mostly underestimated, while equatorial Rossby waves (ER) are overestimated. The models project a moderate future increase in power for the MJO, a robust increase for Kelvin waves (KW) and weaker power values for most other wavenumber-frequency combinations, including higher wavenumber ER. In addition to strengthening, KW also shift toward higher phase speeds (or equivalent depths). Models with a more realistic MJO in their control climate tend to simulate a stronger intensification, and models with a more realistic KW in their control climate tend to simulate a weaker intensification. 

 
The discontinuous Galerkin method for coupling a 1D river model to a 2D shallow water one 
Authors: Draoui Insaf , Lambrechts Jonathan , Legat Vincent , Deleersnijder Eric
Published: March 2022

 Compared to deltas, lakes and estuaries, rivers generally are characterized by their natural downstream flow that can often be dealt with adequately by having recourse to 1D models. The cross-section integrated Saint-Venant equations are widely used in river modeling and engineering applications. In order to ensure the mass conservation the conservative form of the equations is preferred. In this case, the flux and source terms may be formulated in several ways. It is seen, however, that not all of them lead to stable and accurate numerical results. The choice of the convenient unknown and intermediate variables allows getting an optimal stability with fewer numerical adjustments. Furthermore, in a realistic domain, two different issues should be carefully dealt with, namely the relative paucity of geometric data points and the connection to larger water bodies ( delta, lakes ...). Regarding the data interpolation, the reference level for data definition and interpolation is generalized along the river instead of associating a local reference frame to each cross-section, allowing to obtain a smooth, stable source term. As for the connection to a 2D model, a boundary-connected coupling based on flux continuity is adopted. The aforementioned modules are implemented in the framework of a discontinuous Galerkin finite-element model, i.e., the Second-generation Louvain-la-Neuve Ice-ocean Model (SLIM, www.slim-ocean.be). Validation is performed by running the model in idealized configurations. Then, the river-lakes-delta continuum of the Mahakam River (Borneo, Indonesia) is modeled and validation is based on measured water level.
Observations of Inner Core Shear Waves with AlpArray
Authors: Ling On Ki Angel , Stähler Simon , Kim Doyeon , Giardini Domenico , AlpArray Working Group The
Published: March 2022

Although the solidity of Earth’s inner core is evidenced by normal mode data, the direct observation of inner core shear waves (J-waves) has remained challenging for decades due to their small amplitudes. Previous studies have presented evidence of J-waves in different seismic datasets (e.g., Okal and Cansi Y, 1998; Deuss et al., 2000; Cao et al., 2005; Wookey and Helffrich, 2008), however, the observability seems to be highly dependent not only on distance, but also on the location of the source and receiver, suggesting that amplification from specific 3D structures in the deep Earth is necessary to elevate the phase above noise for certain ray paths. Waszek and Deuss (2015) and Tkalčić and Phạm (2018) also found J-waves in global stacks and global correlation wavefield respectively, but these average over all possible source-receiver geometries and inner core structure.

To improve phase identification and discrimination, we use an approach that combines the array method of slant stacking and polarization filtering to enhance linearly polarized signals with the expected slowness and incident angle. We apply this technique on the data of the AlpArray Seismic Network, a large-scale seismic network in Europe that consists of over 600 broadband stations with a mean station spacing of 30-40km. An arrival consistent with PKJKP (in reference travel time, slowness, and polarization) is found from events in the source region reported by Cao et al. (2005). We present an overview of PKJKP candidate paths over distance based on observations with AlpArray. We also examine whether these observations correspond to specific depths or azimuths and investigate the effects of anisotropy or other three-dimensional earth structures​​​​​​.
The geometry of scales: chameleon attractors
Authors: Alberti Tommaso
Published: March 2022

