bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetostratigraphic evidence for post-depositional distortion of osmium isotopic records in pelagic clay: implications for mineral flux estimates
Authors: Usui Yoichi , Yamazaki Toshitsugu
Published: March 2021

Deep-sea sediment sometimes lacks biostratigraphic or radiometric age constraints. Chemical stratigraphy and magnetostratigraphy is useful for dating it. Oxic pelagic clay contains Fe-Mn oxyhydroxides that can retain seawater 187Os/188Os values, and its age can be estimated by fitting the isotopic ratios to the seawater 187Os/188Os curve. On the other hand, the stability of Fe-Mn oxyhydroxides is sensitive to redox change, and it is not clear whether the original 187Os/188Os values are always preserved in sediments. However, due to the lack of independent age constraints, the reliability of 187Os/188Os ages of pelagic clay have never been tested. Magnetostratigraphy is often unsuccessful for pelagic clay older than a few Ma, which has been attributed to diagenesis. Here we report multiple polarity reversals in ca. 35 Ma pelagic clay around Minamitorishima Island, which is inconsistent with a 187Os/188Os age model. In a ~5 m thick interval, previous studies correlated 187Os/188Os data to a brief (<1 million years) isotopic excursion in the late Eocene. Paleomagnetic measurements revealed at least 12 polarity zones in the interval, indicating a >2.9 – 6.9 million years duration. Quartz and feldspars content showed that while the paleomagnetic chronology gives reasonable eolian flux estimates, the 187Os/188Os chronology leads unrealistically high values. These results suggest that the low 187Os/188Os signal has diffused from an original thin layer to the current ~5 m interval, causing an underestimate of the deposition duration. The preservation of the polarity patterns indicates that a mechanical mixing such as bioturbation cannot be the main process for the diffusion, so diagenetic re-distribution of Fe-Mn oxyhydroxides and associated Os may be responsible. The paleomagnetic chronology presented here also demands reconsiderations of the timing, accumulation rate, and origins of the high content of rare-earth elements and yttrium in pelagic clay around Minamitorishima Island. It is also indicated that old oxic pelagic clay can be a faithful paleomagnetic recorder, and success of magnetostratigraphy depends on sedimentation rate and polarity length rather than diagenesis.

Usui, Y., Yamazaki, T. Earth Planets Space 73, 2 (2021). https://doi.org/10.1186/s40623-020-01338-4
Identification and Quantification of Sediment Organic Carbon in the Inter-tidal Wetlands of Eastern Coast of China
Authors: Ding Yan , Wang Dongqi
Published: March 2021

Inter-tidal wetlands at mangroves, salt marshes and sea grass bed are important carbon reservoirs that play a significant role in climate change mitigation. However, the lack of large-scale quantification and source identification of sediment organic carbon (SOC) in inter-tidal wetlands hampers the assessment of carbon storage potential in these systems. In this research, we hypothesized that SOC in the inter-tidal wetlands of Chinese East Coast were mainly from three potential sources (terrestrial soil, marine phytoplankton, local C3 and C4 plants as mangrove and salt marsh plants ). Based on elemental ratios and stable carbon isotope of core sediment from the inter-tidal wetlands along the east coast of China, we quantified the contribution of organic carbon (OC) sources and explored the hydrological and plant drivers controlling the variations of OC source contribution among different coastal environmental settings. We found SOC in the large estuaries (river runoff more than 50 billion m3/a) originated predominantly from terrestrial soil OC (46±9%), while the primary OC source of the smaller estuaries was marine phytoplankton OC (61±14%). These results suggested that the contribution of terrestrial soil OC increased with river runoff, whereas the share of marine phytoplankton OC decreased with runoff. Moreover, while mangroves played a substantial role in carbon storage at the southern part of the coast, our estimates revealed a sharp decline in the contribution of mangrove OC since the 1980s. These findings indicate carbon storage in the inter-tidal wetlands varies among contrasting coastal environmental conditions and among wetlands with different ages, providing implications for inter-tidal wetlands as an important carbon sink in the global carbon budget.
An Assessment of CYGNSS Ocean Wind Speed Products
Authors: Hammond Matthew , Foti Giuseppe , Gommenginger Christine , Srokosz Meric , Floury Nicolas
Published: March 2021

Global Navigation Satellite System-Reflectometry (GNSS-R) is an innovative and rapidly developing approach to Earth Observation that makes use of signals of opportunity from Global Navigation Satellite Systems, which have been reflected off the Earth’s surface. CYGNSS is a constellation of 8 satellites launched in 2016 which use GNSS-R technology for the remote sensing of ocean wind speed. The ESA ECOLOGY project aims to evaluate CYGNSS data which has recently undergone a series of improvements in the calibration approach. Using CYGNSS collections above the ocean surface, an assessment of Level-1 calibration is presented, alongside a performance evaluation of Level-2 wind speed products. L1 data collected by the individual satellites are shown to be generally well inter-calibrated and remarkably stable over time, a significant improvement over previous versions. However, some geographical biases are found, which appear to be linked to a number of factors including the transmitter-receiver pair considered, viewing geometry, and surface elevation. These findings provide a basis for further improvement of CYGNSS products and have wider applicability to improving calibration of GNSS-R sensors for remote sensing of the Earth.
Large-scale siliciclastic input during the Paleocene-Eocene Thermal Maximum in the North Sea Basin
Authors: Jin Simin , Kemp David , Jolley David , Vieira Manuel , Huang Chunju
Published: March 2021

The Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) was the most marked climate warming event of the Cenozoic, and a potentially useful deep time analogue for understanding environmental responses to anthropogenic carbon emissions and associated warming. The response of sedimentary systems to the large-scale climate changes of the PETM are, however, still uncertain. Here, we present an extremely thick (~140 m) record of the PETM in cores from a well in the North Sea, offshore UK. In this well, a thick Paleocene-Eocene interval is developed owing to uplift of the East Shetland Platform in the late Paleocene. Carbon isotope data through this well, coupled with detailed sedimentological analysis, show that the PETM interval is contemporaneous with >200 sandstone turbidites layers. Mud deposition without turbidites dominated sedimentation below and above the PETM. These observations support previous work from other localities highlighting how climate warming during the PETM likely drove substantial changes in hydrological cycling, erosion and sediment supply. Spectral analysis of turbidite recurrence in the PETM interval suggests that the abundance of turbidites was modulated in part by ~21 kyr astronomical precession climate cycles, further emphasizing a potential climatic control on turbidite sedimentation. In detail, we note a kiloyear-scale time lag between onset of the PETM carbon isotope excursion and the appearance of turbidites in the succession, highlighting a delay between PETM carbon release and warming and the basin-wide response in sediment supply.
Early results of the evaluation of the JRA-3Q reanalysis
Authors: Harada Yayoi , Kobayashi Shinya , Kosaka Yuki , Chiba Jotaro , Tokuhiro Takayuki
Published: March 2021

The Japan Meteorological Agency (JMA) is conducting the third Japanese global atmospheric reanalysis named Japanese Reanalysis for Three Quarters of a Century (JRA-3Q) using the JMA operational data assimilation system that has been upgraded and improved since the Japanese 55-year Reanalysis (JRA-55) was conducted. Main points of improvement in the specifications of the data assimilation system are as follows (specifications of the JRA-55 data assimilation system are shown in parentheses for comparison): Vertical levels are increased up to 100 (60) layers; The top level of the system is 0.01 (0.1) hPa; The inner model resolution for 4D-Var is also increased up to TL319 (T106); Various parameterization schemes have been improved and several new schemes have been implemented. In addition, we use observations newly rescued and digitized by the ERA-CLIM and other projects as well as newly reprocessed and improved satellite observations. As for GNSS radio occultation, bending angle is assimilated up to 60 km (refractivity up to 30 km).

The early results show that both overestimation of precipitation in the tropics and dry bias in the middle troposphere are diminished compared with those in JRA-55, and the representation of diabatic heating rate is also improved. In addition, biases of surface heat fluxes and radiation fluxes at the top of the atmosphere are also reduced.
In-stream turbines for sustainable hydropower development in the Amazon river basin
Authors: Chaudhari Suyog , Brown Erik , Quispe-Abad Raul , Moran Emilio , Mueller Norbert , Pokhrel Yadu
Published: March 2021

Given the ongoing and planned hydropower development projects in the Amazon River basin, appalling losses in biodiversity, river ecology and river connectivity are inevitable. These hydropower projects are proposed to be built in exceptionally endemic sites, setting records in environmental losses by impeding fish movement, altering flood pulse, causing large-scale deforestation, and increasing greenhouse gas emissions. With the burgeoning energy demand combined with the aforementioned negative impacts of conventional hydropower technology, there is an imminent need to re-think the design of hydropower to avoid the potentially catastrophic consequences of large dams. It is certain that the Amazon will undergo some major hydrological changes in the near future because of the compounded effects of climate change and proposed dams, if built with the conventional hydropower technology. In this study, we present a transformative hydropower outlook that integrates low-head hydropower technology (e.g., in-stream turbines) and multiple environmental aspects, such as river ecology and protected areas. We employ a high resolution (~2km) continental scale hydrological model called LEAF-Hydro-Flood (LHF) to assess the in-stream hydropower potential in the Amazon River basin. We particularly focus on quantifying the potential and feasibility of employing instream turbines in the Amazon instead of building large dams. We show that a significant portion of the total energy planned to be generated from conventional hydropower in the Brazilian Amazon could be harnessed using in-stream turbines that utilize kinetic energy of water without requiring storage. Further, we also find that implementing in-stream turbines as an alternative to large storage-based dams could prove economically feasible, since most of the environmental and social costs associated with dams are eliminated. Our results open multiple pathways to achieve sustainable hydropower development in the Amazon to meet the ever-increasing energy demands while minimizing hydrological, social, and ecological impacts. It also provides important insight for sustainable hydropower development in other global regions. The results presented are based on a manuscript under revision for Nature Sustainability.
 Intraseasonal Variability of Cloud Cover in Midlatitudes during Boreal Winter
Authors: Satoh Reona , Nishi Noriyuki , Mukougawa Hitoshi
Published: March 2021

We investigated the spatial structure of the intraseasonal variation (15-30 day) in cloud cover in the mid-latitudes during winter. We attempted to interpret the spatial pattern of clouds in　the context of Rossby waves.

