bluuebunny/crossref_metadata_2025 huggingface dataset:
Observed and simulated variations of marine partial pressure of CO2 within the central North Sea: The choice of the bulk air-sea flux formula matters
Authors: Paetsch Johannes , Macovei Vlad A. , Voynova Yoana G. , Petersen Wilhelm , Möller Lennart
Published: February 2023

The partial pressure of carbon dioxide (pCO2) in surface waters is influenced by physical, chemical and biological variables. The interplay of these environmental variables is shown along a section in the central North Sea between Immingham (UK) and Halden (Norway) for the year 2013. Both, underway measurements by ships of opportunity and the results of a high resolution 3D – biogeochemical model show very high pCO2 values near the UK coast and reduced values near the Norwegian coast. This pattern is due to high UK river loads at the western part and the outflow of Baltic water along the Norwegian coast at the eastern part of the section. Seasonal variations within the central North Sea off the coastal waters exhibit both the influence of temperature and biological activities. During the phytoplankton growth seasons, the pCO2 is considerably lowered by the biological uptake of dissolved inorganic carbon and concurrently increased by higher sea surface temperatures.The model is able to reproduce observed winter pCO2 values using a variety of different bulk air-sea flux formulas. However, during spring and summer, the use of these formulas results in overestimated simulated pCO2 values. Only the application of a formula which takes the presence of surfactants into consideration improved the simulated pCO2 values. The latter formula exhibits lower piston velocities for the exchange of CO2 between atmosphere and ocean than the common formulas.
Spontaneous Earthquake generation Experiments by Controlling Shear Stress in a Rotating Shear Apparatus
Authors: Hamada Yohei , Hirose Takehiro , Tanikawa Wataru , Suzuki Takahiro
Published: February 2023

Earthquake faults are stationary in a critical state where they either slip or not.The fluid pressure fluctuation in the fault zone at this critical state is thought to be one of the factors that cause a variety of earthquakes that progress from slow to fast. This process of earthquake generation has been studied using the conventional "slip displacement - rate control" method, however, this does not reproduce the process of initiation and acceleration of slip as natural earthquake generation. In this study, we conducted experiments to induce spontaneous fault slip using a rotating friction apparatus that can control torque and fluid pressure rather than slip rate.First, as a simple experiment, a sample (standard SiO2) whose frictional behavior was measured at low and constant velocity was used to continuously and gradually increase torque (0.3 N-m/s) under normal stress of 5 MPa. Slip started when the torque reached 200 N-m (corresponding to a shear stress of 4 MPa and a coefficient of friction of 0.8) and gradually accelerated to 170 microns/sec, at an acceleration of 20 micron/s/s. We also conducted an experiment in which the fluid pressure was increased in steps after the axial pressure and torque were applied at fixed values in advance, and similar acceleration behavior was obtained here as well. For both experiments, the termination velocity was 170 microns/sec and did not accelerate to the cm/sec order, which was set as the limit. These could have reproduced the onset of the slow earthquake, but it is also possible that the result may have been due to experimental problems that the torque was not controlled and decreased with the onset of the slip. The presentation will include this and other experimental results, as well as the interpretation of the torque-controlled experimental results and initiation of slow earthquake.
On the chemical purity and oxygen isotopic composition of a-cellulose extractable from higher plants and the implications for climate, metabolic and physiological studies
Authors: Zhou Youping
Published: February 2023

