bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Litter Incorporation on Soil Detachment Processes on the Loess Plateau of China
Authors: Liu Jiaxin
Published: March 2022

Plant litter incorporation into soil is a widespread phenomenon in the natural environment. Accurate estimation of the soil detachment capacity ( Dc ) driven by overland flow under litter incorporation effects is crucial for improving soil erosion prediction. However, the effects of litter incorporation on soil detachment processes are often ignored, and the temporal variation of Dc under litter incorporation effects remains unclear for the Loess Plateau of China. In this study, we conducted flume tests to determine the temporal variation of Dc for soils incorporating two typical plant litters ( Bothriochloa ischaemum (L.) Keng. litter, and Artemisia sacrorum Ledeb. litter) between May 2017 and October 2018 (a 524-day period). Furthermore, the key factors
affecting Dc were identified. Our results showed that the temporal variation in Dc was consistent across the different soil treatments (two litter incorporation treatments and one bare soil control), showing a rapid decline and then fluctuating at a low level, with Dc ranging from 0.115 to 6.876 kg m−2 s−1 . Incorporation of litter effectively reduced Dc , with the Dc of soil treatments incorporating litter being 15% to 29% lower than that of bare soil (2.110 kg m−2 s−1 ). Further analysis showed that the temporal variation in Dc was mainly affected by the development of a physical soil crust. Dc can be successfully estimated using a nonlinear equation incorporating flow shear stress and soil cohesion (R2 = 0.77, NSE = 0.65), which represent the erosive force and soil erosion resistance, respectively. Our study reveals the important role of plant litter in the soil detachment process and aids the understanding of soil erosion pathways. Further studies are needed to investigate the effects of a physical soil crust on the soil detachment process driven by overland flow.
Cloud tracking in geostationary satellite data: Comparison of two Matching Methods
Authors: Müller Felix , Seelig Torsten
Published: March 2022

Tracking clouds in satellite data has multiple applications. It is used for short-term weather forecasting as well as long-term weather and climate analyses. Our long-term goal is to investigate cloud lifecycles under different conditions, such as marine or continental areas, over deserts, or in areas with increased anthropogenic aerosols. This is a key element in understanding cloud radiation effects and the human influence on the cloud lifecycle.

To identify clouds and their trajectories, we are using Particle Image Velocimetry (PIV) which is well-known for measuring velocities in fluid dynamics. The algorithm works on the cloud mask from CLAAS2 (Cloud property dataset using SEVIRI v2) by EUMETSAT (2014 Stengel et al, “CLAAS: the CM SAF cloud property dataset using SEVIRI”). The mask is created with a multi-channel approach using satellite data from SEVIRI. However, the presented algorithm can be adapted to work on any geostationary satellite data set. It identifies clouds in the satellite data and computes a velocity field with the next timestep using cross correlation. This velocity field is interpolated onto the individual clouds and the virtual positions (old positions adjusted with velocity field) are then compared against the next timestep of clouds via a matching criterion. Previously only the distance of the centroids was used for this criterion. Now the overlapping area is used as well in sequence with the distance. This improves the capability to track large clouds immensely because they are more likely to have large shifts in their centroid due to a change in shape.

The presented results are twofold. Firstly, we will show a comparison of individual cloud trajectories between both methods to establish a deeper understanding of the methodology. Secondly, we will look at the distributions of the cloud sizes and trajectory lengths for both methods to see the overall improvement that can be gained from the updated matching criterion.
Long term stability of an abandoned construction pit in Eocene flysch rock mass: case study of Bracka street construction site (Split, Croatia)
Authors: Vlastelica Goran , Duhović Ana , Relota Marija
Published: March 2022

Excavations in soft rocks usually have to be performed by blasting with explosives or with heavy pneumatic hammers. However, in a certain period after excavation, their physical and mechanical properties begin to change to a level where even manual excavation can be used. These changes can be significant during the building design life, where the initial design solution of the slope cut may prove inappropriate, sometimes resulting in collapse. In this context, it is necessary to define the causes of changes in the soft rock physical and mechanical properties, and determine all the necessary parameters (primarily strength parameters, but also all others relevant to describe the change in rock properties over time) in all phases of expected change during construction or other applications (such as use of slope area, in case of abandoning the site in certain time period, etc.).

Furthermore, when preparing project documentation for construction, in the part where the calculations of the global stability of the building on the slope are performed, the possibility of significant changes in the shape of the slope during the structure/building design life are usually neglected. Therefore, this paper also presents the Fisher Lehmann model of the change of slope geometry during the period of construction use, and explains the influences of weathering factors on parameters of the soft rock over time by using laboratory simulation of weathering.