 

We used the total cloud cover in H-series dataset (1984-2016) by the International Satellite Cloud Climatology Project (ISCCP) based on the satellite observations, and ERA-Interim re-analysis data (1980-2016) including high, medium, and low cloud covers defined by σ coordinate.

 

We calculated correlation coefficients between the geopotential height at 300hPa (Z300) at a certain position and the cloud covers, meridional wind, and vertical velocity in the surrounding area. The positions of the maximum of high (0.45≧σ) and medium cloud cover (0.8≧σ＞0.45) relative to Z300 are longitudinally constant for all longitudes except the region from east Asia to western part of the Pacific. The position of the maximum of the high cloud cover is located just west of the ridge and just east of the maximum positions of the upward motions of re-analysis vertical velocity and its adiabatic component. These results suggest that the adiabatic upward motion in the southerly wind region west of the ridge contributes to the generation of high cloud cover. In contrast, the position of the maximum of medium cloud cover is located just east of the trough. The position of the maximum of diabatic upward motion, which is consider to be due to condensation process is located near the maximum of medium cloud cover. These results suggest that Rossby waves modulate activity of short-period disturbances with precipitation. Apart from high and medium cloud covers, the position of the maximum of low cloud cover (σ＞0.8) has large longitudinal dependency. While the position of the maximum is located at almost the same as that of medium cloud cover mainly over the continent, the position of the maximum is located just east of the ridge mainly over the ocean.

 

The correlation coefficients between ISCCP total cloud cover and Z300 are statistically significant only over the continent, where the positions of the maximum of high, medium, and low cloud covers are all located east of the trough and west of the ridge.
Permafrost in the Caspian Sea basin in the Late Glacier Era as a possible trigger of the sea transgression: checking the hypothesis using a hydrological model
Authors: Gelfan Alexander , Kalugin Andrey
Published: March 2021

Paleogeographic data give grounds to assert that at the end of the Valdai Ice Age, transgressions of the Caspian Sea took place, and the sea level during these periods exceeded the current one by tens of meters. The physical mechanisms, climatic or others, that could have caused such an extreme sea level rise have not yet been established. At the same time, in the modern Volga basin, traces of very large ancient river channels are widespread, which could have been formed by ancient rivers with the water flow 2-3 times larger than the modern rivers. Thus, the hypotheses of the extreme rise in the Caspian Sea level can be reduced to considering possible sources of the increase in the flow of the ancient rivers. However, the question of possible sources of such a significant river flow remains open. At the end of the Paleocene - beginning of the Holocene, precipitation over the Caspian Sea catchment was not higher than now, the contribution of melted glacial waters in the Late Glacial Era was also insignificant.  Hypotheses about significant changes in the catchment area of the Caspian Sea during those times are not confirmed by paleogeographic data either. In our work, we test the hypothesis that the river inflow into the ancient Caspian Sea could significantly exceed the current inflow due to the spread of post-glacial permafrost over the sea catchment area, which contributed to a decrease in runoff losses due to infiltration into frozen soils.

The physical validity of the above hypothesis was tested using numerical experiments with a hydrological model of the Volga River basin, developed on the basis of the ECOMAG modeling platform. Assuming that the climatic conditions in the modern Volga basin area during the Late Glacial Era were close to the current conditions, numerical experiments were carried out to simulate deep freezing of soil throughout the entire territory of the modern Volga basin area. It is shown that under permafrost conditions, the Volga River runoff increases by 15-20% and does not provide a twofold rise in water inflow into the sea, estimated from paleogeographic data. At the same time, the experiments have shown that such extreme inflow of water into the Caspian Sea could be formed under the conditions of deep freezing of soils and in the absence of seasonal thawing of the frozen catchment area, i.e. at a colder climate than the modern one.
Decadal Prediction of Marine Heatwaves in MPI-ESM
Authors: Hövel Laura , Brune Sebastian , Baehr Johanna
Published: March 2021

Marine Heatwaves (MHWs) are Sea Surface Temperature (SST) extremes that can have devastating impacts on marine ecosystems but can also impact circulation patterns in the ocean and the atmosphere. The variability of MHWs has been studied in historical observations and longterm climate projections, but predictability has only been analyzed on seasonal timescales. Here, we we present the first attempt to study the decadal predictability of MHW days per year in an ensemble of decadal hindcasts based on the Max Planck Institute Earth System Model (MPI-ESM-LR).

