bluuebunny/crossref_metadata_2025 huggingface dataset:
Constraining Climate Projections using Decadal Predictions
Authors: Befort Daniel J. , O’Reilly Christopher H. , Weisheimer Antje
Published: March 2020

There is an increasing demand for robust, reliable and actionable climate information for the near-term future (1-40 years). Seamless information on these time-scales can only be derived from uninitialized climate projections, which however are not aligned with the observed, internal state of the climate system. Another source of information are Initialized predictions for which the observed state is taken into account, but these are only available for the upcoming decade. 

In this study, we test in how far decadal predictions can be used to constrain uninitialized projections to obtain skillful predictions on time-scales beyond decades. This is done by selecting a sub-ensemble of uninitialized projections, which are chosen by their proximity to the decadal predictions ensemble mean. This framework is applied to surface air temperatures from CMIP5 simulations over the North Atlantic Gyre region, as decadal predictions show largest added value over projections for this region. Skill is measured using anomalous correlation coefficient (ACC) and root-mean-square-error (RMSE). Results show that ACC values for forecast years 10-15 for the constrained sub-ensemble are similar to those derived for the non-constrained uninitialized ensemble. However, RMSEs are significantly decreased for the constrained sub-ensemble, not only for the first 10 forecast years but also beyond. This is mainly due to the fact that the constrained sub-ensemble has a much higher ability to capture the observed warming trend during the end of the 20th century compared to the uninitialized ensemble mean. Further to these results, the limitations of this framework are discussed, including an assessment of the potential upper limit of added value and it’s dependency on the skill of the decadal forecast system. 

This easy-to-apply framework can be used to provide crucial climate information for mitigation and adaptation strategies by filling the gap between initialized decadal predictions and uninitialized projections.
Application of stratigraphic frameworks and thermochronological data on the Mesozoic SW Gondwana intraplate environment to retrieve the Paraná-Etendeka plume movement.
Authors: Krob Florian , Glasmacher Ulrich A. , Bunge Hans-Peter , Friedrich Anke M. , Hackspacher Peter C.
Published: March 2020

Since plate tectonics has been linked to material flow in the Earth’s mantle, it is commonly accepted that convective motion in the sublithospheric mantle results in vertical deflections and horizontal plate motion on the Earth’s surface. Those mantle flow-driven vertical deflections are recognized through significant signals and traces in the sedimentary records (unconformities and missing sections). Recently, Friedrich et al. (2018) introduced an event-based plume stratigraphic framework that uses such signals in the stratigraphic record to detect the geological evolution near, and on the Earth’s surface in areas of interregional scale caused by mantle plume movement. Information about these dynamic processes is stored in geological archives, such as (1) stratigraphic records of sedimentary basins and (2) thermochronological data sets of igneous, metamorphic, and sedimentary rocks.

For the first time, this research combines these two geological archives and applies them to the Mesozoic SW Gondwana intraplate environment to retrieve the Paraná-Etendeka plume movement prior to the Paraná-Etendeka LIP. We compiled 18 stratigraphic records of the major continental and marine sedimentary basins and over 35 thermochronological data sets including >1300 apatite fission-track ages surrounding the Paraná-Etendeka Large Igneous Province to test the event-based plume stratigraphic framework and its plume stratigraphic mapping to retrieve the timing and spatial distribution of the Paraná-Etendeka plume.

The plume stratigraphic mapping, using the stratigraphic records is suitable to demark a possible plume center, plume margins and distal regions (Friedrich et al., 2018). Thermochronological data reveal centers of a significant thermal Paraná-Etendeka plume influence. Both archives show significant signals and traces of mantle plume movement well in advance of the flood basalt eruptions. Our LTT data combined with stratigraphic records are modeled successfully with respect to a viable mantle plume driven thermal evolution and therefore, we suggest that thermochronological data, in combination with stratigraphy records have the potential to retrieve the Paraná-Etendeka plume movement.
Dynamical constraints on the choice of the North Atlantic subpolar gyre index
Authors: Koul Vimal , Tesdal Jan-Erk , Bersch Manfred , Brune Sebastian , Hátún Hjálmar , Haak Helmuth , Borchert Leonard , Schrum Corinna , Baehr Johanna
Published: March 2020

