bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent trajectory of ocean heat uptake estimated from novel 1972-2017 ocean sea-ice model hindcast simulations
Authors: Huguenin Maurice , Holmes Ryan , England Matthew
Published: March 2021

Uptake and storage of heat by the ocean plays a critical role in modulating the Earth's climate system. In the last 50 years, the ocean has absorbed over 90% of the additional energy accumulating in the Earth system due to radiative imbalance. However, our knowledge about ocean heat uptake (OHU), transport and storage is strongly constrained by the sparse observational record with large uncertainties. In this study, we conduct a suite of historical 1972–2017 hindcast simulations using a global ocean-sea ice model that are specifically designed to account for a cold start climate and model drift. The hindcast simulations are initialised from an equilibrated control simulation that uses repeat decade forcing over the period 1962-1971. This repeat decade forcing approach is a compromise between an early unobserved period (where our confidence in the forcing is low) and later periods (which would result in a shorter experiment period and a smaller fraction of the total OHU). The simulations are aimed at giving a good estimate of the trajectory of OHU in the tropics, the extratropics and individual ocean basins in recent decades. Many modelling studies that look at recent OHU rates so far use a simpler approach for the forcing. For example, they use repeating cycles of 1950-2010 Coordinated Ocean Reference Experiment (CORE) forcing that is consistent with the Ocean Model Intercomparison Project 2 (OMIP-2). However, this approach cannot account for model drift. The new simulations here highlight the dominant role of the extratropics, and in particular the Southern Ocean in OHU. In contrast, little heat is absorbed in the tropics and simulations forced with only tropical trends in atmospheric forcing show only weak global ocean heat content trends. Almost 50% of the heat taken up from the atmosphere in the Southern Ocean is transported into the Atlantic Ocean. Two-thirds of this Southern Ocean-sourced heat is then subsequently lost to the atmosphere in the North Atlantic but nevertheless this basin gains heat overall. Our results help to estimate the large-scale cycling of anthropogenic heat within the ocean today and have implications for heat content trends under a changing climate.
Velocity changes across the Ganos segment of the North Anatolian Fault Zone in NW Turkey from systematic variations in body wave arrival times
Authors: Yalcinkaya Esref , Bohnhoff Marco , Martinez-Garzon Patricia , Görgün Ethem , Pınar Ali , Alp Hakan
Published: March 2021

Imaging and characterizing transform fault sections that are capable to produce large earthquakes is crucial for evaluating seismic hazard and subsequent risk for nearby population centers. The Marmara Fault near the megacity of Istanbul is one of the best defined seismic gaps in the world and its complexity is captured by seismological, geodetic and geological data. A local dense seismic array (MONGAN) provides a high resolution data set allowing to image the Ganos fault separating two different geological units in the western Marmara region. First results of the waveform analysis from this array present systematic early-phase arrivals at the seismic stations located on the northern block of the Ganos fault which comprises geological units including older and more compact materials than that of the southern block. This difference in the arrival times causes the earthquake epicenters to shift further north than the real locations. In this preliminary results, the early-arrivals will be evaluated according to source azimuths and distances, and possible earth models and wave paths will be discussed. The results have implications for rupture directivity during future earthquakes as input for hazard and risk models for the Marmara region.
Ostwald’s step rule: a consequence of growth kinetics and nano-scale energy landscape
Authors: Meister Patrick
Published: March 2021

In his 1897 article on the formation and transformation of solid phases, Friedrich Wilhelm Ostwald described the phenomenon that hydrous sodium chlorate precipitates from an oversaturated solution, despite the fact that this phase is much more soluble than the non-hydrous salt. The fundamental concept, also known as Ostwald’s step rule, is best summarized on page 307 of his article (here translated to English):

“... Such phenomena also frequently occur during melting and condensation of steam and even in homogeneous chemical reactions, and I would like to summarize the previous experiences with this matter in the single phrase that during departure from any state, and the transition to a more stable one, not the under given circumstances most stable state is reached, but the nearest one.“

Despite its major importance for mineral formation under Earth’s surface conditions, this concept is still not fully understood on a mechanistic level. While Ostwald’s step rule is commonly explained with the classical nucleation theory, there are several inconsistencies, especially the conundrum that sometimes stable phases, such as dolomite or quartz, do not form as long as a metastable phase is supersaturated. I propose an alternative interpretation that would be consistent with Ostwald’s (1897) original formulation as well as with several observations from natural environments and laboratory experiments. If “nearest” (in German: “nächstliegend”) is not understood as “thermodynamically most similar”, but as the phase with the lowest kinetic barrier, Ostwald’s step rule should be always valid. The kinetic barrier is surface specific and independent of supersaturation, but it depends on the atomic scale interfacial energy landscape. This concept would better represent the power of Ostwald’s step rule to explain mineral formation processes and how they are affected by chemical and biological influences. New nano-scale analytical techniques in combination with advanced molecular dynamic modelling bear great potential to explain and appreciate the importance of Ostwald’s step rule.
Cross-Bedding and Structural Mapping for Rockfall Assessment of a Tunnel using Hi-Resolution LiDAR (Fribourg, Switzerland)
Authors: Choanji Tiggi , wolff Charlotte , Fei Li , Loiotine Lidia , Gutierrez Amalia , Sun Chunwei , Derron Marc-Henri , Carrea Dario , Jaboyedoff Michel
Published: March 2021

Lithology identification and discontinuity mapping are necessary for rockfall hazard assessment in tunnels. However, the restricted exposure and variability of rock face orientation in tunnels ought to be taken into account. Therefore, using Light Detection and Ranging (LiDAR) technique may significantly contribute to this task.

