bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep subduction and exhumation of continental crust in the Alps
Authors: Froitzheim Nikolaus
Published: March 2020

The Adula Nappe in the Central Alps and the Pohorje Nappe in the Eastern Alps are among the highest-pressure metamorphic complexes in the Alps. In both cases, Variscan continental crust containing post-Variscan intrusions was subducted, during the Cenomanian-Turonian in the case of Pohorje and during the Eocene in the case of Adula.

The Pohorje Nappe is exceptional in that ultrahigh pressures of 3.0 to 4.0 GPa are recorded by different rocks contrasting in rheology: competent lenses of kyanite eclogite and garnet peridotite as well as the surrounding incompetent matrix of diamond-bearing paragneiss. If pressure had been strongly non-lithostatic, rheologically different rock types would be expected to record different pressures. This is not the case, which rather suggests near-lithostatic pressure and, consequently, subduction to >100 km depth. Lu-Hf ages for UHP metamorphism in eclogite and garnet peridotite are similar (c. 96–92 Ma). Paragneiss yielded Permian to Triassic zircon cores and Cretaceous (c. 92 Ma) rims grown during UHP metamorphism. Hence, the rocks were subducted and exhumed together as a coherent, although strongly deformed unit.

The Adula Nappe originated from the southern passive continental margin of Europe. It was buried in and exhumed from a south-dipping subduction zone after Europe-Adria continent collision. Previous interpretations as a tectonic mélange were based on the mixture of gneiss with eclogite and garnet peridotite lenses. However, the eclogites also record an older (Variscan) metamorphism and thus do not represent Mesozoic oceanic crust but pre-Alpine continental basement, just like the gneisses. The Alpine subduction culminated around 37 Ma. Alpine metamorphic pressures show a strong gradient from c. 1.2 GPa at the front of the nappe in the North to >3 GPa in garnet peridotite and eclogite in the southernmost part (e.g. Alpe Arami), over a north-south distance of only c. 40 km. In contrast to Pohorje, indications of UHP metamorphism have not yet been found in the gneissic matrix surrounding eclogite and peridotite. During exhumation, the nappe was intensely sheared and folded but stayed coherent and did not mix with the surrounding units.  The exhumation of the Adula from deep in the subduction zone is recorded by mylonitic shearing in the gneissic matrix. Structures, strain, and textures indicate strongly three-dimensional, non-plane-strain flow. Differential loading, not buoyancy, is proposed to have caused the exhumation.

The main results from these two case studies are: (1) Subduction of continental crust to mantle depth is real and not a misinterpretation of non-lithostatic pressure; (2) not all subducted units are mélanges but some stay coherent during subduction and exhumation.
Streamer discharges in the atmosphere of Primordial Earth
Authors: Enghoff Martin Bødker , Segkos Nikolaos , Dujko Sasa , Chanrion Olivier , Köhn Christoph
Published: March 2020

Motivated by the Miller-Urey experiment suggesting that lightning may have contributed to the origin of life on Earth through the formation of amino acids and carbonic acids, we here investigate the occurrence of electric discharges in the atmosphere of Primordial Earth. We focus on the early stages of lightning in the atmosphere of Primordial Earth, the so-called streamers, thin ionized plasma channels.

We study electron avalanches and potential avalanche-to-streamer transitions by modeling the motion of electrons with a particle-in-cell Monte Carlo code in gas mixtures of H2O:CH4:NH3:H2=37.5%:25%:25%:12.5% [S. L. Miller. Production of Some Organic Compounds under Possible Primitive Earth Conditions. Am. Chem. Soc., 77:9, pp. 2351-2361 (1955)] and N2:CO2:H2O:H2:CO=80%:18.89%:1%:0.1%:0.01% [J. F. Kasting. Earth’s Early Atmosphere. Science, 259:5097, pp. 920-926 (1993)] suggested for Primordial Earth approx. 3.8 Ga ago in different electric fields and for different levels of background ionization mimicking the photoionization process. We compare the evolution of the electron density,  electric field, and electron energies with those for Modern Earth. Finally, we will discuss which conditions favour streamer inception, as well as consequences for discharges on Primordial Earth.
Variability of green-up duration of deciduous broadleaf forests in Central Europe during 2000-2019 based on MODIS NDVI
Authors: Kern Anikó , Marjanović Hrvoje , Barcza Zoltán
Published: March 2020

Spring leaf unfolding is a spectacular recurring event at the mid- and high latitudes that is associated with deciduous vegetation. Several lines of evidence indicate that the timing of spring green-up (i.e. the start of the season, SOS) changed in the past decades resulting in an earlier leaf unfolding - a phenomenon which is considered to be a major indicator of the effects of global warming. Contrary to the timing of the SOS, considerably less attention was paid to studying the dynamics of vegetation green-up, characterized by the leaf unfolding speed or the duration of spring green-up. The importance of studying the spring green-up dynamics lies in the fact that the duration of leaf development and timing of the onset of growth jointly determine the annual cycle of vegetation activity including carbon and energy balance, canopy conductance and evapotranspiration.

