bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards understanding the size distribution, composition and optical properties of freshly emitted dust and its relationship with the parent sediment
Authors: Pérez García-Pando Carlos , González-Florez Cristina , González-Romero Adolfo , Panta Agnesh , Yus-Díez Jesús , Alastuey Andrés , Kandler Konrad , Klose Martina , Querol Xavier , Reche Cristina , Pandolfi Marco , Dupont Sylvain , Etyemezian Vicken , Nikolich George , Escribano Jeronimo , Clark Roger , Elhmann Bethany , Greenberger Rebecca , Tajeddine Kamal , Ivančič Matic
Published: March 2021

The physical and chemical properties of dust, i.e. its particle size distribution (PSD), mineralogical composition, shape and mixing state determine its climate effects. However, the lack of experimental data and understanding of the emitted dust and its relationship with the parent sediment and atmospheric forcing limit the extension of climate and dust models to account for potentially important regional variations in dust properties. In this context, the FRontiers in dust minerAloGical coMposition and its Effects upoN climate (FRAGMENT) project is dedicated to understand, constrain and calculate the global mineralogical composition of dust along with its effects upon climate. In September 2019, we conducted an intensive dust field campaign as a part of FRAGMENT near M’hamid El Ghizlane in Morocco, at the edge of the Sahara Desert. During the measurement period, dust events occurred frequently (about every 1-2 days) with varying intensity.

 

In this contribution, we provide a comprehensive overview and analysis of the sediment and airborne samples collected, and of the time-resolved measurements of dust concentration, PSD, optical properties and atmospheric forcing. We use mineralogical analyses of wet-sieved (totally disturbed) and dry-sieved (minimally disturbed) sediment samples at high particle-size resolution to better understand the fragmentation of sediment aggregates during wind erosion. We analyse the temporal variability of the number and volume PSDs along with the associated size-resolved dust emission fluxes using data from three optical particle counters deployed at different heights. We discuss the size-resolved particle composition, morphology, and mixing-state of the suspended dust determined by single particle analysis with electron microscopy coupled with energy dispersive X-ray detection from samples collected on sticky carbon substrates with cascade impactors, flat-plate samplers, and free-wing impactors. Finally, scattering coefficients at 450, 525 and 635 nm and seven different angles (from 0º to 90º) obtained with a polar nephelometer and absorption coefficients at 370, 470, 520, 590, 660, 880 and 950 nm obtained with an aethalometer are used to analyse the variability of extensive and intensive optical parameters, such as scattering and absorption Ångström exponents (SAE and AAE), backscatter fraction (BF) and multi-wavelength single scattering albedo (SSA) for both PM2.5 and PM10 dust fractions in combination with PSD and meteorological measurements.
What is a Glacier? Assessing Ice Dynamic Thresholds
Authors: Florentine Caitlyn
Published: March 2021

The current global Randolph Glacier Inventory (RGI V6) minimum area cutoff is 0.01 km2. Including features this small empowers comprehensive assessments of global glacier water resources. It also enables high-resolution glacier hindcasts, ensuring that sites where modern glacier extent is now diminutive are charted and not overlooked. Yet the automated and manual mapping techniques used to generate RGI glacier outlines do not necessarily discriminate based on ice motion. There is currently no RGI mask that discerns between glaciers that likely still deform under their own weight (classic glacier) versus glaciers that are unlikely to satisfy this criterion (stagnant ice patch). Here is a highly simplified, data-driven attempt to develop a globally complete ice dynamic mask. Features are treated as simple slabs, with area given by the RGI database, order of magnitude thickness derived from volume-area power law scaling, and median surface slope derived from topography data (RGI-TOPO dataset, beta release). Driving stress is calculated using these inputs and assuming material density 900 kg m-3. This is repeated using varying elevation data sources, the globally complete consensus ice thickness estimate, and sparse direct ice thickness measurements (GlaThiDa), to explore driving stress sensitivity to different slab representations. Slabs with driving stress less than 105 Pa are interpreted as features where the ambient driving stress is insufficient to overcome the yield strength of ice. Uncertainty analysis and comparison against ice motion observations determines if these sub 105 Pa slab features reliably mask RGI glaciers that are no longer in motion. This approach serves as a first cut at developing a reproducible, systematic way of discerning between classic glaciers (bodies of ice that move) versus other cryosphere features. This may enhance consistency across technical analyses within the glaciological research community and science communication with policy makers.
Landslide detection by machine learning on high-resolution DEMs
Authors: Niculita Mihai
Published: March 2021

Machine learning algorithms are increasingly used in geosciences for the detection of susceptibility modeling of certain landforms or processes. The increased availability of high-resolution data and the increase of available machine learning algorithms opens up the possibility of creating datasets for the training of models for automatic detection of specific landforms. In this study, we tested the usage of LiDAR DEMs for creating a dataset of labeled images representing shallow single event landslides in order to use them for the detection of other events. The R stat implementation of the keras high-level neural networks API was used to build and test the proposed approach. A 5m LiDAR DEM was cut in 25 by 25 pixels tiles, and the tiles that overlayed shallow single event landslides were labeled accordingly, while the tiles that did not contain landslides were randomly selected to be labeled as non-landslides. The binary classification approach was tested with 255 grey levels elevation images and 255 grey levels shading images, the shading approach giving better results. The presented study case shows the possibility of using machine learning in the landslide detection on high-resolution DEMs.
Seasonal Analysis of Air-Sea CO2 Flux Variability in the North Atlantic and the Southern Ocean 
Authors: Rustogi Paridhi , Landschuetzer Peter , Brune Sebastian , Baehr Johanna
Published: March 2021