Combined changing the geometry of the slope and the properties of the rock can have a negative impact on the safety of the structure, which is explained and shown through an example of an abandoned construction pit at Bračka Street in Split, where the stability of neighboring residential houses is endangered. By using appropriate mathematical models of the slope morphology change, results of long term slope monitoring by TLS and appropriate software for slope stability analysis (Slide 2, RocScience), the time span in which the instability can occur for Bračka Street case study is determined for multiple possible future intervention scenarios.  
Linking the Nazca plate rigid motions to the megathrust earthquakes occurring along the Chilean subduction zone
Authors: Martin de Blas Juan , Iaffaldano Giampiero , Tassara Andrés , Melnick Daniel , Moreno Marcos
Published: March 2022

It is typically assumed that the relative plate motions are not affected by temporal stress changes occurring during the seismic cycle, which comprises a phase of slow buildup of stress (interseismic phase) followed by a phase of sudden release of stress accompanied by rapid fault slip (coseismic phase). However, small- to medium-sized tectonic plates experience a reduced viscous resistance at their base, making the torques necessary to change their motions comparable to those generated by large earthquakes.

Here we explore whether the motions of medium-size tectonic plates experience temporal variations associated with earthquake-cycle stresses. In particular, we focus on the kinematics of the Nazca plate (NZ) in relation to the most recent Mw>8 megathrust earthquakes occurring across the Chilean trench (e.g., 2010 Maule and 2015 Illapel earthquakes). We utilise available GNSS time series to explore links between the recent (i.e., past two decades) plate kinematics and the seismic cycle of megathrust earthquakes occurring along the Chilean subduction zone. Our approach differs from classical studies on the earthquake-cycle induced deformation of the plate boundary region in that it focuses on the potential impact of large earthquakes onto rigid whole-plate kinematics.
Spatial and temporal distribution of physical and CO2 properties in the English Channel based on voluntary observing ships between 2006 and 2021
Authors: Brandon Margaux , Lefèvre Nathalie , Khvorostyanov Dimitry , Diverrès Denis
Published: March 2022

Spatial and temporal evolution of sea surface temperature, salinity and CO2 properties are studied in the English Channel (EnC) (48.8°N-5.2°W and 51.2°N-1.5°E) from 2006 to 2021. In situ measurements are collected using voluntary observing ships (VOS) as part of the ICOS program, during repeated transects every year, providing a good temporal coverage to study monthly to interannual variability in the area. The analysis of the longitudinal distribution of the parameters highlights a strong east-west difference. SST decreases from West to East in winter and spring, while the opposite gradient is observed at the end of summer and in autumn. During the month of July, a strong SST gradient up to 3 °C is observed around 3°W. Along the transect, the salinity slightly decreases from West to East, with a higher variability in the Eastern EnC. Mean SST in the EnC varies between 9 in March and 17°C in August-September and the mean difference between sea-water fCO2 and atmospheric fCO2 (ΔfCO2) ranges from -45 µatm at the end of spring/beginning of summer to 40 µatm in autumn. Differences in seasonality and variability are observed between the Western and Eastern EnC. For example, a strong sink of CO2 is observed in summer in the Western EnC, while in the Eastern EnC, the strongest sink occurs in spring. These CO2 sinks are associated with a rise in biological activity as shown by the very high surface Chl-a concentrations observed from satellite images. To better understand the physical and biological processes behind the fCO2 variations, relations between parameters are examined. Finally, interannual evolution of SST, SSS and CO2 properties are discussed to assess the long-term changes in this region.
A CMIP6 evaluation of summer synoptic circulations linked to short-term droughts over Europe
Authors: Herrera Lormendez Pedro , John Amal , Douville Hervé , Matschullat Jörg
Published: March 2022

Automated classifications of atmospheric circulations are a well-known tool to characterize large-scale patterns that predominantly determine day-to-day weather variations. Through its potential influence on the relative frequency of circulation patterns, global warming can also enhance or mitigate the occurrence of extreme weather events.

Here, we use a subset of 22 CMIP6  global climate models (GCMs) to assess their ability to capture these recurrent circulation patterns and their implication for the European climate and its projected changes.

We investigate links between synoptic circulations and short-term meteorological drought events that span one month. We employ the automated Jenkinson-Collison classification to determine daily atmospheric features based on mean sea-level pressure. We compute the conditional probability of dry days related to each circulation type. Furthermore, we confirm the influence of these patterns on the occurrence of dry months by computing the monthly relative frequency anomalies of the synoptic circulations given months where the Standardized Precipitation Index (SPI) was below minus 1. We evaluate the ability of the historical runs of global climate models (GCMs) to reproduce the observed features from the ERA5 reanalyses over the 1961-1990 reference period. Links between the mean directional flow characteristics of the circulation types and the dry days and months are well represented by most GCMs. The most robust relationships were found for the anticyclonic, easterly, and low flow types. These circulations are generally associated with a lack of precipitation and therefore show higher than average occurrences during dry months. 
Orbital forcing of early Eocene hyperthermal events: A new benthic foraminiferal record from the Indian Ocean, 50-51 Ma
Authors: Kirby Nicola , Batenburg Sietske , Leng Melanie , Dunkley Jones Tom , Edgar Kirsty
Published: March 2022