The 18O/16O ratio of a-cellulose in land plants has proved of interest for climate, environmental, physiological and metabolic studies. Reliable application of such ratio may be compromised by the presence of hemicellulose impurities in the a-cellulose product obtainable with current extraction methods, as the impurities are known to be isotopically different from that of the a-cellulose. We firstly compared the quality of hydrolysates of “a-cellulose products” obtained with four repre-sentative extraction methods (JAYME and WISE; BRENDEL; ZHOU; LOADER) and quantified the hemicellulose-derived non-glucose sugars in the “a-cellulose products” from 40 land grass species using GC/MS. Secondly, we performed com-pound-specific oxygen isotope analysis for the hydrolysates using GC/Pyrolysis/IRMS. These results were then compared with the bulk isotope analysis using EA/Pyrolysis/IRMS of the “a-cellulose products”. We found that the ZHOU method afforded overall the highest purity a-cellulose as judged by the minimal presence of lignin, and the second lowest presence of non-glucose sugars in the investigated grass species. Isotopic analysis then showed that the O-2~O-6 of the a-cellulose glucosyl units were all depleted in 18O by 0.0-4.3 mUr (with an average of 1.9 mUr) in a species-dependent manner relative to the a-cellulose products. The positive isotopic bias of using a-cellulose product instead of the glucosyl units stems mainly from the fact that the pentoses that dominate hemicellulose contamination in the a-cellulose product are relatively enriched in 18O (compared to hexoses) as they inherit only the relatively 18O-enriched O-2~O-5 moiety of sucrose, the common bio-chemical precursor of pentoses and hexoses in cellulose, and are further enriched in 18O by the (incomplete) hydrolysis. Failure to prepare a-cellulose with the highest possible purity, free from lignin and hemicellulose contamination, can bias predictions based on mechanistic models linking a-cellulose oxygen isotope composition to plant growth conditions.
Reducing biases and representation errors in the global historical insitu upper-air network
Authors: Haimberger Leopold , Ambrogi Federico , Voggenberger Ulrich
Published: February 2023

In preparation for the next generation Copernicus reanalysis ERA6, we aim at augmenting the global insitu upper-air dataset with additional data and metadata, in order to reduce observation and representation errors in those data. For all available data, the balloon drift is calculated from the available wind data information. Also the actual launch time is supplied for as many ascents as possible, to reduce representation errors. Results indicate that background departures (from ERA5) are almost uniformly reduced for temperature, humidity and wind, with strongest reductions near the extratropical jet streams, if balloon drift is taken into account. The data set also contains background departures, calculated offline, for data not assimilated in ERA5, which helps spotting spurious data episodes. Background departures were calculated with respect to ERA5, before 1940 a bias-adjusted version of the NOAA/CIRES/DOE reanalysis v3 was used as reference. For the first time, we also include ascents launched from ships. The background departures form the basis for comprehensive statistics-based adjustment of biases in temperature, wind direction and also humidity, using the RAOBCORE/RICH method. The corresponding software has been completely rewritten in python and has an improved handling of data gaps. Results from bias-adjusted records indicate realistic spatial trend heterogeneity and very good fit to reprocessed satellite data products. Background departures from ERA5 increase substantially when going back to the early 1950s and 1940s, even after bias adjustments,  but are still better than departures found when comparing to the 20th century reanalysis.  
Tibetan Plateau surface albedo responds instantly to both snow coverage and depth
Authors: Miao Xin , Guo Weidong , Li Wenkai , Cao Yipeng
Published: February 2023

The Tibetan Plateau snow cover is characterized by rapid changes on a weekly time-scale, which can cause rapid changes in surface albedo. Using snow and surface albedo data from satellite observations, we find that changes in snow coverage on the Tibetan Plateau dominate the rapid changes in surface albedo. However, snow depth also has a distinct effect on rapid changes in surface albedo in some areas especially with unstable snow cover. We test the snow depth-dependent snow albedo parameterization scheme in the land surface model. The results show that whether or not the variation of snow albedo with snow depth is considered directly affects the rapidly changing characteristics of the simulated snow cover on the Tibetan Plateau, which further affects the simulation of surface albedo. These results highlight the rapid response of surface albedo to both snow coverage and depth over the Tibetan Plateau.
The Role of North American Convective Storms on Jet Stream Dynamics: A Negative Potential Vorticity Perspective
Authors: Lojko Alexander , Winters Andrew , Jablonowski Christiane , Payne Ashley
Published: February 2023

