bluuebunny/crossref_metadata_2025 huggingface dataset:
Ozone in the Tropical Troposphere from Sentinel-5P TROPOMI data: CCD and CSL results
Authors: Eichmann Kai-Uwe , Weber Mark , Heue Klaus-Peter , Burrows John P.
Published: March 2020

The TROPOspheric Monitoring Instrument (TROPOMI), on board the Sentinel 5 precursor (S5p) satellite, was launched in October 2017. The TROPOMI instrument has high spatial resolution and daily coverage of the Earth. About two years of level 2 data (version 1.1.5/1.1.7) of ozone and cloud properties (fraction and height) are available. Using the OFFL GODFIT ozone and OCRA/ROCINN CRB cloud dataset, we derived tropical tropospheric ozone using the convective cloud differential method for tropical tropospheric column ozone (TTCO) [DU] and the cloud slicing method for upper tropospheric ozone volume mixing ratios (TUTO) [ppbv].

The CCD algorithm was optimized for TROPOMI with respect to the reference sector Above Cloud Column Ozone field (ACCO). It was adjusted in time and latitude space in order to reduce data gaps in the daily ACCO vectors. Also, daily total ozone maps were used to minimize the error in stratospheric ozone differences.

The CHOVA algorithm (Cloud Height induced Ozone Variation Analysis) was developed to fully exploit with the S5p instruments characteristics. A temporal sampling of cloud/ozone data is not necessary for the high amount of S5p measurements. The spatial sampling is 2° latitude/longitude grid boxes. CHOVA results are quality checked based on the statistical properties of cloud, ozone and retrieval parameters to exclude unreliable TUTO values.

Comparisons with ozone sondes show a good agreement for both methods taking into account the principal differences between a sonde point measurement and a satellite sampled mean value. 

The work on TROPOMI/S5P geophysical products is funded by ESA and national contributions from the Netherlands, Germany, Belgium, and Finland.
Identifying source regions at the Princes Elisabeth station in Antarctica, using dispersion modelling tools: a case study
Authors: De Causmaecker Karen , Mangold Alexander , Walgraeve Christophe , Van Overmeiren Preben , Mattielli Nadine , Gili Stefania , Delcloo Andy W.
Published: March 2020

During the time period December 2019 – January 2020, a lot of biomass burning has been ongoing in the Southern Hemisphere. This led to a large amount of fine dust being emitted and transported into the atmosphere of the Southern Hemisphere.

With the dispersion model FLEXPART, we will simulate these fires, using the CAMS Global Fire Assimilation System (GFAS) which assimilates fire radiative power (FRP) observations from satellite-based sensors in order to reproduce daily estimates of biomass burning emissions. Also information on the injection height is available.

Aerosol fluxes and sources in Antarctica and its closely associated Southern Ocean are poorly constrained, in particular the particle chemistry. A detailed understanding of present-day atmospheric transport pathways of particles and of volatile organic compounds (VOC) from source to deposition in Antarctica remains essential to document biogeochemical cycles and the relative importance of natural and anthropogenic compounds. Within the CHASE project (chase.meteo.be), the Royal Meteorological Institute of Belgium, Ghent University and the Université Libre de Bruxelles are doing research at the Belgian research station Princess Elisabeth (71.9°S, 23.3°E; East Antarctica, Dronning Maud Land) on the physical-chemical composition of both atmospheric particles, particles in surface snow particles as well as of VOCs. Since 2018, samples are taken both near the Belgian research station Princess Elisabeth (active sampling with pumps) and on a transect to the coast (passive samplers and surface snow samples).

In this contribution we will thoroughly investigate the atmospheric transport pathways of the recent biomass burning plumes, and in particular to what extent parts of these plumes have reached Antarctica. The measured chemical signatures of atmospheric particles and VOCs will help to constrain the simulations of the dispersion model.
Public views of ecological security barrier projects contributions towards sustainable development goals in Tibet plateau
Authors: Liu Xiaoxing , Zhao Wenwu
Published: March 2020

Tibet Plateau plays an important role in protecting the ecological security of China and even Asia, to ensure its normal and effective ecosystem function, a series of ecological security barrier protection and construction projects have been implemented. The sustainable development goals(SDGs) of the United Nations can provide a broad framework for optimizing and coordinating the ecological security barrier protection and construction projects. The public to the understanding of ecological security barrier projects and sustainable development goals can influence their decision making and participation. We determine public understanding of the projects through its contribution to SDGs. Using the results of department questionnaire in Linzhi City (n=176), we identified nine projects contribution to sustainable development goals and different cognitive patterns for them. Soil and water loss control project and sand control project have more contributions to SDSs , while the contributions of returning grazing to grassland and pest control project and traditional energy substitution project in agricultural and pastoral areas to SDGs are relatively small. Soil and water loss control project is to realize the basic requirements and management goals largest contributor, sand control project is the largest contributor to achieving the expected goals. From the cognitive patterns we see individual differences in participants, but the dominant cognitive patterns among individuals are identified. We put forwards suggestions for optimizing ecological security barrier projects to promote the achievement of the United Nations Sustainable development goals.
Volcanic submarine hydrothermal activity from satellites : regional mapping and temporal evolution in shallow water systems
Authors: Martelat Jean-Emmanuel , Escartin Javier , Barreyre Thibaut
Published: March 2020