The early Eocene greenhouse climate is characterised by a series of ‘hyperthermal’ events, defined by transient negative excursions in marine carbonate carbon and oxygen isotopes. Proxy records of the larger magnitude hyperthermal events are consistent with massive carbon release to the ocean-atmosphere system and associated with global warming and ocean acidification. Such events therefore represent the best analogues for current anthropogenic climate change. However, the causes and nature of smaller early Eocene hyperthermals, particularly through the early Eocene Climatic Optimum (EECO), are less well understood. We know that hyperthermal events are paced by the 100 kyr (short) and 405 kyr (long) eccentricity cycles, indicating that Earth’s orbital parameters play a key role in driving carbon cycle perturbations, but the precise forcing mechanisms remain unclear. Additionally, few continuous records of the smaller, orbitally-paced hyperthermals exist and there have been no published high-resolution climate records from the Indian Ocean so far from this interval. High-resolution records across the full spectrum of hyperthermal events and from multiple ocean basins are needed to fully identify their cause(s). Here, we constrain the nature and magnitude of environmental change during hyperthermal events O-T in the Indian Ocean using a new, high-resolution benthic stable isotope record from IODP Expedition 369 Site U1514, Indian Ocean, from 50-51 Ma. Using spectral analysis techniques, we identify the dominant periodicities in the benthic stable isotope record and investigate the phasing between stable isotopes and other environmental records from Site U1514, including sedimentary Ca/Fe. We compare the Site U1514 stable isotope record with environmental records across this time interval from other sites to determine the synchronicity of climate and carbon cycle changes between different ocean basins, aiming to further examine the forcing mechanisms of these early Eocene hyperthermal events. 
The Crust and Uppermost-Mantle Structure of the Turkana Depression: Insights from Surface-Wave Analysis
Authors: Kounoudis Rita , Bastow Ian , Ebinger Cynthia , Ogden Christopher , Ayele Atalay , Bendick Rebecca , Mariita Nicholas , Kianji Gladys , Musila Martin , Sullivan Garrett
Published: March 2022

Multiple geoscientific studies along the Main Ethiopian and Eastern rifts have revealed that extension via magma intrusion now prevails over plate stretching as the primary mechanism for strain accommodation throughout the crust and mantle lithosphere. However, problematic in this picture is where the Main Ethiopian and Eastern rifts meet, across the low-lying, broadly-rifted, and as-yet poorly-studied Turkana Depression which separates the elevated Ethiopian and East African plateaus. We have so far revealed through body-wave tomography (Kounoudis et al., 2021), that the Depression does not lack mantle dynamic support in comparison to the plateaus, suggesting a significantly thinned crust, resulting from superposed Mesozoic and Cenozoic rifting, most likely explains its low elevations. Slow uppermost-mantle wavespeeds imply the presence of either melt-intruded mantle lithosphere or ponded asthenospheric material below lithospheric thin-spots induced by the region’s multiple rifting phases. To better illuminate the Depression’s lithosphere-asthenosphere system, we conduct a surface-wave analysis to image crust and uppermost-mantle structure using data from the NSF-NERC funded Turkana Rift Arrays Investigating Lithospheric Structure (TRAILS) project broadband seismic network. In particular, we investigate the presence of melt, whether the lithosphere is melt-rich, melt-poor, and/or if ponded zones of asthenosphere exist below variably thinned lithosphere. Group velocity dispersion curves, measured using data from local and regional earthquakes, yield the first high resolution fundamental mode Rayleigh-wave group velocity maps for periods between 4 and 40s for the Turkana Depression. In collaboration with the ongoing TRAILS GPS project, we explore how these results relate to present-day versus past episodes of extension.

 

Kounoudis, R., Bastow, I.D., Ebinger, C.J., Ogden, C.S., Ayele, A., Bendick, R., Mariita, N., Kiangi, G., Wigham, G., Musila, M. & Kibret, B. (2021). Body-wave tomographic imaging of the Turkana Depression: Implications for rift development and plume-lithosphere interactions. G3, 22, doi:10.1029/2021GC009782.
Hydroacoustic mapping of geogenic reefs, a matter of technique: a practical example from the Baltic Sea
Authors: Papenmeier Svenja , Feldens Peter
Published: March 2022

Geogenic reefs are hotspots for benthic organisms including fish. Given their ecosystem importance, the European Union has protected them by law and demands an area-wide mapping. The German federal agency for nature conservation together with scientific experts has lately published a guideline to map reefs in the Baltic Sea. Reef delineation is based on hydroacoustic backscatter mosaics which are divided and interpreted in 50x50 m cells. Each cell is categorized according to the number of boulders present:  none, 1-5, and more than 5 boulders. The categorization is strongly dependent on the data quality, hydroacoustic frequency used and technique of boulder identification (manual or automatic). By comparing data with different frequencies interpreted each manually and automatically we will demonstrate the importance of appropriate data for reef delineation.
Investigating the interaction between snowmelt runoff and road in the activation of hillslope instabilities affecting a landslide-prone mountain basin through a multi-modeling approach
Authors: Mauri Luca , Cucchiaro Sara , Grigolato Stefano , Dalla Fontana Giancarlo , Tarolli Paolo
Published: March 2022

