bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of a Strong Zonal Jet Stream on the Temporal Evolution of Baroclinic Eddies
Authors: Hadas Or , Kaspi Yohai
Published: March 2020

The midlatitude storm tracks are one of the most prominent features of the extratropical climate. Much of our understanding of what controls the storm tracks comes from linear theory of baroclinic instability, which explains generally most of the observed response of storms to the general circulation. One example to where this approach is lacking is the Pacific midwinter minimum, a decrease in the eddy activity over the Pacific storm track during midwinter when baroclinicity is at its peak due to extremely strong zonal jets. A similar response was found recently for the Atlantic storm track, in correlation to periods of strong zonal jets. Following on these findings we study the effect of strong zonal jet streams on eddy activity in the midlatitudes. In order to isolate the effect of the jet strength we used several idealized GCM experiments with different jet strengths, and analyze the formed storm track from a Lagrangian perspective by using a storm tracking algorithm. In both the Eulerian analysis and analysis of the tracks a strong reduction of high level eddy activity is prominent, as well as a modest weakening of the low-level activity. The observed response is then further analyzed by studying the connection between the upper and lower wave and how it changes with jet-stream intensity. 

 
Oceanic tidal signals in satellite magnetic data: quo vadis?
Authors: Grayver Alexander , Olsen Nils , Finlay Chris , Kuvshinov Alexey
Published: March 2020

The continuous high-quality geomagnetic field measurements delivered by the Swarm satellite constellation trio have enabled reliable global mapping of the magnetic signature of ocean tides for several tidal constituents. These signals provide geophysical constraints on the average electrical conductivity profile of the upper mantle below the oceans. In principle, these signals can also sense lateral variations of the electrical conductivity in the oceanic upper mantle, although the amplitude of these effects is small. Additionally, the long-term changes in the climatology of the ocean can be potentially detected by the magnetic satellite signals. Both applications put additional demands on the accuracy and resolution of the extracted signals. This contribution discusses potential ways to meet the required demands and evaluates the feasibility of using the magnetic signature of ocean tides for studying these effects.
Mesoscale variability of the aerosol distribution as determined from ceilometer measurements
Authors: Wiegner Matthias , Geiß Alexander , Mattis Ina , Meier Fred , Ruhtz Thomas
Published: March 2020

The spatial distribution of aerosol particles is relevant for studies on the radiation budget, for the verification of chemistry transport models, or for air quality studies just to name a few. As the distribution is highly variable the requirements to measurements are very demanding. As a consequence it is often assumed that the aerosol distribution is "relatively homogeneous", i.e., measurements at one site are representative for a larger area.

By exploiting 2 years of measurements from 12 ceilometers located in the area of Munich and Berlin, Germany, we have investigated the spatial differences between locations separated between 3~km and 50~km. For this purpose we have used the mixing layer height (MLH), a quantity often used when the vertical aerosol distribution should be described by a single parameter. The MLH was determined by the COBOLT-algorithm (Geiß et al., 2017). It was found that the MLHs at different locations inside the two cities are highly correlated and agree within a few tens of meters. However, the maximum extension of the mixing layer from April to September was found to be significantly larger in Berlin compared to Munich.

Geiß, A., Wiegner, M., Bonn, B., Schäfer, K., Forkel, R., von Schneidemesser, E., Münkel, C., Chan, K. L., and Nothard, R. (2017): Mixing layer height as an indicator for urban air quality?  Atmos. Meas. Tech., 10, 2969-2988, https://doi.org/10.5194/amt-10-2969-2017, 2017.
Integrating e-infrastructures for remote climate data processing
Authors: Pagé Christian , Som de Cerff Wim , Plieger Maarten , Spinuso Alessandro , Klampanos Iraklis , Atkinson Malcolm , Karkaletsis Vangelis
Published: March 2020

Accessing and processing large climate data has nowadays become a particularly challenging task for end users, due to the rapidly increasing volumes being produced and made available. Access to climate data is crucial for sustaining research and performing climate change impact assessments. These activities have strong societal impact as climate change affects and requires that almost all economic and social sectors need adapting.

The whole climate data archive is expected to reach a volume of 30 PB in 2020 and up to 2000 PB in 2024 (estimated), evolving from 0.03 PB (30 TB) in 2007 and 2 PB in 2014. Data processing and analysis must now take place remotely for the users: users typically have to rely on heterogeneous infrastructures and services between the data and their physical location. Developers of Research Infrastructures have to provide services to those users, hence having to define standards and generic services to fulfil those requirements.

It will be shown how the DARE eScience Platform (http://project-dare.eu) will help developers to develop needed services more quickly and transparently for a large range of scientific researchers. The platform is designed for efficient and traceable development of complex experiments and domain-specific services. Most importantly, the DARE Platform integrates the following e-infrastructure services: the climate IS-ENES (https://is.enes.org) Research Infrastructure front-end climate4impact (C4I: https://climate4impact.eu), the EUDAT CDI (https://www.eudat.eu/eudat-collaborative-data-infrastructure-cdi) B2DROP Service, as well as the ESGF (https://esgf.llnl.gov). The DARE Platform itself can be deployed by research communities on local, public or commercial clouds, thanks to its containerized architecture.