Understanding the variability and drivers of air-sea CO2 fluxes on seasonal timescales is critical for resolving the ocean carbon sink's evolution and variability. Here, we investigate whether discrepancies in the representation of air-sea CO2 fluxes on a seasonal timescale accumulate to influence the representation of CO2 fluxes on an interannual timescale in two important ocean CO2 sink regions – the North Atlantic basin and the Southern Ocean. Using an observation-based product (SOM-FFN) as a reference, we investigate the representation of air-sea CO2 fluxes in the Max Planck Institute's Earth System Model Grand Ensemble (MPI-ESM GE). Additionally, we include a simulation based on the same model configuration, where observational data from the atmosphere and ocean components is assimilated (EnKF assimilation) to verify if the inclusion of observational data alters the model state significantly and if the updated modelled CO2 flux values better represent observations.

We find agreement between all three observation-based and model products on an interannual timescale for the North Atlantic basin. However, the agreement on a seasonal timescale is inconsistent with discrepancies as large as 0.26 PgC/yr in boreal autumn in the North Atlantic. In the Southern Ocean, we find little agreement between the three products on an interannual basis with significant seasonal discrepancies as large as 1.71 PgC/yr in austral winter. However, while we identify regional patterns of dominating seasonal variability in MPI-GE and EnKF, we find that the SOM-FFN cannot demonstrate robust conclusions on the relevance of seasonal variability in the Southern Ocean. In turn, we cannot pin down the problems for this region.
Isostasy amplifies relative sea-level change on continental-scale deltas
Authors: Morón Sara , Blum Mike , Salles Tristan , Frederick Bruce , Farrington Rebecca , Ding Xuesong , Mallard Claire , Mather Ben , Moresi Louis
Published: March 2021

The nature and contribution of flexural isostatic compensation to subsidence and uplift of passive margin deltas remains poorly understood. We performed a series of simulations to investigate flexural isostatic responses to high frequency fluctuations in water and sediment load associated with climatically-driven sea-level changes. We use a parallel basin and landscape dynamics model, BADLANDS, (an acronym for BAsin anD LANdscape DynamicS) that combines erosion, sedimentation, and diffusion with flexure, where the isostatic compensation of the load is computed by flexural compensation. We model a large drainage basin that discharges to a continental margin to generate a deltaic depocenter, then prescribe synthetic and climatic-driven sea-level curves of different frequencies to assess flexural response. Results show that flexural isostatic adjustments are bidirectional over 100-1000 kyr time-scales and mirror the magnitude, frequency, and direction of sea-level fluctuations, and that isostatic adjustments play an important role in driving along-strike and cross-shelf river-mouth migration and sediment accumulation. Our findings demonstrate that climate-forced sea-level changes set up a feedback mechanism that results in self-sustaining creation of accommodation into which sediment is deposited and plays a major role in delta morphology and stratigraphic architecture.
Towards inferring the variability in oceanic CO2 fluxes at high latitudes using atmospheric O2 observations
Authors: Mayot Nicolas , Le Quéré Corinne , Manning Andrew , Keeling Ralph , Rödenbeck Christian
Published: March 2021

The oceanic CO2 sink displays year-to-year to decadal variabilities which are not fully reproduced by global ocean biogeochemistry models, especially in the high-latitude oceans. Oceanic CO2 is influenced by the same climate variability and the same ecosystem processes as oceanic oxygen (O2), although in different proportions. Unlike for CO2, oceanic O2 flux is not influenced directly by the rise in atmospheric CO2, and therefore its variability reflects purely climatic and biogeochemical variability and trends. Therefore, natural climate variability and changes in oceanic processes controlling air-sea exchanges of CO2 can be studied by focusing on oxygen (O2), where the signal is unencumbered by direct anthropogenic influence. A global time series of oceanic O2 flux was obtained by building a global O2 budget, with an approach similar to the one used for the global carbon budget. The global O2 budget is based on atmospheric O2 observations and fossil fuel statistics, and infers the partitioning of the land and ocean fluxes using constant C:O2 ratios for land processes. One key result of this analysis is that air-sea O2 exchange induced significant year-to-year variability in observed atmospheric O2. Estimates of regional oceanic O2 fluxes were obtained from an atmospheric transport inversion analysis that inferred air-sea O2 exchange based on global atmospheric O2 observations and a global atmospheric transport model. For the Southern Ocean, a comparison was made between time series of winter oceanic O2 fluxes from this inversion method and winter mixed layer depths from Argo floats. Results from this comparison confirmed the previously suggested relationship between the winter ocean mixing and air-sea O2 exchange, which might be controlled by the climate variability induced by the Southern Annular Mode. Finally, these global and regional air-sea O2 fluxes were compared with outputs from six global ocean biogeochemistry models to examine their current skills in simulating O2 variability. Preliminary results suggested that all models underestimated the interannual variability in oceanic O2 fluxes, however they were able to simulate some of the observed multi-annual variability in O2 fluxes at high latitudes. We discuss the implications for the model’s representation of the variability in CO2 fluxes.
Forest fine root biomass and soil CNP stoichiometry across three different biogeographical regions in Croatia
Authors: Ostrogović Sever Maša Zorana , Dimoski Doroteja , Anić Mislav , Marjanović Hrvoje
Published: March 2021