Synoptic-scale filaments of negative potential vorticity (PV) in the northern hemisphere tropopause can form adjacent to the jet stream in the presence of convection and moderate shear (i.e., severe thunderstorm environments). Case-studies have shown that synoptic-scale negative PV can influence in-situ jet stream dynamics. Negative PV arises due to strong vorticity in convective updrafts, driven by the horizontal gradient of diabatic heating (O < 10 km).  Its origin from scales not resolvable by contemporary global weather models can thus also impinge on jet stream forecast skill.Nevertheless, little is still known about the characteristics of synoptic-scale negative PV. How frequently is it observed? And what are its ‘typical’ impacts on the jet stream?Focusing on North America where severe thunderstorms are frequent, we design an algorithm that tracks the temporal evolution of closed contours of upper-level, negative PV air using ERA5 data. We composites instances in which it is in close-proximity to (‘interacts with’) the jet stream and assess its dynamical response. The role of negative PV on jet evolution and its downstream response over the Atlantic is facilitated through a combination of lagged composite analysis and K-means clustering.Our composite results in combination with preliminary high-resolution model simulations highlight that elongated bands of negative PV frequently interact with the jet stream, intensify jet wind maxima and may serve as an amplification source for Rossby waves.
Monitoring the Role of Temporal Land Cover Changes on Mountain Hazard Susceptibility in Beas Valley, Himachal Pradesh, India
Authors: Ghosh Sayanta , Lata Renu , Gouda Krushna Chandra
Published: February 2023

In the last 50 years, drastic change in the spatio-temporal variation of climate patterns have been observed over the Indian Himalayan Region (IHR) resulting increase in the frequency of Extreme Weather Events (EWE) such as cloud burst, flash flooding, land slide etc. Change in climate parameters has direct impact and consequence on the Himalayan ecosystem, which in turn adversely affects livelihood of people living in the high altitude area. Also, alteration in Land Use Land Cover (LULC) have occurred rapidly in the already vulnerable IHR for the last few decades. Few studies have carried out to analyse the impact of land cover changes and regional climate variability on mountain hazard susceptibility in different parts of the world. But there’s a lack of such type of study in high altitude areas of IHR. Here, we have made an attempt to assess the impact of regional climate variability (Precipitation, Air Temperature, Soil Moisture, Relative Humidity) as well as spatio-temporal variations in LULC on the increasing frequency of EWE in Beas river basin of Kullu district, India. For this purpose, using multi-temporal LANDSAT data and high resolution Terra Climate monthly data, temporal Land Cover Changes as well as climate variability over the period of 21 years, i.e., from the year 2000 to 2020 for Beas valley of Kullu district, India have been assessed. Disaster data highlights a drastic increase of 378% in the average occurrence of EWE during present years (i.e., 2016 to 2020) than that of last 16 years (2000 to 2015). Socio-economic survey have been carried out in the disaster prone villages of Beas basin to study people perception.  68.6% respondents believe that the increase in EWE is due to change in climate pattern. It is observed from LULC change detection that a massive increase in Agricultural land, including orchard expansion, of 123 % occurred during the year 2020 than that of 2000 in Beas Valley. Also, there’s a sharp increase of 40.63 % in settlement areas which includes the tourism activities such as hotels, restaurants, etc. during the year 2020 than that of 2000. The average rise in average air temperature is observed as 0.53° Celsius in study area over the period of 21 years. Annual precipitation shows a decrease of 76 mm to 325 mm during the year 2020 than that of year 2000 whereas the number of extreme rainfall days increases by 33.3% within the same interval. Outcome of the paper will be helpful in better understanding the impact of land cover dynamics and regional climate variability on the frequency of EWE in the Beas Valley of Kullu district, Himachal Pradesh, India.KeywordsIndian Himalayan Region, Extreme Weather Events, LULC, Climate Variability, Livelihood Security
Comparison of deep learning approaches to monitor trash screen blockage from CCTV cameras
Authors: Vandaele Remy , Dance Sarah L , Ojha Varun
Published: February 2023