More specifically, two distinct Use Cases for the climate science domain will be presented. The first will show how an open source software to compute climate indices and indicators (icclim: https://github.com/cerfacs-globc/icclim) is leveraged using the DARE Platform to enable users to build their own workflows. The second Use Case will demonstrate how more complex tools, such as an extra-tropical and tropical cyclone tracking software (https://github.com/cerfacs-globc/cyclone_tracking), can be easily made available to end users by infrastructure and front-end software developers.
Uncertainty of discharge measurement using salt dilution
Authors: Hauet Alexandre , Florvaag-Dybvik Kristoffer , Dahl Mads-Peter Jakob , Kvernhaugen Frode Thorset , Møen Knut Magne , Sentlinger Gabriel
Published: March 2020

Discharge measurement using salt dilution is an old method, but it has been recently more and more used thanks to the development of new sensors making it possible to measure conductivity and compute discharge in real-time. Salt dilution is very well suited for turbulent rivers, such as mountain streams. The ISO standard ISO 9555 propose a normative framework to estimate uncertainty, but it was published in 1994 and is now obsolete for new sensors and computational capabilities. In this article, we propose a complete framework to compute the uncertainty of a salt dilution gauging following the GUM (Guide to the expression of uncertainty in measurement) method that take into account the following error sources:  (i) the uncertainty in the mass of salt injected, (ii)  the uncertainty in the measurement of time, (iii) the uncertainty in the Conductivity to Concentration law, (iv) the uncertainty if a measurement conductivity is out of the range of the Conductivity to Concentration law, (v) the uncertainty in the computation of the area under the conductivity curve, (vi) the uncertainty due to a not perfect mixing of the tracer if the mixing length between injection and the probes is not reached (vii) the uncertainty due to a loss or a gain of tracer between the injection and the probes if tracer can be adsorbed for example and (viii) the uncertainty due to unsteadiness of the flow  i.e. variation of discharge during the measurement. The method for computing each uncertainty source is presented and the new framework is applied to a set of real measurements and compared to the expertise of field hydrologists.
Total column water vapor retrieval for TROPOMI/S5P observations in the visible blue band
Authors: Chan Ka Lok , Slijkhuis Sander , Valks Pieter , Köhler Claas , Loyola Diego
Published: March 2020

We present a new total column water vapor (TCWV) retrieval algorithm in the visible blue band for the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 Precursor (S5P) satellite. Retrieving water vapor columns in the blue band has numerous advantages over longer wavelengths. Measurements in the blue band are more sensitive at lower troposphere over oceans due to higher surface albedo at this wavelength band. In addition, no correction for spectral saturation effects is required as water vapor is optically thin in this spectral band. The blue band algorithm uses the differential optical absorption spectroscopic (DOAS) technique to retrieve water vapor slant columns. The measured water vapor slant columns are converted to vertical column using air mass factors (AMFs). The new algorithm has an iterative optimization module to dynamically find the optimal a priori water vapor profile. The dynamic a priori algorithm makes use of the fact that the vertical distribution of water vapor is strongly correlated to the total column. This makes it better suited for climate studies than usual satellite retrievals with static a priori or vertical profile information from chemistry transport model (CTM).

The new algorithm is applied to TROPOMI observations to retrieve TCWV. Due to the long measurement record of GOME-2, the new algorithm is also used to retrieve TCWV from GOME-2. The TCWV data set is validated by comparing to the GOME-2 TCWV operational product retrieved in the red spectral band, MODIS and SSMIS satellite observations. In addition, the new TCWV data set is also compared to ground based sun-photometer and radiosonde measurements. Water vapor columns retrieved in the blue band are in good agreement with the other data sets, indicating that the new algorithm derives precise results. Therefore, it was selected for the S5P Processor Algorithm Laboratory (PAL) project as a future operational product. This algorithm can also be used for the forthcoming Copernicus Sentinel S4 and S5 missions.
From Faults and Fluids to Mountain Belt Dynamics
Authors: von Hagke Christoph
Published: March 2020

For understanding the formation of mountain belts it is necessary to gain quantitative insights on fault and fracture mechanics on multiple scales. In particular, for addressing the role of fluids on larger processes, it is inevitable to constrain fault and fracture geometries at depth, as well as gain insights on how fluids influence fault mechanics. At least partly, the future of such analyses lies in exploiting large data sets, as well as in multi- and interdisciplinary research.