A historical carved tunnel in the Upper Marine Molasse (a poorly consolidated sandstone) of the City of Fribourg (Switzerland) was then investigated by fieldwork and LiDAR. Interestingly, it appears that in addition to joints and layering, some specific sedimentary structures, i.e. cross-bedding, have an important role in the tunnel roof stability. Cross-bedding is a sedimentary structure that can be identified clearly by the geometry of layer within one or more beds in a series of rock strata that does not run parallel to the plane of stratification.

In order to detect and analyse these sedimentary structures, the intensity of the backscattered LiDAR signal is analysed using the Oren-Nayar reflectance model, which considers range, incidence angle, scanned surface geometry (i.e. roughness). It provides corrected values of intensities that make possible to distinguish and identify geometry of cross-beddings in the tunnel.

An analysis of structural discontinuities was also performed using Coltop Software which identified joint sets developed inside the tunnel. Based on this approach, lithology characterizations, orientation of each discontinuity and bedding structures could be identified in point clouds confidently for understanding the mechanisms of potential rockfalls in the tunnel.
Fluid pressurisation and earthquake propagation in the Hikurangi subduction zone
Authors: Aretusini Stefano , Meneghini Francesca , Spagnuolo Elena , Harbord Christopher , Di Toro Giulio
Published: March 2021

In subduction zones, seismic slip at shallow crustal depths can lead to the generation of tsunamis. Large slip displacements during tsunamogenic earthquakes are attributed to the low coseismic shear strength of the fluid-saturated and non-lithified clay-rich fault rocks. However, because of experimental challenges in confining these materials, the physical processes responsible of the coseismic reduction in fault shear strength are poorly understood. Using a novel experimental setup, we measured pore fluid pressure during simulated seismic slip in clay-rich materials sampled from the deep oceanic drilling of the Pāpaku thrust (Hikurangi subduction zone, New Zealand). Here we show that seismic slip is characterized by an initial decrease followed by an increase of pore pressure. The initial pore pressure decrease is indicative of dilatant behavior. The following pore pressure increase, enhanced by the low permeability of the fault, reduces the energy required to propagate earthquake rupture. We suggest that thermal and mechanical pressurisation of fluids facilitates seismic slip in the Hikurangi subduction zone, which was tsunamigenic about 70 years ago. Fluid-saturated clay-rich sediments, occurring at shallow depth in subduction zones, can promote earthquake rupture propagation and slip because of their low permeability and tendency to pressurise when sheared at seismic slip velocities.
Stable isotope (carbon, hydrogen) variation in plants and lake surface sediments from northwestern Canada
Authors: Lattaud Julie , Haghipour Negar , Eglinton Timothy , Broeder Lisa
Published: March 2021

Hydrogen isotope ratios of leaf waxes are used to reconstruct past hydroclimate because they are correlated to meteoric/growth water hydrogen isotopes. The interpretation of these signatures from ancient sedimentary archives relies on a thorough understanding of the drivers of modern isotope variability. Studies in the high latitudes, regions that are particularly valuable in light of their vulnerability to rapid climate change, are scarce. We studied modern vegetation (22 plants) in two areas in the Northwestern Territories (Canada): Herschel Island and Peel Plateau, to understand the stable isotope variability found in plants of Arctic regions. Bulk biomass stable carbon isotope and radiocarbon composition have been measured as well as fatty acids (wax lipids coating the plant leaves) stable carbon and hydrogen isotopes. Furthermore, lake surface sediments and river bank sediments from the Mackenzie River Delta (surrounded by the same plants) have been similarly studied. Bulk carbon isotope composition of the plants show strong difference between plant type, i.e. herbs, shrubs, lichen and moss, as shown in previous studies. Whereas the commonly used average chain length (ACL) is not useful to differentiate the plants. In term of compound-specific isotope ratios, herbs are generally 2H-enriched in comparison to shrubs as shown in other regions of the world, and the C28 fatty acid present the most differences amongst plant type (from ~ -207‰ for herbs to ~ – 240‰ for shrubs). No major difference between the areas is noted indicating that the ~ 250 km (Herschel Island 69.5⁰N and Peel Plateau 67.3⁰N) have no impact on the hydrogen isotope composition of the fatty acids. As such we decided to compare the plant with the lake surface sediments (from the Mackenzie Delta, located between Herschel Island and the Peel Plateau). Short-chain fatty acids, sourced from organisms growing in the lake, from isolated lakes shows 2H-enriched isotopic values indicating the effect of increased evaporation in the lake during summer plant growth. Whereas long-chain fatty acids do not show any differences and are enriched compared to the shorter-chain (~ -260‰ for long-chain vs ~ -260‰ to - 280‰ for short-chain). In conclusion, differences between plant fatty acids seems to be best represented by the C28 fatty acid, indicating the potential to reconstruct past vegetation and hydrological conditions in the region using lacustrine archives.
What mechanisms trigger coastal flow slides?
Authors: Barrineau Patrick
Published: March 2021