Risk assessment at active volcanic islands link to populated areas is of first importance. We evaluate the potential of satellite imagery to map and monitor the activity of shallow-water hydrothermal systems, which are often found at volcanic islands. For this study, we used publicly available data and proprietary WorldView-2 satellites images, with spectral bands that can penetrate up to water depths of 30 m. Shallow water hydrothermal sites are visible on satellite imagery, primarily with publicly available data, demonstrating the potential of satellite imagery to study and monitor shallow water hydrothermal activity. We focus our work on volcanic islands, showing intense near-shore, shallow-water hydrothermal activity, and distinct styles of hydrothermal venting. Satellite imagery constrains regional outflow geometry and the temporal variability or stability of these systems. Milos Island shows hydrothermal outflow associated with reflective mineral precipitates and/or bacterial mats, which are stable over time (2010-2014). These outflows locally define polygonal patterns likely associated with hydrothermal convection in porous media. In Kueishantao Island individual hydrothermal plumes charged with particles are visible at the sea surface, and display great variability in intensity and distribution of plume sources (2002-2019). Worldwide we have identified ~15 shallow water hydrothermal sites with satellite imagery, that are similar to either the Milos system (e.g., Vulcano and Panarea, Italy), or the Kueishantao system (numerous sites in Pacific volcanic islands). This study demonstrates that satellite imagery can be used to map and monitor different types of shallow-water hydrothermal systems, at regional scale, and monitor their evolution. Satellite data provides not only regional and temporal information on these systems, unavailable to date, but also the regional context for follow-up in situ field data and observations (e.g., instrumental monitoring, sampling, observations and mapping with divers or AUVs) to understand both the nature and dynamics of these systems, and ultimately the associated fluxes.
The changing global methane budget. NERC’s MOYA, ZWAMPS and methane reduction projects, and the need for better tropical information and mitigation.
Authors: Nisbet Euan G. , Lowry David , Fisher Rebecca E. , France James L. , Allen Grant , Lee James
Published: March 2020

The UK NERC MOYA Global Methane Budget consortium (2016-2020) tracks the changing methane burden, with time series measurement of methane and its isotopes at remote sites, field campaigns in the Arctic, Europe, and Tropics, and through modelling studies. The methane rise that began in 2007 and accelerated in 2014 has continued, as apparently has the isotopic shift to lighter, more C-12 rich values (Nisbet et al. 2019, GBC).

MOYA flight campaigns in S. America (Bolivian Amazonia) and Africa (including ZWAMPS, an aircraft campaign over Upper Congo wetlands around Lake Bangweulu, Zambia), have shown significant tropical emissions from wetlands, cattle and fires. Isotopic values of emissions from wetlands and cattle show strong C4 plant input. Fire is a major source, including biomass burning of seasonal C4 grassland and also of C3 leaf litter in wooded savanna. MOYA campaigns have also identified widespread and significant urban and rural air pollution in tropical Africa from crop waste and urban waste fires, including plastic burning.

MOYA’s work has identified strong opportunities for reducing anthropogenic emissions, and highlights the need for better emissions quantification in tropical nations. Mitigation is feasible not only in northern nations, for example drastically cutting fossil fuel emissions, but also is urgently necessary in tropical nations, where much better inventory information is urgently needed. Natural sources such as wetlands are intractable to mitigation, and emissions are likely to increase, with climate warming feeding warming. Cost-effective low technology actions in tropical nations, such as covering landfills with soil, and reducing waste fires, would have significant impact on emissions. Emission reduction from landfills, sewage, and waste fires, especially around the rapidly growing tropical megacities would also bring significant health benefit by cutting air pollution.

Sharp near-future reductions in anthropogenic methane emissions are indeed possible (Nisbet et al. Rev Geophys. 2020), and are probably inexpensive compared to other ways of decarbonation, but cutting methane will need strong action, including determined effort from tropical nations.
Future response of precipitation extremes over the Nordic region in a convection-permitting regional climate model
Authors: Lind Petter , Belušić Danijel , Kjellström Erik , Wang Fuxing , Toivonen Erika , Pedersen Rasmus A. , Matte Dominic , Dobler Andreas
Published: March 2020