We investigate the use of CCTV cameras and deep learning to automatically monitor trash screen blockage. Trash screens are installed to prevent debris from entering critical parts of river networks (pipes, tunnels, locks,...). When the debris piles up at the trash screens,  it  may block the waterway and can cause flooding. It is thus crucial to clean blocked trash screens and avoid flooding and consequent damage. Currently, the maintenance crews must manually check a camera or river level data or go on site to check the state of the screen to know if it needs cleaning. This wastes valuable time in emergency situations where blocked screens must be urgently cleaned (e.g., in case of forecast  heavy rainfall). Some initial attempts at trying to predict trash screen blockage exist. However, these have not been widely adopted in practice.  CCTV cameras can be easily installed at any location and can thus be used to monitor the state of trash screens, but the images need to be processed by an automated algorithm to inform whether the screen is blocked.With the help of UK-based practitioners (Environment Agency and local councils), we have created a dataset of 40000 CCTV trash screen images coming from 36 cameras, each labelled with blockage information. Using this database, we have compared 3 deep learning approaches to automate the detection of trash screen blockage: A binary image classifier, which takes as input a single image, and outputs a binary label that estimates whether the trash screen is blocked.
An approach based on anomaly detection which tries to reconstruct the input image with an auto-encoder trained on clean trash screen images.  In consequence, blocked trash screens are detected as anomalies by the auto-encoder.
An image similarity estimation approach based on the use of a siamese network, which takes as input two images and outputs a similarity index related, in our case, to whether both images contain trash. 
Using performance criteria chosen in discussion  with practitioners (overall accuracy, false alarm rate, resilience to luminosity / moving fields of view, computing capabilities), we show that deep learning can be used in practice to automate the identification of blocked trash screens. We also analyse the strengths and weaknesses of each of these approaches and provide guidelines for their application.
Flood inundation mapping along a downstream river segment
Authors: Sarchani Sofia , Tsanis Ioannis
Published: February 2023

According to the IPCC, Eastern Canada is an area where heavy precipitation events are likely to intensify. The Humber River basin is a medium-sized basin located in the Greater Toronto Area, in Southern Ontario, Canada, which is exposed to severe storms resulting in flash floods. A severe storm that passed by the city of Toronto on July 8, 2013 caused a flood with damages across the area, including blackouts and citizens trapped in public transportation and vehicles. Hydro-meteorological stations close to the basin’s outlet, in the urban section, recorded 60-63 mm of rain in two-three hours. The analysis of the examined river segment, including several bridge structures, is performed with two hydraulic models (1D and 2D) by using a high-resolution DTM and two flow hydrographs as input boundary conditions. The 2D hydraulic model provides more detailed results regarding the maximum flood depths, flood wave velocities, and arrival times of maximum depths, at every grid cell of the computational mesh. In comparison, the 1D model provides results at cross-sectional level, and interpolates them in the intermediate positions. The differences between the two models in low-height bridge locations are considerable. The 2D model can be improved by enforcing grid cells at bridges’ locations. However, there is a risk of possible instabilities in solving the shallow water equations by assuming a Courant number kept in low levels. Moreover, during storm events, water level gauges in situ measurements can improve calibrating both hydraulic models. The probable increase in precipitation heights due to climate change indicates the necessity for effective flood risk management in the urban area of the city of Toronto. On-going research concerns the effect of projected extreme precipitation on peak runoff and downstream flood impacts via climate model datasets.
Drought behaviour in Barcelona from its instrumental precipitation series (1786-2022)
Authors: Barriendos Josep , Hernández María , Gil-Guirado Salvador , Barriendos Mariano , Olcina-Cantos Jorge
Published: February 2023