Some beaches regularly experience a rapid decrease in volume due to ‘coastal flow slides’. These events visually resemble subaerial landslides, but are subaqueous and located along river or tidal channels. Along a steeper shoreface, material eroded from the upper beach can be stored in deep water. In some cases, these events can remove thousands of cubic meters (m3) of beach sand in a few hours.

On several occasions in recent years, a flow slide has formed at Seabrook Island, South Carolina (USA). As of January 2021, there have been five events observed since July 2016. Surveys of a January 2017 event show the slide displaced ~25,000 m3 into deep water (15–20 m) along North Edisto River Inlet. This volume is comparable to hillside-scale slides observed in mountainous regions like the Blue Ridge, and similar-scale failures have been observed in the Netherlands, France, and Australia (Mastbergen, 2019).

The Seabrook flow slide is consistently located along a marginal flood channel of a relatively large ebb-dominant inlet, just below a quarrystone revetment protecting an upland development. In this particular location, erosion of the dry beach could cause undermining of the revetment. Historical charts suggest a small inlet was located along this portion of the beach as recently as ~1920. Reviews of available rainfall and water level data suggest exceptional (ie – near-record daily total) rainfall events and spring tide levels may coincide with observed flow slide events.

This study analyzes available meteorological, water level, geotechnical, and historical shoreline data to identify mechanisms affecting repeat coastal flow slide events at Seabrook Island (SC). A combination of excessive rainfall, spring tidal currents, and sediment characteristics all appear to affect these events. Because of the unpredictability of these events, and the dynamic nature of the inlet channel adjacent to this portion of the island, it is difficult to observe events in situ and identify specific mechanisms triggering flow slides. While a hard structural solution is unlikely to effectively mitigate the hazard in this location, providing an excess of beach sand may help maintain a shallower shoreface slope and mitigate future flow slides.
RAT (Robustness Assessment Test): a straightforward evaluation of hydrological model robustness to a changing climate
Authors: Andréassian Vazken , Santos Léonard , Sonnenborg Torben , de Lavenne Alban , Lindström Göran , Nicolle Pierre , Thirel Guillaume
Published: March 2021

Hydrological models are increasingly used under evolving climatic conditions. They should thus be evaluated regarding their temporal transferability (application in different time periods) and extrapolation capacity (application beyond the range of known past conditions). In theory, parameters of hydrological models are independent of climate. In practice, however, many published studies based on the Split-Sample Test (Klemeš, 1986), have shown that model performances decrease systematically when it is used out of its calibration period. The RAT test proposed here aims at evaluating model robustness to a changing climate by assessing potential undesirable dependencies of hydrological model performances to climate variables. The test compares, over a long data period, the annual value of several climate variables (temperature, precipitation and aridity index) and the bias of the model over each year. If a significant relation exists between the climatic variable and the bias, the model is not considered to be robust to climate change on the catchment. The test has been compared to the Generalized Split-Sample Test (Coron et al., 2012) and showed similar results.

Here, we report on a large scale application of the test for three hydrological models with different level of complexity (GR6J, HYPE, MIKE-SHE) on a data set of 352 catchments in Denmark, France and Sweden. The results show that the test behaves differently given the evaluated variable (be temperature, precipitation or aridity) and the hydrological characteristics of each catchment. They also show that, although of different level of complexity, the robustness of the three models is similar on the overall data set. However, they are not robust on the same catchments and, then, are not sensitive to the same hydrological characteristics. This example highlights the applicability of the RAT test regardless of the model set-up and calibration procedure and its ability to provide a first evaluation of the model robustness to climate change.

 

References

Coron, L., V. Andréassian, C. Perrin, J. Lerat, J. Vaze, M. Bourqui, and F. Hendrickx, 2012. Crash testing hydrological models in contrasted climate conditions: An experiment on 216 Australian catchments, Water Resour. Res., 48, W05552, doi:10.1029/2011WR011721

Klemeš, V., 1986. Operational testing of hydrological simulation models, Hydrol. Sci. J., 31, 13–24, doi:10.1080/02626668609491024

 
Validation of satellite OClO products from S5P/TROPOMI and MetopA and B/GOME2 
Authors: Pinardi Gaia , Van Roozendael Michel , Hendrick François , Meier Andreas , Richter Andreas , Wagner Thomas , Gu Myojeong , Friess Udo , Strong Kimberly , Brognar Kristof , Alwarda Ramina , Querel Richard , Yela Margarita , Prados-Roman Cristina , Valks Pieter
Published: March 2021

Chlorine dioxide is an indicator for chlorine activation in the stratosphere, of importance for understanding spring-time ozone depletion processes in the polar regions of both hemispheres. Within the EUMETSAT AC SAF working group, chlorine dioxide (OClO) was retrieved from the GOME-2 instruments on MetOp-A and MetOp-B platforms, respectively over the time periods 2007-2016 and 2012-2016. Moreover, recent work performed as part of the S5p+ Innovation programme has led to the creation of an additional dataset derived from the TROPOMI instrument, extending the OClO time series in 2018-2020.