The North Atlantic Subpolar Gyre (SPG) has been widely implicated as the source of large-scale changes in the subpolar marine environment. However, inconsistencies between different indices of SPG strength based on Sea Surface Height (SSH) observations have raised questions about the active role SPG strength and size play in determining water properties in the eastern subpolar North Atlantic (ENA). Here, by analyzing SSH-based and various other SPG-strength indices derived from observations and a global coupled model, we show that the interpretation of SPG strength-salinity relationship is dictated by the choice of the SPG index. Our results emphasize that SPG indices should be interpreted cautiously because they represent variability in different regions of the subpolar North Atlantic. Idealized Lagrangian trajectory experiments illustrate that zonal shifts of main current pathways in the ENA and meridional shifts of the North Atlantic Current (NAC) in the western intergyre region during strong and weak SPG circulation regimes are manifestations of variability in the size and strength of the SPG. Such shifts in advective pathways modulate the proportions of subpolar and subtropical water reaching the ENA, and thus impact salinity. Inconsistency among SPG indices arises due to the inability of some indices to capture the meridional shifts of the NAC in the western intergyre region. Overall, our results imply that salinity variability in the ENA is not exclusively sourced from the subtropics, instead the establishment of a dominant subpolar pathway also points to redistribution within the SPG.
Basin-wide homogenization of soft-bottom benthic communities in the wake of anthropogenic habitat degradation in the northern Adriatic Sea
Authors: Zuschin Martin , Haselmair Alexandra , Gallmetzer Ivo , Wieser Anna , Tomasovych Adam
Published: March 2020

We studied the origin and collapse of Holocene benthic baseline communities in the northern Adriatic Sea from sediment cores and surface grab samples at eight widely spaced sites. They cover areas with sedimentation rates spanning two orders of magnitude, with different nutrient input and with different degrees of time-averaging, ranging from decadal to millennial temporal resolution. Data from sediment cores indicate that during the transgressive phase and maximum flooding, sea-level and establishment of the modern circulation pattern determined the development of benthic communities in shallow-water, vegetated habitats with epifaunal biostromes and, in deeper waters, with bryozoan meadows. After sea-level stabilization, the composition of these baseline communities remained relatively uniform and started to change markedly only with the intensification of human impacts in the late highstand, leading to a dominance of infauna and a decline of epifauna at all sites. This profound ecological change reduced species richness, increased the abundance of infaunal suspension feeders, and led to a decline of grazers and deposit feeders. Live-dead data from grab samples give deeper insight into the degree of anthropogenic impact in historical times. At all sites the living assemblages differ strongly from the death assemblages. At some sites from oligotrophic settings with low sedimentation rates, a total overturn in the community composition is obvious: formerly abundant species have disappeared completely, while the living assemblage is numerically dominated by species that were not present before. Even at sites, which are characterized by physically stressful conditions (i.e., high sedimentation rates in the Po delta), some species that were abundant in the death assemblage have totally disappeared from the living assemblage. Comparison with the dataset from sediment cores documents the recent establishment of an impoverished community, which has no analogue in the Holocene history of the northern Adriatic Sea.
Measuring and tracking nighttime inversions within a forest canopy
Authors: Schilperoort Bart , Coenders-Gerrits Miriam , Savenije Hubert
Published: March 2020

One of the challenges of flux measurements above tall canopies, is that parts of the canopy can be decoupled from the atmosphere above. This decoupling can, for example, occur when the forest understory is colder than the air above, limiting exchange through convection. While concurrent above and below canopy eddy covariance (EC) measurements help with addressing the decoupling issue, these are still disconnected point measurements and do not show what is happening along the entire vertical profile. For this, Distributed Temperature Sensing (DTS) can give additional insights, as it can perform continuous temperature measurements along a vertically deployed fiber optic cable.

Measurements were performed at the ‘Speulderbos’ forest site in the Netherlands, where a 48 m tall measurement tower is located in a stand of 34 m tall Douglas Fir trees.  We measured a vertical temperature profile through the canopy using DTS (from the surface up to 32 m). The measurement frequency was ~0.5 Hz, with a vertical resolution 0.30 cm, and data was collected for two months. The fiber optic cable used had a diameter of 0.8 mm, allowing a sufficiently quick response to temperature changes. With this data we were able to detect the presence, height, and strength of inversions. The inversions appeared to occur mostly at night. The height of the inversion showed a bistable behavior, either staying around 1 m above the ground, or at approximately 16 m, which is just below the dense branches of the canopy.

By locating and tracking inversions within the canopy, decoupling events can be studied and explained in more detail. If vertical DTS profiles are available at a site, these can be used for filtering EC measurements as well. While more research will be needed before a wide application at flux sites is possible, this study can serve as a ‘proof-of-concept’ and demonstrates how vertical DTS profiles can help understand problematic flux sites.
A new method for computing horizontally anisotropic background error covariance matrices for data assimilation in ocean models.
Authors: Gonzalez-Ondina Jose M , Sampson Lewis , Shapiro Georgy
Published: March 2020

Current operational ocean modelling systems often use variational data assimilation (DA) to improve the skill of the ocean predictions by combining the numerical model with observational data. Many modern methods are derivatives of objective (optimal) interpolation techniques developed by L. S. Gandin in the 1950s, which requires computation of the background error covariance matrix (BECM), and much research has been devoted into overcoming the difficulties surrounding its calculation and improving its accuracy. In practice, due to time and memory constraints, the BECM is never fully computed. Instead, a simplified model is used, where the correlation at each point is modelled using a simple function while the variance and length scales are computed using error estimation methods such as the Hollingsworth-Lonnberg  or the NMC (National Meteorological Centre). Usually, the correlation is assumed to be horizontally isotropic, or to have a predefined anisotropy based on latitude. However, observations indicate that horizontal diffusion is sometimes anisotropic, hence this has to be propagated into BECM. It is suggested that including these anisotropies would improve the accuracy of the model predictions.