Fine root biomass (FRB) is a small but important forest ecosystem pool due to its direct role in ecosystem functioning through belowground carbon and soil nutrient cycling. At the global scale there is evidence that FRB correlates with meteorological parameters, e.g. precipitation and air temperature. Moving from global to regional and local scales other environmental parameters, primarily related to site soil characteristics, become more important.
In this research, we investigated which soil parameters are important as drivers of fine root biomass in three different biogeographical regions in Croatia, namely the Continental, the Alpine and the Mediterranean.  We collected data on soil and site characteristics at 242 locations. Soil parameters include bulk density, texture, pH and C, N and P content, while site parameters were latitude, longitude, elevation, precipitation, air temperature and forest type (Coniferous, Broadleaves, and Maquis/Garigues). Fine root biomass was estimated from soil samples collected at 2-8 positions at each location. Soil was sampled down to 30 cm depth in the mineral layer with a split-tube sampler, and analysed for three depths, i.e. 0-10 cm, 10-20 cm, and 20-30 cm depth.
Across entire dataset, FRB was affected by precipitation, elevation, forest type, soil depth, and soil C/P and N/P relations. Moving down to each biogeographical region separately, a stronger effect of soil phosphorus was observed for the Mediterranean region.
The ASKOS experiment for the validation of Aeolus L2A aerosol product 
Authors: Marinou Eleni , Amiridis Vasslis , Mavropoulou Ioanna , Baars Holger , Kazadzis Stelios , Rosoldi Marco , Ene Dragos , Barreto Africa , Casadio Stefano , Zenk Cordula , Sciare Jean , Mocnik Grisa , Kandler Konrad , Stuut Jan-Berend , Rodrigez Sergio , Knipertz Peter , Rutz Thomas , Komppula Mika , Daskalopoulou Vassiliki , Hloupis George ,   ASKOS team
Published: March 2021

For the in-orbit calibration and validation of the Aeolus products, ESA organized the Aeolus Tropical campaign, which will take place on June-July 2021 at Cape Verde region. During the campaign, Aeolus underfights will be performed with several aircrafts (by DLR, NASA, LATMOS, and the University of Nova Gorica (UNG)) and advanced ground-based instrumentation will be deployed in Mindelo island within ASKOS (https://askos.space.noa.gr/) experiment. ASKOS observations will provide an unprecedented dataset for the aerosol and wind conditions in the region, in order to provide reference values for the Cal/Val of the mission. Apart from the main aerosol Cal/Val objective of ASKOS, the foreseen synergistic activities will provide a wealth of information to address scientific questions posed by the participating groups on dust characterization, transportation and it’s impact of radiation and cloud formation.

Here, we report on the status of the ASKOS preparations for the evaluation of the aerosol and cloud product, focusing on the instrumentation requirements and availability, as well as the engagement of the scientific community so far. ASKOS will deploy advanced ground-based and airborne remote sensing and in-situ instrumentation, including the full ACTRIS aerosol and cloud remote sensing/in-situ facilities and airborne in-situ sensors to be operated on drones and/or aircrafts. The main ground-based remote sensing instrumentation in Cape Verde will consist of sophisticated lidar systems, including the EVE lidar, a circular polarization system that is tailored to mimic the Aeolus measurement from ground, the multi-wavelength Polly-XT and the WALL-E prototype for detecting particle orientation. The instrumentation will also include sun-photometers such as AERONET-CIMEL, but also polarimeters to advance microphysical retrievals for non-spherical particles such as dust. Cloud remote sensors including a cloud radar and a microwave radiometer will operate in parallel along with meteorological radiosondes. In-situ sensors at surface and onboard UAVs and light aircrafts will be available. ASKOS will be fully supported by several operational modeling simulations for meteorological and atmospheric composition forecasting. ASKOS will remain open to contributions from other communities and research groups and more synergies will be pursued in the future.