In this talk I will present results from variety of geological settings, including dilatant faults at Mid-Ocean Ridges, the Oman Mountains, the Khao Kwang fold-trust belt in Thailand, and the European Alps. I will show how multi-scale studies and the use of large data sets helps constraining fluid migration in mountain belts, fault geometries, as well as possible feedbacks between fluid flow and strain localization. Results are then applied to discuss the role of mechanical stratigraphy on structural style in foreland fold-thrust belts.
Influence of subduction zone complexities on teleseismic records
Authors: Perez Alemany Hector , Sladen Anthony , Monteiller Vadim , Delouis Bertrand
Published: March 2020

Small and large subduction earthquakes are mostly occurring underwater away from seismic networks. Teleseismic
data are thus essential to characterize these seismic events. Nevertheless, teleseismic waveform modeling is usually performed using 1D velocity models that do not take into account the effects associated to heterogenities near the source, such as bathymetry and the dipping of the subducted oceanic plate. With traditional simulation tools, it is computationally too expensive to simulate high frequency seismic waves propagation at the global scale. We circumvent this problem with a hybrid method that limits the full 3D simulation to the subduction
area while assuming a 1D model at the global scale. We study the impact of these complexities at different frequencies. We highlight the strong influence of the water column and low velocity regions (e.g. accretionary prism). In some cases, the influence extends to relatively long periods, above 20s. We also investigate the influence of refined Green's function on finite-fault inversions, as even small changes are expected to have a strong impact on the inferred slip distribution.

 

 
Does slow and steady win the race? Using the model species Arabidopsis halleri to remediate industrially polluted soils
Authors: Dietrich Charlotte , Bilnicki Kamil , Korzeniak Urszula , Briese Christoph , Nagel Kerstin A. , Babst-Kostecka Alicja
Published: March 2020

Hyperaccumulating plants possess complex physiological traits, which allow them to thrive in soils contaminated with trace metal elements (TME). In this study, we address an important but severly understudied aspect of plant responses to TME contamination in industrially polluted soils: root system development. In this context, we present the most detailed spatiotemporal analysis of root systems in a pseudometallophyte species to date. We exposed two contrasting ecotypes of the TME hyperaccumulating model species A. halleri to various treatments of their native and foreign soils. To overcome methodological challenges that have so far prevented an in-depth understanding of root-soil interactions under TME excess, we combined rhizoboxes and multitemporal digital imaging in a novel phenotyping approach. This allowed us to assess root architectural changes as a valuable indicator of plant performance in non-metalliferous (NM) and metalliferous (M) environments, as well as under horizontal layer applications of M and NM soils. We show that environment rather than ecotype determines root growth in A. halleri and that soil properties can cause a cost of tolerance in M soil or induce TME-foraging in NM soil. Importantly, root propagation into M soil was promoted by a non-contaminated “capping” layer that facilitated initial plant development. Growing on this capping layer in the early stage provides plants with a robust and optimal root system that facilitates seedling establishment and subsequent development under TME excess. These findings are relevant for practical applications related to phytoremediation. This matter is urgent, considering that industrial pollution is spreading and hyperaccumulating species are threatened by habitat loss.
U-Pb calcite dating  and isotopic fluid signatures of extensional fault gouges affecting the Penninic Frontal Thrust : implications for exhumation of the seismogenic zone.
Authors: Bilau Antonin , Rolland Yann , Schwartz Stéphane , Dumont Thierry , Brigaud Benjamin , Gautheron Cécile , Pinna-Jamme Rosella , Deschamps Pierre , Godeau Nicolas , Guihou Abel , Melleton Jérémie
Published: March 2020

Coupled fluid characterization and absolute dating of fracture networks may provide insights into the understanding of critical stages of evolution of a growing orogen. As a result of the collision between the European and Apulian plates, the Alps have experienced several evolutionary stages comprising continental subduction, nappe stacking, thick- to thin-skin tectonics in relation with the frontal propagation of a fold and thrust belt, and extensional reactivation of the major Penninic Frontal Thrust (PFT). Current evolution of the orogen (Tricart et al., 2001, 2007 and Sue et al., 2007) shows an ongoing extensional seismic activity along PFT while borders of the orogenic system remain in compression. The transition from compression to extension along the PFT remains unconstrained.

This study aims to constrain the time of the PFT inversion and provide a characterization of the tectonic structures through time during the formation of upper Durance normal fault system. For this, we applied several novel dating techniques (in-situ U-Pb calcite and (U-Th)/He hematite dating techniques). In addition, we determined the geochemical signature of the fluids trapped (calcite crystallization) deformation by δ13C and δ18O stable isotope analysis of calcites to constrain the fluid reservoirs, and thus the size of the involved tectonic structures. Stable isotopes show that the fluids associated with the early extensive structures bear isotopic signatures close to those of their host rocks, indicating a fluid at equilibrium and thus a close system in agreement with the small (mm-cm) size of mostly ductile structures. In a second stage, connection of veins and fractures lead to major fault formation (metric to kilometric scale structures) show isotopic signatures in agreement with ascending metamorphic fluids, featuring an open system along the PFT.