We present a new method to compute the BECM which allows to extract horizontal anisotropic components from observational data. Our method, unlike current techniques, is fundamentally multidimensional and can be applied to 2D or 3D sets of un-binned data. It also works better than other methods when observations are sparse, so there is no penalty when trying to extract the additional anisotropic components from the data.

Data Assimilation tools like NEMOVar use a matrix decomposition technique for the BECM in order to minimise the cost function. Our method is well suited to work with this type of decomposition, producing the different components of the decomposition which can be readily used by NEMOVar.

We have been able to show the spatial stability of our method to quantify anisotropy in areas of sparse observations. While also demonstrating the importance of including anisotropic representation within the background error. Using the coastal regions of the Arabian Sea, it is possible to analyse where improvements to diffusion can be included. Further extensions of this method could lead to a fully anisotropic diffusion operator for the calculation of BECM in NEMOVar. However further testing and optimization are needed to correctly implement this into operational assimilation systems.
Improving age models for abrupt climate changes during the last glacial by pattern recognition
Authors: Turner Mark , Harrison Sandy
Published: March 2020

Quaternary records provide an opportunity to examine how regional climates and vegetation reflect global climate changes comparable in magnitude and velocity to those expected during the 21st century.  The Dansgaard-Oeschger (D-O) cycles of the last glacial period provide the best documented examples of such rapid climate warmings (Greenland interstadials, GIs). However, the age models of pollen records that document regional responses to D-O events are, in general, poorly constrained beyond the radiocarbon timescale. Here we use a pattern-recognition approach, based on matching oscillations in palaeoclimate records to a template of D-O events seen in the Greenland record, to provide better constrained age models. We create a series of templates of Greenland Interstadials (GIs) and compare these to a normalised and detrended time series from a target record using a sliding window and measuring goodness-of-fit using Euclidian distance. We show that this approach can identify D-O events in well-dated records, including reproducing the Greenland record itself. We then apply this approach to the less well-constrained pollen records from the last glacial period from southern Europe. The re-aligned age models permit a more robust comparison of the reconstructed vegetation and climate changes through time and across sites, allowing for regional differences in the response to individual GIs to be identified.
Fast determination of surface water mass changes using regional orthogonal functions
Authors: Ramillien Guillaume , Seoane Lucia
Published: March 2020

Approaches based on Stokes coefficient filtering and « mass concentration » representations have been proposed for recovering changes of the surface water mass density from along-track accurate GRACE K-Band Range Rate (KBRR) measurements of geopotential change. The number of parameters, i.e. surface triangular tiles of water mass, to be determined remains large and the choice of the regularization strategy as the gravimetry inverse problem is non unique. In this study, we propose to use regional sets of orthogonal surface functions to image the structure of the surface water mass density variations. Since the number of coefficients of the development is largely smaller than the number of tiles, the computation of daily GRACE solutions for continental hydrology, e.g. obtained by Extended Kalman Filtering (EKF), is greatly fastened and eased by the matrix dimensions and conditioning. The proposed scheme of decomposition is applied to the African continent where it enables to very localized sources of (sub-)monthly water mass amplitudes.
Robust measurements of corner frequency, t* and site effect: the iterative cluster event method
Authors: Jian Pei-Ru , Kuo Ban-Yuan
Published: March 2020

Seismic attenuation accompanying the velocity structures demonstrates the variations of the physical and chemical properties of the earth. The t* measurement using the seismic body wave spectrum, however, typically encounters the trade-off of corner frequency, t*, and site effect. Ko et al, [2012] proposed the cluster event method (CEM) that reduced the model parameter numbers by grouping the spatial-closed enough events for those traveling to each station along the adjacent paths and sharing one t*. Yet, the site effects among different stations collected in the same cluster bring the challenges on fitting all spectrum. We adapt the cluster strategy to group multiple nearby events recorded by one station only. Moreover, the new iterative CEM algorithm includes both the spectrum and spectral ratio data which provide constraints on seismic moments and corner frequencies of each earthquake inside the cluster, respectively. The final t* and corner frequencies are determined again by including the side effects which are averaging from spectrum residuals in the initial CEM stage. We applied the iterative CEM for earthquakes recorded at dense deployed F-net and Hi-net by NIED in the Tohoku area, Japan. The multitaper spectrums are retrieved from direct P waves with coda wavetrains tapered. Combining the spectral ratio and spectrum data with proper weightings, our new approach increases the stability of t* measurements contributed from better constrains on the corner frequency estimations.
First in-situ Rb-Sr dating of metasedimentary rocks from the Pontiac subprovince, Superior Craton, Canada. Implications towards the regional metamorphic evolution of the sequence.
Authors: Leventis Nicholas , Zack Thomas , Pitcairn Iain , Högmalm Johan
Published: March 2020