 
Crustal and lithospheric architecture of the Gulf of Mexico and its continental margins from ambient noise Rayleigh wave tomography
Authors: Nguyen Luan C. , Levander Alan , Niu Fenglin , Li Guoliang
Published: March 2021

The Gulf of Mexico formed as a result of continental breakup between the North and SouthAmerican plates and a short period of seafloor spreading in the Late Jurassic-Early Cretaceous. This small ocean basin offers an opportunity to further our understanding of continental rifting processes and the geologic evolution of continental margins during and after rifting. However, previous knowledge of lithospheric structure has been limited to crustal investigations. We constructed a 3D shear-wave velocity model for the Gulf of Mexico region using cross-correlations of the ambient noise field and measurement of vertical component Rayleigh wave phase velocities in the period band 15 to 95 s. We employed continuous data recorded by more than 500 stations in seismic networks in the US, Mexico and Cuba. Our model shows distinct variation in lithospheric structures that reliably identify and constrain the properties of extended continental and oceanic domains. We estimate the depth of the lithosphere-asthenosphere boundary to be in the range of 85-100 km with the thinnest lithosphere under the oceanic region. A low velocity zone is observed below the lithosphere centered at ~150 km depth with a minimum shear-wave velocity of ~4.45 km/s. Lithospheric mantle underlying the offshore Texas Gulf Coast between oceanic lithosphere and unextended continental lithosphere is characterized by reduced shear-wave velocity. This might indicate that extension resulted in permanent deformation of the continental lithosphere. The differential thinning between the crystalline crust and mantle lithosphere suggests that the extended continental lithosphere has cooled and thickened by approximately 30 km since breakup.
Balancing preservation of material and the need for analytical accuracy: Mass requirements of Sphagnum moss from herbarium collections for trace element analysis
Authors: Frost Lukas , Belland Rene , Grant-Weaver Iain , Shotyk William
Published: March 2021

Sphagnum mosses have been used in some of the earliest works in biomonitoring of atmospheric deposition of trace elements (TEs). Since their adoption into the field the Sphagnaceae have become one of the foremost biomonitors. When taken as contemporary samples, these mosses have allowed us to identify spatial variations as well as trends and major changes in atmospheric deposition due to changing policy, technology, industry, and land use. While long term monitoring programs, such as the European Moss Survey, allow us to track these changes through time, these ongoing studies only reach as far back as their start dates. In the case of the European Moss Survey this was 1990. The use of materials already collected and archived in herbaria provides a low-cost method for retrospective analysis of atmospheric deposition of TEs. The critical advantage of herbarium specimens over other historical monitoring method is their high temporal resolution, as their exact collection date is known. Once collected, stored, and protected from atmospheric dust, the concentrations of non-volatile TEs present remain effectively unchanged. The oldest herbarium records can predate industrialisation, but most have records from the beginning of industrialisation, with the frequency of collection increasing in the modern era. Using only the top 2 cm of herbarium specimens of Sphagnum mosses (S. fuscum, S. angustifolium, S. capillifolium, S. magellanicum) found in Canadian ombrotrophic bogs, we will be creating historical reconstructions of atmospheric deposition in northern Alberta since the 1940s and southern Ontario since 1860’s. The first objective is to determine how best to balance preservation of the limited herbarium material available while also using sufficient material to achieve suitable levels of analytical accuracy. As TE analyses using ICP-MS are destructive and some specimens have immeasurable value from a natural history perspective, as little material as possible should be taken for analysis. Grinding of the sample was avoided, to minimize sample loss and the risk of contamination. We compared the measured concentrations obtained with ICP-MS as a function of the mass of Sphagnum digested, using selected herbarium samples as well as two certified, Standard Reference Materials (NIST 1515 and HB36-M2). These analyses allow us to determine the optimal amount of material necessary to balance the analytical accuracy and preservation of material of 4 species of Sphagnum mosses from Alberta over the last 80 years. The results will be compared with the data already available for TE concentrations in age-dated peat cores from the same region.
Olivine-Wadsleyite Transformation within the Subducting Pacific Slab in Kuril
Authors: Li Jiaqi , Chen Min , Ferrand Thomas P.
Published: March 2021

At the top of the mantle transition zone, it is commonly accepted that olivine (α) transforms to wadsleyite (β) at about 410 km depth under equilibrium conditions, i.e., a pressure of ~ 14 GPa and a temperature of ~ 1350 °C. The subsequent wave speed increase upon the α-β phase transition leads to the discovery of the 410-km discontinuity as a global feature seismologically. However, the complex topography of the “410-km discontinuity” is unclear within cold subducted oceanic lithospheres sinking into the lower mantle, partly due to the sparsity of seismic waves sampling the pertaining complex 3-D structures.

This study uses triplicated P waves (~ 2 seconds), most sensitive to the 410-km discontinuity, to invert for the characteristic parameters of its depth and radial wave speed gradients near the discontinuity. Six distinct wave propagation directions are investigated for a carefully chosen earthquake. These directions are sub-parallel to the slab depth contours in the Kuril subduction zone to guarantee a simplified layered earth modeling. Our results show azimuthal variations of the discontinuity depth either above or within the slab.

For example, the 410-km discontinuity is uplifted by 5-10 km at a depth of about 100 km above the slab upper interface. The uplift increases up to 15-20 km when the 410-km discontinuity is closer to, i.e., only 50 km above, the cold slab. This observation is consistent with the expected phase transition in equilibrium with temperatures greater than 1000°C. In contrast, within the cold slab (< 1000°C), the α-β transition exhibits drastic variations of P-wave speed. Our non-gradient-based inversion results show optimal models that place the following unique seismic constraints: 1) a significant P-wave speed increase within the slab (+5.5 ±1.5 %) compared to the ambient mantle; 2) a zone of extremely low wave speed (LVZ) within the slab with a P-wave speed reduction of -14 ±4 %. The observed LVZ is located near a depth of 350 km with an apparent thickness of 15-30 km, which can be much thinner in the direction normal to the slab upper interface.