The aim of our research was to characterize the dynamics of leaf unfolding of deciduous broadleaf forests in the wider Carpathian Basin, located in Central Europe, using satellite remote sensing. The study was based on the Normalized Difference Vegetation Index (NDVI) time-series derived from the MOD09A1 official MODIS products during 2000–2019, the IGBP land cover classification dataset of the MCD12Q1 products, the CORINE 2012 (CLC2012) land cover dataset, the SRTM elevation dataset, and the FORESEE meteorological database. Our results clearly show that there is considerable interannual variability in the green-up duration of the deciduous broadleaf forest during 2000–2019. The last three years had, on average, the shortest (2018) and the two longest (2017 and 2019) recorded green-up durations in the region. Observed variability was partially attributed to the meteorological conditions, namely the extreme weather events occurring during the spring. We demonstrate that the meteorological conditions during the green-up period have a strong effect on the duration. The relationship between the SOS and the green-up duration reveals that the SOS also played an important role as a driver. Our results also reveal considerable elevation dependency both in the green-up duration and also in its correlation with SOS. Multiple linear regression models based on the SOS and the meteorological variables were also created to explain and predict the green-up duration.
Interactive effect of vegetation and climate warming on total microbial and fungal biomass in soil
Authors: Udovenko Maria , Guliyev Vusal , Blagodatskaya Evgenia
Published: March 2020

Soil microbiota ensuring sustainable functioning of terrestrial ecosystems is strongly dependent on climatic conditions and vegetation type. Even within the same climatic zone, active land use alters the size, structure and functioning of the microbial community. We hypothesized that land use effect on soil microbial biomass will be more pronounced under impact of global warming. We also tested whether the biomass of specific microbial group (e.g., fungi) is more sensitive to environmental changes than total microbial biomass.

We proved these hypotheses in the experiments based on Global Change Experimental Facility platform, located at the field research station of the Helmholtz-Centre for Environmental Research in Bad Lauchstädt near Halle, Saxon-Anhalt, Germany. Experimental setup included 50 plots, located in 10 blocks (5 plots per block). Five blocks are under ambient climate and the rest 5 blocks are subjected to a realistic climate change treatment (under conditions predicted by several models of climate change in Central Germany for 2050–2080 period). Five land use types were established in every block: conventional farming; organic farming; intensively used meadow, extensively used meadow and extensively used pasture. We determined soil microbial biomass and its fungal component by chloroform fumigation-extraction method and by ergosterol content, respectively. We found that fungal biomass was more sensitive to intensive land use for crop production than to climate change. The possible mechanisms of such a sensitivity will be discussed.
Paleogene to Quaternary geodynamical evolution of the lowland Central Amazonia inferred by weathering phases dating
Authors: Gautheron Cecile , Cabriolu Cristiana , Pupim Fabiano , Parra Mauricio , Schwartz Stéphane , Pinna-Jamme Rosella , Horbe Adriana , Kern Andrea K. , Oliveria Sawakuchi André
Published: March 2020

The landscape in lowland Amazonia is shaped by large rivers, whose depositional-erosive dynamics built fluvial terraces covered by upland forests. Thus, fluvial deposits distributed across lowland Amazonia are of crucial relevance since they represent the best accessible archives to study the history of environment and climate change. The timing of the assembly of the modern transcontinental Amazon River is considered a key event in the landscape evolution of Amazonia, however, proposed ages range from Miocene, early Pliocene to Pliocene/Pleistocene. Therefore, regional stratigraphic correlations need to improve to ensure a better understanding of reconstructions of past conditions in Amazonia during the Cenozoic. Yet, these are difficult due to the lack of absolute ages to constrain phases of sediment deposition or erosion and weathering. In lowland central Amazonia, past environmental conditions are recorded in the Alter do Chão and Novo Remanso Formations. Both units are dominated by sandy and highly oxidized sediments with scarce paleontological remains complicating the application of biostratigraphy dating methods. The Alter do Chão and Novo Remanso Formations are well exposed in the left margin of the Solimões-Amazon River main stem and show remarkable zones rich in supergene iron weathering products, which has been used to define the stratigraphic boundaries among the Alter do Chão Formation, Novo Remanso Formation and overlying sediments. In this study, we use the (U-Th-Sm)/He dating method on goethite and hematite grains to determine the age of iron-enrichment layers and duricrusts that mark boundary surfaces used to define the stratigraphic framework of the Alter do Chão and Novo Remanso formations. The (U-Th-Sm)/He ages allow to improve chronological constraints for both formations and to discuss the timing of fluvial terraces building and weathering conditions in central Amazonia through time.
Current and future flood risk assessment in the Danube region
Authors: Schröter Kai , Wortmann Michel , Lüdtke Stefan , Hayes Ben , Drews Martin , Kreibich Heidi
Published: March 2020