In 1963 Lorenz discovered what is usually known as “chaos”, that is the sensitive dependence of deterministic chaotic systems upon initial conditions. Since then, this concept has been strictly related to the notion of unpredictability pioneered by Lorenz. However, one of the most interesting and unknown facets of Lorenz ideas is that multiscale fluid flows could spontaneously lose their deterministic nature and become intrinsically random. This effect is radically different from chaos. Turbulent flows are the natural systems when Lorenz ideas can be touched by the hand. They can, indeed, be described via the Navier-Stokes equations, thus conforming to the class of deterministic dissipative systems, as well as, present rich dynamics originating from non-trivial energy fluxes in scale space, non-stationary forcings and geometrical constraints. This complexity appears via non-hyperbolic chaos, randomness, state-dependent persistence and predictability. All these features have prevented a full characterization of the underlying turbulent (stochastic) attractor, which will be the key object to unpin this complexity. 

Here we use a novel formalism to map unstable fixed points to singularities of turbulent flows and to trace the evolution of their structural characteristics when moving from small to large scales and vice versa, providing a full characterization of the attractor. We demonstrate that the properties of the dynamically invariant objects depend on the scale we are focusing on. Our results provide evidence that the large-scale properties of turbulent flows display universal statistical properties that are triggered by, but independent of specific physical properties at small scales. Given the changing nature of such attractors in time, space and scale spaces, we term them chameleon attractors.
Ocean Modeling with Adaptive REsolution (OMARE) – A new multi-scale modeling framework based on NEMO
Authors: Xu Shiming
Published: March 2022

We propose a new ocean modeling framework (OMARE) which supports multi-scale simulation of the ocean through adaptive mesh refinement (AMR). It is based on refactoring NEMO model onto a modern software middleware of JASMIN, which enables, besides AMR, parallel computing platforms (with MPI), dynamic computational load balancing, transparent parallel I/O, etc. We demonstrate the three-level dynamical refinement which span the climate-centric resolution (0.5-deg) and submesoscale-resolving resolution (0.02-deg). The idealized double-gyre test case simulates realistic western boundary current system, and captures the dynamically changing, mesoscale- and submesoscale-rich regions with AMR. We also evaluate and analyze the computational performance of OMARE on typical high-performance computing platforms.
Water quality response to slash-pile burning in a Mediterranean environment (Croatia)
Authors: Delač Domina , Kisić Ivica , Zgorelec Željka , Perčin Aleksandra , Pereira Paulo
Published: March 2022

Slash-pile burning is a common practice in land management across the Mediterranean environment mainly for removing unwanted biomass. This practice is known to have negative effects on topsoil due to high temperatures.  However, the impact on water quality has often been neglected. To address this issue, two experimental burns were conducted: one with moderate (MS), and one with high (HS) severity, to monitor the impact of these practices on water quality. The unburned (UB) treatment, was set aside from the burn treatments. The natural vegetation is composed of Maquis shrubland and meadow plants (Foeniculum vulgare Mill., Elymus repens (L.) Gould, Digitaria sanguinalis (L.) Scop.). The soil type is classified as Leptosol and has a silty clay loam texture with 11.5%, 58.9%, and 29.6% of sand, silt, and clay content, respectively. Treatments were carried out on a sloping terrain (~ 18 °) characteristic of the Mediterranean landscape. Runoff and erosion samples were collected 22 times during the two-year study after major rainfall events. The properties studied were: surface runoff, sediment yield, total carbon in sediment (TC), and water quality parameters such as pH, electrical conductivity (EC), and concentrations of bromine (Br¯), chloride (Cl¯), sulfate (SO42¯), phosphate (PO4³¯), fluoride (F¯), potassium (K⁺), sodium (Na⁺), calcium (Ca²⁺), and magnesium (Mg²⁺). Overall, changes in water quality were consistent with the effects of burning in the first post-burn months, while runoff and sediment yield were more dependent on precipitation patterns, regardless of vegetation cover in the later sampling period. TC had higher levels in HS than in MS, and was increased in both burn treatments at later sampling dates. In the context of changes in water chemistry, the observed effect was more pronounced in HS, while the hydrological response showed high levels in MS. However, the UB also showed significant changes in water quality following major rain events, which was attributed to soil saturation. Our research suggests that slash-pile burning has negative impact on water quality, and it is recommended that biomass be used in other ways, especially in the context of soil and water conservation.