The Pontiac subprovince consists of metaturbidites, plutons and thin ultramafic rock layers of Archean age and lies south of the Cadillac-Larder Lake (C-LL) fault zone which is the boundary between the Pontiac and the extensively mineralized Abitibi Greenstone Belt. The sediments show a Barrovian metamorphic gradient which increases southwards, away from the C-LL fault. The most likely tectonic provenance for the Pontiac sedimentary rocks is that they represent a relic accretionary prism with material derived from both the Abitibi and an older terrane. Zircon U-Pb dating shows that deposition occurred not later than 2685±3 Ma ago and recent, robust Lu-Hf dating of garnets bracketed Pontiac's peak metamorphic conditions at 2658±4 Ma. For this study we used a recently developed LA-ICP-MS/MS method for in-situ Rb-Sr dating of biotite and plagioclase in samples ranging in metamorphic grade (biotite to sillimanite zones) from the Pontiac subprovince. Calibration of the instrument was achieved by repeated ablations on several reference materials (see Hogmalm et al. 2017) which also provided the monitoring of accuracy and precision throughout the analyses. Results show a range in dates between 2550 Ma and 2200 Ma with an average of 2440±50 Ma (2σ). Samples from the staurolite and kyanite zones have a larger range with respect to the other zones, but no significant differences are observed in the data with any method of data handing. These dates are ≈300Ma younger than the peak metamorphism in the area and this is attributed to either overgrowth and re-setting of the Rb-Sr system by a second metamorphic/hydrothermal event, or diffusional resetting with core-rim age variations. Possible influence from the adjacent late syntectonic to post-tectonic monzodiorite-monzonite-granodiorite-syenite (MMGS) plutons dated 2671±4 Ma and the garnet-muscovite-granite series (GMG) dated ≈2650 Ma cannot be ruled out. This study provides insights about the metamorphic history of the sequence and supports previous findings regarding resetting of some isotopic systems with relatively low closure temperatures (≈350-400°C) by later thermal events.
Nonlinearity in the Tropospheric Pathway of ENSO to the North Atlantic
Authors: Jiménez-Esteve Bernat , Domeisen Daniela I.V.
Published: March 2020

El Niño Southern Oscillation (ENSO) can exert a remote impact on North Atlantic and European (NAE) winter climate. This teleconnection is driven by the superposition and interaction of different influences, which are generally grouped into two main pathways, namely the tropospheric and stratospheric pathways. In this study, we focus on the tropospheric pathway through the North Pacific and across the North American continent. Due to the possible non-stationary behaviour and the limited time period covered by reanalysis data sets, the potential nonlinearity of this pathway remains unclear. In order to address this question, we use a simplified physics atmospheric model forced with seasonally varying prescribed sea surface temperatures (SST) following the evolution of different ENSO phases with linearly varying strength at a fixed location. To isolate the tropospheric pathway the zonal mean stratospheric winds are nudged towards the model climatology. The model experiments indicate that the tropospheric pathway of ENSO to the North Atlantic exhibits significant nonlinearity with respect to the tropical SST forcing, both in the location and amplitude of the impacts. For example, strong El Niño leads to a significantly stronger impact over the North Atlantic Oscillation (NAO) than a La Niña forcing of the same amplitude. For La Niña forcings, there is a saturation in the response, with no further increase in the NAO impact even when doubling the SST forcing, while this is not the case for El Niño. These findings may have important consequences for long-range prediction of the North Atlantic and Europe.
Trench-parallel compressive upper plate stress field in the northern Chile forearc from earthquake source mechanisms
Authors: Schurr Bernd , Lehmann Lukas , Sippl Christian , Bloch Wasja
Published: March 2020

Subduction zone forearcs deform transiently and permanently due to the frictional coupling with the converging lower plate. Transient stresses are mostly the elastic response to the spatio-temporally variable plate coupling through the seismic cycle. Long-term deformation depends e.g., on the plate convergence geometry, where obliqueness or change in obliqueness play important roles. Here we use the Integrated Plate Boundary Observatory Chile (IPOC) and additional temporal networks to determine source mechanisms for upper plate earthquakes in the northern Chile subduction zone. We find that earthquakes in the South American crust under the sea and under the Coastal Cordillera show a remarkably homogenous north-south, i.e. trench-parallel, compressional stress field. Earthquake fault mechanisms are dominated by east-west striking thrusts. Further inland, where the lower plate becomes uncoupled, the stress field is more varied with direction east-west to southeast-northwest (approx. convergence parallel) dominating. The peculiar stress-regime above the plate-coupling-zone almost perpendicular to plate convergence direction may be explained by a change in subduction obliqueness due to the concave shape of the plate margin.
Sea state observation using ground-based GNSS-SNR data
Authors: Reinking Jörg , Roggenbuck Ole , Even-Tzur Gilad
Published: March 2020

The signal-to-noise ratio (SNR) data is widely used in GNSS reflectometry to derive water or snow surface heights and surface characteristics like roughness or soil moisture. In a marine environment the attenuation of the SNR oscillation is related to the roughness of the sea surface. It was shown that the significant wave height (SWH) of the water surface can be calculated from the analysis of the attenuation.