Our results show that there are strong regional differences in prediction skill. While many regions show little to no skill, we find in the Subpolar North Atlantic correlation coefficients up to 0.7 for MHW days up to lead year 8. We demonstrate that these correlations mainly arise from correctly predicting the absence of MHWs in individual years. MHW days per year might be successfully predicted by only using yearly mean SST as a proxy, which also demonstrates that in the Subpolar North Atlantic, any increase in SST is accompanied by more MHWs and vice versa.
Strain partitioning within thrust sheets of tectonic windows: Insights from eastern Himalaya
Authors: Das Jyoti , Bhattacharyya Kathakali
Published: March 2021

In a fold-thrust belt (FTB), penetrative strain within thrust sheets vary in its magnitude, orientation and type. Addressing variation in magnitude and orientation of strain from major thrust sheets in a FTB, both along the transport direction and along-strike, enable us to understand the complexity of strain partitioning during orogeny. Tectonic windows provide an opportunity to understand the impact of footwall structures on finite strain geometry and orientations of the overlying thrust sheets. In this study, we investigate how penetrative strain is partitioned from the internal to the external major thrust sheets in the Siang window in far-eastern Arunachal Himalayan FTB. We also compare these results with similar thrust sheets from well preserved tectonic windows in the eastern Himalaya, i.e., the Teesta window of the Sikkim and Kuru Chu window of the Bhutan Himalayan FTB.

We conduct finite strain analysis on quartz grains using Rf-φ, normalized Fry and Shape Matrix Eigenvector methods. The studied lithologies are gneiss for the internal Pelling-Munsiari-Bomdilla thrust (PT) sheet, while quartzite and sandstone dominantly comprise the external Main Boundary thrust (MBT) and the Main Frontal thrust (MFT) sheets. The rocks north of the PT sheet are not accessible. Results from this study indicate that all the studied rocks record an overall flattening strain. Magnitude of the finite penetrative strain decreases from the internal PT sheet to the external MBT, MFT sheets in the Siang window. The long axes of the finite strain ellipsoids (X) generally have a low plunge and vary in bearing, irrespective of the structural positions of the different thrust sheets. Finite strain ellipses are folded along with the thrust sheets indicating that the penetrative strain developed prior to folding of the thrust sheets. The results also indicate that the footwall structures affect the strain geometry in the interior part of the Himalayan wedge. The grain scale shortening percentage is highest for internal PT sheet and it progressively decreases towards the external MFT sheet. The results indicate greater contribution of thrust-parallel stretch than thrust-perpendicular component, in both internal and external thrust sheets in the Siang window. Preliminary results also suggest that the strain magnitude and grain-scale shortening percentage are the lowest, and orientations of X-axes are more variable with respect to the regional transport direction in the far-eastern Siang window as compared to the other westerly lying regional transects of the Himalayan FTB.
Model Description and Evaluation of FIO Earth System Model (FIO-ESM) version 2.0
Authors: Bao Ying , Song Zhenya , Qiao Fangli
Published: March 2021

The First Institute of Oceanography Earth System Model (FIO-ESM) version 2.0 was developed and participated in the Climate Model Intercomparison Project phase 6 (CMIP6). In comparison with FIO-ESM v1.0, all component models of FIO-ESM v2.0 are updated, and their resolutions are fined. In addition to the non-breaking surface wave-induced mixing (Bv), which has also been included in FIO-ESM v1.0, there are three more distinctive physical processes in FIO-ESM v2.0, including the effect of surface wave Stokes drifts on air-sea momentum and heat fluxes, the effect of wave-induce sea spray on air-sea heat fluxes and the effect of sea surface temperature (SST) diurnal cycle on air-sea heat and gas fluxes. The FIO-ESM v2.0 has conducted the CMIP6 Diagnostic, Evaluation and Characterization of Klima (DECK) , historical and futrue scenario experiments. The results of pre-industrial run show the stability of the climate model. The historical simulation of FIO-ESM v2.0 for 1850-2014 is evaluated, including the surface air temperature (SAT), precipitation, SST, Atlantic Meridional Overturning Circulation (AMOC), El Niño-Southern Oscillation (ENSO), etc. The climate changes with respect to SAT and SST global warming and decreasing AMOC are well reproduced by FIO-ESM v2.0. The correlation coefficient of the global annual mean SAT anomaly can reach 0.92 with observations. In particular, the large warm SST bias at the east coast of tropical Pacific from FIO-ESM v1.0, which is a common challenge for all climate models, is dramatically reduced in FIO-ESM v2.0 and the ENSO period within the range of 2-7 years is well reproduced with the largest variation of SST anomalies occurring in boreal winter, which is consistent with observations.
Structure and spatial-temporal relationship of potassic magmatism linked to a continental-scale strike-slip shear zone and post-collisional Cenozoic extension
Authors: Li junyu , Cao shunyun , Cheng Xuemei , Wang Haobo , Li Wenxuan
Published: March 2021