Roads presence and landslides occurrence in steep slope mountain areas are often strictly connected. In recent decades, the use of Airborne Laser Scanning (ALS)-derived high-resolution topographic data amplified the possibilities to better represent landscapes and related physical processes at the basin scale. Additionally, the adoption of topographically-based hydrological models allows to simulating water overland flows dynamics and investigating the occurrence of specific degradative phenomena. In this regard, snowpack melting plays a key role in altering superficial water dynamics in mountain landscapes, but accurate investigation about the interaction between snowmelt runoff and human infrastructures (such as roads) in the occurrence of hillslope failures is still obscure. This research aims to assess the relationship between snowmelt runoff, road presence and terrain instabilities affecting a landslide-prone steep slope mountain meadow (northern Italy). An innovative multi-modeling approach was tested to detect the alteration of snowmelt overflows due to the road’s presence, as well as to investigate its relationship with the activation of a shallow landslide. The role of the road in altering snowmelt runoff was investigated both considering its presence and assuming its absence by a novel Digital Elevation Model (DEM) editing procedure. Different hydrological and slope stability models were interactively implemented, starting from pre-event ALS-derived DEM to propose predictive basin-scale simulations. Results attested the relevant role played by the road in altering snowmelt runoff overland flows, as well as their combined contribution in the foreseen activation of the observed shallow landslide. Starting from on-field observations conducted after the landslide triggering, the accuracy of instabilities predictions was tested through the computation of the Area Under the Receiver Operating Characteristic curve (AUC-ROC) and the Cohen’s kappa-index. This work could be a useful tool for planning mitigation interventions able to reduce the occurrence of similar risk scenarios, also providing specific suggestions for developing and promoting efficient sustainable actions for mountain landscapes.
Vulnerability scenarios for flash floods occurred in Campanian Apennines (South Italy)
Authors: Forte Giovanni , De Falco Melania , Santangelo Nicoletta , Santo Antonio
Published: March 2022

Flash floods are related to short duration and high intensity rainfalls, they are common phenomena in many parts of Europe as well as Italy. These events can result in debris flow, debris flood or water flood. The main differences are in the triggering, propagation, and depositional phases and more importantly in terms of velocity, impact forces and associated damage.
In Campania Region (Southern Italy) these phenomena historically involved the catchments several times, with an increase in frequency in the last decade. They are associated to small watershed – fan systems that fall in the southern Apennines characterized by intermittent flow. The alluvial fans in the outlet zones are highly urbanized, hence the population living in the deposition areas is exposed to high risk. 
In this study, the geomorphic response to flash floods is assessed through magnitude evaluation of some flash floods recently occurred in heterogeneous geological and geomorphological settings in both coastal and inland areas. Each scenario is reconstructed through the mapping of areal extent, water heights, particle sizes and estimate of volumes and built damage aiming at vulnerability definition, a relevant topic considering the global climate changes.
In this study, an approach aimed at developing vulnerability curves is proposed. It is based on a application of a typical method widely adopted in the earthquake engineering that in this case assume as intensity parameter the water height measured in post-event surveys. 
The results are expressed as vulnerability curves at different damage scenarios that can be valuable tools for local authorities, emergency, and disaster planners since they can assist decision making analysis of protection measures for future events.
Satellite Remote Sensingof Melt Ponds and Albedoin the Arctic
Authors: Niehaus Hannah , Istomina Larysa , Malinka Aleksey , Zege Eleonora , Sperzel Tim , Spreen Gunnar
Published: March 2022

A wide variety of surface types are present in the Arctic: Ocean, ice, snow and melt ponds cover the surface featuring a strong heterogeneity. Due to the differences in their albedo the composition of these surface types strongly impacts the radiative feedback and hence the energy budget which is crucial in climate models. During the summer period the variability is particularly high because the increased temperatures lead to melt pond formation. The seasonal development of melt ponds features fast and local changes in fraction of surface types and thus in albedo. To study the ice-albedo feedback and its impact on the Arctic climate, large scale and regular information on these characteristics are necessary. This can be facilitated by the use of satellite remote sensing.
In 2016, the Sentinel-3 mission was launched providing full coverage of the Arctic on a daily basis aside from cloud coverage limitations. The devices these satellites carry include the Ocean and Land Colour Instrument (OLCI) and the Sea and Land Surface Temperature Radiometer (SLSTR). Together these two instruments measure 30 spectral bands at wavelengths between 400 nm and 12 μm. We present the available melt pond fraction and surface albedo products retrieved from the optical Setinel-3 satellite data with the Melt Pond Detector (MPD) algorithm developed by Zege and others. However, these measurements cannot resolve surface type heterogeneity beyond the spatial resolution of 1.2 km and require additional information to enable spectral unmixing of these surface types at a sub-pixel scale. To investigate the performance and enable improvements of the established retrieval, higher resolution satellite imagery is used. The Sentinel-2 twin satellites were launched in 2015 and 2017 and provide spectral measurements in the optical and near-infrared range at a resolution of 10 m whereas the temporal and spatial coverage is limited. A classification algorithm developed by Wang et al. is applied to obtain melt pond fractions of this increased accuracy for the years 2018 to 2021. Here, we present the melt pond fraction for selected Sentinel-2 scenes and their correspondence with the allocated MPD results. These show good agreement for landfast ice areas with distinct melt ponds, while in general drift and resolution issues are likely to be responsible for discrepancies. For the period of June and July 2020, the available and cloud free scenes along the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift track are evaluated. This observation indicates a melt onset on the MOSAiC floe mid of June, roughly one week prior to the vicinity.
How does pit-mound microrelief affect preferential flow and runoff formation in forest soils? A case study using rain simulator and dye tracer
Authors: Juras Roman , Valtera Martin , Jačka Lukáš
Published: March 2022