The current climate change scenario increases the concern for water resource management and for the increase in the frequency of droughts in the Mediterranean region. This work proposes the analysis of the instrumental precipitation series of the city of Barcelona (1786-2022), which extends from the end of the Little Ice Age to the current climatic period. This series, due to its temporal length, constitutes a continuous scenario of pluviometric information that allows the identification and analysis of the periods in which the most severe droughts occur.This work is organized following two main objectives. The first objective consists on the analysis of the values of this precipitation series using different statistical techniques, including drought indices. The second objective is the evaluation of the severity of the most significant drought events that appear in the instrumental precipitation series of Barcelona.To achieve these objectives, the methodologies used in this work consist on the application of some statistical techniques on the instrumental precipitation series, such as the detection of its breaking points. At the same time, this work proposes the application of different drought indices as the SPI index and the SPEI index on the entire instrumental precipitation series of Barcelona (1786-2022). The use of these methodologies allows the comparison between the different droughts included in the instrumental series. These also allow distinguishing the most relevant droughts according to their severity. Two significant examples of the most severe droughts are the ones of the first third of 19th century (1812-1825) and the droughts of the 21st century (1998-2008). We also want to determine the relevance of the current drought (2021-2022) in contrast to the overall instrumental series of precipitation of Barcelona.Additionally to these methodologies and results, for the most significant droughts detected in the precipitation series, it is also proposed to use monthly barometric indices to characterise the general atmospheric circulation of those periods. It would have the aim to contrast the results on the instrumental precipitation series with the synoptic conditions that produce these droughts. This comparison also would help to determine if these conditions have changed over time, especially considering recent decades in the context of current climate change.
Polar lows in a globally coupled storm- and eddy-resolving (2.5 km) climate model (ICON-Sapphire)
Authors: Gutjahr Oliver , Mehlmann Carolin
Published: February 2023

Polar lows are intense subsynoptic cyclones on the meso-α to meso-β scale that develop over polar maritime environments. So far, only regional atmospheric models have been able to resolve polar lows due to their small spatiotemporal scales. Investigations with coupled regional atmosphere-ocean models are limited to a single study. We demonstrate the simulation of polar lows and their effects on the ocean and sea ice with the recently developed storm- and eddy-resolving configuration of the ICOsahedral Nonhydrostatic (ICON) model, called ICON-Sapphire. ICON-Sapphire globally couples the atmosphere, land, sea ice and ocean with a horizontal resolution of 2.5 km.Although we focus on the Nordic Seas, ICON-Sapphire simulates polar lows in the northern and southern hemispheres covering the entire mesoscale. They form in different environments, for instance during marine cold air outbreaks or in low-level baroclinic areas at the marginal sea ice zone. Albeit short-lived phenomena, polar lows considerably affect the underlying ocean in ICON-Sapphire, leading to large heat losses, in particular close to the marginal sea ice zone, where they themselves induce cold air outbreaks. This ICON-Sapphire simulation is the first to show how polar lows interact with sea ice to create leads and polynyas due to strong wind stress. Leads and polynyas induce additional heat loss from the ocean that initiates the formation of new ice. Representing polar lows in global climate models increases the heat loss and ice formation from polar oceans, which are otherwise underestimated.
Pool distribution and molecular composition of organic matter among water-stable aggregate size fractions of karst topsoil across a lithologic sequence from Guizhou, Southwest China
Authors: Lin Qingmei , Chen Shuotong , Feng Xiao , Pan Genxing
Published: February 2023