Severe hydro-meteorological hazards have been increasing during recent decades and, as a consequence of global change, more frequent and intense events are expected in the future. Climate informed planning of adaptation actions needs both consistent and reliable information about future risks and associated uncertainties, and appropriate tools to support comprehensive risk assessment and management. 
The Future Danube Model (FDM) is a multi-hazard and risk model suite for the Danube region which provides climate information related to perils such as heavy precipitation, heatwaves, floods and droughts under recent and future climate conditions. FDM has a modular structure with exchangeable components for climate input, hydrology, inundation, risk, adaptation and visualisation. FDM is implemented within the open-source OASIS Loss Modelling Framework, which defines a standard for estimating ground-up loss and financial damage of disaster events or event scenarios. 
The OASIS lmf implementation of the FDM is showcased for the current and future fluvial flood risk assessment in the Danube catchment. We generate stochastic inundation event sets for current and future climate in the Danube region using the output of several EURO-CORDEX models as climate input. One event set represents 10,000 years of daily climate data for a given climate model, period and representative concentration pathway. With this input, we conduct long term continuous simulations of flood processes using a coupled semi-distributed hydrological and a 1.5D hydraulic model for fluvial floods. Flood losses to residential building are estimated using a probabilistic multi-variable vulnerability model. Effects of adaptation actions are exemplified by scenarios of private precaution. Changes in risk are illustrated with exceedance probability curves for different event sets representing current and future climate on different spatial aggregation levels which are of interest for adaptation planning.
Penguin Life Observatories to monitor the health of the Southern Ocean ecosystems
Authors: Le Bohec Céline , Planas-Bielsa Victor , Trucchi Emiliano , Houstin Aymeric , Cristofari Robin , Eckbo Norith , Fabry Ben , Le Maho Yvon , Winterl Alexander , Richter Sebastian , Eisen Olaf , Zitterbart Daniel
Published: March 2020

Long-term time series are essential to detect, understand and predict the impacts of anthropogenic pressures on ecosystems. This applies to both physical and biological data collections. However, systematic data collections on the biological component of the ecosystems are still scarce compared to Earth sciences, and biological time series are usually not sufficiently long to draw unambiguous inferences concerning trends. To fill this gap and assess the vulnerability of Antarctic and subantarctic ecosystems, but also develop tools for action plans to protect Southern Ocean, we aim (and already started) to setup a circumpolar network of Penguin Life Observatories. These upper-trophic-level seabirds can be considered as adequate bio-indicators of changes (due to e.g. climate change, overexploitation or pollution) occurring in the Southern Ocean food webs and ecosystems globally. Implementing cutting-edge technological innovations (e.g. automatic radiofrequency identification (RFID), weighing and camera-tracking systems, mobile RFID antennas deployable on site or mounted on remote-operated vehicles and biologgers), electronic Penguin Life Observatories gather information on land to assess population dynamics/trends, and at sea to explore their seasonal and inter-annual distribution and foraging strategies according to the environmental variability. In addition to increasing our knowledge on fundamental characteristics of these sentinel species, penguins play an important role as umbrella species, which offer us precious tools to map marine biological hotspots and design Marine Protected Areas (MPAs).
Geomorphological evidence of icefield-style glaciation in the Šumava/Bayerischer Wald mountains, Central Europe
Authors: Margold Martin , Krause David
Published: March 2020

The Šumava/Bayerischer Wald mountains are located to the north of the eastern Alps, at the borders of present-day Austria, Bavaria and the Czech Republic. The Šumava/Bayerischer Wald belong to the Variscan mountain ranges of central Europe; these ranges hosted mountain glaciers at the times when the region of central Europe formed a broad unglaciated corridor between the glaciated Alps and the southern margin of the Fennoscandian Ice Sheet. While the region was home to some of the early studies into Pleistocene glaciations in the 19th century, there is still uncertainty both about the maximum extent of Pleistocene glaciation and its chronology. With the availability of high-resolution digital elevation data it is now possible to map the geomorphological traces of glaciation better than before.

We mapped glacial geomorphology from high-resolution digital elevation data for the entire mountain range. We newly find evidence of glacial erosion outside of the well-developed and earlier studied glacial cirques. Widespread traces of glacial erosion in the relatively low-relief, high-elevated central portion of the range indicate that the maximum Pleistocene extent of glaciation might have taken the form of an icefield. The scarcity of glacial depositional landforms beyond the well-developed glacial cirques (the moraines of which have earlier been dated to Marine Isotope Stage 2) may indicate that the icefield existed during one or more of the earlier cold stages of the Pleistocene and most of the depositional landforms formed by those glaciations have since been denudated. Quantitative geochronology would have the potential to correlate the occurrence of the inferred icefield in the Šumava/Bayerischer Wald mountains with the glaciations of the eastern Alps.
TanDEM-X for Cryosphere Applications
Authors: Hajnsek Irena , Fischer Georg , Parrella Giuseppe , Bernhard Philipp , Leinss Silvan
Published: March 2020

In this presentation the focus is laid on cryospheric applications served by the single-pass interferometer TanDEM-X. The German Radar mission TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is already successfully in operation since 2010 and is delivering continuously data over the Earth surfaces.

The main mission objective was the generation of a global and consistent digital elevation model (DEM) with a spatial resolution of 12m and a relative vertical height accuracy of 2 m. For this at least two global acquisitions where needed and innovative algorithms where developed to process the data into a global high resolution DEM. In addition to the high resolution DEM also a 90-m DEM was generated to facilitate the comparability with the former SRTM DEM. Beyond the generation of DEMs super-test sites have been establish to collect continuously data over a limited area of interest and to demonstrate and develop new algorithms to support application development. In addition TanDEM-X supports the demonstration and application of new SAR techniques, with focus on multi-static SAR, polarimetric SAR interferometry, digital beam forming and super resolution.