Keywords: burning, runoff, rainfall, vegetation, water conservation

Acknowledgment: The work was supported by the Croatian science foundation under the project “Influence of Summer Fire on Soil and Water Quality” (IP-2018-01-1645).
Paleoenvironmental reconstruction in East Africa at a critical period of hominin dispersion out-of-Africa (150-80 kyr)
Authors: Porchier Cecile A. , Maslin Mark A. , Hill Tom , Williams David M. , Cox Eileen , Mackay Anson W. , Swann George E.A. , Leng Melanie J.
Published: March 2022

Climate may have played a critical role in early hominin evolution and dispersion, with rapid changes from humid to hyper-arid observed in East African palaeoclimate records. Many studies show linkages between these climate changes and hominin speciation and dispersion; however, few of them have focused on annual to decadal climate variability. This new study presents paleoenvironmental records (diatom assemblages and oxygen isotopes in diatom biogenic silica, d18Odiatom) from the Ol Njorowa Gorge in Kenya. The study site is located west of the African Rift Valley, from where important hominin dispersals are believed to have taken place. The study site preserves a stratigraphic record of interbedded diatomite beds spanning a key period of theorised hominin dispersals; 150,000 to 80,000 years ago. In this study, diatom assemblages and d18Odiatomrecords are used to understand past changes in moisture and precipitation patterns over East Africa as well as changes in lake water chemistry. d18Odiatom has been used in both lacustrine and oceanic settings since the early 2000s. It is however an under-utilised proxy that holds great potential, especially for diatomites from exposed lake beds where carbonate material is scarce or inexistant. The study also uses high resolution scanning XRF data from diatomite blocks to develop an age model for the diatomite beds at an annual timescale.
Improved Arctic sea ice forecasting by combining ensemble Kalman filter with a Lagrangian sea ice model
Authors: Cheng Sukun , Chen Yumeng , Aydogdu Ali , Bertino Laurent , Carrassi Alberto , Rampal Pierre , K. R. T. Jones Christopher
Published: March 2022

 Advanced data assimilation methods can improve the forecast of Arctic sea ice, which has been widely used in climate modeling systems to merge observations into simulations. We apply the deterministic Ensemble Kalman filter (DEnKF) to a Lagrangian sea ice model, neXtSIM for sea ice forecast. neXtSIM is computationally solved on a time-dependent evolving mesh, causing a key challenge for applying the EnKF since the mesh grid number and positions are generally different in each ensemble member. The DEnKF analysis is performed on a fixed reference mesh, where model variables are interpolated between the reference mesh and the individual ensemble meshes before and after the assimilation. An ensemble-DA forecasting system for Arctic sea ice forecast based on neXtSIM is built by assimilating the OSI-SAF sea ice concentration (SIC) and the CS2SMOS sea ice thickness (SIT). The ensemble is generated by perturbing atmospheric and oceanic forcing online throughout the forecast. We evaluate the impact of sea-ice assimilation on the Arctic winter sea-ice forecast skills against the satellite observations and a free run during the 2019-2020 Arctic winter. Significant improvements in modeled SIT indicate the importance of assimilating CS2SMOS thickness. While the improvement of SIC and ice extend are clearly observed only in the case with daily assimilating OSI-SAF SIC, which avoids the constraint of daily loaded ocean variables. We found that assimilating a special observation gives the best forecast skill of the relevant variables. With a proper assimilation strategy, neXtSIM as a stand-alone sea ice model could perform computationally efficiently and maintain good forecast skills compared with coupled models.
Monitoring of Martian water ice clouds over one Martian Year with TGO/ACS-MIR
Authors: Stcherbinine Aurélien , Montmessin Franck , Vincendon Mathieu , Wolff Michael , Korablev Oleg , Fedorova Anna , Trokhimovskiy Alexander , Lacombe Gaetan , Baggio Lucio , Irbah Abdenour , Braude Ashwin
Published: March 2022

The Atmospheric Chemistry Suite (ACS) MIR channel onboard the ESA-Roscosmos Trace Gas Orbiter (TGO) (Korablev et al., 2018, 2019) probes the Martian atmosphere in the 2.3 – 4.2 µm spectral range using the Solar Occultation technique. ACS-MIR has now provided infrared observations of the Martian atmosphere over more than one and a half regular Martian Year since the end of the 2018/MY34 Global Dust Storm (GDS).