The attenuation depends strongly on the relation between the coherent and the incoherent part of the scattered power. The correlation length of the sea surface governs the incoherent part and varies with respect to the direction of the line of sight relative to the wave direction. The resulting anisotropic characteristic of the attenuation yields a directional pattern of the cutoff angle at which the coherence is lost. The cutoff angle can be deduced from the attenuation of the SNR data, from which the wave direction can be derived. The contribution will recapitulate the relation between the sea state and the cutoff angle based on sea surface simulations and present the analysis of experimental data from a GNSS station in the North Sea.

A sea state observation would be incomplete without an information about the wave period. The wave period does not influence the SWH but the correlation length of the sea surface. Hence, for a particular SWH, different peak wave periods should yield different correlation length for a line of sight in the wave direction. Analysis based on sea surface simulations show that it should be possible to derive the peak wave period as a function of the SWH and the maximum cutoff angle of the SNR attenuation. The results of this analysis will be presented here, too.
A study on how environmental conditions affect shipping noise propagation in the north Arabian Sea
Authors: Devoto Francesco , Shapiro Georgy , Gonzalez-Ondina Jose M
Published: March 2020

The anthropogenic underwater noise has a negative effect on the marine fauna in the form of the damage on communication and echolocation of marine mammals, body malformations of fish and invertebrates, higher mortality of eggs and zooplankton. Anthropogenic underwater noise is recognised as a form of pollution by the Convention on Migratory Species, the International Maritime Organization and the European Commission. The noise generated by ships is considered to be the main contributor to the underwater noise with the potential to impact marine ecosystems on a global scale, and this is why the shipping noise is the focus of this study. In the upper ocean the oceanographic parameters are subject to the seasonal changes, formation of the seasonal and daily thermoclines, fronts, filaments and eddies which may influence the underwater sound propagation.

One of the most popular sound propagation models is the Range-dependent Acoustic Model (RAM) [Collins, 1995] which is based on the solution of the parabolic equation. However, RAM requires a significant number of environmental data such as bathymetry, seabed characteristics and sound speed distribution in 3D, which is often difficult to obtain. Additionally, the model is relatively slow and computationally expensive in particular in the case of multiple sound sources (ships). To overcome this limitation, simplified acoustic propagation models have been developed. One of these is the energy flux model (EFM) which assumes the homogenous sound speed distribution in all 3 directions. The advantage to use the EFM is to have a fast and efficient model, which produces results in minutes on a typical desktop PC. However, the EFM may produce results which are not very accurate in the areas with significant variability of sound speed.

The purpose of this study is to compare the EFM against RAM in an area of significant spatial and temporal variability. We set up the EFM that computes shipping noise for a frequency of 50Hz in the northern Arabian Sea including the Gulf of Oman and the Persian/Arabian Gulf. The noise at source is calculated using the modified Ross formula [Erbe et al., 2012] and ships locations and velocity, are obtained from the Marine Traffic project. We also set up RAM for the same input parameters as the EFM plus the 3D sound speed distribution calculated form our operational ocean model for the Arabian Sea.

In order to assess the effect of 3D variability of sound speed in the ocean, we have compared the EFM against the reference RAM in winter and summer season, and calculated the statistics showing the differences between the models under the same input conditions. The analysis shows the seasonal and inter-annual dependence of the differences in the received level of noise at different depths, as well the role of the thermocline, eddies and fronts in modifying propagation of acoustic energy from surface ships.
Global water scarcity reduction requires water quality solutions
Authors: van Vliet Michelle T.H. , Jones Edward R. , Flörke Martina , Franssen Wietse H.P. , Hanasaki Naota , Wada Yoshihide , Yearsley John R.
Published: March 2020

Water scarcity threatens people in various regions, and has predominantly been studied from a water quantity perspective. However, the provision of water for human uses and environmental health is dependent on both sufficient water availability but also appropriate water quality for the intended use.

Our study presents the first estimates of global water scarcity driven by both water quantity and water quality issues and including impacts of desalination and treated waste-water reuse. We have developed a new water scarcity framework combining model simulations of multiple global hydrological models and global surface water quality models (water temperature, salinity, organic pollution, nutrients) and spatially-explicit datasets of desalination and treated wastewater reuse capacities globally.