There is an increased need for more detailed climate information from impact researchers, stakeholders and policy makers for regional-to-local climate change assessments. In order to design relevant and informative planning strategies on these scales it is important to have reliable climate data and information on high spatial O(1km) and temporal (daily to sub-daily) scales. Such high-resolution data is also beneficial for climate impact modellers as input to their models, e.g. hydrological or urban models that operate on regional to local scales. It has been established that regional climate models (RCMs) provide added value compared to coarser global climate models (GCMs) or re-analysis (e.g. ERA-Interim). However, RCMs with standard spatial resolution O(10 − 50km) still suffer from inadequacies in representing important regional-to-local climate phenomena and characteristics, both from the implied ”smoothening” effect within each grid cell which limits the representation of fine scale surface forcings, and the need to parameterize small-scale processes like atmospheric convection. The latter particularly invokes uncertainties in future climate responses of short-duration precipitation extremes such as flash-floods. Here, we compare 20-year simulations with a very high resolution (3 km grid spacing) convection permitting regional climate model (CPRCM) with a standard high-resolution (12 km grid spacing) convection parameterized RCM and their abilities to simulate the climate characteristics of the Nordic region in Europe, with particular focus on precipitation extremes. The study covers both recent past (with boundary data from ERA-Interim and the EC-Earth GCM) and the end of the 21st century (boundary data from EC-Earth using the RCP8.5 radiative forcing scenario). The high model grid resolution combined with the extensive simulated time period which enables assessment on climatological time scales makes this study one of very few for this region.
Open and reproducible science: from theory to equations, algorithms and plots
Authors: Schymanski Stan , Kunčar Jiří
Published: March 2020

Scientific theory is commonly formulated in the form of mathematical equations and new theory is often derived from a set of pre-existing equations. Most of us have experienced difficulty in following mathematical derivations in scientific publications and even more so their transfer into numerical algorithms that eventually result in quantitative tests and data plots. The Python package Environmental Science using Symbolic Math (ESSM, https://github.com/environmentalscience/essm) offers an open and transparent way to (a) verify derivations in the literature, (b) ensure dimensional consistency of the equations, (c) perform symbolic derivations, and (d) transfer mathematical equations into numerical code, perform computations and (e) generate plots.

Here we present an example workflow using jupyter notebooks illustrating the capabilities of the package from (a) to (e), including recently added advanced features.
Study of seasonal and short-term temperature variations in the middle atmosphere using cosmic muons
Authors: Tramontini Matias , Rosas-Carbajal Marina , Nussbaum Christophe , Gibert Dominique , Marteau Jacques
Published: March 2020

In the last decades, large particle-physics experiments have shown that muon rate variations detected in underground laboratories are sensitive to regional, middle-atmosphere temperature variations. Therefore, muon measurements may be used to study middle-atmosphere dynamics, including short-term phenomena such as Sudden Stratospheric Warmings. In this work we use a portable muon detector conceived for geosciences applications. We study seasonal and short-term variations in the middle-atmosphere’s temperature by analyzing a year of continuous muon measurements at the Mont Terri underground rock laboratory. This site is located in the Jura Mountains in north-western Switzerland, at a depth of ~300 meters below the Earth's surface. We observe a direct correlation between middle‐atmosphere seasonal temperature variations and muon rate. Muon rate variations are also sensitive to the abnormal atmosphere heating in January-February 2017, associated to a major Sudden Stratospheric Warming that in a few days increased the zonal mean temperature in the polar region by more than 20 K. We estimate the effective temperature coefficient for our particular case and found that it agrees with theoretical models and with those calculated from large neutrino experiments under comparable conditions. Finally, we discuss the implications of our observations for the Atmospheric Sciences community.
Changes on Totten glacier dependent on oceanic forcing based on ISMIP6
Authors: Haubner Konstanze , Sun Sainan , Zipf Lars , Pattyn Frank
Published: March 2020

Totten glacier is draining 68% of the Aurora basin, East Antarctica, - an equivalent to 3.5m global sea level rise. Further, Totten’s thickness and velocity have been fluctuating during the last decades showing periodic speed-ups and thinning.

We investigate the effect of different ocean forcing on Totten glacier using the state-of-the-art ice sheet model BISICLES and based on the high-resolution data sets BedMachine Antarctica and REMA (Morlighem et al., 2019; Howat et al., 2019). Our simulations (2015-2100) are following the ISMIP6 setup and are based on CMIP5 & CMIP6 AOGCM outputs under RCP8.5 and RCP2.6. The contribution to sea level at 2100 varies between plus and minus 6mm. For all scenarios, we see thinning at the sides of Totten glacier in the slower flowing areas, but only climate models with sub-shelf melt rates that are at least 8m/a above the reference melt rates (1995 – 2017) lead to thinning and acceleration across Totten's grounding line. In agreement with ISMIP6 results, non-local quadratic melt rates adjusted to present day conditions at Pine island glacier, West Antarctica, results in the highest sub-shelf melt rates for all AOGCMs (up to 80m/a locally).