These observations indicate a layer of destabilized olivine (LVZ) exists inside the slab. The α-β transition involves atomic diffusion highly dependent on temperature. Once olivine becomes unstable within a cold wedge, it cannot directly transform into wadsleyite. The drastic P-wave speed reduction is likely caused by the sudden grain-size reduction induced by the phase transition, and possibly also by the transient (meta)stability of an intermediate phase, the ω-olivine, under substantial shear stress during the transformation within the cold wedge of the sinking slab.
Libera – Observing and Understanding Earth’s Energy Budget
Authors: Hakuba Maria Z. , Pilewskie Peter , Stephens Graeme ,   Libera Science Team
Published: March 2021

The recently selected NASA mission Libera, named for the daughter of Ceres in Roman mythology, will provide continuity of the Clouds and the Earth’s Radiant Energy System (CERES) Earth radiation budget (ERB) observations from space.

Seamless extension of the ERB climate data record is achieved by acquiring integrated radiances over the CERES FM6-heritage broad spectral bands in the shortwave (0.3 to 5 μm), longwave (5 to 50 μm) and total (0.3 to beyond 100 μm). To gain deeper insight into shortwave energy deposition, Libera adds a split-shortwave band (0.7 to 5 μm) that allows to provide deeper insight into shortwave energy deposition.

Libera’s advanced detector technologies is based on vertically aligned black-carbon nanotubes with closed-loop electrical substitution radiometry to achieve radiometric uncertainty of approximately 0.2%. Additionally, a wide field-of-view camera is employed to provide scene context and explore pathways for separating future ERB missions from complex imagers.

This presentation will summarize Libera’s attributes and mission goals, as well as some of the applications of the camera radiances, and the role of the additional split-shortwave channel that splits the shortwave band into its visible and near-IR contributions. This split is vital for the better understanding of shortwave absorption, feedbacks, and planetary albedo variability. The hemispheric symmetry of planetary albedo, as observed by CERES, is not achieved by most state-of-the-art climate models and is associated with long-standing biases in circulation and cloud properties. We will exemplify the study of processes relevant to albedo symmetry by means of CMIP6 simulations that provide the visible and near-IR fluxes.
Surface streaming on nonbreaking wind waves
Authors: Tsai Wu-ting , Lu Guan-hung
Published: March 2021

The energetic, coherent vortical motions in the aqueous surface layer beneath the wind waves dominate the liquid-phase controlled transport processes across the air-water interface. Through interacting with the interface, these coherent vortices manifest themselves by forming quasi-streamwise, high-speed streaks on the wind waves. The density of these streamwise streaks, which can be quantified by the transverse spacing of streaks, thus characterizes the interfacial transfer contributed by the coherent vortices. The formation of surface streaming on the wind waves is geometrically similar to the low-speed streaks observed in the turbulent wall layers. It is generally accepted that the mean spanwise spacing between these low-speed streaks, when scaled by the viscous length, would exhibit a universal value of 100. Observations in wind-wave flumes, however, show that the transverse scale between high-speed streaming on nonbreaking wind waves is narrower than that between low-speed streaks next to no-slip wall. Comparative numerical simulations of shear flow bounded by flat and wavy surfaces are conducted to explain the variation. Analysis of the vorticity transport in the simulated flows bounded by a wavy surface reveals that the presence of surface waves enhances the production of streamwise enstrophy and, consequently, intensifies the generation of quasi-streamwise vortices that form the elongated streaks.
This work is supported by the Taiwan Ministry of Science and Technology (107-2611-M-002 -014 -MY3 and 110-2923-M-002 -014 -MY3).
The Arctic Rain on Snow Study
Authors: Barrett Andrew , Serreze Mark
Published: March 2021

When rain falls on an existing cover of snow, followed by low temperatures, or falls as freezing rain, it can leave a hard crust. These Arctic rain on snow (ROS) events can profoundly influence the physical environment, animals, and human livelihoods. Impacts can be immediate (e.g., on human travel, herding, or harvesting) or evolve or accumulate, leading, for example, to massive starvation-induced die offs of reindeer, caribou and musk oxen. The international Arctic Rain on Snow Study (AROSS) will detect and catalogue ROS events, and study their impacts, addressing human-environment relationships, associated meteorological conditions, and challenges in their detection. We offer a path forward to anticipate and mitigate impacts through knowledge co-production. Although ROS events can be detected, and their intensity and trends across the Arctic region evaluated by combining data from satellite remote sensing, atmospheric reanalyses and meteorological station records, information most germane to impacts, such as the thickness of ice layers, how ice layers form within a snowpack, and antecedent conditions that can amplify impacts, can only be obtained through collaboration with local and Indigenous knowledge-holders.
The sustainable development implications of carbon removal technologies in the context of net-zero climate pathway. 
Authors: Apeaning Raphael
Published: March 2021

Achieving a global net-zero emission pathway around mid-century is a critical precondition to limiting global warming to well below 1.5°C. The role of carbon dioxide removal technologies (CDR) such as direct air capture (DAC) and enhanced weathering (EW) have gained centre stage in the discourse of net-zero emission policies. Using an integrated energy-economy-climate modelling tool called GCAM, this study examines the broad sustainability implications of deploying CDR technologies of a global net-zero pathway. Specifically, the applies several Sustainable Development Goals (SDG) indicators as a lens to assesses the synergies and trade-offs associated with upscaling the deployment of DAC and EW technology options.