Today it is known through observations, delivered by satellites and conventional observing systems that the Cryosphere reacts very sensitively to climate change. However, the feedbacks to the global climate system are not well understood, impairing predictions of the impact of future climate change. Improved observational data have been provided to better quantify the main cryospheric processes and improve the representation of the Cryosphere in climate models. TanDEM-X data (product but also interferometric data) have been used from an international science team for a diversity of cryosphere applications. The presentation will provide an overview of the operation status of TanDEM-X and will focus on the applied cryopheric applications so far applied. Examples of the detection of permafrost features, the estimation of the firn-line zone, derivation of vertical ice structure, the mass loses of  over ice sheets and sea ice height estimation will be presented.
Sensing small-scale structures in the troposphere with tomographic principles (IAG working group)
Authors: Moeller Gregor , Ao Chi , Adavi Zohreh , Brenot Hugues , Sá André , Hajj George , Hanna Natalia , Kitpracha Chaiyaporn , Pottiaux Eric , Rohm Witold , Shehaj Endrit , Trzcina Estera , Wang Kuo-Nung , Wilgan Karina , Zhang Kefei
Published: March 2020

Within the International Association of Geodesy (IAG), a new working group was formed with the intention to bring together researchers and professionals working on tomography-based concepts for sensing the neutral atmosphere with space-geodetic techniques. Hereby the focus lies on Global Navigation Satellite Systems (GNSS) but also on complementary observation techniques, like Interferometric Synthetic Aperature Radar (InSAR) or microwave radiometers, sensitive to the water vapor distribution in the lower atmosphere.

In the next four years (2019-2023), we will address current challenges in tropospheric tomography with focus on ground-based and space-based measurements, the combination of measurement techniques and the design of new observation concepts using tomographic principles. While geodetic GNSS networks are nowadays the backbone for troposphere tomography studies, further local densifications, e.g. at airports, cities or fundamental stations are necessary to achieve very fine spatial and temporal resolution. Besides, the combination of ground-based GNSS with other microwave techniques like radio occultation or InSAR seems to be beneficial due their complementary nature. Therefore, several further developments in the field of tropospheric tomography are required. This includes more dynamical tomography models - adaptable to varying input data, advanced ray-tracing algorithms for the reconstruction of space-based observations and the coordination of a benchmark campaign.

In this presentation, we will give an overview about the current challenges in tropospheric tomography and the objectives of working group. The latter will also include standards for data exchange and therefore, make tomographic products available for the assimilation into numerical weather prediction models but also for various other disciplines, which rely on accurate wet refractivities or derived products like tropospheric signal delays.
Diurnal variations and source apportionment of ozone at the summit of Mount Huang, a rural site in Eastern China
Authors: Gao Jinhui
Published: March 2020

Comprehensive measurements were conducted at the summit of Mount (Mt.) Huang, a rural site located in eastern China during the summer of 2011. They observed that ozone showed pronounced diurnal variations with high concentrations at night and low values during daytime. The Weather Research and Forecasting with Chemistry (WRF-Chem) model was applied to simulate the ozone concentrations at Mt. Huang in June 2011. With processes analysis and online ozone tagging method we coupled into the model system, the causes of this diurnal pattern and the contributions from different source regions were investigated. Our results showed that boundary layer diurnal cycle played an important role in driving the ozone diurnal variation. Further analysis showed that the negative contribution of vertical mixing was significant, resulting in the ozone decrease during the daytime. In contrast, ozone increased at night owing to the significant positive contribution of advection. This shifting of major factor between vertical mixing and advection formed this diurnal variation. Ozone source apportionment results indicated that approximately half was provided by inflow effect of ozone from outside the model domain (O3-INFLOW) and the other half was formed by ozone precursors (O3-PBL) emitted in eastern, central, and southern China. In the O3-PBL, 3.0% of the ozone was from Mt. Huang reflecting the small local contribution (O3-LOC) and the non-local contributions (O3-NLOC) accounted for 41.6%, in which ozone from the southerly regions contributed significantly, for example, 9.9% of the ozone originating from Jiangxi, representing the highest geographical contributor. Because the origin and variation of O3-NLOC was highly related to the diurnal movements in boundary layer, the similar diurnal patterns between O3-NLOC and total ozone both indicated the direct influence of O3-NLOC and the importance of boundary layer diurnal variations in the formation of such distinct diurnal ozone variations at Mt. Huang.
Greenland fjord productivity under climate change - multiproxy late-Holocene records from two contrasting fjord systems
Authors: Bang Kvorning Anna , Beate Thomsen Tania , Oksman Mimmi , Seidenkrantz Marit-Solveig , Pearce Christof , Joest Andersen Thorbjørn , Ribeiro Sofia
Published: March 2020