U-Pb dating on calcite was successful on several samples despite high common lead concentrations. Two fault gouge samples associated with kilometric scale faults gave ages between 3.5 Ma and 2.5 Ma. These structures are a signature of the paleoseismic activity wich occured some 2.5-3.5 Ma ago when the wall domain of PFT was few km depth. Moreover, (U-Th)/He hematite dating was used on slickensides of the same fault system. Preliminary ages of 2.5, 1.5 and 15 Ma were obtained. The 15 Ma age is interpreted as a minimum age inversion of the PFT, while other ages overlap with the U-Pb calcite ages. This multidisciplinary inverstigation in the Western Alps helps to constrain the exhumation history of the paleo-seismogenic zone related to the inversion of the PFT.
Uncertainties in the stability field of UHP hydrous phases (10-A phase and phase E) and deep-slab dehydration: potential implications for fluid migration and water fluxes at subduction zones
Authors: Cerpa Nestor G. , Padrón-Navarta José Alberto , Arcay Diane
Published: March 2020

The subduction of water via lithospheric-mantle hydrous phases have major implications for the generation of arc and back-arc volcanism, as well as for the global water cycle. Most of the current numerical models use Perple_X [Connolly et al., 2009] to quantify water release from the slab and subsequent fluid migration in the mantle wedge. At UHP conditions, the phase diagrams generated with this thermodynamic code suggest that the breakdown of serpentine and chlorite leads to the near complete dehydration of the lithospheric mantle before reaching a 200-km depth. Laboratory experiments, however, have observed the stability of the 10-Å phase and the phase E in natural bulk compositions, which may hold moderate amounts of water, beyond the stability field of serpentine and chlorite [Fumagalli and Poli, 2005; Maurice et al., 2018]. Here, using 2D thermo-mechanical models, we explore to what extent the presence of these hydrous phases may favor a deeper subduction of water than those predicted by Perple_X.

We perform end-member models in terms of slab temperature and thickness of hydrated lithospheric mantle entering at trench. The computed geotherms within the uppermost subducted mantle show that the stability field of mantle hydrous phases around 600-800°C and 6-8 GPa is crucial for predictions of water fluxes. We point out that the lack of systematic experiments at these P-T conditions, as well as the absence of 10-Å and E phases in current thermodynamic databases, prevent accurate estimates of deep water transfers. We nonetheless build a phase diagram based on current experimental constraints that includes approximations of their stability field and qualitatively discuss the potential implications for fluid migration in the back-arc mantle wedge and water fluxes.
Statistics of Zebra stripes at Saturn magnetosphere
Authors: Sun Yixin , Liu Ying , Hao Yixin , Roussos Elias , Zong Qiugang , Zhou Xuzhi , Yuan Chongjing , Krupp Norbert
Published: March 2020

Multi bands electron flux enhancement are found via Cassini /LEMMS PHA measurements.  The enhancement extends extremely large Lshells from L=10 to even L=5 at energy from 100 keV to 1 MeV, which is quite different from previously recognized injection events at Saturn but similar to Zebra Stripes identified at Earth.  Cases are presented by Hao et al showing the evolution of a Zebra Stripe event, and statistics here will show the spatial distribution of stripe events . The result shows that Zebra Stripe is indeed universal at Saturnian inner magnetosphere, although there exists a day-to-night asymmetry. The evolution time of stripes observed by Cassini is around 40 hours indicating the occurrence frequency  of impulsive electric field which lead to this convection process. The existence of Zebra Stripes provides an insight into the formation and dynamics of giant planets' radiation belts and magnetosphere.
Reconstructing the Cordilleran Ice Sheet in northern British Columbia during the Late Pleistocene climate reversals
Authors: Dulfer Helen , Margold Martin
Published: March 2020

The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet. Deglaciation of the CIS following the Last Glacial Maximum (LGM) directly affected atmosphere and ocean circulation, eustatic sea level, and human migration from Asia to North America. It has recently been shown that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. Data on glacial isostatic adjustment and cosmogenic nuclide exposure ages indicate that abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the Younger Dryas cooling caused the expansion of alpine glaciers across the mountains of western Canada. However, the mountainous subglacial terrain makes it challenging to reconstruct the regional-scale deglaciation dynamics of the ice sheet, and its configuration during this period of rapid change remains poorly constrained. 