The ISMIP6 ocean melt scheme is based on a feedback given the simulated ice draft change: the thermal forcing of the ocean model is taken from the ocean layer closest to the bottom of the ice shelf at the current simulation step. Simulations not including this feedback lead to higher mass loss than the standard ISMIP6 scenario including the feedback.
The effect of cloud cover on the radiation-, energy- and carbon balance of a seasonally dry tropical forest in Brazil (Caatinga)
Authors: Verhoef Anne , Moura Magna S. B. , Nóbrega Rodolfo
Published: March 2020

The Caatinga is a seasonally dry tropical forest, which is the dominant vegetation type in the northeastern region of Brazil. Its many plant species have adapted to the semiarid climate through different biophysical and physiological traits and drought survival strategies. In recent years, this region has endured a number of prolonged droughts that have adversely affected this already severely water-limited region. Despite the relatively small amounts of rainfall (with annual rainfall ranging approximately between 100–800 mm/year), there is an almost perpetual occurrence of clouds due to the regional atmospheric circulation; broadly speaking cumulus or cumulonimbus in the rainy season, and mostly stratocumulus during the transition from wet to dry, and dry seasons.  We studied the effect of cloud cover on the radiation balance, as well on the surface energy- and carbon balance of a pristine Caatinga area from 2011 to 2018.

This study used radiation and weather data obtained from a SONDA BSRN radiation station, as well from a flux tower installed in the study area; both were near the urban areaofPetrolina, Brazil. Furthermore, radio-sounding data collected nearby were employed to obtain column integrated atmospheric water vapour, to estimate atmospheric emissivity.

We derived cloudiness from a number of indirect methods (using shortwave- and longwave incoming radiation) at diurnal, seasonal and multi-year timescales. We also employed observed cloud cover data, including those from sky-cameras, for verification.

Estimates of clear-sky atmospheric emissivity were required to determine cloud cover.  These were obtained from well-known equations (e.g., Brunt, Brutsaert and Prata) using tower air temperature and/or vapour pressure; calibration of the constants in these equations was required and their performance varied considerably. Occasionally, there were large differences between column integrated atmospheric water vapour and near-surface humidity; this had implications for estimates of atmospheric emissivity and hence of cloud cover.

Seasonal variations in turbidity varied by a factor of 2. Clear-sky conditions occurred for between 8-18% of the time, with the lowest percentage occurring for the wettest year (2011).

Despite its considerable effect on the radiation balance, the variation in cloud cover had a relatively modest effect only on the energy- and carbon balance fluxes. This has implications for our understanding of the Caatinga vegetation functioning, as well as for the development and testing of land surface models for this ecosystem.

This work has been supported by The Natural Environment Research Council (NE/N012488/1) and Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco (Caatinga-FLUX Phase 2 APQ 0062-1.07/15).
Seismic source inversion using Hamiltonian Monte Carlo and a 3-D Earth model in the Japanese Islands
Authors: Simutė Saulė , Krischer Lion , Boehm Christian , Vallée Martin , Fichtner Andreas
Published: March 2020

We present a proof-of-concept catalogue of full-waveform seismic source solutions for the Japanese Islands area. Our method is based on the Bayesian inference of source parameters and a tomographically derived heterogeneous Earth model, used to compute Green’s strain tensors. We infer the full moment tensor, location and centroid time of the seismic events in the study area.

To compute spatial derivatives of Green’s functions, we use a previously derived regional Earth model (Simutė et al., 2016). The model is radially anisotropic, visco-elastic, and fully heterogeneous. It was constructed using full waveforms in the period band of 15–80 s.

Green’s strains are computed numerically with the spectral-element solver SES3D (Gokhberg & Fichtner, 2016). We exploit reciprocity, and by treating seismic stations as virtual sources we compute and store the wavefield across the domain. This gives us a strain database for all potential source-receiver pairs. We store the wavefield for more than 50 F-net broadband stations (www.fnet.bosai.go.jp). By assuming an impulse response as the source time function, the displacements are then promptly obtained by linear combination of the pre-computed strains scaled by the moment tensor elements.

With a feasible number of model parameters and the fast forward problem we infer the unknowns in a Bayesian framework. The fully probabilistic approach allows us to obtain uncertainty information as well as inter-parameter trade-offs. The sampling is performed with a variant of the Hamiltonian Monte Carlo algorithm, which we developed previously (Fichtner and Simutė, 2017). We apply an L2 misfit on waveform data, and we work in the period band of 15–80 s.

We jointly infer three location parameters, timing and moment tensor components. We present two sets of source solutions: 1) full moment tensor solutions, where the trace is free to vary away from zero, and 2) moment tensor solutions with the isotropic part constrained to be zero. In particular, we study events with significant non-double-couple component. Preliminary results of ~Mw 5 shallow to intermediate depth events indicate that proper incorporation of 3-D Earth structure results in solutions becoming more double-couple like. We also find that improving the Global CMT solutions in terms of waveform fit requires a very good 3-D Earth model and is not trivial.
High-resolution dataset assessing methane concentrations and modelling the carbon dynamics within Europe's second largest delta, the Danube River Delta
Authors: Canning Anna , Körtzinger Arne
Published: March 2020