Soil organic matter (SOM) is a key player in soil functioning and services in forest lands, which had been subject to accelerated land degradation particularly in karst terrain in Southwest China. So far, there had been poor knowledge of pool and molecular composition of SOM associated with soil aggregates across lithologic origins of karst soil. In this study, undisturbed topsoil (0-10 cm) samples were collected in forest lands on sandstone (SS), dolomite (DS) and limestone (LS) sedimentary rocks in a karst terrain from Guizhou, Southwest China. Changes in SOM pool distribution and molecular composition of water-stable aggregates were explored using size and density fractionation and GC/MS detection of extracted biomarkers. The OC content ranged from 41.05 g kg-1 on SS to 50.94 g kg-1 while the mean weight diameter of sand-free soil water-stable aggregates ranged from 420.9 μm on SS to 544.4 μm on DS, across the lithologic sequence. With biomarker molecular assay, the higher SOC storage was relevant to the higher abundance of plant-derived organics (lignin, cutin, suberin, wax and phytosterols) in macro- and micro- aggregates. Whereas, the higher OC in silt & clay fraction of topsoil on DS and LS could be explained by the higher abundance of microbial lipids plus cutin and suberin. Also, the higher ratio of (Ad/Al)v to (Ad/Al)s of silt-clay fraction pointed to a stronger degradation of lignin thereby. Thus, the forest soil of dolomite and limestone origin preserved a relatively high level of SOC storage in topsoil, mainly with accumulation of POC physically protected in macro- and micro- aggregates. Moreover, the high SOC of topsoil on dolomite could also be attributed to enrichment of SOC in the clay silt fraction, mainly with mineral association of microbially degraded OCs.
Temperature fluctuation promotes the thermal adaptation of soil microbial respiration
Authors: Zhang Yan , Nie Ming
Published: February 2023

Microbial respiration is the main process contributing to soil carbon (C) loss and is simultaneously regulated by changes in mean temperature and temperature fluctuation. The magnitude of the feedback between soil microbial respiration and increased mean temperature may decrease (i.e., thermal adaptation) or increase over time, and accurately representing this feedback within models improves predictions of soil C loss rates. However, climate change entails changes not only in mean thermal conditions but also in the patterns of temperature fluctuation, and whether temperature fluctuation could also cause thermal adaptation has never been addressed. Here, we collected soil samples from 6 sites along a 2,000-km-long west-east transect extending across subtropical forests in China and used them in an incubation experiment involving various temperature regimes to explore how temperature fluctuation influences the thermal response of soil microbial respiration and the underlying mechanisms of this process. We revealed that soil biomass-specific microbial respiration (Rmass) was significantly lower with increasing temperature fluctuation during incubation regardless of the assay temperature, while a positive relationship between Rmass and temperature was observed under increased constant incubation temperature. Structural equation modelling further indicated that increased bacterial species turnover and reduced substrate affinity (Km) promoted the decrease in Rmass associated with greater temperature variation. Our results demonstrate that if such an adaptive response of soil microbial respiration occurs under greater temperature variation, the stimulatory effect of climate warming may be less than that predicted and thus may not increase atmospheric CO2 concentrations as much as anticipated.
Closure and parameterization of sub-micron aerosols’ hygroscopicity and it’s seasonal variability over the Western Ghats, India
Authors: Ray Avishek , Pandithurai Govindan , Mukherjee Subrata , Kumar Anil V , Hazra Anupam
Published: February 2023

Hygroscopicity of atmospheric aerosol primarily depends on the size and chemical composition of the particle and is important for estimating anthropogenic aerosol radiative forcing. Hygroscopicity is highly related to the activation of aerosols to Cloud Condensation Nuclei (CCN), and hence plays a crucial role in cloud formation and modulating its properties. However, due to limitations of measurement techniques, seasonal variation in size segregated aerosol hygroscopicity (k) is not available over the Indian region.  This study presents ‘k’ as derived from a Humidified Tandem Differential Mobility Analyzer (HTDMA) over the High Altitude Cloud Physics Laboratory (HACPL) in the Western Ghats, India for more than a year (from May 2019 to May 2020).  The average hygroscopicity values of aerosol particles of diameters 32, 50, 75, 110, 150, 210, and 260 nm at 90% RH conditions are 0.189, 0.177, 0.163, 0.170, 0.183, 0.199, 0.207 respectively during the entire observation period.  k was observed to decrease with an increase in size in the Aitken mode regime (32-75 nm) and an increase in the accumulation mode (110-260 nm).  Seasonal variation of hygroscopicity for a wide range of particle diameters is reported which is highly demanding as there is a change in the air mass flow pattern in each of the seasons.  The diurnal cycle of hygroscopicity showed a prominent peak during the midnight to early morning hours followed by a decrease in the forenoon hours and a secondary peak in the afternoon hours.  k is found to be higher in pre-monsoon as compared to the winter season as Chl is approximately 3% higher in pre-monsoon and NH4Cl is highly hygroscopic among the assumed chemical composition.  Assuming the internal and external mixing of aerosols, the closure study yields chemically derived hygroscopicity (kchem) overestimates as compared to kHTDMA though the assumption of external mixing of aerosols improved the values of predicted k. CCN derived hygroscopicity (kccn) underestimates as compared to hygroscopicity derived from HTDMA measurements. Both kchem and kccn are found to follow the similar diurnal variation of kHTDMA. Thus, the kchem and   can be used as a proxy of  in the absence of direct HTDMA measurements. Using kchem and  in numerical models will propagate systematic bias in aerosol to CCN activation processes so a parameterization of hygroscopicity with dry diameter of sub-micron particles is developed and that could be used for a closer real-atmospheric value of hygroscopicity.Keywords: Hygroscopicity, Parameterization, sub-micron aerosols
Towards an ITRF2020 plate motion model
Authors: Altamimi Zuheir , Métivier Laurent , Rebischung Paul , Collilieux Xavier , Chanard Kristel
Published: February 2023