Based on the best techno-economic performance estimates of DAC and EW technologies, the results show that these technologies can provide about 10.2GtCO2/year of negative emission by 2065. The upscaling of these CDR technologies can substantially reduce the short-to-medium term mitigation cost by about 54.3 %. This policy cost reduction has potential to ameliorate the adverse economic impact of a net-zero pathway by enhancing the SDG targets of No Poverty (i.e. SDG 1) & Decent work and economic growth (i.e. SDG 8). The results also reveal that CDR technologies can reduce the global temperature overshoot by 0.2°C (i.e. SDG 13 (Climate Change)). Further, these CDR solutions can substitute the demand of bioenergy, which in turn leads to major gains in the reduction of cropland (i.e. SDG 15 (Life on Land)).

The enormous transformations in the global energy system to meet the high energy demand for CDR technologies can lead to substantial trade-offs. For instance, the result points to a 27.3% increase in fossil fuel use, nuclear fuel, and carbon sequestration. This trend is counter to the SDG of “responsible consumption and production” (i.e. SDG 12). Also, due to the high capital cost associated with CDR technologies, deploying these technologies at scale has the potential to exacerbate the average cost of energy. Relatively, the increase in energy prices can have adverse effect affordability of energy (i.e. SDG (Affordable and clean energy)). Finally, the result shows other potential security trade-offs in the food and water sectors. Overall, the results provide instructive policy insights about the importance of designing strategies that balance the short and long-term costs and risks of net-zero and CDR technologies.
Leveraging clustering and geostatistics to improve the modeling of sub-grid land-atmosphere interactions in Earth system models
Authors: Chaney Nathaniel , Torres-Rojas Laura , Simon Jason
Published: March 2021

Multi-scale spatial heterogeneity over the land surface (meter to km scales) can play a pivotal role in the development of clouds and precipitation. To model this process within Earth system models (ESMs; ~100 km spatial resolution), sub-grid reduced-order modeling approaches are used. More specifically, state-of-the-art ESMs sub-divide the land surface of each grid cell into representative clusters (e.g., forest, lakes, and grasslands) that are learned a-priori from available high-resolution satellite remote sensing data (e.g., STRM, Landsat and Sentinel-2) via clustering. However, until recently, these clusters have remained spatially agnostic making it infeasible to infer spatial statistics of the modeled sub-grid heterogeneity over land that are required by the atmospheric model to ensure proper development of simulated convection (e.g., spatial correlation length of surface evaporation). This presentation will introduce an approach that leverages the precomputed cluster positions in space to construct an effective and efficient approach to assemble the experimental semivariogram from the sub-grid clusters within ESMs. As a proof of concept, we will show results by applying the novel method on sub-grid model output from the HydroBlocks land surface model over a 100 km domain centered at the Southern Great Plains site in Oklahoma, United States. Furthermore, to illustrate the added-value that the experimental semivariograms will have towards improving the modeling of land-atmosphere interactions, we will illustrate the results from large-eddy simulations over the domain that show how differences in correlation length of surface fluxes can have, at times, a dramatic impact on the development of clouds and convection in the atmosphere. When implemented in ESMs, this new approach will make it possible to infer the modeled sub-grid spatial organization of the surface fluxes (e.g., sensible heat flux) per time step with negligible increases in computation expense.
Vertical distribution of excess ice in icy sediments and its statistical estimation from geotechnical data (Tuktoyaktuk Coastlands, Northwest Territories)
Authors: Castagner Ariane , Gruber Stephan , Brenning Alexander
Published: March 2021

Excess ice can be found in the form of massive ice and within icy sediments and is an important variable to quantify as it strongly influences the geomorphic response of landscapes to permafrost thaw. The melting of excess ice in the Western Canadian Arctic has led to thaw subsidence and an increase in the number and size of thaw slumps observed across the Northwest Territories which cause issues to Northern infrastructure and affect fluvial and lacustrine watersheds. The Inuvik-Tuktoyaktuk Highway (ITH) is the first all-weather road to reach the Canadian Arctic Coast and its planning and construction has resulted in a significant cryostratigraphic dataset of 566 boreholes, which forms the basis of this contribution. Although visible ice is often recorded in boreholes, it is not a reliable measure of excess ice content on its own and there is currently no reliable method to estimate the excess ice content of boreholes based on commonly available geotechnical data. In this study, a 16-borehole subset of the ITH dataset for which samples were processed for volumetric excess ice content is used to train a beta regression model that predicts the excess ice content of stratigraphic intervals in the study area based on interval depth, visible ice content, surficial geology, and material types. The resulting predictions are compared to recorded massive ice intervals in the same boreholes and show that excess ice within icy sediments can significantly contribute to potential thaw strain and should be considered alongside massive ice when making thaw strain estimates.
Estimating the diffusion length in the deepest section of ice cores; A case study for MIS19 in Dome-C
Authors: Laepple Thomas , Münch Thomas , Kunz Torben , Casado Mathieu , Hoerhold Maria
Published: March 2021