Adakite‐like potassic rocks are widespread in post-collisional settings and provide potential insights into deep crustal or crust-mantle interaction processes including asthenosphere upwelling, partial melting, lower crustal flow, thickening and collapse of the overthickened orogen. However, petrogenesis and compositional variation of these adakite‐like potassic rocks and their implications are still controversial. Potassic magmatic rocks are abundant developed in the Jinshajiang–Ailaoshan tectono-magmatic belt that stretches from eastern Tibet over western Yunnan to Vietnam. Integrated studies of structure, geochronology, mineral compositions and geochemistry indicate adakite-like potassic rocks with different deformation are exposed along the Ailaoshan-Red River shear zone. The potassic felsic rocks formed by mixing and partial melting between enriched mantle-derived ultrapotassic and thickened ancient crust-derived magmas. The mixing of the mafic and felsic melts and their extended fractional crystallization of plagioclase, K-feldspar, hornblende and biotite gave rise to the potassic magmatic rocks. Zircon geochronology provide chronological markers for emplacement at 35–37 Ma of these adakite-like potassic rocks along the shear zone. Temperature and pressure calculated by amphibole-plagioclase thermobarometry range from 3.5 to 5.9 kbar and 650 to 750 ℃, respectively, and average emplacement depths of ca. 18 km for granodiorite within this suite. In combination with the results of the Cenozoic potassic magmatism in the Jinshajiang–Ailaoshan tectono-magmatic belt, we suggest that in addition to partial melting of the thickened ancient continental crust, magma underplating and subsequent crust-mantle mixing beneath the ancient continental crust have also played an important role in crustal reworking and strongly affected the rheological properties and density of rocks. The exhumation underlines the role of lateral motion of the Ailaoshan-Red River shear zone initiation by potassic magma-assisted rheological weakening and exhumation at high ambient temperatures within the shear zone.
Resource Nexus Methodological Framework: Making the Nexus Operational
Authors: Laspidou Chrysi , Kofinas Dimitrios , Ramos Eunice Pereira
Published: March 2021

The well-established Water Energy Food Nexus, meaning the investigation of the three subsystems as a whole complex of interlinkages and trade-offs has been a revolutionary step towards holistic system thinking. More Nexuses have occurred and have been studied through the last decades, expanding the central WEF triplet. Sim4Nexus has acknowledged the importance of expanding the triplet to a quintet, also including the land uses and the climate change as core components, towards a holistic analysis that targets to climate change mitigation and adaptation actions and resource efficiency. In this work, we present the methodological framework developed and tested on multiple case studies of various particularities and scales. We present an assessment workflow of numerous steps and iterations that includes, among others, the conceptual and bio-physical modelling of the quintet synergies and trade-offs, the exploitation of existing databases and thematic models, the stakeholder mapping and engagement, the policy analysis, the formulation of narratives, the pre-nexus assessment, the workshops, the System Dynamic Modeling, the Science-Policy interface, and the Serious Gaming. The aim of this work is to transfer the experience and lessons learnt of a demanding, trans-disciplinary and intersectoral work and provide a roadmap for future Nexus—not necessarily the specific quintet—analysis efforts.
A web-based visual-analytics tool for ad-hoc campaign planning in terrestrial hydrology
Authors: Nixdorf Erik , Eggert Daniel , Morstein Peter , Kalbacher Thomas , Dransch Doris
Published: March 2021

A deeper understanding of the Earth system as a whole and its interacting sub-systems depends, perhaps more than ever, not only on accurate mathematical approximations of the physical processes but also on the availability of environmental data across temporal and spatial scales. Even though advanced numerical simulations and satellite-based remote sensing in conjunction with sophisticated algorithms such as machine learning tools can provide 4D environmental datasets, local and mesoscale measurements continue to be the backbone in many disciplines such as hydrology. Considering the limitations of human and technical resources, monitoring strategies for these types of measurements should be well designed to increase the information gain provided. One helpful set of tools to address these tasks are visual-analytical data exploration frameworks integrating qualified multi-parameter data from different sources and tailoring well-established computational and visual methods to explore and analyze it. In this context, we developed a smart monitoring workflow to determine the most suitable time and location for event-driven, ad-hoc monitoring in hydrology using soil moisture measurements as our target variable.

The Smart Monitoring workflow consists of three main steps. First is the identification of the region of interest, either via user selection or recommendation based on spatial environmental parameters provided by the user. Statistical filters and different color schemes can be applied to highlight potentially relevant regions. During the second step time-dependent environmental parameters (e.g., rainfall and soil moisture estimates of the recent past, weather predictions from numerical weather models and swath forecasts from Earth observation satellites) for those relevant regions can be evaluated to identify suitable time frames for the planned monitoring campaign. Lastly, a detailed assessment of the region of interest is conducted by applying filter and weight functions in combination with multiple linear regressions on selected input parameters. Depending on the measurement objective (e.g highest/lowest values, highest/lowest change), the most suitable areas for monitoring will subsequently be visually highlighted. Based on the common road network an efficient route for a corresponding monitoring campaign can be derived for the identified regions of interest and directly visualized in the visual-analytical environment
Multi-decadal climate variability in the tropical stratosphere coupled to the Pacific
Authors: Iglesias-Suarez Fernando , Wild Oliver , Kinnison Douglas E. , Garcia Rolando R. , Marsh Daniel R. , Lamarque Jean-François , Ryan Edmund M. , Davis Sean M. , Eichinger Roland , Saiz-Lopez Alfonso , Young Paul J.
Published: March 2021