The distribution of rainwater and subsurface runoff formation in forest soil can be strongly affected by soil disturbance and microrelief. This study analyses preferential pathways of dyed water after artificial rainfall on a forested slope with pits and mounds formed by historical tree uprooting.

Two heavy rain experiments were carried out using a special tailored rainfall simulator. The first plot was situated above the pit-mound transition. The second (control) plot was situated at a nearby undisturbed surface. The soil profiles were excavated after the rainfall simulation and the dyed stained patches indicating preferential flow were photographed. Subsequently, advanced image analysis was performed to assess differences in water flow patterns in both soil profiles.

The results show contrasting dyed patterns in soil, indicating significant differences in the preferential flow and runoff formation at each plot. The dye-stained patches revealed in image analysis indicated much higher water entry into subsoil of pit profile (31 % of area) than in control plot (8 %). These findings support our previous hypothesis about the significant impacts of terrain depressions formed by tree uprooting on preferential flow and subsurface runoff formation. These terrain disturbances may redirect shallow subsurface flow and force the redistribution of water into deep subsoil layers.  The effects of pit-mound microrelief on the hydrology of forested slopes should be considered in future hydrological modelling and land management.
Quantifying the relationship between flood and wind damage over North-West Europe, in a present and future climate
Authors: Bloomfield Hannah , Bates Paul , Shaffrey Len , Hillier John , James Rachel , Pianosi Francesca
Published: March 2022

Strong winds and extremes in precipitation are capable of producing devastating socio-economic impacts across Europe. Although it is well known that individually these drivers cause billions of Euros of damage, their combined impacts are less well understood. Previous work has typically either focused on daily or seasonal timescales, demonstrating that compound wind and precipitation events are commonly associated with passing cyclones or particularly wet and windy years respectively. This study systematically investigates the relationships between national wind and flood damage metrics at all timescales ranging from daily to seasonal during the winter season. This work is completed using high resolution meteorological reanalysis and river flow datasets to explore the historical period (1980-present). As well as this, data from the UKCP18 climate projections at 2.2km and 12km resolution is used to understand historical sampling uncertainty, and the possible impacts of future climate change.

The correlation between national aggregate wind gusts and precipitation peaks at ~10 days; whereas, the correlation between national aggregate wind gusts and river flows peaks at ~3 weeks. When using more impact focussed metrics of compound wind and flood events, such as storm severity and flooding indices, the strongest correlations are seen at seasonal timescales. Results show the historical correlation between wind and flood damage becomes weaker as the definition of the metrics become more impact focussed, and this is true across all timescales from daily to seasonal. This change in relationship is of key importance to the insurance industry who require actionable information based on both the meteorological hazards and on the exposure of their portfolios. The work is designed to support climate analytics for financial institutions, as part of the UK Centre for Greening Finance and Investments (UKCGFI). Results incorporating the impacts of climate change on compound wind and flood events will also be discussed.
Variability in Irminger Sea convection and hydrography from 2003 through 2020
Authors: de Jong Femke , Le Bras Isabela , Trafford McRaven Leah , Sterl Miriam , Duyck Elodie , Fried Nora
Published: March 2022

The Atlantic Meridional Overturning Circulation (AMOC) is an important component of the climate system. Results from the OSNAP (Overturning in the Subpolar North Atlantic Program) moored array show that the largest contribution to both the total overturning and its variability originates from the Irminger Sea and Iceland Basin. Deep convection in the Irminger Sea strongly impacts the transformation of buoyant to dense waters. Additionally, its localization in the center of the basin directly affects the basin’s horizontal density gradients that drive transport. However, the strength of convection varies greatly from winter to winter and is expected to weaken as a result of strengthening stratification forced by climate change. How exactly the Irminger Sea convection responds to stratification versus forcing is not known.