This study analyses the quality of both OClO slant column (SCD) datasets by comparing them to ground-based DOAS zenith-sky measurements at a selection of 8 stations in Arctic and Antarctic regions: Eureka (80°N), Ny Alesund (79°N), Kiruna (68°N), Harestua (60°N), Marambio (64°S), Belgrano (78°S), Neumayer (71°S) and Arrival Heights (78°S). To allow for comparison with satellite data, ground-based OClO spectral analyses are performed using yearly fixed reference spectra recorded at low SZA in the absence of chlorine activation. Furthermore, an additional bias-correction is applied in post-processing to generate a consistent long-term OClO data record covering the 2007-2020 period.

Daily comparisons of satellite and ground-based SCD data pairs corresponding to similar SZA conditions are performed, assuming similar stratospheric light paths in satellite nadir and ground-based zenith-sky geometries. Daily mean OClO SCD time-series show that satellite and ground-based observations agree well at all stations in terms of short-term variability and seasonal variation. Linear regression plots show a correlation coefficient R of about 0.97, a slope of 0.9 and an intercept of less than 1x1013 molec/cm² for TROPOMI, while for GOME-2 results are more noisy and tend to be biased low, with correlation coefficients between 0.76 and 0.88, slopes between 0.65 and 0.74 and intercepts up to 2.4 x1013 molec/cm².
Analysis of the spatial distribution and characteristics of the rock glaciers in the Ampato, Vilcanota and La Viuda Cordilleras southern and central Peru 
Authors: Medina Katy , Loarte Edwin , Badillo-Rivera Edwin , León Hairo , Bodin Xavier , Huggel Christian
Published: March 2021

Rock glaciers (RG) are visual evidence of mountain permafrost, and are one of the most important geomorphological features in the Peruvian Andes. The main objective of this research was to determine the spatial distribution of RG, their degree of activity, as well as their morphological and climatic characteristics in Cordilleras Vilcanota (Southeast), Ampato (Southwest) and La Viuda (Center). For this study, we used high-resolution images from Google Earth-Pro, SASPlanet and a DEM ALOS PALSAR (12.5 m) to identify and digitize the RG based on their geomorphological attributes, and we derived  the potential incoming solar radiation (PISR), based on the DEM . The WorldClim dataset (1970-2000) was used to determine the mean annual air temperature (MAAT) and the precipitation in the analyzed zones.

The Cordillera Ampato, with 139 RGs, presents the lowest minimum altitude of the RGs inventory (4537 m a. s. l.), the lowest MAAT (-0.4°C), lower slope (18°) and concentrates the highest PISR (1083 kWh/m2). The Cordillera Vilcanota concentrates a lower number of RGs (54), a higher minimum altitude of RGs (4733 m a. s. l.) and a relatively higher MAAT (1.9°C). Comparing both southern Cordilleras with respect to Cordillera central (La Viuda), it has the lowest amount of RG (8), a higher minimum altitude of RG (4747 m a. s. l.), higher slope (23°), higher MAAT (2.2°C) and lower persistence of snow cover. With regard to the RG activity, it was found that the quantity of active RG compared to inactive RG is in a proportion of 1.6 in Cordillera Ampato and 0.2 in Cordilleras Vilcanota and La Viuda.

Finally, the spatial distribution analysis shows that the greatest amount of RGs is located in the southern zone, decreasing towards the northern regions of Peru while the opposite occurs with the average MAAT of the RG, that is, the MAAT decreases as the RG moves to southern regions of Peru. On the other hand, the SW zone (dry climate) concentrates the largest amount of RG compared to the SE zone (wet climate). In addition, the topoclimatic parameters condition the formation of RG in the Cordilleras of study. 
Internal Wave Generation by a Combination of Tidal and Steady Currents
Authors: Bai Xiaolin , Lamb Kevin , da Silva José
Published: March 2021

In the presence of topography, two main contributors for internal wave energy are tide-topography interaction transferring energy from the barotropic tide to internal tides, and lee wave generation when geostrophic currents or eddying abyssal flows interact with topography. In the past few decades, many studies considered the respective contribution of the oscillating flows or steady background flows, but few investigations have considered both.  