Our results show that 40% of the world’s population currently lives in regions with severe water scarcity, which is driven by a combination of water quantity and quality issues. Impacts of water quality are in particular high in river basins in eastern China. Here, excessive water withdrawals and polluted return flows degrade water quality, exacerbating water scarcity. Our results show that expanding desalination and treated wastewater reuse capacities can strongly reduce water scarcity in most river basins, although the side-effects (e.g. brine production, high energy demands and costs) must be considered. We conclude that effective water scarcity reduction requires that we expand our focus from conventional measures, which mainly focus on improving water supply for sectoral uses, to solutions that also promote water quality improvements.

 

 
Increased Arctic Ocean sea ice loss through the Canadian Arctic Archipelago under a warmer climate
Authors: Howell Stephen , Brady Mike
Published: March 2020

The ice arches that ring the northern Canadian Arctic Archipelago have historically blocked the inflow of Arctic Ocean sea ice for the majority of the year. However, annual average air temperature in northern Canada has increased by more than 2°C over the past 65+ years and a warmer climate is expected to contribute to the deterioration of these ice arches, which in turn has implications for the overall loss of Arctic Ocean sea ice. We investigated the effect of warming on the Arctic Ocean ice area flux into the Canadian Arctic Archipelago using a 22-year record (1997-2018) of ice exchange derived from RADARSAT-1 and RADARSAT-2 imagery. Results indicated that there has been a significant increase in the amount of Arctic Ocean sea ice (103 km2/year) entering the northern Canadian Arctic Archipelago over the period of 1997-2018. The increased Arctic Ocean ice area flux was associated with reduced ice arch duration but also with faster (thinner) moving ice and more southern latitude open water leeway as a result of the Canadian Arctic Archipelago’s long-term transition to a younger and thinner ice regime. Remarkably, in 2016, the Arctic Ocean ice area flux into the Canadian Arctic Archipelago (161x103 km2) was 7 times greater than the 1997-2018 average (23x103 km2) and almost double the 2007 ice area flux into Nares Strait (87x103 km2). Indeed, Nares Strait is known to be an important pathway for Arctic Ocean ice loss however, the results of this study suggest that with continued warming, the Canadian Arctic Archipelago may also become a large contributor to Arctic Ocean ice loss.
Sampling errors on convective scales: What can we learn from a 1000-member ensemble?
Authors: Necker Tobias , Weissmann Martin , Ruckstuhl Yvonne , Ruiz Juan , Miyoshi Takemasa , Anderson Jeffrey
Published: March 2020

Current regional forecasting systems particularly aim at the forecast of convective events and related hazards. Most weather centers apply high-resolution ensemble forecasts that resolve convection explicitly but can only afford a limited ensemble size of less than 100 members. Given that the degrees of freedom of atmospheric models are several magnitudes higher implies sampling errors. Sampling errors and fast error growth on convective scales in turn lead to a low predictability. Consequently, improving initial conditions and subsequent forecasts requires a better understanding of error correlations in both space and time.
For this purpose, we conducted the first convective-scale 1000-member ensemble simulation over central Europe. Several 1000-member ensemble forecasts are investigated during a high impact weather period in summer 2016 using ensemble sensitivity analysis. Spatial and spatiotemporal correlations are used to quantify sampling errors on convective scales. Correlations of the 1000-member ensemble forecast serve as truth to assess the performance of different localization approaches. Those approaches include a standard distance-based localization technique and a statistical sampling error correction method as proposed by Anderson (2012). Our study highlights advantages and disadvantages of existing methods and emphasises the need of different localization approaches for different scales and variables. Several results are published in Necker et al (2020a) and (2020b).
Spatial variability in biomass burning in the northern extratropics since the Last Glacial Maximum
Authors: Kesner David , Harrison Sandy , Blyakharchuk Tatiana , Edwards Mary , Garneau Michelle , Magnan Gabriel , Prentice Colin
Published: March 2020

Fire is an important environmental and ecological process in northern high latitude environments. It is currently unclear how fire regimes will change in response to current environmental change in this region and the implications this may have for ecosystem processes and human societies. We reconstruct changes in biomass burning since the Last Glacial Maximum in the northern extratropics (>45°N), using data from the Global Charcoal Database complemented by new records from Canada, Beringia and Russia. A clustering machine-learning algorithm (K-means) is used to delimit regions that show similar burning histories. Comparison of the regional trajectories of change in biomass burning provides insights into the environmental drivers of fire. Generalised linear modelling is then used to explore the independent roles of climate, vegetation changes and human activities on changes in fire regimes for each region and for the northern extratropics as a whole. This study provides quantitive information about the differential importance of the drivers of changes in fire regimes in different regions and at different timescales since the Last Glacial Maximum, and provides insights about how these may influence future fire regimes across this region.