To recover very old climate information from ice core records, one needs to interpret the deepest part of an ice core. As the oldest record, the Dome-C ice core can serve as an analogue for the Beyond EPICA Oldest Ice Core that is currently being drilled.

Pol et al., EPSL 2010 analyzed high resolution water isotope data from the Dome-C ice core and found evidence for a limited preservation of climate variability in the deep section of the core due to mixing and diffusion. For instance, for Marine Isotope Stage 19, the study estimated a mixing/diffusion length between 40 and 60 cm, a value more than double than what is predicted by current firn and ice diffusion models. Knowing the diffusion length is important to interpret the isotope signal and is the basis to deconvolve climate records. As a result, it is key to bridge the gap in the estimation of the diffusion length between potentially biased statistical methods and firn and ice diffusion models.
We review this diffusion length estimate for MIS19, and also outline a new general method how to estimate the diffusion length in highly thinned deep ice.  This approach presents an important tool for better characterizing the preservation of the climate signal in old ice and thus for designing optimal sampling and recovery strategies.

 
Observing Baltic Sea exchanges: results from a new multi-platform autonomous observatory
Authors: Queste Bastien , Swart Sebastiaan , Biddle Louise
Published: March 2021

The Skagerrak and Kattegat are a narrow and shallow channel separating the North Sea and Baltic Sea. This highly dynamic area plays a key role in transforming water masses which flow into and oxygenate deep regions of the Baltic. This site is also a region of important carbon export, through advection down into and through the Norwegian Trench. This rich and productive ecosystem is strained by intensive human activity and shows strong coupling between biological and physical processes at a range of scales. 

We present data from a new autonomous observatory funded by the Voice of the Ocean Foundation. We compare data obtained from two underwater gliders and autonomous surface vehicles with that collected through regional monitoring programmes. Empirical variograms highlight the strong coupling between biological and physical parameters and the prevalence of small-scale processes not usually resolved in this region. We also present event-scale case studies showing variability in the coastal current and small scale export events. Finally, we outline the technical infrastructure and innovations of the Voice of the Ocean observatories and how to access its open data. 
Climate response to anthropogenic aerosols and related SST variabilities including ENSO in the Asian monsoon region
Authors: Kitabayashi Sho , Takahashi Hiroshi G.
Published: March 2021

Over the past decades, the emission of anthropogenic aerosols in the Asian monsoon region is increasing. This change alters the climate condition, such as the Asian monsoon precipitation, through the aerosol–radiation and –cloud interactions (ACI). Previous studies pointed out that the slow response to aerosols, through the SST change induced by ACI, particularly around the Maritime Continent (MC), was the primary component of climate response to aerosols. Dynamical ocean feedbacks through ACI modify the Asian monsoon circulations and precipitation. Over and around the MC, the amount of aerosol was likely to be affected by the El Niño–Southern Oscillation (ENSO). 

The aim of the study is to evaluate the climate response to anthropogenic aerosols in the Asian monsoon region. Also, we understand the relationship with SST change, including ENSO. To isolate the impact of anthropogenic aerosols, we analyzed the historical climate experiment (HIST) and the climate experiment with fixed aerosols at the preindustrial era (hist-piAer), which were provided in the CMIP6. As a result, the climatological mean surface air temperature in HIST was lower over most parts of the world than that in hist-piAer. However, a warm surface air temperature signal was found in the northern part of India, particularly in JJA during the rainy season. Also, there were dry signals in India and other Eurasia regions. We will also analyze fixed-SST historical simulation to identify physical process, including SST-related process.
Information content in the rainfall observed by INSAT-3D and IMERG: An intercomparison study over the north eastern region of India
Authors: Chakravorty Aniket , Kundu Shyam Sundar , Raju Penumetcha Lakshmi Narasa
Published: March 2021

There has been a noticeable increase in the application of artificial intelligence (AI) algorithms in various areas, in the recent past. One such area is the prediction of rainfall over a region. This application has seen crucial advancement with the use of deep sequential learning algorithms. This new approach to rainfall prediction has also helped increase the utilization of satellite data for prediction. As, AI based prediction algorithms are based on data, the characteristics of it dominates the accuracy of the prediction. And one such characteristic is the information content in the data being used. This information content is classified into redundant information (information of past states in the current state) and new information. The performance of the AI based rainfall prediction depends on the amount of redundant information present in the data being used for training the AI model, more the redundant information (less the new information content) more accurate will be the prediction. Various entropy based measure have been used to quantify the new information content in the data, like permutation entropy, sample entropy, wavelet entropy, etc. This study uses a new measure called the Wavelet Entropy Energy Measure (WEEM). One of the advantages of WEEM is that it considers the dynamics of the process spread across different time scales, which other information measures have not considered explicitly. Since, the dynamics of rainfall is multi-scalar in nature, WEEM is a suitable measure for it. The main goal of this study is to find out the amount of information being generated by INSAT-3D and IMERG rainfall at each time step over the North Eastern Region of India, which will dictate the suitability of the two rainfall product to be used for AI based rainfall prediction.
Isotopic evidence reveals  persistent microbial residues in soil
Authors: Hofmockel Kirsten , Bell Sheryl , Kasanke Chris
Published: March 2021