The LOCO (Long-term Ocean Circulation Observations) mooring recorded convection in the central Irminger Sea from 2003 through 2018. This record is now continued by the OOI (Ocean Observatory Initiative) mooring, deployed nearby in 2014. The combined record of the two moorings showcase the variability of Irminger Sea convection through this 17-year period. This includes the deepest (>1600 m) convection observed in the basin, forced by the exceptionally strong winter of 2014-2015, as well as several winters (in 2010-2011 and 2019-2020) where convection was inhibited by strong upper ocean stratification. The Irminger Sea hydrography changed as a result. The basin warmed and became more saline and stratified during the initial period with weak convection. This trend was halted during the intermittent convection in the mid-2010s. After 2014-2015, the upper 1500 m of the basin cooled and became fresher as a result of stronger convection in the subsequent winter, which led to denser water classes and weaker upper to mid-ocean stratification in the center of the basin. These hydrographic changes and their impact on the cross-basin density gradients are reflected in the Irminger Current transport.

The long record of the Irminger Sea hydrography shows the respective influence of atmospheric buoyancy forcing versus stratification on deep convection. In terms of stratification, we see the effects of both ocean memory in the upper 1500 m of the water column, during prolonged periods of weak or strong convection, and more sudden changes in the uppermost (~100 m) ocean. These insights will help to better predict how Irminger Sea convection will respond to future stratification changes.
Ice stream dynamics and ice margin retreat of the last Laurentide Ice Sheet in the Northwest Territories, Canada
Authors: Dulfer Helen E. , Stoker Benjamin J. , Margold Martin , Stokes Chris R. , Clark Chris D. , Ó Cofaigh Colm , Evans David J.A.
Published: March 2022

The Laurentide Ice Sheet (LIS) was the largest of the ephemeral Pleistocene ice sheets in the Northern Hemisphere, with a Last Glacial Maximum (LGM) ice volume similar to the modern Antarctic ice sheet. A recent inventory of paleo-ice streams across the LIS shows many similarities with present-day ice streaming in Antarctica, where ice streams account for approx. 90% of mass loss. However, in the Mackenzie Lowlands of the Northwest Territories, Canada, the paleo-ice stream record is enigmatic. Previous work has identified a number of large paleo-ice streams, including the Mackenzie Trough, Anderson, Bear Lake and Fort Simpson ice streams, however, their extent, configuration, temporal relationship to each other and spatial evolution over time remains poorly constrained. Consequently, their impact on the rate and style of deglaciation of the northwestern sector of the LIS is poorly understood.

Here we utilise the newly available high resolution Arctic DEM (0.5 m resolution) to re-map glacial landforms across the Mackenzie Lowlands in greater detail (area >800,000 km2). We then use this landform record to reconstruct the ice dynamics in this region following the well-established approaches of flowset mapping and the glacial inversion method. The high resolution data allow us to present a detailed reconstruction of LGM ice flow over the Mackenzie Lowlands and resolve the configuration and evolution of ice streams over time. The landform record suggests that the ice streams operated time-transgressively during deglaciation, switching on and off at different times. While ice contact landforms, such as moraines, lateral and submarginal meltwater channels and ice-contact deltas, show the overall retreat of the LIS towards the Keewatin Dome in the east, in several regions the ice retreat record is complex, suggesting interlobate ice configurations with multiple ice retreat directions.
Variational data assimilation for advanced cross-scale ocean modelling.
Authors: Stefanelli Marco , Jansen Eric , Aydogdu Ali , Federico Ivan , Coppini Giovanni , Pinardi Nadia
Published: March 2022

Eight of the top ten most populated cities in the world are located by the coast. The improvement of the coastal ocean representation is a key topic to understand the  present and near-future ocean state and predict its evolution under climate change conditions.

The coastal ocean is difficult to model due to the presence of complex coastlines, interaction with inland waters, rapid changes in  topography and highly space-time variability of the phenomena involved. Unstructured-grid models are used to partially attenuate this source of errors in cross-scale (from open sea to coastal regions) oceanographic modelling. On the other hand, the data assimilation methodologies to improve the unstructured-grid models in the coastal seas is being developed only recently (e.g., Aydogdu et al., 2018; Bajo et al., 2019) and needs more advancements.  

Here, we show preliminary results from the coastal ocean forecasting system SANIFS (Southern Adriatic Northern Ionian coastal Forecasting System, Federico et al., 2017) based on SHYFEM fully-baroclinic unstructured-grid model (Umgiesser et al., 2004)  interfaced with OceanVar (Dobricic and Pinardi, 2008; Storto et al., 2014), a state-of-art variational data assimilation scheme, adopted for several systems based on structured grid (e.g. regional CMEMS for Mediterranean and Black Seas, marine.cmems.eu).

In OceanVar, Empirical Orthogonal Functions (EOFs) method is used to reduce the dimensionality of computation removing the statistically less significant modes and to correlate observations and model background in the water column;  while the increments are spread horizontally using the recursive filter method. While this method is typically only used to model covariances between neighbouring points in a structured grid, the algorithm has now been generalised and successfully implemented also for unstructured grids.

Preliminary results show that temperature and salinity observations from Argo profilers improve the ocean state. Future steps will also include sea level assimilation. 