 
(Non)-radial propagation of the solar wind flow
Authors: Němeček Zdeněk , Ďurovcová Tereza , Šafránková Jana , Šimůnek Jiří , Richardson John D. , Urbář Jaroslav
Published: March 2020

The solar wind aberration due to non-radial velocity components and the Earth orbital motion is important for the overall magnetosphere geometry because the magnetospheric tail is aligned with the solar wind flow. This paper investigates an evolution of non-radial components of the solar wind flow along the path from the Sun to 6 AU. A comparison of observations at 1 AU and closer to or further from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Wind, ACE, Spektr-R, THEMIS B and C, Helios 1 and 2, Mars-Express, Voyager 1 and 2) shows that (i) the average values of non-radial components vary with the distance from the Sun and (ii) they differ according to solar wind streams.
Relations of velocity and magnetic field fluctuations in the minimum variance frames
Authors: Šafránková Jana , Němeček Zdeněk , Němec František , Verscharen Daniel , Ďurovcová Tereza , Pitňa Alexander
Published: March 2020

The analysis of magnetic field and velocity fluctuations in corresponding minimum variance frames revealed that: (1) Minimum variance and mean magnetic field directions would be similar but these two directions are often perpendicular, especially in the high-beta environment, and a number of perpendicular cases decreases with the scale length; (2) Compressibility computed in the minimum variance frame generally increases with frequency but the increase is not monotonic; it exhibits two breaks observed for the magnetic field as well as for velocity fluctuations with approximately the same break frequencies. (3) We suggest that the first break can be connected with a change of pure Alfven to kinetic Alfven modes and the second break approximately coincides with the transition from the inertial to kinetic scales.
BioFe delivery to the Southern Ocean through glacial systems
Authors: Winter Kate , Woodward John , Dunning Stuart , Raiswell Robert
Published: March 2020

Glacial systems transfer sediment, rich in essential nutrients and bioavailable iron (BioFe) from continental sources to the ocean through iceberg transport, resulting in Heinrich layers during deglacial phases. The Southern Ocean is currently nutrient-rich but iron limited, so any increase in continental sediment supply could enhance primary productivity in the Southern Ocean and ultimately drawdown atmospheric CO2; potentially limiting predicted global temperature rise. The contribution of continental sediments to this negative climate feedback loop, termed the ‘Fe hypothesis’ has yet to be considered in IPCC reports. As other sources of BioFe are decreasing, global temperatures are warming, and CO2 levels are rising at glacial terminations it is now critical to assess BioFe flux through the glacial system. In this project, we use established laboratory procedures to extract nanoparticulate Fe from Antarctic sediments, recovered from nunataks, glacial moraines and debris bands in wind scoured blue ice areas in and around the Sør Rondans Mountains in East Antarctica (72°S, 24°E). These coastal margin mountains channelise ice (and entrained sediments) from the polar plateau towards the local Roi Baudouin Ice Shelf, at flow speeds of 30 – 60 m a-1. Concentrations of FeA - comprising fresh ferrihydrite (potentially bioavailable) and FeD - comprising all remaining (oxyhydr)oxide Fe are reported at all sites, with elevated concentrations along nunataks that define the edges of deep subglacial valleys which support ice flows over 2 km thick. Terrestrial surveys of these nunataks, combined with ice penetrating radar data and numerical modelling studies show how these nutrient-rich sediments are entrained and transported through the ice, from continental Antarctica, to the Southern Ocean, where ice-influenced phytoplankton blooms have been reported.
Groundwaters, an educational network
Authors: Mourau Fabrice
Published: March 2020

Many schools are involved within  an educational network called "Groundwater" (“Eaux souterraines” in French). In Partnership with universities (Aix-Marseille University, Université Côte d’Azur), the National Education, the speleology federation and a Speleological association (SpeleH2O), this collaborative project enhances the discovery of the underground world by pupils and their teachers. The project offers three main originalities: (1) students are going on the field to visit karst (including the caves), (2) water data are recorded in-situ continuously with probes (Electric conductivity, Temperature, Depth), (3) knowledge and skill are learned through an interdisciplinary approach in classroom. Technical and educational support is provided to develop teaching aids in class and in the field. To date, fifteen caves and four rivers are instrumented with the collaboration of the EDUMED observatory. Fifteen middle and high schools belonging to the project are using data to teach water cycle in carbonated environment. The main objective is to propose a multidisciplinary work around water dynamic and her societal issues : the sustainable development and the natural hazards.
Iron-based water treatment residuals as sorbent of heavy metals and metalloids
Authors: Wołowiec Magdalena , Komorowska-Kaufman Małgorzata , Pruss Alina , Rzepa Grzegorz , Bajda Tomasz
Published: March 2020

The ever-increasing water pollution caused by an increase in industrial activity in developing countries is a major worldwide problem. Heavy metal contamination is particularly dangerous because of their toxic and carcinogenic nature as well as harmful effects on human and animal health. Over the past decades, considerable efforts have been made to develop effective technologies for removing heavy metals from water. Adsorption seems to be the most promising out of the many methods. Conventional adsorbents used to remove heavy metals include activated carbon or clay minerals. However, due to the need for waste management, waste products have recently become very popular, especially industrial wastes containing iron and/or aluminum oxides. One of the possible sorbent are water treatment residuals (WTRs) which are generated during drinking water treatment process. The aim of this work was to examine the possibility of using residuals from deironing of underground water (G-WTRs) as effective sorbents of Cd (II), Pb(II), Zn(II), Cu(II), Cr(III), Cr(VI) P(V), and As(V) as a function of initial concentration, pH, temperature and time.