Wetlands are known to be significant sources for CH4, yet vary between potential sources and sinks for CO2. However, in regards to the budgets and processes, they are still considered to have high uncertainties, inconsistencies and a general lack of data overall. One key wetland region in Europe is the Danube River Delta. It is the second largest delta in Europe, consisting of the vastest compact reed bed zone in the world, intertwined with rivers, lakes and channels. It is sourced with water from a drainage basin of 817,000 km2, with the Danube River originating in Germany before travelling 2,857 km to the Black Sea. However, considering the potential pollution effects within this terminal zone, as well as the delta being one of the most important wetlands in Europe for its ecological value alone (and therefore fragile), few studies have focused on the dynamics within the carbon cycle. During 2017, three field campaigns across three seasons measured high resolution, small-scale spatial and temporal variability for pCO2, CH4, O2 and ancillary parameters within the lakes, rivers and channels with the use of a surface water flow-through package. Given the flexibility of the system, we were able to conduct day-night cycles and extensive mapping transects. We discovered day-night cycles showing significant variation of CH4 concentrations within the lakes and channels, as well ‘hot spot’ anomalies showing potential ground water sourcing and extreme CH4 concentrations flowing in from the reed beds. Although reasoning for supersaturation in surface waters are under continuous debate, we conclude a potential reason for such dynamic diel variation within the lake may be due to biomass decomposition and extensive macrophyte concentrations creating a temporarily anoxic zone during the day with mixing during the night, such as previously suggested. On top of this, with the use of discrete data collected from the same water source simultaneously, we were able to model alkalinity, dissolved inorganic carbon and pH to examine both 24 h cycles across lakes and day-night dynamics, giving an in-depth glimpse into the carbonate system. Through the extensive mapping, we successful extracted diel variations for pCO2 and the carbonate species across the lakes with the use of just day-light data, allowing for spatial and temporal variations to be distinguished. We confirm the boundaries between channels and lakes are intertwined as much as they are with the wetlands, and how small extreme anomalies can only begin to be explained with such high-resolution data, even more so in combination with modelled data.
Impact of soil sample pre-treatment on microbial carbon use efficiency and associated parameters
Authors: Schroeder Julia , Kammann Lisa , Tebbe Christoph C. , Poeplau Christopher
Published: March 2020

The 18O-labelling method is a powerful tool for studying soil microbial carbon use efficiency (CUE), as the label itself does not affect the soil microbial carbon metabolism. Beside parameters of soil microbial activity, the DNA extracted within this method can be used to gain information on soil microbial metagenome, e.g. community composition. Amongst others, the 18O-CUE method can support studies on the impact of land use change on the soil microbial metabolism and thus soil carbon dynamics.

As soil sample handling and length of incubation prior to analysis have been shown to affect measured parameters of soil microbial activity (e.g. Birch-effect) and community, different sample preparation measures are recommended in the literature depending on the focus of the study. However, so far the sensitivity of CUE and associated parameters to sample pre-treatment is unknown. We therefore tested i) how different sample pre-treatments (freezing, drying, and fresh) affect the parameters of soil microbial metabolism and community measured within the 18O-CUE method. In order to determine the potential to use the 18O-CUE in land use change studies we tested ii) if mentioned parameters of the two compared systems forest and cropland were - if applicable -affected in a similar way.

Based on five different paired sites (cropland and forest each), we evaluated the effects on the CUE and associated parameters (respiration, soil microbial biomass C, DNA extracted, abundance of fungi, bacteria and archaea) of six pre-treatments for soil samples via the 18O-CUE method: (i) direct analysis of field-fresh soil samples, analysis after pre-incubation of (ii) field-fresh, (iii) air-dried, (iv) oven-dried, (v) frozen at -20°C and (vi) in-situ frozen soil samples (dry ice and subsequently liquid N2).

Among all pre-treatments, the pre- incubation of 14 days as such had the strongest effect on metabolic parameters. Furthermore, while individual parameters (respiration, microbial biomass C) were influenced by the pre-treatment the 18O-CUE was relatively insensitive. We therefore conclude that not only fresh but also archived, dried soil samples can be used to obtain representative CUE values. Drying soil samples and rewetting led to increased fungal abundance in the forest soil, while this was not the case for croplands.
Integrating model and data over the Southern Ocean at the Last Glacial Maximum to better understand the sea-ice cover
Authors: Lhardy Fanny , Bouttes Nathaëlle , Roche Didier , Crosta Xavier
Published: March 2020

 At the interface of the atmosphere and the oceans, sea ice is a thin and reactive layer which depends on the surface temperatures of the two and with significant impact on both. In this vein, sea ice affects the regional energy budget due to its high albedo, modulates the transfer of gas and energy at the ocean-atmosphere by its simple presence and modifies the water column vertical structure through brine rejection during freezing and freshwater input during melting. As the densification of surface waters can lead to deep water formation, sea ice has an impact on deep ocean circulation (Ferrari et al. [2014], Marzocchi et al. [2019]).