Here we use the glacial landform record to reconstruct the ice sheet configuration for the central sector of the CIS, over the Cassiar and Omineca Mountains in northern British Columbia, during the Late Pleistocene climate reversals. We present the first regional-scale reconstruction of the CIS following the Bølling-Allerød warming, whereby the ice sheet was reduced to a labyrinth of valley glaciers fed by ice dispersal centres located over the Skeena Mountains in the south and Coast Mountains in the west. Additionally, numerous lateral and terminal late glacial moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS during the Younger Dryas. Cross-cutting relationships indicate that the valley glaciers of the CIS were slower to respond to the Younger Dryas cooling than the mountain glaciers.
Dust storms, blackouts and 50°C in the shade: Exploring the Roots of Humankind with MATLAB
Authors: Trauth Martin H.
Published: March 2020

Geoscientists from the University of Potsdam reconstruct environmental changes in East Africa over the past five million years. Micro-organisms such as diatoms and rotifers, clay minerals and pollen, thousands of years old, help to reconstruct large lakes and braided rivers, dense forests and hot deserts, high mountains and deep valleys. This is the habitat of our ancestors, members of a complicated family tree or network, of which only one single species, Homo sapiens, has survived. MATLAB is the tool of choice for analyzing these complicated and extensive data sets, extracted from up to 300 m long drill cores, from satellite images, and from the fossil remains of humans and other animals. The software is used to analyze to detect and classify important climate transitions in climate time series, to detect objects and quantify materials in microscope and satellite imagery, to predict river networks from digital terrain models, and to model lake-level fluctuations from environmental data. The advantage of MATLAB is the use of multiple methods with one single tool. Not least because of this, the software is also becoming increasingly popular in Africa, as shown by the program of an international summer school series in Africa and Germany for collecting, processing, and presenting geo-bio-information.
Variability of ocean stratification, sea ice coverage and bioproduction off NE Greenland in the Late Glacial to Holocene reconstructed from planktic foraminifer morphotypes
Authors: Spielhagen Robert F. , Mackensen Andreas
Published: March 2020

We use stable isotope data from different morphotypes of the polar species Neogloboquadrina pachyderma in a sediment core from the NE Greenland continental margin (79°N) as proxies for the variability of salinity, ice coverage, and bioproductivity/carbon fluxes. Stable oxygen and carbon isotopes (d18O, d13C) were measured on both thin- and thick shelled specimens of planktic foraminifers N. pachyderma. Since this species is known to attain the thick carbonate crust of adult specimens in deeper water, the isotopic difference between thick-shelled (morphotypes 1 and 2, according to Eynaud, 2011) and thin-shelled specimens (morphotypes 4 and 5) is proposed to reflect the salinity difference between subsurface and near-surface waters. In Late Glacial sediments only minor d18O differences between the morphotypes suggest an upper water mass structure with only minor salinity differences. The high d13C difference of >0.5‰ is ascribed to strong quantitative differences in the decomposition of isotopically light organic carbon within the upper water column (likely from intense ice coverage and reduced bioproductivity) which precludes that the d18O similarities merely result from a reduced vertical migration activity of the foraminifers. After 13 ka, a series of d18O spikes (amplitudes >1.5‰ in morphotypes 4/5) preserved in laminated sediments reflects a strong freshwater event at the NE Greenland margin, likely related to the export of freshwater from the Arctic Ocean and/or the decay of the nearby outer Greenland Ice Sheet. Within these spikes, d18O and d13C differences of N. pachyderma morphotypes reach maximum values, pointing at extreme salinity differences in the upper few hundred meters of the water column and likely high portions of isotopically light dissolved inorganic carbon from terrestrial sources (meltwater). In the Holocene, d18O differences are reduced to ca. 0.5‰ and relatively low d13C differences may indicate an activity of organic carbon decomposition reaching significantly deeper in the water column than in the glacial and deglacial, possibly related to a more open ice cover, enhanced bioproduction and higher C fluxes.

Reference

Eynaud, F., 2011. Planktonic foraminifera in the Arctic: potentials and issues regarding modern and quaternary populations. IOP Conf. Series, Earth and Environmental Science 14, 012005, doi:10.1088/1755-1315/14/1/012005
Numerical modelling of groundwater seepage and landscape evolution along the Canterbury coast, South Island, New Zealand
Authors: Clavera-Gispert Roger , Micallef Aaron
Published: March 2020

Groundwater has been implicated as an important geomorphic agent in landscape evolution. The link between groundwater seepage and landscape evolution remains controversial and poorly quantified, however. Groundwater weathering and erosion processes have not been quantified in terms of mechanisms, rates or resulting morphologies. Experimental and numerical analyses of these processes have been based on simplistic assumptions about flow processes and hydraulic characteristics. There is also a paucity of process-based observations and detailed instrumental studies of seepage erosion and weathering due to the long timescales involved and the complexity of the process. Numerical modelling, in particular Landscape Evolution Modelling (LEM), is a valuable tool that can allow us to better understand the spatial and temporal evolution of landscapes by groundwater seepage, particularly when integrated with field data.

 

Here we report preliminary results from a study focusing on the Canterbury coast of the South Island, New Zealand. The study area, located between the Ashburton and Rakaia Rivers, comprises a 20 m high coastal cliff of sandy gravels with isolated sand bodies that features a series of box canyons. Field visits carried out in 2017 and 2019 allowed us to characterise the geological framework of the area and monitor the formation and evolution of box canyons by groundwater seepage. We used Landlab, an open source framework written in python, to build a LEM for the study area.  The code includes a simplified groundwater model using the Dupuit approximation, the calculation of the drainage area, as well as erosion processes using diffusion and a power law functions.