This work is a starting point in order to improve our forecast of local extreme events (e.g. heat waves and storm surge) which are statistically increasing in number and intensity in the Mediterranean region due to climate change.
Direct and inverse scattering transform analysis of stochastic nonlinear wavefields
Authors: Gelash Andrey
Published: March 2022

The numerical direct and inverse scattering transform applications represent a broad topic of nonlinear wave field studies [1]. Here we investigate various stochastic nonlinear wavefields with the dominant role of a large number of solitons within the one-dimensional nonlinear Schrodinger equation model. First, applying the recently developed direct scattering transform numerical scheme allowing accurate identification of the complete wavefield scattering data [2,3], we find distributions of all soliton parameters (amplitudes, velocities, positions, and phases). Then, using the previously developed numerical tools of solving the inverse scattering problem for a large number of solitons [4], we reconstruct the solitonic content of the initial wave field, which allows us to estimate the role of solitons in the initial wave field composition. Finally, we discuss the obtained scattering data distributions, paying particular attention to the correlations in parameters of different solitons. The presented accurate characterization of soliton positions and phases in stochastic nonlinear wavefields can be used in further studies of such important realms of nonlinear physics as spontaneous modulation instability development [5] and integrable turbulence growing [6].

 

The work was supported by Russian Science Foundation grant No. 20-71-00022.

 

[1] A. Osborne, Nonlinear Ocean Waves (Academic Press, New York, 2010).

[2] A. Gelash, and R. Mullyadzhanov, Physical Review E, 101(5), 052206, 2020.

[3] R. Mullyadzhanov, and A. Gelash, Optics Letters, 44(21), 5298-5301, 2019.

[4] A. A. Gelash and D. S. Agafontsev, Physical Review E 98, 042210, 2018.

[5] D. S. Agafontsev and V. E. Zakharov, Nonlinearity 28, 2791, 2015.

[6] D. S. Agafontsev and V. E. Zakharov, Low Temperature Physics, 46(8), 786-791, 2020.
 Functional transformation of Ecological-production-living land use and Eco-environmental effects in Ningxia
Authors: Xu yaotao
Published: March 2022

[Objective] to clarify the spatial distribution pattern of land use and the change of eco-environmental quality effect caused by its transformation in Ningxia. [Method] Based on the four high-precision remote sensing interpretation images of land use status from 1990 to 2018, the regional land use classification system of Ningxia was constructed according to the leading function of "Sansheng" land, and the geographic information Atlas method, eco-environmental quality index, center of gravity transfer model and the ecological contribution rate of land use transformation were adopted. [Results] from 1990 to 2018, the production land increased by 14.3%, the living land increased by 29.1%, and the grassland ecological land decreased by 138.1km2 per year; The overall eco-environmental quality index of Ningxia has deteriorated, from 0.455 in 1990 to 0.438 in 2018. The area of medium quality area accounts for about 65% of the whole region, forming the main body of eco-environmental quality; According to the center of gravity model, the eco-environmental quality in northern Ningxia has been improved; From 1990 to 2018, the improvement and deterioration of regional ecological environment in Ningxia coexisted, and the trend of ecological environment deterioration was greater than that of improvement. [Conclusion] the quality of ecological environment in Ningxia has decreased, and the run of agricultural production land on forage ecological land is the main reason.
Mapping the 410-km and 660-km discontinuities across the European Alps using noise correlations 
Authors: Lu Yang , Bokelmann Götz
Published: March 2022

The mantle transition zone is delineated by seismic discontinuities at approximately 410-km and 660-km depth. The lateral variations in reflectivity and depth of the two seismic discontinuities reflect changes in mineralogy composition, thermal state, and water content, that is key to understanding the Earth’s dynamics. Traditional imaging methods based on the analysis of earthquake signals, such as seismic tomography and receiver function analysis, are often limited by earthquake occurrence and uncertainties related to the earthquake source parameters. Recent studies demonstrated the feasibility of recovering body waves from noise correlations, providing new prospects for imaging deep Earth [e.g., Poli et al., 2012; Boué et al., 2013]. 

In this study, we map the 410-km and 660-km discontinuities beneath the European Alps using reflected body waves recovered from noise correlations. To that end, we compute noise correlations using four years of continuous recordings from ∼1200 broadband stations in the greater Alpine region. To enhance the signal-to-noise ratio of the body-wave reflection phases, for each station pair, we stack daily noise correlations in selected time spans with a high level of near vertical-incident body waves and less dominant surface waves [Lu et al., 2021]. We further stack noise correlations of station pairs with common/nearby reflection points to obtain local zero-offset reflection waveforms. The retrieved P410P and P660P reflection phases clearly reveal lateral variations of both reflectivity and depth of the two discontinuities in the studied region, providing new constraints in addition to existing results from earthquake tomography and receiver function analysis. Besides, this study also sheds light on the strategies to recover deep reflection phases from noise correlations.

[1] Boué, P., Poli, P., Campillo, M., Pedersen, H., Briand, X., & Roux, P., 2013. Teleseismic correlations of ambient seismic noise for deep global imaging of the Earth, Geophys. J. Int., 194(2), 844-848.