Recent studies have noted that tropical mid-stratospheric ozone decreased in the 1990s and has remained persistently low since. Current analyses suggest that these observations are linked to dynamical processes rather than being chemically-driven, although this has not been fully explored. Using measurements and chemistry-climate model simulations, we show that 50 ± 10% of these observed trends can be accounted for through multi-decadal variability in the Brewer-Dobson circulation (BDC) tied to the Pacific Ocean sea surface temperatures (the Interdecadal Pacific Oscillation, or IPO), via dynamical and chemical couplings. Moreover, accounting for this low frequency variability in the BDC can also help interpret previous observationally-derived changes in that circulation since year 1979. Overall, these findings demonstrate strong links between stratosphere-troposphere variability at decadal time scales and their potential importance for future ozone recovery detection.
Variations in sedimentology, mineralogy and geochemistry on a turbiditic continental margin during an early Eocene negative carbon isotope excursion
Authors: Martínez-Braceras Naroa , Payros Aitor , Arostegi Javier , Dinarès-Turell Jaume
Published: March 2021

Expanded deep-marine sedimentary successions were deposited on the North Iberian continental margin in Eocene times. These deposits are well exposed along accessible coastal cliffs of the Biscay province, being of great interest for paleoenvironmental and paleoclimatic studies. This study dealt with the 110 m-thick lower Ypresian (early Eocene) succession from Solondota, which is mainly composed of hemipelagic limestones and marls interspersed with abundant turbidites.

Biomagnetostratigraphic and geochemical records allowed correlation of a prominent negative carbon isotope excursion (CIE) with the Ypresian hyperthermal event J, also known as C24n.2rH1. In order to disentangle the environmental evolution of the Solondota turbiditic area during the CIE, high-resolution sedimentological, geochemical (stable isotopes, major, minor and trace elements) and mineralogical (general and clay mineralogy) studies were carried out. The large size of the dataset hindered straightforward identification of relevant variables and interpretation of their relationships. However, a multivariate analysis provided invaluable information about significant trends and variations in the dataset, avoiding empirical or arbitrary selection of representative elements. A good correspondence was found between some elemental trends obtained from the analysis and the sedimentological and mineralogical records. Major and minor elements from the hemipelagic fraction across the Solondota CIE suggest a temporarily more humid continental climate, which caused increased terrigenous material input into the marine environment. While fine-grained terrigenous sediment boosted hemipelagic carbonate dilution, the coarser terrigenous sediment was transported by temporarily more frequent and voluminous turbidity currents. Thus, the results from the Solondota CIE show similarities with deep marine records from other early Eocene minor hyperthermal events. Taking everything into account, this study demonstrates the validity of deep-marine turbiditic successions for providing reliable sedimentological, mineralogical and geochemical records of paleoclimatic significance. Indeed, the expanded nature of turbiditic continental margin successions provides paleoenvironmental records at very high resolution, enriching, and perhaps improving, the commonly condensed and sometimes discontinuous record of hemipelagic-only successions.

 

Research funded by the Spanish Government project MCI PID2019-105670GB-I00 and the Basque Government project IT-930-16. NM-B received a pre-doctoral grant from the Basque Government and a post-doctoral Dokberri grant from the University of the Basque Country.
Beyond friction-velocity thresholds: a new look on eddy-covariance flux filtering and impact on ecosystem C flux estimates
Authors: Peltola Olli , Aurela Mika , Kolari Pasi , Mammarella Ivan , Papale Dario , Vesala Timo , Laurila Tuomas
Published: March 2021

Global eddy-covariance (EC) flux measurement networks have provided invaluable insights into ecosystem-atmosphere exchanges of gases, energy and momentum. However, EC technique underestimates surface fluxes during periods when the turbulent flow is decoupled from the surface and this deficiency casts a shade on the validity of EC flux networks. The decoupling can happen for instance when strongly stably stratified air layers or thick forest canopies inhibit vertical mixing. These so-called decoupling periods are typically identified using friction-velocity (u*) and periods when u* is below a site-specific threshold are removed from EC flux time series. This approach has at least two weaknesses: 1) it relies on uncertain site-specific threshold values and 2) it does not consider changes in processes hindering the flow coupling to the surface. Furthermore, it can be questioned whether u* is a correct metric for the strength of turbulent mixing. In this study we utilize recently proposed method which overcomes the above-mentioned weaknesses of u* filtering. The method is based on a comparison between vertical wind speed standard deviation and work done against forces (buoyancy and canopy drag) hindering the movement of a downward propagating air parcel. Via this comparison the need for site-specific thresholds is in theory alleviated. We utilize data from various contrasting EC sites to 1) evaluate whether the new method is free from site-specific thresholds also in practice, 2) compare the flux filtering methods in different conditions and 3) assess the effect of these methods on ecosystem respiration, gross primary productivity and carbon (C) balance estimates. These results will help to assess the robustness of ecosystem C flux estimates made in the past with EC and give clues on how to move forward with EC measurements during the decoupled periods.
Gravity wave driven seasonal variability of temperature differences between ECMWF IFS and lidar measurements at 54S in the lee of the Southern Andes
Authors: Gisinger Sonja , Polichtchouk Inna , Reichert Robert , Dörnbrack Andreas , Kaifler Bernd , Kaifler Natalie , Rapp Markus , Sandu Irina
Published: March 2021