 

The model computes the evolution of the coastal landscape during 1 year. The initial topography is obtained from a 1x1m DEM and the initial conditions are derived from the fieldwork. Several examples have been run using different aquifer recharge rates and hydraulic conductivity. The results suggest that the factor that controls the inception erosion is the spatial variability in permeability and initial topography, whereas the evolution of the canyon is controlled by the seepage flow, which depends on the hydraulic conductivity and the erosivity of the sediments.
Climate, Mixing, and Carbon Budgets in a LGM set-up of CESM
Authors: Jochum Markus , Vettoretti Guido , Chase Zanna , Nuterman Roman
Published: March 2020

We use a free running Last Glacial Maximum (LGM) setup of CESM1 with its full ecosystem model to understand which processes are responsible for the large difference in atmospheric CO2 concentration between the LGM  and 1850 CE.
Just by accounting for the changed orbital forcing  and replacing today's bathymetry and icesheet orography with their Peltier et al. (2015) LGM reconstructions, leads to a 55 ppm difference in atmospheric CO2.  Additional experiments with increased aolian iron fluxes make it plausible that IPCC class ESMs can reproduce the processes that were hypothesized to be important for the observed low LGM CO2 concentration.

A second focus of our study is the connection between sea level, ocean turbulence and the strengths of the various carbon pumps. Including the full amount of the suggested increase in ocean mixing during the LGM would lead to a 20 ppm larger CO2 concentration.This suggests that either mixing during the LGM is not understood yet, or that ESMs may indeed misrepresent one or more aspects of the various carbon pumps.

We conclude with a discussion of uncertainties within the model setup, in particular with regards to the assumed structure of ocean mixing.
The influence of the large-scale circulation on the thermodynamic profiles in the trades from a Lagrangian perspective
Authors: Villiger Leonie , Aemisegger Franziska , Boettcher Maxi , Wernli Heini
Published: March 2020

In the tropical winter trades of the North Atlantic in the vicinity of Barbados four different mesoscale organisation patterns of clouds – sugar, gravel, flower, fish - are observed regularly. Each pattern is associated with a distinct cloud amount and radiative footprint. Therefore, the relative occurrence frequency of these patterns affects the global radiative budget. As shown by a recent study (Bony et al. 2019, Geophysical Research Letter), the occurrence of the four patterns is controlled by the near-surface wind speed and the strength of lower tropospheric instability. It is however not yet clear, whether these cloud patterns occur preferably in specific larger-scale flow configurations. These can be associated for example with upper-level wave breaking in the extratropics and different positions and strengths of low-level subtropical anticyclones.

Lower tropospheric air parcels at different altitudes in the trades are expected to have different transport histories associated with distinct diabatic processes such as radiative effects, phase changes within and below clouds and turbulent mixing. The diabatic processes encountered during transport modulate the thermodynamic properties of the air parcels and therefore influence the vertical thermodynamic structure of the atmosphere in the trades.

In this study, the impact of large-scale air mass advection on the thermodynamic profiles over Barbados is analysed for each of the four mesoscale organisation patterns observed during EUREC4A. The airmass transport history is characterised for different homogenous atmospheric layers. These layers are identified based on vertical pseudo-soundings above the Barbados Cloud Observatory (BCO) using ECMWF analysis data for cases where profiles agree well with independent observations from balloon soundings. The large-scale circulation within the 10 days prior to the sounding is considered for computing the trajectories of the air masses arriving in these layers. Backward trajectories are calculated with three-dimensional analysis wind fields. Thereby, the thermodynamic history and large-scale circulation configuration associated with the four cloud organisation patterns is described from a Lagrangian perspective. In addition, composites of the sea level pressure field provide information whether the four patterns co-occur with systematically differing positions and/or intensities of subtropical anticyclones. In future work, stable water isotopes will be used as observational tracers to find supportive evidence of the characterised transport history.
The use of TROPOMI retrievals in the operational CAMS forecast and data assimilation system
Authors: Inness Antje , Ades Melanie , Agusti-Parareda Anna , Barre Jerome , Engelen Richard , Flemming Johannes , Garrigues Sebastien , Kipling Zak , Parrington Mark , Peuch Vincent-Henri , Ribas Roberto , Suttie Martin
Published: March 2020

The Copernicus Atmosphere Monitoring Service (CAMS, atmosphere.copernicus.eu) led by ECMWF is one of the major users of TROPOMI data. TROPOMI ozone retrievals have been routinely assimilated in the operational CAMS system since December 2018 and help CAMS to provide good quality daily ozone analyses and 5-day forecasts. CO, NO2, HCHO and SO2 retrievals from TROPMI are currently monitored in the operational CAMS system and CH4 in the CAMS GHG system. This means that the data are routinely compared with the CAMS atmospheric composition fields, but do not influence the CAMS analyses yet. Howerver, assimilation tests with TROPOMI CO, NO2, SO2 and CH4 data are ongoing and it is hoped that the routine assimilation of these species in the  CAMS system can begin later this year.