We analyzed this ACS-MIR dataset to detect the presence of water ice particles in the Martian atmosphere and retrieve their size from the 3 μm atmospheric absorption signature. Each observation results in a vertical profile of ice particle size within the cloud layer, with a vertical resolution of a few kilometers. The temporal and spatial sampling provided by the 2-hour period of TGO’s orbit allows us to observe the seasonal and latitudinal trends of the water ice clouds, with variations of about 20 to 40 km of the cloud’s altitude.

The method was first applied solely to the 2018/MY34 GDS year (Stcherbinine et al., 2020). This first study notably revealed the presence of small-grained clouds at very high altitudes (above 100 km) at the onset of the MY34 GDS, along with the presence of large water ice particles (reff > 1.5 µm) up to 65 km during the storm.

Data acquired during MY35, where no GDS occurred, provides a reference to be compared with the observations obtained during the MY34 GDS. We observe that the maximum altitude of the water ice clouds increases by about 10 km during the GDS compared to a nominal year, which suggests that the GDS significantly impacts water ice cloud distribution.
Our Heliosphere and its Interstellar Interaction: A Solar Cycle of Global Observations and Discoveries
Authors: McComas David
Published: March 2022

The supersonic solar wind and its embedded magnetic field continuously flow outward in all directions from the sun. This magnetized plasma inflates a bubble – the heliosphere – in the very-local interstellar medium (VLISM). The Interstellar Boundary Explorer (IBEX) mission launched in late 2008 and has been continuously returning 3-D global images of Energetic Neutral Atoms (ENAs) that derive from ion populations in the heliosheath and beyond. Now spanning more than a full solar cycle, IBEX’s all-sky maps and observations uniquely inform the global outer heliosphere and its evolving interstellar interaction. Insights from IBEX, in concert with in situ observations by the two Voyager spacecraft, which were transiting two different trajectories through the outer boundaries of the heliosphere contemporaneously with IBEX, have led to a true scientific revolution in our understanding of the outer heliosphere and its interstellar interaction. This Hannes Alfvén Medal Lecture will summarize some of the many discoveries and “firsts” from the IBEX mission and their implications for the outer heliosphere and VLISM. Finally, we will also look forward to the promise of the even more advanced Interstellar Mapping and Acceleration Probe (IMAP) mission, which is under development and slated to launch in 2025.
Ice-load induced salt movement – insights into the controlling parameters from numerical modelling
Authors: Lang Jörg , Hampel Andrea
Published: March 2022

Subsurface salt movement is primarily driven by differential loading, which is typically caused by tectonics or sedimentation. During glacial periods, the weight of an ice sheet may represent another source of differential loading. In salt-bearing basins affected by Pleistocene glaciations, however, it often remains unresolved if young deformations at salt structures were triggered by ice loading or represent a continuation of late Cenozoic activity. Numerical modelling can help distinguishing ice-load-induced deformation from halotectonic movement unrelated to salt-ice interaction. A prerequisite for obtaining conclusive model results is the appropriate choice of the rheological behaviours and parameters of the modelled materials.

Finite-element simulations (ABAQUS) were conducted to test and improve existing models of the interaction between salt structures and ice sheets. The models comprise two-dimensional plane-strain sections based on a simplified geological cross-section of a viscoelastic salt structure with elastic overburden and basement rocks. Different parameter sets for the rheology of salt and overburden rocks, including linear versus non-linear viscosity of the salt, were tested to gain insight into the main controlling factors.