Microbial derivatives and necromass are dominant sources of soil organic matter (SOM), yet the specific microbiological and geochemical reactions leading to the persistence of microbial compounds in SOM remains to be discovered. Identification of the microbial taxa and classes of microbial-derived compounds that are selectively preserved may enhance our ability to manage SOM, particularly in agroecosystems. We examined how perennial and annual biofuel cropping systems influence the production and selective preservation of microbial residues. Our experiment was replicated on a sandy and a silty loam to test the relative importance of microbial (biotic) and mineral (abiotic) filters on necromass accumulation and persistence. Using a 13C-labeling incubation experiment, we tested the effects of cropping system and soil texture on the production and persistence of microbial-derived residues. Soils were collected from sandy loams at the Kellogg Biological Station (MI, USA) and silty loams at the Arlington Agricultural Research Station (WI, USA). These soils were amended with 13C-labeled glucose, which was rapidly incorporated into microbial biomass. After 2 months, ~50% of the added 13C remained in the bulk soil. Approximately 30% of the 13C remaining in the bulk soil was recovered in the lipid, protein, and metabolite pools. Lipids contained the most 13C (16%) and the contribution was similar in both soils. Both soils had similar protein pools, but protein from the sandy loam was significantly more enriched than protein from the silty loam. The pool of metabolites was small, but highly enriched, suggesting substantial recycling over the 2-month incubation. The majority (40%) of the whole soil 13C persisted in the SOM even after repeat extractions. The remaining ~30% of the whole soil 13C was recovered in a complex of remaining unknown debris that separates from the soil at the solvent interphase with the protein but could not be solubilized. We provide novel evidence of the carbon pools that contribute to persistent microbial residues in soil. Our results suggest that metabolites may be more important than was previously recognized. Ongoing work is identifying the labeled metabolites and characterizing the chemistry of the highly enriched protein residue fraction.
Virtual energy storage-gain due to spatiotemporal coordination of wind-, solar- and hydropower over Europe
Authors: Wörman Anders , Mewes Daniela , Riml Joakim , Bertacchi-Uvo Cintia , Pechlivanidis Ilias
Published: March 2021

The functionality of a renewable electricity system in Europe depends on long-term climate variations, uneven spatiotemporal distribution of renewable energy, and constraints of storage and electric transmission. In particular, hydropower offers a large capacity for energy storage and production flexibility, but only stands for a minor part of the total energy potential. Here we explored the spatial and temporal power variance of a combined system consisting of wind-, solar- and hydropower availability for a 35-year period based on historical hydro-meteorological data from large parts of Europe. A spectral analysis of these historical time-series shows that spatiotemporal coordination within the power system can potentially contribute with a “virtual” energy storage capacity that is many times higher than the actual energy storage capacity contained in the existing hydropower reservoirs in Europe. Such virtual energy storage capacity implies reduced water storage demand, hence, indirectly contributes to reduced constraints of the food-water-energy nexus also in a wider system perspective. This study focused on the theoretical maximum potential for virtual energy storage, but the feasibility of this potential is limited by the uncertainty associated with production optimization and the meteorologic forecasts of future energy availability.
Observation of a giant tabular iceberg calved from Amery Ice shelf based on multiple remote sensing data
Authors: Liu Xuying
Published: March 2021

Amery Ice Shelf is  the largest ice shelf in East Antarctica. Large calving event occurs every thirty to forty years as recorded. The latest calving event happened in September 2019, leading to the birth of a giant tabular iceberg. We used satellite imagery and altimeter data from multiple sources to monitor the evolution of the iceberg from October 2019 to October 2020. The evolution of iceberg area is measured with Sentinel-1 images,  and the change of freeboards was derived from CryoSat-2, Sentinel-3 SRAL, and ICESat-2 profiles. Compared with topography of Amery Front before calving, we found the temporal freeboards of the iceberg show a trend of descending after calved from Amery Ice Shelf, which indicates overall basal melting process. While the freeboards of Amery Front remain stable within a year before calving. We also calculated the freeboard changes of  30 footstep intersections from different altimeter profiles on the iceberg. The results show different changing patterns of freeboards, varying from  4.72m to -3.1m, which indicates there is basal re-freezing process as well as basal melting at the bottom of the iceberg. Furthermore, we studied the correlation between freeboard change and sea surface temperature. This study reveals that the use of different remote sensing data can provide more detailed observations on Antarctic icebergs.