In this talk, we consider the joint effects of tidal and steady currents to investigate internal wave generation and propagation on the Amazon shelf, a hotspot for internal solitary wave (ISW) generation. The Amazon Shelf is off the mouth of the Amazon River in the southwest tropical Atlantic Ocean, affected by strong tidal constituents over complex bottom bathymetry and a strong western boundary current, the North Brazilian Current (NBC). Both satellite observations and numerical modelling are used in this study. Satellite observations provide a clear visualization of the wave characteristics, such as temporal and spatial distributions, propagating direction and its relation to background currents. Based on parameters from satellite observations and reanalysis dataset, we set up a model to numerically investigate the dynamics of the ISW generation. We demonstrate that the small-scale topography contributes to a rich generation of along-shelf propagating ISW, which significantly contribute to the ocean mixing and potentially cause sediment resuspension. Moreover, the ISW-induced currents also contribute to the sea surface wave breaking as observed by satellite measurements. In addition, statistics based on a decade of satellite images and numerical investigations on seasonal variations of the ISWs and the NBC improve our understanding of the generation and evolution of these nonlinear internal waves in the presence of background currents.
Hydrology without Dimensions
Authors: Porporato Amilcare
Published: March 2021

 

Dimensional analysis offers an ideal playground to tackle complex hydrological problems. The powerful dimension reduction, in terms of governing dimensionless groups, afforded by the PI-theorem and the related self-similarity arguments is especially fruitful in case of nonlinear models and complex datasets. After briefly reviewing these main concepts, in this lecture I will present several applications ranging from hydrologic partitioning (Budyko's curve) and stochastic ecohydrology, to global weathering rates and soil formation, as well as landscape evolution and channelization. Since Copernicus-dot-org asks me to add at least 25 words to the abstract, I would like to thank the colleagues who supported my nomination for the Dalton medal and my many collaborators.
Spontaneous inertia-gravity wave generation from mesoscale eddies
Authors: Zhao Bo , Xu Zhenhua , Li Qun , Wang Yang , Yin Baoshu
Published: March 2021

An exact geostrophic vortex generate spontaneously inertia-gravity waves (IGWs) with spiral patterns via singularity instability mechanism. In the vertical direction, the energy of the IGWs is dominated by mode-1 in the generation and propagation processes, leading to weak dissipation and long-distance propagation. The amplitude of the IGWs increases linearly with the Rossby number in the range 0.04–0.1. Additionally, the IGWs emitted from an anticyclonic vortex are stronger than those radiated from the cyclonic vortex. Anticyclonic and cyclonic geostrophic vortices transfer roughly 0.54% and 0.41% of their kinetic energy to IGWs in this transient generation process, respectively. However, quasi-geostrophic mesoscale eddies are decomposed to balanced geostrophic component and unbalanced near-inertial oscillations with different timescales. Near-inertial waves (NIWs) also can be generated as a forced response to the nonlinear coupling of the geostrophic component and high-frequency oscillations of the quasi-geostrophic eddies. Afterwards, the NIWs resonate with the near-inertial oscillations and share the same horizontal wavenumbers with the eddy. Generally, an anticyclonic mesoscale eddy can emit much stronger NIWs than does a cyclonic eddy. The NIW intensity strengthens exponentially with the Rossby number. The spontaneous generated NIWs represent an effective pathway for mesoscale eddy energy skin and non-negligible contribution to the global NIW energy.
Estimating water change at Earth's surface using GRACE gravity and GPS positioning: Inferring groundwater change in the United States
Authors: Argus Donald , Wiese David , Martens Hilary , Anderson Mackenzie , Peidou Athina , Elmer Matthias , Borsa Adrian , Knappe El , Landerer Felix
Published: March 2021

We estimate change in total water and its components each month from January 2006 to the Present using geodetic observations from space and complementary hydrologic measurements.  Estimates of changes in total water inferred from GPS elastic displacements are used to strengthen the spatial resolution of GRACE observations of mass change, resulting in sharper images of water change.  We furthermore distinguish between different components of water change.  Change in surface water in man's artificial reservoirs and natural lakes are known from gauging measurements of water levels.  The distribution and magnitude of snow accumulation is inferred from sticks and scales on the ground.  We remove the effect of surface water and snow to infer change in water in the ground, consisting of soil moisture and groundwater.  This determination is bringing powerful insights into understanding the water cycle.  We are finding more water to be lost during drought and gained during heavy precipitation than in the hydrology models, suggesting that the hydrology models must be revised to have a greater capacity to store water in the ground.  Not all rain and melting snow that falls on the mountains of California, Oregon, and Washington is found to runoff into rivers taking water to the ocean.  Rain and melting snow is instead found to infiltrate the ground in the wet fall and winter and and to be parched from the ground in the dry spring and summer.

 
PFAS immobilization using in-situ application of colloidal activated carbon at a geologically complex site
Authors: Fagerlund Fritjof , Niarchos Georgios , Ahrens Lutz , Berggren Kleja Dan , Bergman Jonny , Larsson Anna , Leonard Gareth , Forde Jim , Ribeli Erik , Persson Henning , Gottby Lijana
Published: March 2021

Due to the exceptional persistence and resistance to degradation of per- and polyfluoroalkyl substances (PFASs), novel technologies for in-situ treatment and remediation of these pollutants are urgently needed. While there is still a need for more evidence from well-documented field applications, a promising technique is the use of activated carbon (AC) sorbents that can immobilize PFASs in groundwater and thereby prevent further spreading of the contaminants.