 Around 21,000 years ago, the glacial period called the LGM was marked by extensive ice sheets in the Northern Hemisphere, a consequent lower sea-level, and lower atmospheric CO2 concentrations than today’s. However, the processes driving these lower atmospheric CO2 concentrations are still not fully understood. Paleotracer data (Curry and Oppo [2005]) suggest that the Antarctic Bottom Water was a poorly ventilated and voluminous water mass, therefore efficiently trapping carbon. Proxies also allow for the reconstruction of LGM sea ice (de Vernal et al. [2013]), and their studies have indicated both an extended Southern Ocean sea ice and an enhanced seasonality (Gersonde et al. [2005], Allen et al. [2011], Benz et al. [2016]).

 Models are very helpful to investigate the potentially complex response of the climate system to any perturbation. The Paleoclimate Modelling Intercomparison Project (now in phase 4) has proposed standardized LGM boundary conditions which notably allows for an evaluation of the model performance under cold conditions. During past PMIP phases, the simulation of the LGM deep ocean circulation has proven to be challenging (Otto-Bliesner et al. [2007], Muglia and Schmittner [2015]), which could be linked – at least partially – to the limitations in modelling past sea-ice changes (Goosse et al. [2013], Roche et al. [2012]).

 In this study, the iLOVECLIM model – of intermediate complexity – (Goosse et al. [2010]) is used under the PMIP4 experimental design with both the ICE-6G-C and GLAC-1D topographies. The simulated sea ice is compared with a recent compilation of proxy data (Crosta, pers. com.). We look for potential sources of the observed model-data discrepancies using different model configurations. We examine in particular the simulated SSTs compared to MARGO [2009] data and show a regional and seasonal model-data disagreement that is quite consistent with the sea-ice model-data comparison.
Modulation of PDO in the Arctic tropospheric warming
Authors: Suo Lingling , Gao Yongqi , Gastineau Guillaume , Liang Yu-Chiao , Ghosh Rohit , Tian Tian , Zhang Ying
Published: March 2020

The Arctic amplified warming under global warming is one of the prominent climate change events during the past several decades. Arctic sea ice retreat contributed the majority of the near-surface warming, and little to the mid-troposphere warming. The remote factors might contribute to or modulate the aloft Arctic warming.

Here we performed a multi-model joint-analysis to study the role of the Pacific decadal oscillation, which is one of the most important recurring ocean-atmosphere variability in the climate system, in the tropospheric Arctic warming. In the multi-model simulation, PDO reduced the Arctic warming trend during 1979-2013 significantly in spring, Autumn and early winter season from the near-surface to the upper troposphere. The reduction of warming reaches 0.3 / 0.2 °C per decade in the upper / lower troposphere.
Impacts of stratospheric ozone extremes on Arctic high cloud
Authors: Smith Karen , Maleska Sarah , Virgin John
Published: March 2020

Stratospheric ozone depletion in the Antarctic is well known to cause changes in Southern Hemisphere tropospheric climate; however, due to its smaller magnitude in the Arctic, the effects of stratospheric ozone depletion on Northern Hemisphere tropospheric climate are not as obvious or well understood. Recent research using both global climate models and observational data has determined that the impact of ozone depletion on ozone extremes can affect interannual variability in tropospheric circulation in the Northern Hemisphere in spring. To further this work, we use a coupled chemistry-climate model to examine the difference in high cloud between years with anomalously low and high Arctic stratospheric ozone concentrations. We find that low ozone extremes during the late twentieth century, when ODS emissions are higher, are related to a decrease in upper tropospheric stability and an increase in high cloud fraction, which may have contributed to Arctic surface warming via a positive longwave cloud radiative effect in the past few decades compared to other regions. A better understanding of how Arctic climate is affected by ODS emissions, ozone depletion and ozone extremes will lead to improved predictions of Arctic climate and its associated feedbacks with atmospheric fields as ozone levels recover.
Including hydrologic signatures in the calibration of a groundwater-surface water model to improve representation of artificial drain
Authors: Stisen Simon , Schneider Raphael , Lajer Højberg Anker
Published: March 2020

About half of the Danish agricultural land is artificially drained to make land arable and increase crop yield. Those artificial drains, mostly in the form on tile drains, have a significant effect on the groundwater flow patterns and the whole water cycle. Consequently, the drainage system must also be represented in hydrological models that are used to understand and simulate, for example, recharge patterns, groundwater flow paths, or the transport and retention of nutrients. However, representation of drain in regional- and large-scale hydrological models is challenging due to i) issues with scale, ii) a lack of data on the distribution of the drain network, and iii) a lack of direct observations of drain flow. This calls for more indirect methods to inform such models.

We assume that drain flow leaves a signal in certain hydrograph signatures, as it impacts the generation of streamflow. Based on a dataset of observed discharge covering all of Denmark, and simulation results from regional-scale hydrological models, we use machine learning regressors to shed light on possible correlations between hydrograph signatures and artificial drainage. Building up on this step, we run a series of calibration exercises on a hydrological model of the agriculturally dominated Norsminde catchment, Denmark (~100 km2). The model is set up in the DHI MIKE SHE software, as distributed coupled groundwater-surface water models with a grid size of 100 m. The different calibration exercises differed in the objective functions used: either we only use conventional stream flow metrics (KGE), or also include hydrograph signatures that showed sensitive towards drain flow in our regression analysis. We then evaluate the results from the different calibration exercises, in terms of how well the model reproduces directly observed drain flow, and spatial drainage patterns.