The Greenland Ice Sheet has been losing mass at an increasing rate over the past decades due to atmospheric and oceanic warming. As a result, freshwater discharge from the Greenland Ice sheet has doubled in the last two decades and is expected to strongly increase in the future, with a large impact on the functioning of coastal marine ecosystems. While glacier runoff delivers nutrients and labile carbon into the fjords, an increase in sediment inputs is expected to have a negative impact in primary productivity, due to increased turbidity and subsequent reduction in available light for photosynthesis. Bridging modern satellite, historical and paleo-records is a key approach, as our capacity to project future scenarios requires an understanding of long-term dynamics, and insight into past warm(er) climate periods that may serve as analogues for the future. We will present results from a master’s project developed within the framework of project GreenShift: Greenland fjord productivity under climate change. Two high-resolution sediment core records from two contrasting fjord systems in NE and SW Greenland were analysed to assess the impact of Greenland Ice Sheet melt on sediment fluxes and primary productivity, focusing on the time period from the Little Ice Age until present. The overall goal of this work is to gain a better understanding of the possible linkages between GIS melt and productivity in Greenland fjord systems, with a view to improve future projections. We followed a multiproxy approach including grain-size distribution, organic carbon and biogenic silica fluxes; and dinoflagellate cyst analyses. Our preliminary results show an overall trend towards sea-surface freshening in recent decades for both fjords influenced by land-terminating (NE) and marine-terminating (SW) glaciers, alongside with important differences both in terms of sedimentary organic composition and dinoflagellate cyst assemblages.  
Assessing Typhoon Risk Using Multi-model Ensemble Forecasts for Disaster Risk Reduction
Authors: Leckebusch Gregor C. , Ng Kelvin S.
Published: March 2020

Understanding high impact land-affecting tropical cyclones (TCs) is of crucial importance due to its potential to cause high socioeconomic damages and losses to many coastal areas.  However, due to the rarity of extreme severe TCs and the lack of persistent long-term meteorological observations, it is difficult to construct a robust risk assessment of high impact TCs based solely on historical records.  This poses a problem from the disaster risk reduction (DDR) perspective, e.g. for the development of financial instruments, as the estimate of occurrence probabilities above damage relevant thresholds remains highly uncertain. In this study, we present an overview and first results of our current project – INtegrated threshold development for PArametric Insurance Solutions (INPAIS), which demonstrates a way forward to improve expected occurrence probabilities of those events for the Western North Pacific (WNP).

We introduce a new approach to construct a TC event set for the WNP based on multi-model ensemble global forecasts – the THORPEX Interactive Grand Global Ensemble (TIGGE) dataset in combination with an impact-based tracking algorithm for Typhoons. This event set contains physically consistent events, which were forecasted but not necessarily realised in the observed past. With respect to the physical characteristics of these forecasted, but not realised events, they are not distinguishable from real TC events. This approach will allow to analyse data equivalent to more than 10,000 years.

In addition to the TC-related wind information, the TC-related precipitation, which is physically consistent with the associated TC, can also be obtained. This provides an opportunity to analyse the compound TC risk (wind and precipitation) using physically consistent data for the WNP. We further demonstrate how this information can be used to improve existing financial instrument for DRR, e.g. parametric insurance solution which is offered by many re-insurance companies, such that resilience and post-disaster recovery speed of society can be improved.
The structural architecture of the Whataroa Valley at the Alpine Fault (New Zealand) from first-arrival tomography and reflection imaging using an extended 3D VSP survey
Authors: Lay Vera , Buske Stefan , Bodenburg Sascha Barbara , Kleine Franz , Townend John , Kellett Richard , Savage Martha , Schmitt Douglas , Constantinou Alexis , Eccles Jennifer , Lawton Donald , Bertram Malcolm , Hall Kevin , Kofman Randolph , Gorman Andrew
Published: March 2020

The Alpine Fault along the West Coast of the South Island (New Zealand) is a major plate boundary that is expected to rupture in the next 50 years, likely as a magnitude 8 earthquake. The Deep Fault Drilling Project (DFDP) aims to deliver insight into the geological structure of this fault zone and its evolution by drilling and sampling the Alpine Fault at depth.  

Here we present results from a 3D seismic survey around the DFDP-2 drill site in the Whataroa Valley where the drillhole penetrated almost down to the fault surface. Within the glacial valley, we collected 3D seismic data to constrain valley structures that were obscured in previous 2D seismic data. The new data consist of a 3D extended vertical seismic profiling (VSP) survey using three-component receivers and a fibre optic cable in the DFDP-2B borehole as well as a variety of receivers at the surface.

The data set enables us to derive a reliable 3D P-wave velocity model by first-arrival travel time tomography. We identify a 100-460 m thick sediment layer (average velocity 2200±400 m/s) above the basement (average velocity 4200±500 m/s). Particularly on the western valley side, a region of high velocities steeply rises to the surface and mimics the topography. We interpret this to be the infilled flank of the glacial valley that has been eroded into the basement. In general, the 3D structures implied by the velocity model on the upthrown (Pacific Plate) side of the Alpine Fault correlate well with the surface topography and borehole findings.