In Arboga Sweden a small fire-fighting training area connected to aviation industry is contaminated by PFAS from aqueous film forming foams (AFFFs). This site has been characterized for PFAS contamination and hydrogeological parameters affecting the spreading of contaminants with the groundwater in a few smaller site investigations since 2016 and continuous monitoring since 2018. In November 2019 colloidal activated carbon (CAC) was injected in a pilot-scale test to study the capability of CAC to immobilize PFASs in a part of the contamination plume.

The complex geology of the site made the injection of CAC challenging and special measures had to be taken to avoid excessive preferential flow of the CAC particles even at low-pressure injection. The injection pattern was modified and CaCl2 was injected downstream of the CAC injection to reduce CAC mobility and create a defined zone of CAC intercepting the PFAS plume in the groundwater, thus acting like a PFAS-immobilizing permeable barrier.

PFAS concentrations were initially reduced by 74% (for a sum of 11 PFASs) directly downstream of the CAC-barrier. However, a few months later PFAS concentrations rebounded to levels equally high or higher than before CAC injection, after which the levels have been going down again. The reasons to the rebound are likely connected to seasonal changes and fluctuations in the groundwater flow directions, causing bypass of the permeable CAC barrier. Lessons learned from applying CAC injections at this field site include the key importance of understanding the groundwater flow patterns and its temporal variability. CAC was able to produce significant reduction in PFAS concentrations (74%), but only when the PFAS plume was properly intercepted. The results illustrate the challenges with application of permeable barrier techniques particularly at geologically complex field sites. At such sites, sorbents for immobilization of PFAS plumes in groundwater should be applied in the most straightforward location where a year-round interception of the plume can be obtained.
Assigning responsibility for country-level warming to individual major emitters
Authors: Beusch Lea , Nauels Alexander , Gudmundsson Lukas , Schleussner Carl-Friedrich , Seneviratne Sonia I.
Published: March 2021

Human influence on climate is not usually disentangled in the contribution of single emitters, especially when assessing changes and impacts in individual countries. However, such information could help individual countries understand their role in driving climate change and thus aid them in committing to fair and evidence-based emission reduction targets. Here, we quantify the contribution of single emitters to country-level median warming and extremes based on historical emissions and currently pledged policy targets. Thereby, we focus on the five largest historical emitters – China, the United States of America, the European Union, India, and Russia. While large ensembles are needed for this task, the computational burden of running full Earth System Models (ESMs) renders it impossible to answer our question with actual ESMs. Instead, we combine a physical global mean temperature emulator (Meinshausen et al., 2009) with a statistical spatially-resolved ESM emulator (Beusch et al., 2020) to create millions of temperature field time series. Our setup accounts for three major sources of uncertainty: (i) uncertainty in the global temperature response to greenhouse gas emissions, (ii) uncertainty in the regional response to global warming, (iii) uncertainty due to internal climate variability. 

We find that historically rare hot years (occurring about once every 100 years in pre-industrial times) are expected at least every second year in 89 % (likely range: 71 – 100 %) of all countries by 2030. Without the emissions of the top five emitters over the time period during which policy makers had been informed about the looming anthropogenic climate crisis, i.e., after the first IPCC report of 1990, it would be 40 % (10 – 64 %) of all countries instead. Furthermore, when considering all current and projected emissions until 2030, 8 % (0 – 54 %) of countries are headed towards surpassing 2.0 °C of warming since pre-industrial times by 2030. If all nations followed the same per capita emissions as the USA since the 2015 Paris Agreement, the percentage of countries surpassing 2.0 °C by 2030 would amount to 78 % (24 – 96 %). Generally, northern high latitude countries experience the largest changes in median warming and tropical Africa the largest changes in extremes. Our results emphasize the relevance of individual emitters, and in particular the top five emitters, in driving regional climate change across different time periods.

Beusch, L., Gudmundsson, L., and Seneviratne, S. I. (ESD, 2020): https://doi.org/10.5194/esd-11-139-2020

Meinshausen, M., Meinshausen, N., Hare, W. et al. (Nature, 2009): https://doi.org/10.1038/nature08017
Ecosystem services in coastal wetlands: Investigating bio- and hydro-mechanical traits of salt marsh vegetation
Authors: Keimer Kara , Steinigeweg Charlotte , Kosmalla Viktoria , Lojek Oliver , Schürenkamp David , Schröder Boris , Goseberg Nils
Published: March 2021

Biodiversity and nature conservation play an increasingly important role with growing societal awareness, which is reflected in current European legislative frameworks such as the Marine Strategy Framework Directive or the Water Framework Directive, calling for integrative solutions and restoration of good environmental status. Salt marshes provide ecosystem services which can help mitigate climate change and sea level rise threats and simultaneously address coastal squeeze problems. The periodical submergence due to tidal changes creates a special ecosystem with different zones delineated by a landward increasing marsh elevation, which are inhabited by different plant and animal communities. In addition to their ecological value, salt marshes provide coastal protection, as they dissipate wave energy and stabilize otherwise exposed coastal soil lining sea dikes.  