Despite including hydrologic signatures in the calibration process, the representation of drain flow in large-scale models remains challenging. Eventually, the insight gained from this and similar studies will be incorporated in the National Water Resources Model for Denmark, to help improving national targeted regulation of nitrate application through fertilizers.
Did the rise of highly-transpiring angiosperms influenced Cretaceous climate ? A modelling approach with the IPSL atmosphere-land surface model.
Authors: Bres Julia , Sepulchre Pierre , Vuichard Nicolas , Viovy Nicolas
Published: March 2020

The Cretaceous angiosperm radiation was a major event for terrestrial plant evolution, and flowering plants represent more than 94 % of present-day plant diversity. The fossil record shows that angiosperm leaf vein densities reached particularly high values (> 12 mm/mm2) between the Albian and the Cenomanian (108–94 Ma) compared to gymnosperms (~ 2.5 mm/mm2). Empirical models also suggest that stomatal conductance to water vapour increases as a response to higher leaf vein densities. How much do this shift to higher values of stomatal conductance have modified the continental transpiration budget, and ultimately global hydrological cycle ? To address this question we used the IPSL coupled atmosphere-vegetation model forced by Cretaceous boundary conditions, and built plant functional types including stomatal conductance values consistent with the fossil record. We quantify the transpiration fluxes through different sensitivity experiments and explore the vegetation-atmosphere feedbacks and their impact on the Cretaceous climate.
Paleomagnetic data of the Siberian Mesoproterozoic rocks (Udzha Uplift, Northern Siberia)
Authors: Pasenko Aleksandr , Savelev Aleksandr , Malyshev Sergey
Published: March 2020

In spite of the fact, that during the last two decades some number of new paleomagnetic poles, more or less meeting the modern standards of quality [Van der Voo, 1993], have been obtained for Mesoproterozoic of Siberia [Evans et al., 2016]. The problem of the Precambrian segment of the apparent polar wander path (APWP) for Siberia, rests still to be far from its solution.

The latter, obviously, hampers the elaboration of Precambrian paleogeographic reconstructions, solution of numerous other important tasks of the Earth Sciences.

The Late Precambrian key section of the Udzha Uplift seemed to be one of the most promising object to elaborate the Mesoproterozoic segment of APWP of the Siberian platform. Until recently, the rocks composing this section have been considered to be of the Mesoproterozoic and Vendian age.

As a result of isotope studies in recent years, the age of formations of the Udzha Uplift has been significantly increased (1386±30 Ma, apatite, U-Pb, [Malyshev et al., 2018]). In particular, age of the Udzha Fm, which forms the uppermost part of the Udzha riphean sequence is considered currently to be Mesoproterosoic. On the base of our new paleomagnetic data this formation has been formed about the same time as the Khaypakh Fm from the Olenek Uplift (NE Siberia), whose Mesoproterozoic age has been established earlier from independent isotopic data [Zaitseva et al., 2017].

During last several years we have carried out the paleomagnetic studies of Late Precambrian rocks of the Udzha Uplift including the Mesoproterozoic Udzha and Unguokhtakh formations as well as intrusions representing two Mesoproterozoic magmatic events.

In this abstract we present new paleomagnetic poles for the Mesoproterosoic rocks (1500 Ma, ca.1400 Ma, 1385 Ma) of the Siberian platform.

These paleomagnetic poles significantly complement the Mesoproterozoic segment of APWP of the Siberian Platform.

The studies were supported by the Russian Science Foundation project № 19-77-10048.
Always delayed? Holocene and current evolution of Pasterze Glacier, Austria
Authors: Nicolussi Kurt , Dusch Matthias , Drescher-Schneider Ruth , Kellerer-Pirklbauer Andreas , Maussion Fabien
Published: March 2020

The glaciers in the Alps are currently shrinking, in some cases dramatically, due to progressive warming. At some glaciers this recession has made it possible to find tree remains and other organic material at or near the termini. At Pasterze Glacier, such findings have been made since about 1990, allowing new insights into the Holocene evolution and variability of this glacier. Initially, only relocated wood and peat boulders were collected, but around 2010 an in-situ locality became ice-free. Tree remains and other organic material from this site have mainly provided dates for a period of more than a thousand years in the middle Holocene (around 6 ka) proving a continuously smaller extent of this glacier during this period compared to today. Furthermore, a comparative interpretation of all available, some 80 radiocarbon and dendro dates suggests that Pasterze Glacier was probably at least from about 10.2 ka to about 3.5 ka continuously shorter compared to the extent around 2010 AD. For the last nearly 2800 years there is no similar evidence of comparable small glacier extents. Finally, after the early- to mid-Holocene retreat phase, a relatively delayed increase of Pasterze Glacier during the early Neoglacial (in the Alps after about 4 ka) can be deduced. Other glaciers almost reached or even exceeded the later LIA dimensions already during this period.