[2] Lu, Y., Pedersen, H.A., Stehly, L., and AlpArray Working Group, 2022. Mapping the seismic noise field in Europe: spatio-temporal variations in wavefield composition and noise source contributions, Geophys. J. Int., 228(1), 171-192.

[3] Poli, P., Campillo, M., Pedersen, H., and L. W. Grp, 2012. Body-wave imaging of Earth’s mantle discontinuities from ambient seismic noise, Science, 338(6110), 1063-1065.
Identifying different source contributions of formaldehyde using long-term MAX-DOAS measurements of atmospheric trace gases
Authors: Donner Sebastian , Dörner Steffen , Artaxo Paulo , Beirle Steffen , Buxmann Joelle , Campbell David , Kumar Vinod , Müller Detlef , Remmers Julia , Rolfe Samantha M. , Sinha Vinayak , Walter David , Wagner Thomas
Published: March 2022

Multi-AXis (MAX)-Differential Optical Absorption Spectroscopy (DOAS) measurements use spectra of scattered sun light recorded under different elevation angles. Such measurements allow the retrievals of tropospheric vertical column densities (VCDs) and aerosol optical depths (AODs) as well as vertical profiles of atmospheric trace gases and aerosols for the lower troposphere. Further, this kind of measurement enables the simultaneous observation of multiple trace gases, e.g. formaldehyde (HCHO), glyoxal (CHOCHO) and nitrogen dioxide (NO2), with one measurement setup. Together with international partners, we run several long-term MAX-DOAS measurements at different places around the globe and conducted intensive measurement campaigns at various locations. These campaign data sets include both stationary and mobile (car and ship MAX-DOAS) measurements. For our measurements self-built so-called Tube MAX-DOAS instruments were used which cover a wavelength range of approximately 302 to 465 nm with a FWHM of around 0.65 nm.

In the presented study, we focus on measurements of tropospheric formaldehyde which is mainly secondarily produced by reactions from precursor substances. However, in small amounts it can also be emitted directly by anthropogenic and biogenic activities. Further, HCHO plays an important role in atmospheric chemistry. As secondarily produced HCHO is an intermediate product of basic oxidation cycles of other hydrocarbons (also referred to as volatile organic compounds (VOCs)) observations of HCHO can be used as an indicator for VOCs. Since our measurements were taken at different places with different underlying meteorological and environmental conditions, our large data set allows to gain insights into the contributions from different sources and chemical processes covering various geographic and environmental conditions. Here, it is important to note that compared to satellite instruments, MAX-DOAS instruments have a much higher sensitivity to boundary layer HCHO (by a factor of 10 or more).

In this presentation we try to identify different pollution levels, source contributions and chemical regimes of formaldehyde by combining HCHO VCDs, surface values and profiles with the same properties of other trace species such as NO2, CHOCHO and aerosols. The results will be compared for four measurement sites, namely the stations at Mainz/Germany, Bayfordbury/United Kingdom, Mohali/India and the Amazonian Tall Tower Observatory (ATTO) measurement site/Brasil.
Satellite-based coastal bathymetry for annual monitoring on the Mediterranean coast: A case study in the Balearic Islands
Authors: Viana-Borja Sandra , Fernández-Mora Angels , Stumpf Richard P. , Navarro Almendros Gabriel , Caballero de Frutos Isabel
Published: March 2022

More than 60% of the world's population lives near coastal zones. These are the most productive as well as the most vulnerable ecosystems in the world. Considering these, among other factors, the study of coastal zones is a matter of vital importance, so that it is necessary to have accurate information for an appropriate coastal management. The shallow bottom topography is considered one of the most critical parameter in coastal studies, because of its significance in different areas such as industry, navigation, defense, aquaculture, tourism, maritime planning, and environmental management, among others. The bathymetry is one of the biggest challenges for coastal engineers and scientists, since it is quiet complex to gather accurate data and to keep it updated because it is a time-consuming and very expensive process. In recent years, satellite-derived bathymetry (SDB) has emerged as an alternative to the most common survey techniques. In the present case study, a recently developed multi-temporal SDB model is applied to overcome problems associated with turbidity and noise effects. This model had been applied in many areas of the Caribbean and EEUU coasts with outstanding performance, providing an accurate bathymetry of the selected areas. In this case, it has been analyzed the bottom topography changes in the Cala Millor beach (Mallorca Island, Spain) between 2018, 2019 and 2020, using images from the Sentinel-2A/B twin mission of the Copernicus Programme. ACOLITE processor has been applied to Sentinel-2 L1A images for atmospheric and sunglint correction. The study aims at demonstrating the effectiveness of this model in the Mediterranean region to show its consistent performance on distinct geographic zones around the world, in addition to improving the results with a composited multi-temporal image selected automatically. Showing the confidence of this capability to be applied in any micro-tidal coast around the world may enhance the existing survey methods and highly contribute to the scientific knowledge by providing scientists and engineers with new science-based tools to better understand coastal zones.

 