A reliable velocity model is not only valuable by itself but it is also required as input for prestack depth migration (PSDM). We performed PSDM with a part of the 3D data set to derive a structural image of the subsurface within the Whataroa Valley. The top of the basement identified in the P-wave velocity model coincides well with reflectors in the migrated images so that we can analyse the geometry of the basement in detail.
Ocean-only FAFMIP: Understanding Regional Patterns of Ocean Heat Content and Dynamic Sea Level Change
Authors: Todd Alexander , Zanna Laure , Gregory Jonathan
Published: March 2020

A rise in global mean sea level is a robust feature of projected anthropogenic climate change using state-of-the-art atmosphere-ocean general circulation models (AOGCMs). However, there is considerable disagreement over the more policy-relevant regional patterns of sea level rise. The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) aims to improve our understanding of the mechanisms controlling regional and dynamic sea level change. In FAFMIP, identical air-sea buoyancy and momentum flux perturbations are applied to an ensemble of different AOGCMs, to sample the uncertainty associated with model structure and physical processes. Our novel implementation applies FAFMIP perturbations to an ensemble of OGCMs. This framework enables an estimate of the unknown atmosphere-ocean feedbacks, by comparing the coupled and ocean-only response to surface flux perturbations.

Comparing the response to idealised FAFMIP forcing with more realistic, increasing CO2 forcing, much of the spread in regional sea level projections for the North Atlantic and Southern Ocean arises from ocean model structural differences. Ocean-only simulations indicate that only a small proportion of this spread is due to differences in the atmosphere-ocean feedback. Novel tendency diagnostics indicate the relative effect of resolved advection, parametrised eddies, and dianeutral mixing on regional and dynamic sea level change. This study helps to reduce uncertainty in regional sea level projections by refining our estimates of atmosphere-ocean feedbacks and developing our understanding of the physical processes controlling sea level change.
Intensified hydrological cycle during the Early Eocene Climatic Optimum (EECO) recorded in the Xining Basin, NE Tibet
Authors: Meijer Niels , Dupont-Nivet Guillaume , Licht Alexis , Roperch Pierrick , Rohrmann Alexander , Woutersen Amber , Hoorn Carina , Barbolini Natasha , Sun Aijun , Abels Hemmo , Meyer Hanno , Nowaczyk Norbert
Published: March 2020

The evolution of Asian climate during the Cenozoic is traditionally linked to shifts in paleogeography such as the proto-Paratethys Sea incursions and uplift of the Tibetan Plateau driving monsoonal circulation and affecting the mid-latitude westerlies in Central Asia. In contrast, the role of global climate in the Asian hydrological cycle remains unclear. Here, we present a new stratigraphic record from the terrestrial Xining Basin in central China, which covers the Early Eocene Climatic Optimum (EECO), a period characterized by long-term global warmth and elevated atmospheric CO2 levels. The record is dated using magnetostratigraphy and extends the previously studied Paleogene strata down to 50.9 Ma (chron C23n). We use a variety of paleoclimate proxies, to derive the hydroclimatic evolution of the basin at this time. The lithostratigraphy is characterized by organic-rich mudrocks and gypsum beds (reaching TOC contents of up to 1.7%) interpreted as an alluvial mudflat to saline lake. The higher organic content of the strata indicates either increased organic productivity or preservation, both of which suggest a wetter depositional environment during the EECO. This is corroborated by palynological records showing a large increase in the abundance and diversity of trilete spores, indicating a wetter biome at this time. In addition, the d13C values of the bulk organic matter and leaf waxes (both C29 and C31), suggest a reduction in water stress on plants and a wetter environment as well. These observations are in stark contrast to the arid red beds, evaporites and xerophytic pollen observed in the underlying Cretaceous-Paleocene strata and overlying middle-late Eocene deposits. The peak global warmth of the EECO is thus clearly linked to an intensified Asian hydrological cycle suggesting a major driving role for global climate.

 
Examination and Projection of Urbanization Effect on Summertime Hot Extremes in China
Authors: Liao Weilin , Li Dan , Liu Xiaoping
Published: March 2020

Extreme hot events have profound impacts on human health. Especially, consecutive hot days without heat relief during nighttime can significantly increase the rates of mortality and morbidity. Using an urbanized global earth system model and treating urban and rural land as subgrid units, the urbanization effect on long-term changes in three types of summertime hot extremes (i.e., independent hot days, independent hot nights, and compound events) is simulated under the present-day climate and two future scenarios in China. The model is first evaluated using a homogenized observational dataset drawn from over 2,000 meteorological stations. The results show that the model can well capture urban and rural temperature changes during the historical period from 1961 to 2000. The urban and rural temperatures are both increased under two future scenarios, but the urban heat island intensities (i.e., urban minus rural) do not show significant changes. However, urbanization has a significant impact on the frequencies of summertime hot extremes under two future scenarios. The increasing frequencies of independent hot days and independent hot nights in urban areas are less than that in rural areas, but more importantly, the increasing frequency of compound events in urban areas is larger than that in rural areas. This suggests that urbanization will aggravate the trend of the extreme hot events changing from independent hot days and independent hot nights to compound events, and seriously increase the health risks of urban residents in the future.
Modified Shuttleworth-Wallace model for monitoring evapotranspiration over complex surface: Relationship between the surface resistances and remotely sensed stress indexes
Authors: Elfarkh Jamal , Er-Raki Salah , Ezzahar Jamal , Chehbouni Abdelghani , Aithssaine Bouchra , Amazirh Abdelhakim , Khabba Said , Jarlan Lionel
Published: March 2020