Moreover, Pasterze Glacier is also lagging behind the current climatic changes, i.e., its extent is not in equilibrium with the current warming. This circumstance is not only proven by the rapid recession during recent years, but also by simulations with the glacier model OGGM. The simulation results show on the one hand that Pasterze glacier has to melt back for several more kilometres to reach equilibrium with the climatic conditions of 1980-2010. On the other hand, this also documents that the recent climate conditions are already sufficient to allow a recession comparable to the early and middle Holocene stages of this glacier. Both the delayed increase in extent during the early Neoglacial and the considerably delayed current recession can be explained by the size of the glacier and the topographic conditions.
Sensitivity analysis of MOHID-Land model. Calibration and validation of Ulla river watershed.
Authors: Oliveira Ana , Ramos Tiago B. , Simionesei Lucian , Pinto Lígia , Neves Ramiro
Published: March 2020

Nowadays flood warning systems are extremely important since they can provide critical information that can protect property and save lives. These systems should alert about whether a flood should be expected, when it will occur and how severe it will be.

A warning system can be based on the analysis of historical events and a good monitoring system or it can be based on the capacity of predict the channel flow in key locations. In the second case, these type of systems, known as forecast systems, consider the meteorological predictions as driving forces for a hydrological model which estimates the channel flow for the next few hours and days, considering the processes that take place in a watershed. A hydrological forecast can only be reliable when a good calibration and validation of watershed processes is performed.

This study aims to calibrate and validate the channel flow in Ulla river watershed (Galicia, Spain) using MOHID-Land model considering a sensitivity analysis of some parameters and user’s options that can affect model results. MOHID-Land model is a physically based, fully distributed model that considers four compartments or mediums: atmosphere, porous media, soil surface and river network. Water dynamics is computed through the different mediums using mass and momentum conservations equations.

The model was firstly implemented in the studied domain with a resolution of 500 m. Data inputs included the digital Global Digital Elevation Model from NASA with a resolution of 30 m; the Corine Land Cover map from 2012 with a resolution of 100m; the soil hydraulic properties from the multilayered European Soil Hydraulic Database with a resolution of 250 m; hourly meteorological data (precipitation, solar radiation, wind velocity, air temperature, surface pressure and dew point temperature) from ERA5-Reanalysis with a resolution of 31 km; and daily total outflow for three reservoirs present in this watershed.

The sensitivity analysis was performed to test the impact of grid and elevation data source resolution, cross-sections geometry, soil parameters, vertical soil discretization, surface and channel Manning coefficients, the infiltration process and deactivation of different modules such as porous media and vegetation on streamflow. The results of these tests were compared with a reference simulation by the analysis of flow duration curves.

The hydrological model was calibrated and validated in 4 hydrometric stations not influenced by reservoirs and the river flows considering the reservoirs operation were compared with measured values in 2 hydrometric stations. Four statistical parameters (R2, RMSE, PBIAS and NSE) were used to evaluate model performance at a daily scale which was considered good.
Investigating Seismic Anisotropy of the Madeira and Canaries Hotspots Using Teleseismic and Local Shear-Wave Splitting with the SIGHT project
Authors: Schlaphorst David , Silveira Graça , Mata João
Published: March 2020

Madeira and the Canary Islands, located in the eastern North Atlantic, are two of many examples of hotspot surface expressions. Their tracks have been reconstructed to past locations close to the south-western part of the Iberian Peninsula and north-western Africa, respectively. Furthermore, due to their close proximity, an interconnected origin of these two hotspots has been proposed but details remain unclear. A better understanding of the crust and upper mantle structure beneath these islands is needed to investigate this potential connection.

The subsurface structure has an influence on the stress field, which can be investigated studying seismic anisotropy patterns of the region. Seismic anisotropy leads to variations in the speed of seismic waves as a function of the direction of wave propagation. In the crust an orientation in the direction of maximum stress is observed, commonly being parallel to the alignment of fractures or cracks. In the upper mantle the orientation is influenced by mantle flow. A widely used method to identify anisotropy is the observation of shear-wave splitting of data from teleseismic events. In case of multiple anisotropic layers, including measurements from local events it is possible to distinguish crustal from upper mantle influences.

As part of the SIGHT project (SeIsmic and Geochemical constraints on the Madeira HoTspot), we carried out the first detailed study of seismic anisotropy beneath both archipelagos, using teleseismic SKS and local shear-wave splitting measurements of data collected from land stations of seismic networks located on Madeira and the Canary Islands.

Significant changes, both in orientation and delay time, can be observed on short length-scales on the order of tens of kilometres, matching major geological features such as, for example, the major rift zone on Madeira island. In a further step, we compare these results to previous studies of crustal and upper mantle anisotropy focusing on north-western Africa and the Iberian Peninsula to investigate the nature of the lithospheric corridor between the present day hotspot positions and the Atlas-Gibraltar region.

This is a contribution to project SIGHT (Ref. PTDC/CTA-GEF/30264/2017). The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – IDL.