The "Gute Küste Niedersachsen" research project investigates which environmental properties account for livable and safe coastal conditions along temperate climate coastlines, focusing on the symbiosis of human settlements, nature conservation and sustainable coastal protection. Specifically, the identification of vegetation-mediated ecosystem services within salt marshes at the North Sea coast of Lower Saxony, Germany is addressed here. The overarching goal of the transdisciplinary project is to gain knowledge of natural or nature-based systems and their processes within real-world laboratories at the coast to incorporate proven ecosystem services into standardized coastal protection design guidelines and promote integrated coastal zone management.

Methods include field observations and experiments, hydraulic laboratory experiments and numerical simulations over the course of 5 years. During the first years, a systematic observation of vegetation regarding distribution patterns, growth, density, and bio-mechanical (e.g. flexural rigidity, area moment of inertia) as well as root properties (e.g. root length density, tensile strength) and their respective seasonality is conducted. Through comprehensive monitoring covering large areas of halophytic meadows, a physical model of heterogeneous salt marshes will be developed. Simultaneous measurements of environmental parameters covering waves, currents and soil properties yield a comprehensive data set for analysis, numerical and analytical modeling purposes. 

Hydraulic experiments modeling the wave-vegetation-soil interaction will be devised based on field data, developing dynamically and geometrically scaled vegetation surrogates. Besides vegetation properties aboveground, a focus will be on previously sparsely considered root system effects that is hypothesized to govern erosional processes in salt marshes.
Representative climate projections for the North Sea and Baltic Sea
Authors: Dieterich Christian , Gröger Matthias , Höglund Anders , Wilcke Renate A. I. , Meier H. E. Markus
Published: March 2021

Robust estimations of uncertainty for climate projections on the regional scale are highly needed but are still challenging. Regional climate projections rely on downscaling global climate scenarios. Typically, a number of different global climate models are downscaled to assess the inherent model uncertainty. The more models, the more robust the estimate of model uncertainty. However, this strategy is time consuming and so ensembles of regional projections are usually smaller than ensembles of global projections which can lead to an underestimation of regional uncertainty. With an increasing number of available global projections regional downscaling becomes increasingly expensive. We use a regional ensemble of coupled atmosphere-ice-ocean scenarios and a ensemble of ocean-ecosystem scenarios for the Baltic Sea to explore the effect of model selection on the representation of model uncertainty. Using a number of climate indices to characterize the regional system we apply a model selection that is representative of the original ensemble in terms of ensemble spread. We use existing algorithms to generate orthogonal patterns of climate change for the Baltic Sea. A small number of patterns is used to represent the climate change and its uncertainty in physical and biogeochemical parameters of the Baltic Sea. We show that climate change signals in atmosphere, ocean and ecosystem are coherent and that atmospheric or oceanic indices can be used to select global climate models for an ensemble of representative regional ecosystem scenarios for the Baltic Sea. Since the atmospheric climate in the regional climate model is close to its representation in the global climate model that latter can be used to perform an initial model selection.
Isotopic Measurements of Carbonyl Sulfide: The First Results from Semi-continuous Outside Air Measurements in the Netherlands
Authors: Baartman Sophie L. , Popa Maria Elena , Krol Maarten , Röckmann Thomas
Published: March 2021

Carbonyl sulfide (COS) is the most abundant sulfur-containing trace gas in the atmosphere, with an average mixing ratio of 500 parts per trillion (ppt). It has a relatively long lifetime of about 2 years, which permits it to travel into the stratosphere. There, it likely plays an important role in the formation of stratospheric sulfur aerosols (SSA), which have a cooling effect on the Earth’s climate. Furthermore, during photosynthetic uptake by plants, COS follows essentially the same pathway as CO2, and therefore COS could be used to estimate gross primary production (GPP). Unfortunately, significant uncertainties still exist in the sources, sinks and global cycling of COS, which need to be overcome. Isotopic measurements of COS could be a promising tool for constraining the COS budget, as well as for investigating its role in the formation of stratospheric sulfur aerosols.

Within the framework of the COS-OCS project, we developed a new measurement system at Utrecht University, that can measure d33S and d34S from COS from small air samples of 2 to 5 L. The aim of the project is to perform a global-scale characterization of COS isotopes by measuring seasonal, latitudinal and altitudinal variations in the troposphere and stratosphere. We will present the newest results from a series of semi-continuous outside air measurements in the Netherlands during the fall and early winter of 2020/2021. The measurement results are interpreted with the help of backward trajectory analyses to characterize the influence of different wind directions and air origins on the COS concentration and isotopic composition.
Multi-decadal past and future temperature and precipitation trends in the Peruvian Andes
Authors: Potter Emily , Orr Andrew , Fyffe Catriona , Quincey Duncan , Ross Andrew , Burns Helen , Hellström Robert , Medina Katy , Loarte Edwin , Llacza Alan , Jacome Gerardo , Hosking Scott , Pellicciotti Francesca
Published: March 2021

The Peruvian Andes contain the vast majority of the world’s tropical glaciers. Warming temperatures due to climate change have caused a dramatic shrinking of these glaciers, posing a threat to water supplies. Two of the most heavily glacierised areas of Peru are the Cordillera Blanca,  which includes the Rio Santa River Basin to the north of Peru, and the Cordilleras Urubamba, Vilcabamba, and Vilcanota towards the south.