The G-WTRs were poorly crystalline and composed predominantly of ferrihydrite with minor calcite and quartz admixture. The main chemical components were iron (32%) and calcium (17%). Specific surface area was 144 m2/g with a total pore volume of 0.181 cm3/g. The proportion of micropores was 29%, mesopores occupied the greatest volume – 54%, while micropores the lowest volume – 17%.

Cation sorption efficiecy was almost 100%, in the case of anions it ranges between 50 – 100%. Sorption capacity increased with an increase in the initial pollutant concentration. Adsorption of the metal cations was higher with and increasing pH of the solution and the best results were obtained for pH 6.0 to 7.0. While anions were preferably sorbed in lower pH. Sorption was the efficient in the temperature range of 20-40 ℃. The greatest differences in the sorption efficiency were observed within the first 2 – 4 h. The possible sorption mechanism was chemisorption.

The results showed that G-WTRs can be effective and cheap sorbents of heavy metals and metalloids. However, further research including desorption process as well as the long-term stability of formed metal-G-WTRs complexes.

Acknowledgments: This work was financed by the National Science Centre, Poland Grant No. 2017/27/N/ST10/00713.
Chemistry of Atmospheric Brown Carbon
Authors: Laskin Alexander
Published: March 2020

Fundamental understanding of the complex chemistry of light absorbing atmospheric aerosols (aka Brown Carbon - BrC), their physico-chemical properties and environmental impacts is a challenging task because no single method of analytical chemistry is capable of providing the full range of analytical chemistry information. Micro-spectroscopy approaches can visualize individual particles and their internal structures; however, they largely exclude molecular-level information, and are limited to elemental and chemical bonding characterization. Contemporary methods of high-resolution mass spectrometry can provide detailed information on the molecular content of BrC, but these methods use bulk particle samples and provide no knowledge of the individual particle composition. Therefore, application of complementary analytical methods of chemical analysis is necessary for comprehensive characterization of aerosol properties ranging from bulk molecular composition of BrC constituents to microscopy level details of individual particles. Combined assessment of the results provided by complementary analytical chemistry techniques offers unique insights to understand the composition and physico-chemical properties of BrC aerosols determining their effects on air quality and climate. This presentation will give an overview of recent field and laboratory studies of BrC with an overall goal to understand fundamental relationship between chemical transformations of airborne particles and their environmental and climate impacts.
Probability models of asperity constructed in terms of co-seismic displacements along surface rupture zones
Authors: Li Zhengfang , Zhou Bengang
Published: March 2020

          Usually, an earthquake of magnitude Mw6.0 or greater can produce a rupture zone on the surface of the Earth’s ground. And displacements can be observed along such a rupture zone, called co-seismic displacements. Although these surface displacements are somewhat different from slip on the rupture plane of the causative fault, which is often vertical or sub-vertical, there exists a certain proportional relationship between them. It means that major slip at depth can produce bigger co-seismic displacements on the ground. As assumed above, major fault slip is generated by asperities. Thus it is possible to establish an asperity model in terms of data of ground co-sesimic displacements.

          Asperity models can be used to describe heterogeneities of the rupture plane of the fault as an earthquake source. This work follows such an idea that an asperity is defined as a region in which the slip is larger by a prescribed amount than the average slip over the entire fault. Because co-seismic displacements along a surface rupture zone depend on slip on the subsurface fault, we attempt to construct probability distribution model for a seismic source in terms of such displacements observed on the ground. Using data of 10 historical earthquakes of Ms7.0 or greater in western China, we make a statistical analysis to distributions of co-seismic displacements on surface rupture zones, yielding the probability distribution model based on a series of ratios of maximum displacements to the average ones in intervals on the rupture. Then, upon the lower and upper limit values of these ratios, we infer the asperities along the rupture zones and analyze further the relationships between asperity parameters, rupture geometries, and earthquake magnitudes based on real data of more earthquakes. Finally, we use the data of the 2001 Kunlunshan Mw7.8 event to test this approach for construction of probability model of asperity and discuss its possible application to assessment of seismic hazard. 

Keywords:  Probability model of asperity, fault slip, surface rupture, co-seismic displacement