The main goal of this work was to evaluate the potential of the Shuttleworth-Wallace (SW) model for mapping actual crop evapotranspiration (ET) over complex terrain located within the foothill of the Atlas Mountain (Morocco). This model needs many input variables to compute soil (rss) and vegetation (rsv) resistances, which are often difficult to estimate at large scale particularly soil moisture. In this study, a new approach to spatialize rss and rsv based on two thermal-based proxy variables is proposed. Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) derived from LANDSAT data were combined with the endmember temperatures  for soil (Tsmin and Tsmax) and vegetation (Tvmin and Tvmax), which are simulated by a surface energy balance model, to compute the temperature of the two components, namely the soil (Ts) and the vegetation (Tv). Based on these temperatures, two thermal proxies (SIss for soil and SIsv for vegetation) were calculated and related to rss and rsv, with an empirical exponential relationship (with a correlation coefficient (R) of about 0,6 and 0,5 for soil and vegetation, respectively). The proposed approach was firstly evaluated at a local scale, by comparing the results to observations by an eddy covariance system installed over an area planted with olive trees intercropped with wheat. In a second step, the new approach was applied over a large area which contains a mixed vegetation (tall and short vegetation) crossed by a river to derive rss and rsv, and thereafter to estimate ET. A Large aperture scintillometer (LAS) installed over a transect of 1.4 km and spanning the total area is used to validate the obtained ET. The comparison confirms the ability of the proposed approach to provide satisfactory ET maps with an RMSE and R2 equal to 52.51 W/m2 and 0.80, respectively.
The modeling responses of heat budget in the Eastern China Seas to global warming
Authors: Tian Di
Published: March 2020

Impacts of climate change on heat budget in the Eastern China Seas (ECSs) are estimated under the historical, RCP4.5 and RCP8.5 scenarios using an atmosphere-ocean coupled regional climate model system (REMO/MPIOM). Solar radiation contributes the largest heat source of the ECSs. The heat gain achieved by solar radiation is overruled by thermal radiation, latent heat flux and sensible heat flux released at the ocean surface. The air-sea heat exchange thus cools the ECSs, whereas an overall warming is found for the ECSs. An increased oceanic heat transport by ocean currents balances this reduced heat supply by the sea surface heat fluxes. In particular, the water transport through Taiwan Strait brings the largest amount of heat into the ECSs. Despite of an inward heat transport onto the ECS shelf caused by the Kuroshio intrusion occurring northeast of Taiwan, overall, the shelf break section acts as a heat sink for the ECSs. The net heat gain/loss by the Tsushima Strait is marginal. Under the climate projection scenarios, the net heat loss from the shelf break section reduces, probably associated with the change in surface wind. Thus the net heat transported into the ECSs through the lateral boundaries increases slightly under these scenarios, leading to an overall warming of the ECSs, relative to 20C run. Noteworthy, the warmer SST, along with strengthened wind, further enhances the surface evaporation, providing a negative feedback onto the net effect of oceanic transport.
New pH evidence for changes in intermediate South East Pacific carbon storage during the last deglaciation
Authors: Euverte Romain , Michel Elisabeth , Bassinot Franck , Rae James , Gray William , Trudgill Molly
Published: March 2020

The leading hypotheses proposed to explain the rise in atmospheric CO2 during the last glacial to interglacial transition proposes enhanced carbon transfer from the intermediate and deep oceans to the atmosphere via the intensification of southern ocean upwelling. To test this scenario, we generated a high resolution record of boron isotopes (d11B) and B/Ca (proxies for pH and carbonate ion concentration, respectively) measured on shells of the benthic foraminifera C. wuellestorfi from a marine sedimentary core located at intermediate depth (1536m) on the Chilean margin. Our records confirm the link between changes in ocean circulation and variations in the carbonate chemistry at this site. The data also reveal the increase of intermediate water pH at the very late LGM, before the beginning of the deglaciation and the rise in atmospheric pCO2. To account for this observation, we suggest the existence of an early release of carbon from the intermediate ocean to the atmosphere in response to sea ice retreat occurring at the same time. The lack of any clear increase in atmospheric CO2 suggests that this release of intermediate ocean carbon was compensated by enhanced biological pumping.
Early diagenesis in benthic foraminifera under anoxic conditions from the Landsort Deep, Baltic Sea (IODP Site M0063)
Authors: Ni Sha , Quintana Krupinski Nadine , Groeneveld Jeroen , Knudsen Karen Luise , Persson Per , Somogyi Andrea , Brinkmann Inda , Seidenkrantz Marit-Solveig , Filipsson Helena L.
Published: March 2020