All tested configurations show ice load-driven salt flow and deformation of the salt structure and the overburden rocks. The advance of an ice sheet towards the salt structure causes lateral salt flow away from the load into the salt structure and thus uplift at the surface above the salt structure. Complete ice coverage leads to downward displacement of the salt structure and subsidence at the surface. The downward displacement is accompanied by lateral expansion of the salt structure, which is controlled by the elasticity of the overburden rocks. After unloading, the displacements are largely restored by the elasticity of the materials. In all models, the observed deformation was limited to a few metres and no permanent reactivation of salt structures occurred. The deformation is generally larger in models with linear viscous salt than in those applying non-linear viscosity. Considering the low stress caused by a several hundreds of metres thick ice sheet and the time scales of several thousands of years, the application of a linear viscosity appears to be appropriate. The elastic parameters strongly impact the results, with lower Young's moduli leading to larger deformation. Our model results highlight the importance of a careful parameter choice, regarding both the viscous and elastic behaviour of the modelled materials.
Upper Arctic Ocean hydrography during the year-round MOSAiC expedition in the context of historical observations
Authors: Vredenborg Myriel , Rabe Benjamin , Tippenhauer Sandra , Schulz Kirstin ,   Team MOSAiC OCEAN
Published: March 2022

The Arctic Ocean is characterized by complex processes coupling the atmosphere, cryosphere, ocean and land and undergoes remarkable environmental changes due to global warming. To better understand this system of unique physical, biogeochemical and ecosystem processes and their recent changes, the year-round ice drift experiment Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) was conducted from autumn 2019 to autumn 2020.

In this study we analyse temperature and salinity measurements of the upper Arctic Ocean taken during MOSAiC with different devices, i.e. on an ice-tethered profiler, a microstructure profiler and water sampler rosettes operated from the ship as well as through an ice hole on the ice floe. Combining all these measurements provides us an exceptional data resolution along the MOSAiC track. Moreover, we compare these observations with a comprehensive dataset of historical hydrographic data from the region.

Along the MOSAiC track we find signatures of a convective lower halocline (Fram Strait branch), as well as advective-convective lower halocline (Barents Sea branch). We see pronounced changes in the salinity and temperature of the lower halocline in comparison to the historical data, in particular, at the beginning of the drift. Furthermore, we show polar mixed-layer and upper halocline conditions in relation to seasonality and local surface conditions. We put the warm Atlantic Water temperature in the context of historical observations and investigate indications for the presence of Pacific Water.
Phanerozoic record of northern Ellesmere Island, Canadian High Arctic, resolved through 40Ar/39Ar and (U-Th)/He geochronology
Authors: Schneider David , Powell Jeremy
Published: March 2022

Geochronological studies illuminate our understanding of the tectono-stratigraphic evolution of the Arctic Ocean, submarine features, continental shelves and adjoining landmasses. The Franklinian and Sverdrup basins of the Canadian High Arctic preserve a near-continuous Phanerozoic succession detailing the geologic evolution of the northern Laurentian margin from the Neoproterozoic to Cenozoic. Whereas previous studies have documented the structural and stratigraphic record of several episodes of orogenesis and first-order depositional cycles related to Circum-Arctic evolution, supporting geochronological data are sparse because the logistical challenges associated with fieldwork at high latitudes resulting in poor temporal resolution on the magnitude and timing of: 1) accretion of the Pearya terrane to the Laurentian margin; 2) the Devonian to Carboniferous Ellesmerian orogeny; and 3) Paleogene Eurekan deformation. In an effort to constrain the age of these tectonic episodes, we applied 40Ar/39Ar and (U-Th)/He low-temperature geochronology to major polydeformed NE-SW trending strike-slip fault zones that bisect the Pearya terrane and Franklinian Basin of northern Ellesmere Island, Canada. Total fusion 40Ar/39Ar dating was conducted on 165 single muscovite grains from 22 samples. Age dispersion was sample dependent, with some samples exhibiting robust Paleozoic ages corresponding to the assembly and accretion of the Pearya terrane, and other samples yielding intra-sample date dispersion that spanned the late Paleozoic and Mesozoic, indicative of a previously unreported post-Ellesmerian and pre-Eurekan history. Zircon (U-Th)/He dates from 11 samples (n: 73) and apatite (U-Th)/He data from 6 samples (n: 21) are largely Eocene in age, with dominant populations of c. 48 Ma and c. 41 Ma, respectively. Inverse thermal history modelling of (U-Th)/He data indicates episodic Mesozoic burial and unroofing that coincide with changes in the regional stress regime from dominant N-S to WNW-ESE compression, and rapid cooling during the nascent (>53 Ma) and initial (53 Ma to 47 Ma) phases of Eurekan deformation. The improved geochronologic resolution of the eastern Canadian High Arctic will allow better correlation to offshore structural features and to deformation events on the Greenland plate and Svalbard archipelago.
The relative impacts of initialisation and climate forcing in coupled ice sheet-ocean modelling: application to Pope, Smith and Kohler glaciers
Authors: Goldberg Daniel , Holland Paul
Published: March 2022