In this presentation we will give an update on the use or TROPOMI data in the CAMS system and show the latest results from the monitoring and asimilation tests carried out with the TROPOMI data by CAMS.
Investigating the reasons for poor model performance in a changing climate
Authors: Duethmann Doris , Blöschl Günter , Parajka Juraj
Published: March 2020

Hydrological models are often applied to estimate climate change impacts on hydrology. However, several studies demonstrated that hydrological models do not perform well when applied under changing climate conditions. In order to decide on the way forward for improving hydrological modelling in climate change contexts, it is important to understand the reasons for poor performance in a changing climate, but there are only a few studies on this topic.

Here we revisit a study in Austria that demonstrated the inability of a conceptual model to simulate the discharge response to increases in precipitation and air temperature. We set up hypotheses for the differences between the observed and simulated changes in discharge and test these using simulations with various modifications of the model (including modifications of the input data, model calibration, and model structure).

The baseline model overestimates discharge trends over 1978−2013, on average over all 156 catchments, by 93 ± 50 mm yr−1 per 35 years. Accounting for vegetation dynamics in the calculation of reference evaporation based on a satellite-derived vegetation index, reduces the difference between simulated and observed discharge by 35 ± 9 mm yr−1 per 35 years. Inhomogeneities in the precipitation data, caused by a variable number of stations and, to a lesser degree, climate variability effects on the undercatch error, can explain 44 ± 28 mm yr−1 per 35 years of this difference. Extending the calibration period from 5 to 25 years, varying the objective function by including annually aggregated discharge data, or estimating evaporation with the Penman-Monteith instead of the Blaney-Criddle approach has little influence on the simulated discharge trends. The model structure problem with respect to vegetation dynamics has important implications for studies in a climate change context. Our results furthermore highlight the importance of using precipitation data based on a stationary input station network for studying observed hydrologic changes.
Energetic ion depletions near Europa and Io: the effect of plumes and atmospheric charge exchange
Authors: Huybrighs Hans , van Buchem Christiaan , Blöcker Aljona , Roussos Elias , Krupp Norbert , Dols Vincent , Yoshifumi Futaana , Barabash Stas , Witasse Olivier , Holmberg Mika
Published: March 2020

Introduction

The flux of energetic ions (protons, oxygen and sulfur) near the Galilean moons were measured by the Energetic Particle Detector (EPD) on the Galileo mission (1995 - 2003). Near Galilean moons (such as Io and Europa) depletions of the energetic ion flux, of several orders of magnitude, were identified.

Such energetic ion depletions can be caused by the absorption of these particles onto the moon’s surfaces or by the loss due to charge exchange with neutral molecules in the atmospheres or potential plumes. To interpret the depletion features in the EPD data, a Monte Carlo particle tracing simulation has been conducted. The expected fluxes of the energetic ions are simulated under different scenarios including those with and without an atmosphere or plume. By comparing the simulated flux [YF1] to the EPD data, we investigate the cause of the depletion features with particular focuses on Europa and Io flybys.

Results

For Europa we report the following findings:

For flyby E12 we find that a global atmosphere should produce a depletion region along the trajectory that is symmetrical to the closest approach, for energetic protons in the energy range of 80-220 keV. No such feature is visible in the data. Upper limits of the atmosphere are consistent with surface densities (⩽ 108 cm-3) and scale heights (50-350 km) of previous studies. We find that a depletion of energetic protons (80-220 keV) occurring before closest approach is consistent with the field perturbations associated with a plume. This plume features coincides in time with the plume reported by Jia et al., 2018.

For flyby E26 we find that the depletions of energetic protons (80-220 keV) are consistent with a simulation that takes into account the perturbations of the fields as calculated by an MHD simulation and atmospheric charge exchange. Furthermore, a depletion feature occurring shortly after closest approach is consistent with the field perturbations associated with a plume, located near the plume reported by Arnold et al., 2019.

From these investigations, we confirm, independently from previous reports, that the Galileo spacecraft could have passed near plumes.

For Io we report the following results:

We identify regions of proton (80-220 keV) depletions during Io flybys I24, I27 and I31 extending beyond one Io radius. The depletions features are not consistent with Io as an inert body. We investigate atmospheric charge exchange as a cause for the depletions.
Late Holocene Varve Chronology and High-Resolution Records of Precipitation in the Central Tibetan Plateau
Authors: Ji Kejia , Zhu Erlei , Chu Guoqiang , Hou Juzhi
Published: March 2020