The chemical composition of foraminiferal calcite is widely used for studying past environmental conditions and biogeochemistry. However, high rate of microbial-derived organic matter degradation and abundant dissolved metal sources in sediment and pore waters may impede the application of paleoenvironmental proxies due to formation of secondary carbonates on the outside and/or inside of foraminiferal tests. Secondary carbonate precipitation severely alters the foraminiferal geochemistry and can be difficult to eliminate through standard cleaning procedures for foraminiferal trace element analyses. Here we present results of the mineral composition and formation sequence of diagenetic coatings on the tests of foraminifera formed under extreme anoxic conditions in the Baltic Sea deepest basin (the Landsort Deep, IODP Exp. 347, Site M0063), as well as changing trace element concentrations of authigenic carbonates on the test on a millennial time-scale. The focus is on the diagenetic carbonates present on the tests of the low-oxygen tolerant benthic foraminiferal species Elphidium selseyensis and Elphidium clavatum. We applied geochemical and imaging methods by using scanning electron microscope imaging (SEM) and energy dispersive spectroscopy (EDS), synchrotron-based x-ray fluorescence microscopy (nano-XRF), RAMAN spectroscopy and laser ablation (LA)-ICP-MS, in order to ascertain the sedimentary diagenetic processes, and the foraminiferal authigenic mineral formation sequence. The authigenic carbonates were enriched in Mg, Mn, Fe and Ba, depending on the redox environmental conditions when the authigenic carbonates were precipitated. In particular, concentrations of redox-sensitive elements such as Mn and Fe were increased in bottom waters and sedimentary pore waters under oxygen-depleted conditions in the Landsort Deep, which resulted in Mn- and Fe-enriched carbonate formation. The diagenetic alteration on foraminiferal tests provides potential opportunity to investigate past sedimentary redox environment and primary productivity in the Baltic Sea.
Drift of buoyant objects in the Baltic sea – model data analysis
Authors: Bethere Liga , Valainis Aigars , Sennikovs Juris , Bethers Uldis
Published: March 2020

Marine debris and pollution of the sea is well recognized problem. Knowledge of the potential destination and time of arrival for buoyant or nearly buoyant contaminants as, for example, microplastics, is necessary for effective policy planning.

This work analyzes characteristics of buoyant objects in the Baltic Sea using simulations of Lagrangian particle movement. Simulations are based on current and wind model data. Initially particles are regularly distributed (spaced 5 km) over the Baltic Sea and a new simulation and particle release is started every day over a period of 10 years – years 2008-2017. It is assumed that upon reaching the coast particle gets washed out on the coast.

The aim of this work was to acquire following 3 drift characteristics for possible buoyant object movement in the Baltic Sea:

How many days does it take from different regions of the Sea to reach the coast, what regions (clusters) can be identified that share similar behavior for different seasons;

Which coastal regions are most at risk – which regions get particles washed out the most;

What are main pathways for the particles – which sea regions affect which coastal regions the most.

As the distributions of floating time and location are non-normal then the methods of Symbolic Data Analysis (SDA) were used. To be more exact, statistics from each sea point or coastal segment was described by empirical distribution function (histogram) and differences/similarities were calculated using squared Wasserstein distance. The simulations cover multiple seasons – therefore the difference between seasons is also examined for each of 3 drift characteristics.

Part of the research is supported from the Latvian Academy of Sciences, project lzp-2018/1-0162 DRIMO - DRIft MOdelling for pollution reduction and safety in the Baltic Sea, 2018 - 2021.
Disentangling the groundwater response to Earth and atmospheric tides reveals subsurface processes and properties
Authors: Rau Gabriel , McMillan Timothy , Cuthbert Mark , Andersen Martin , Timms Wendy , Blum Philipp
Published: March 2020

In situ quantification of subsurface hydro-geomechanical properties is challenging and requires significant effort. Evolving research illustrates that subtle harmonic components in groundwater head measurements caused by Earth and atmospheric tides can be utilised to explore groundwater systems with little effort compared to traditional investigations. One long standing problem has been that, for dominant tidal components, Earth and atmospheric tides occur at the same frequency which prevents the use of the groundwater response to their individual forcing to infer subsurface properties. While Acworth et al. (2016) offered a way forward, their approach has assumptions that limit the applicability. Here, we illustrate an extended method that disentangles the borehole water level response and attributes magnitude and phase to their individual drivers. As a result, we obtain individual changes in harmonic properties of the drivers and their groundwater response (amplitude ratio and phase shift) using borehole water level records from different locations. In conjunction with groundwater flow and poroelastic theory, these properties can be used to infer the state of confinement, quantify specific storage and hydraulic conductivity as well as barometric efficiency of the formation. Further, because the stresses imposed by Earth and atmospheric tides are volumetric and uniaxial, respectively, their individual responses can be used to reveal strain anisotropy. Our new approach is passive, i.e. it only requires the measurements of atmospheric and groundwater pressure records, and can provide further insight into subsurface processes and properties using information hidden in standard pressure records.

 

Acworth, R. I., Halloran, L. J. S., Rau, G. C., Cuthbert, M. O., and Bernardi, T. L. ( 2016), An objective frequency domain method for quantifying confined aquifer compressible storage using Earth and atmospheric tides, Geophys. Res. Lett., 43, 11,671–11,678, doi:10.1002/2016GL071328.