Due to the topographic and climatic complexity of the regions, spatial variations in precipitation and temperature are high, and spatially distributed high-resolution climate data can offer a crucial tool to understand those variations, in a way which is not possible from limited, individual ground stations. Here we present a new high-resolution climate dataset over both regions, created by bias-correcting Weather Research and Forecasting (WRF) model output at 4 km spatial resolution against observations. 

The spatial variation in precipitation differs over the two river basins. In the region of the Cordillera Blanca, precipitation mostly increases with elevation and distance upstream. Around the southern cordilleras, there are regions of greater precipitation near the mountains and glaciers which lie further downstream, but the high elevations of the cordillera Vilcanota, further upstream, are much drier. Analysis of the precipitation and temperature trends from 1980 to 2018 demonstrates a clear warming trend in both regions. The precipitation trends are less uniform, with the Rio Santa showing a general trend for increasing precipitation, but with a less clear trend over the higher, glacierised regions of the valley. Around the Cordilleras Urubamba, Vilcabamba and Vilcanota, there is no clear trend in precipitation over recent decades.

Using a range of CMIP5 models, the high-resolution precipitation and temperature datasets are statistically projected into the future, using quantile mapping. Future trends in precipitation and temperature are analysed over both regions, and the inter-model variability in the CMIP5 models is examined.

 
 The source characteristics and tsunami resonance effect of the 2020 Samos earthquake in Eastern Aegean
Authors: Hu Gui , Feng Wanpeng , Wang Yuchen , Li Linlin , He Xiaohui , Karakas Cagil , Tian Yunfeng
Published: March 2021

On October 30 2020 11:51 UTC, a Mw 6.9 normal fault earthquake occurred off the northern coasts of Samos Island, Eastern Aegean, Greece. Over a 120 people were killed and more than 1000 people were injured during the seismic sequence. The quake produced a moderate tsunami that swapped the coastal areas of Izmir (Turkey) and Samos (Greece) with inundation heights up to ~3 m. Finding the source of such a tsunami has been puzzling as a normal fault earthquake with Mw 6.9 would not be considered significant enough to generate metric-scale waves. Furthermore, the lack of near-field observations has made the identification of the seismogenic fault responsible for the mainshock difficult. In this study, we infer the source characteristics from multiple observation data, including InSAR, GPS, teleseismic waves and tsunami waves. We first  generate two Sentinel-1 co-seismic interferograms with a maximum Line of Sight (LOS) change of 8 cm on the coastal areas at the Samos island. We obtain a north-dipping fault model, which can slightly better explain the geodetic observations and teleseismic P waves. To understand the potential tsunami source, we use several earthquake slip models collected from different research groups to conduct tsunami simulations.  Comparing simulated tsunami waveforms with those measured at 6 local tide gauges, we show that the north-dipping fault can fit tsunami records better than the south-dipping fault. The north-dipping fault hypothesis is also further supported by the spatial distributions of the aftershocks. The spectral analysis of tsunami waveforms at selected tide gauges suggests that the tsunami period band is within 4.6 ~ 21.3 min and the primary wave period is ~14.2 min. Using this wave period as an indirect constraint, we show that the source dimension of our slip model can produce tsunami waveforms with similar wave period. We also find high-energy wave of the Samos earthquake that lasted 20 h, and fundamental oscillation periods of Sığacık Bay are remarkably close to some dominating tsunami periods. We infer the coseismic seafloor displacement alone is not enough to create disastrous effects on coastal cities; therefore we suggest that the tsunami waves may have been amplified by local coastline and tsunami resonance with local bay, or another source, e.g. triggered landslides.
Aerosol-forced AMOC changes in CMIP6 historical simulations.
Authors: Menary Matthew , Allan Richard , Robson Jon , Booth Ben , Cassou Christophe , Gregory Jonathan , Hodson Dan , Jones Colin , Mignot Juliette , Ringer Mark , Sutton Rowan , Wilcox Laura , Zhang Rong , Gastineau Guillaume
Published: March 2021

The Atlantic Meridional Overturning Circulation (AMOC) has been, and will continue to be, a key factor in the modulation of climate change both locally and globally. However, there remains considerable uncertainty in recent AMOC evolution. Here, we show that the multi-model mean AMOC strengthened by approximately 10% from 1850-1985 in new simulations from the 6th Coupled Model Inter-comparison Project (CMIP6), a larger change than was seen in CMIP5. Across the models, the strength of the AMOC trend up to 1985 is related to a proxy for the strength of the aerosol forcing. Therefore, the multi-model difference is a result of stronger anthropogenic aerosol forcing on average in CMIP6 than CMIP5, which is primarily due to more models including aerosol-cloud interactions. However, observational constraints - including a historical sea surface temperature fingerprint and shortwave radiative forcing in recent decades - suggest that anthropogenic forcing and/or the AMOC response may be overestimated.