In November 2017, the DLR Institute of Atmospheric Physics started running the ground-based Compact Rayleigh Autonomous Lidar (CORAL) at the southern tip of South America in Rio Grande that is located at the east coast of Argentina in the lee of the Andes. We used this independent (i.e., not assimilated in the ECMWF IFS) and high-resolution lidar data of the year 2018 and some individual months in 2019 and 2020 to investigate middle atmosphere temperature deviations in IFS analyses and short-term forecasts at higher mid-latitudes in the southern hemisphere (54 S).

 

We found a generally good agreement between IFS and CORAL temperature data below 45 km altitude and the calculated monthly mean temperature deviations are smaller than +/-2 K.  The temperature deviations are more variable in time and the sign of the monthly mean deviations varies throughout the year above 45 km altitude. There, the largest positive differences (+2 K), i.e. IFS temperatures were too warm, are found for May 2018. The largest negative differences (-10 K), i.e. IFS temperatures were too cold, are found for August 2018.  The standard deviation of the temperature differences is significantly larger (up to 15 K) and increases with altitude in the winter half year (April to September 2018) compared to the summer half year. The better agreement of IFS temperature with ground-based lidar measurements in the summer months previously reported in literature for the northern hemisphere also manifests for the southern hemisphere and more recent cycles of the IFS. The largest temperature differences above 45 km altitude in the winter half year are due to gravity waves (GWs) and it was found that amplitude and phase deviations are equally important at the location of Rio Grande. In general, the IFS underestimates GW potential energy density in the middle atmosphere, especially within the sponge layer. Monthly mean GW potential energy density at 45-60 km altitude gets up to four times larger when the sponge is removed but is still less than 50 % of the amount of GW potential energy density found in the CORAL data.

 
Decorrelative Mollifier Gravimetry
Authors: Freeden Willi
Published: March 2021

The lecture highlights arguments that, coming from multiscale mathematics, have fostered the advancement of gravimetry, as well as those that, generated by gravimetric problems, have contributed to the enhancement in constructive approximation and numerics. Inverse problems in gravimetry are delt with multiscale mollifier decorrelation strategies. Two examples are studied in more detail: (i) Vening Meinesz multiscale surface mollifier regularization to determine locally the Earth's disturbing potential from deflections of vertical, (ii) Newton multiscale volume mollifier regularization of the inverse gravimetry problem to derive locally the density contrast distribution from functionals of the Newton integral and to detect fine particulars of geological relevance. All in all, the Vening Meinesz medal  lecture is meant as an  \lq \lq appetizer'' served to enjoy the tasty meal "Mathematical Geoscience Today'' to be shared by geoscientists and mathematicians in the field of gravimetry. It provides innovative concepts and locally relevant applications presented in a monograph to be published by Birkhäuser in the book series “Geosystems Mathematics” (2021).
From avalanche-obstacle interaction processes to physics-based impact pressure calculations – an insight from DEM simulations
Authors: Kyburz Michael Lukas , Sovilla Betty , Gaume Johan , Ancey Christophe
Published: March 2021

Calculating snow avalanche impact pressure is an essential task for safe construction and hazard mapping in mountainous regions. Although the avalanche-obstacle interaction crucially depends on the flow regime, practitioners mostly assume that the impact pressure is similar to the dynamic pressure in inviscid fluids, that is, it is proportional to the square velocity weighted by an empirical drag coefficient. Field measurements indicate that the drag coefficients cover more than one order of magnitude. In the absence of a physics-based framework, setting the right drag coefficient requires good working knowledge and experience from practitioners. Indeed, even for trained engineers it may be unclear how the impact pressure depends on the expected flow regime, on obstacle width, or on terrain configuration. To address these questions, we simulate the avalanche impact pressure on obstacles of varying geometry for four distinct avalanche flow regimes using the Discrete Element Method and a cohesive contact model. The results allow us to quantify the influence of the obstacle width and shape on the average impact pressure, as well as the detailed pressure distribution on the obstacle surface. Furthermore, we propose a novel method for estimating the drag coefficient based on simple geometrical considerations and key characteristics of avalanche flow. Our results are validated using experimental data from the Vallée de La Sionne test site, and make a step forward in the derivation of a physics-based framework for computing snow avalanche impact pressures for varied flow regimes depending on obstacle shape and dimensions.
Development and characterization of a seismic source model for the Jalisco-Colima-Michoacán region, Western Mexico
Authors: Peláez José A. , Sawires Rashad , Santoyo Miguel A. , Henares Jesús
Published: March 2021

The Mexican subduction zone, the Gulf of California spreading center, as well as the triple junction point around the Jalisco and the Michoacán Blocks, represents the most active seismogenic belts inducing seismic hazard in the Jalisco-Colima-Michoacán region. Herein, considering such seismotectonic setting, we have developed a new seismic source model for the surrounding of this zone to be used as an input to the assessment of the seismic hazard of the region.