Precise age controls are fundamental prerequisites for reconstructing past climate and environment changes. Lakes on the Tibetan Plateau are one of the important archives for studying past climate and environment changes. However, radiocarbon ages for lake sediment core are subject to old radiocarbon reservoir effects, which caused severe problems in constructing age controls for lake sediment cores, especially on the Tibetan Plateau (TP). Here we present a varve chronology over the past 2000 years at Jiang Co on the central TP. The clastic-biogenic varves comprise of a coarse-grained layer and a fine-grained layer observed by petrographic microscope and Electron Probe Micro Analyzer. Varve chronology is supported by measurements of 210Pb and 137Cs, which is further used to determine the radiocarbon reservoir ages in the past ~2000 years. The percentage of coarse-grain layer thickness within single varves was considered as proxy for precipitation as the coarse grains were mainly transported by runoff, which is highly correlated with local meteorological observation. During the past 2000 years, the precipitation records show centennial-scale fluctuations that are consistent with regional records. The varve chronology at Jiang Co provides a valuable opportunity to examine variation in reservoir ages on the TP and a robust chronology for reconstructing paleoclimate.
Integration of multi parameters geophysical models using PCA : application to geothermal exploration
Authors: ars jean-michel , Tarits Pascal , Hautot Sophie , Bellanger Mathieu , Coutant Olivier
Published: March 2020

Geophysical exploration of natural resources is challenging because of complex and/or narrow geological structures to image. Geophysical models should provide an image at a scale large enough to understand the complex geology but with the adequate resolution to resolve features like faults. One solution to overcome this difficulty is to integrate large multiphysics datasets to provide complementary insight of the geology. New approaches involve joint inversion of all datasets in a common process where models are coupled together. Geometrical or quantitative interpretation of the joint models image several physical properties shaping the same pattern of the target resources. In reality, models resulting from joint inversion are still challenging to interprete. Most of the joint inversion techniques are based on parameters relationship or geometrical constraint which imply common interfaces between models. This assumption may be wrong since geophysical methods have different sensitivity to the same geological object.

Geophysical integration cover a wide range of approach from the visual interpretation of model presented side by side to sophistical statistical analyses such as automatic clustering. We present here a geophysical models integration based on principal component analysis (PCA). PCA allow to gain insight on a multi-variable system with high level of interaction. PCA aims to reorganize the system by finding a new set of variables distributed along new orthogonal axis and keeping most of the variance from the data. Thus geophysical interaction are highlighted along components that can be interpreted in terms of patterns. We applied this integration method to gravity, ambient noise tomography and resistivity models obtained from joint inversion in the framework of unconventional geothermal exploration in Massif Central, France. PCA of the log-resistivity, the density contrast and the Vs velocity model has 3 independent components. The first one (PC1) representing 69% of the total variance of the system is highly influenced by the parameter coupling enforced in the joint inversion process. PC1 allows to point to geophysical structures that may be related to the geothermal system. The second component (PC2) represents 22% of the total variance and is strongly correlated to the resistivity distribution The correlation with the surface geology suggests that it may be a fault marker. The third component (PC1: 9% of the total variance) is still above the nul hypothesis and seems to describe the 3D geometry of the geological units. This statistical approach may help the geophysical interpretation into a possible geothermal conceptual model

 
Spatial variability and driving factors of carbon in typical estuarine sediments in northern China
Authors: Yu Zhitong , Wang Xiujun , Hu Luojia , Yao Wei
Published: March 2020

Studying the carbon dynamics of estuarine sediment is crucial to understanding of carbon cycle in the coastal ocean. This study is designed to investigate the spatial variability of organic (TOC) and inorganic carbon (TIC), and to explore the mechanisms regulating their dynamics in the Yellow River Estuary (YRE) and Liao River Estuary (LRE). Based on data of the surface sediment cores, we found that TIC (6.3-20.1 g kg-1) was much higher than TOC (0.2-4.4 g kg-1) in the YRE, but TIC (0.4 - 4.2 g kg-1) much lower than TOC (0.1 - 8.7 g kg-1) in the LRE. Both TOC and TIC were generally higher to the north than to the south in the YRE, and higher offshore than nearshore in the LRE, primarily due to the differences in kinetic energy level (i.e., higher to the south and nearshore). The ranges of C:N and δ13Corg were smaller in the YRE (2.1 - 10.1 and -24.26‰ ~ -22.66‰) than in the LRE (0.8 - 13.4 and -27.80‰ ~ -22.12‰). Our analysis suggested that TOC was mainly from marine sources in the YER, except in the southern shallow bay where approximately 75% of TOC was terrigenous. The contribution of terrestrial sources TOC was much higher in the nearshore area than in the offshore area in the LRE. The overall low levels of TOC were due to profound resuspension that could cause enhanced decomposition. On the other hand, high levels of TIC resulted partly from higher rates of biological production, and partly from decomposition of TOC associated with sediment resuspension. The isotopic signiture in TIC seems to imply that the latter is dominant in forming more TIC in both the YRE and LRE, and there may be transfer of OC to IC in the water column. Further studies with integrative and quantitative approaches are needed not only to assess the spatial and temporal variations of major carbon forms in the water column and sediments, but also to quantify the contributions of various sources and transformations among the different carbon pools, which aims to better understand the carbon cycle in northern China in a changing climate.