Dynamically coupled ice sheet-ocean models are beginning to be used to study the response of the Antarctic Ice Sheet to fluctuations in ocean temperatures. However, initialising a coupled ice-ocean model for realistic settings is challenging and can introduce nonphysical transients. The extent to which such transients can affect model evolution and projection is unclear. Here, we use a synchronously-coupled model of ice-ocean dynamics to investigate the evolution of Pope, Smith and Kohler Glaciers, West Antarctica, over the next half-century. Two methods of coupled initialisation are used: in one, the ice-sheet model is constrained to fit observed velocities in its initial state; in the other, the model is constrained with both velocities and grounded thinning rates over a 4-year period while forced with simulated ocean melt rates. For each method, two climate scenarios are considered -- one where ocean conditions during this initialisation period persist indefinitely, and one where the ocean is in a permanent ``warm'' state -- as well as two ice-sheet basal sliding laws. At first, the model runs initialised with thinning rates exhibit volume loss much closer to observed values than those initialised with velocity only, but after 1-2 decades the forcing primarily determines rates of retreat. This ``crossover’’ timescale is expected to vary by glacier, however. Under the ``warm’’ scenario, grounding line retreat of ~30 km is simulated for Smith and Kohler, but it is questionable whether this will continue due to narrowing of submarine troughs and limiting of heat transport by controlling obstacles.
ToolBoxSWOT - A Python library dedicated to synthetical SWOT-like data for pre-launch river hydrodynamics studies.
Authors: Ricci Sophie , Emery Charlotte , Piacentini Andrea
Published: March 2022

The upcoming Surface Water and Ocean Topography (SWOT) satellite mission will provide a global and high resolution measurement of river water surface elevation. This product issued from large swath interferometry altimetry will be combined with high fidelity hydrodynamics solvers thanks to data assimilation algorithms to allow for river discharge estimation and prediction. Before launch, the SWOT-HR hydrology simulator is used to produce synthetic SWOT observation at each overpass time, adding the radar measurement error, such as layover and thermal noise, to the water elevation issued from a golden run simulation. 

The ToolBoxSWOT is a chain of python scripts that formats the time varying hydrodynamic model outputs into a temporal sequence of water elevation raster data files used as inputs for SWOT-HR. A Digital Elevation Model, a geolocalized series of bathymetric profiles and river centerline are used to map the outputs of the hydrodynamic models onto the expected regular and high resolution 2D grid requested by SWOT-HR. The toolbox gathers strategies adapted to various levels of knowledge from well-known to unknown catchments. The ToolBoxSWOT is available on git and is provided with a container featuring the proper environment that embeds Python3, QGIS3, QGDAL and GRASS78. The ToolBoxSWOT was applied over a well-known reach of the Garonne river for which a DEM and gauge data are available as well as on the Brahmaputra river, using SWOT only-derived data. The toolbox allows the generation of various observation data sets available for the SWOT-hydrology community.