This new model is based on revised Poissonian earthquake (1787-2018) and focal mechanism (1963-2015) catalogs, as well as crustal thickness data and all information about the geometry of the subducting slabs. The proposed model consists of a total of 37 area sources, comprising the three different possible categories of seismicity: shallow crustal, interface subduction, and inslab earthquakes. A special care was taken during the delimitation of the boundaries for each area source to ensure that they represent a relatively homogeneous seismotectonic region, and to include a relatively large number of earthquakes that enable us to compute, as reliable as possible, seismicity parameters.

Actually, the sources zones were delimited following the standard criteria of assessing a probabilistic seismic hazard, being characterized in terms of their seismicity parameters (annual rate of earthquakes above Mw 4.0, b-value, and maximum expected magnitude), mean seismogenic depth, as well as the predominant stress regime. The proposed seismic source model defines and characterizes regionalized potential seismic sources that can contribute to the seismic hazard at the Jalisco-Colima-Michoacán region, providing the necessary information for seismic hazard estimates.
The signature of the tropospheric gravity wave background in observed mesoscale motion
Authors: Stephan Claudia , Mariaccia Alexis
Published: March 2021

How convection couples to mesoscale vertical motion and what determines these motions is poorly understood. We diagnose profiles of area-averaged mesoscale divergence from measurements of horizontal winds collected by an extensive upper-air sounding network of a recent campaign over the western tropical North Atlantic, the Elucidating the Role of Clouds-Circulation Coupling in Climate (EUREC4A) campaign. Observed area-averaged divergence amplitudes scale approximately inversely with area equivalent radius. This functional dependence is also confirmed in reanalysis data and a global freely-evolving simulation run at 2.5 km horizontal resolution. Based on the numerical data it is demonstrated that the energy spectra of inertia gravity waves can explain the scaling of divergence amplitudes with area. At individual times, however, few waves can dominate the region. Nearly monochromatic tropospheric waves are diagnosed in the soundings by means of an optimized hodograph analysis. For one day, results suggest that an individual wave directly modulated the satellite observed cloud pattern. However, because such immediate wave impacts are rare, the systematic modulation of vertical motion due to inertia-gravity waves may be more relevant as a convection-modulating factor. We propose an analytic relationship between energy spectra and divergence amplitudes, which, if confirmed by future studies, could be used to design better external forcing methods for regional models.
Thermodynamic optimality principles in Earth sciences
Authors: Schymanski Stanislaus J. , Dewals Benjamin , Dijkstra Henk A. , Ozawa Hisashi , Zehe Erwin
Published: March 2021

Ecohydrological systems are a result of long-term co-evolution of soils, biota and atmospheric conditions, and often respond to perturbations in non-intuitive ways. Their short-term responses can be explained and sometimes predicted if we understand the underlying dynamic processes and if we can observe the initial state precisely enough. However, how do they co-evolve in the long-term after a change in the boundary conditions? In 1922, Alfred Lotka hypothesised that the natural selection governing the evolution of biota and composition of ecosystems may be obeying some thermodynamic principles related to maximising energy flow through these systems. Similar thoughts have been formulated for various components of the Earth system and individual processes, such as heat transport in the atmosphere and oceans, erosion and sediment transport in river systems and estuaries, the formation of vegetation patterns, and many others. Different thermodynamic optimality principles have been applied to predict or explain a given system property or behaviour, of which the maximum entropy production and the maximum power principles are most widespread. However, the different studies did not use a common systematic approach for the formulation of the relevant system boundaries, state variables and exchange fluxes, resulting in considerable ambiguity about the application of thermodynamic optimality principles in the scientific community. Such a systematic framework has been developed recently and can be tested online at:

https://renkulab.io/projects/stanislaus.schymanski/thermodynamic_optimality_blueprint

In the present study, we illustrate how such a common framework can be used to classify and compare different applications of thermodynamic optimality principles in the literature, and discuss the insights gained and key criteria for a more rigorous testing of such principles.
A General Solution to the Rank Deficient Integer Least Squares and its Application to GNSS Positioning
Authors: Tagliaferro Giulio
Published: March 2021

The contribution will present a general solution for the estimation of rank deficient integer parameters. A procedure will be presented that allows the computation of integer estimable function for any integer rank deficient least squares problem. The procedure is then applied to GNSS estimation problems. In the framework of undifferenced and uncombined GNSS models, the specific solution to some rank deficient integer least squares model will be presented, namely: the choice of pivot ambiguities in a network of receivers, GLONASS positioning, codeless positioning in the presence of ionospheric delay, satellite specific pseudorange biases estimation in the presence of ionospheric delay. It will been shown how the developed theory generalize previous results and ad hoc solutions present in the literature. Numerical results from real GNSS data will be presented too.