For various geodetic and geophysical applications, users need to have access to a Plate Motion Model (PMM) that is consistent with the ITRF2020 frame. The aim of this paper is to evaluate different possible approaches for determining a PMM from the horizontal velocities of a subset of the ITRF2020 sites away from plate boundaries, Glacial Isostatic Adjustment regions and other deformation zones. Compared with the ITRF2014-PMM, we assess in particular the performance of a PMM based on ITRF2020 velocity field, which contains more sites in some large tectonic plates, such as North and South Americas, Australia, and to some extent Antarctica. Using a global inversion of all plates all together, with full variance-covariance information, the angular velocities of these plates are expected to be improved in the ITRF2020 plate motion model. We also investigate the impact of subtracting GIA horizontal velocity predictions of different models before adjusting for angular plate velocities. Early results will be presented and discussed.
Missing Obliquity Signal in Late Paleocene and Early Eocene Climate Records due to Solar System Chaos
Authors: Zeebe Richard
Published: February 2023

The dynamical evolution of the solar system is chaotic with a Lyapunov time of only ~5 Myr for the inner planets. Due to the chaos it is fundamentally impossible to accurately predict the solar system's orbital evolution beyond ~50 Myr based on present astronomical observations. We recently developed a method to overcome the problem by using the geologic record to constrain astronomical solutions in the past. Our resulting optimal astronomical solution (called ZB18a) shows exceptional agreement with geologic records to ~58 Ma (Myr ago) and a characteristic resonance transition around 50~Ma. Here we show that ZB18a and integration of Earth's and Mars' spin vector based on ZB18a yield reduced variations in Earth's and Mars' orbital inclination and Earth's obliquity (axial tilt) from ~58 to ~48 Ma. The changes in the obliquities have important implications for the climate histories of Earth and Mars. For instance, reduced variations in Earth's obliquity from ~58 to ~48 Ma would have affected Earth's climate across the late Paleocene - early Eocene (LPEE). Remarkably, a nearly ubiquitous phenomenon in long-term geologic records across the LPEE is a very weak or absent obliquity signal. We propose here that the reduced amplitude in Earth's obliquity, as predicted by our astronomical solution ZB18a, contributed to the weak/absent obliquity signal in geologic records from ~58 to ~48 Ma. Dynamical chaos in the solar system hence not only affects its orbital properties, but also the long-term evolution of planetary climate through eccentricity and the link between inclination and axial tilt.
Lagrangian trajectories to assess marine plastic pollution distribution in the Canary Islands
Authors: Cividanes García Marcos , Aguiar González Borja , Gómez Cabrera May , Herrera Ulibarri Alicia , Martínez Sánchez Ico , Rodríguez Santana Ángel , Machín Jiménez Francisco José
Published: February 2023

The increasing presence of plastics in the ocean is a harmful problem for marine ecosystems and the socio-economic sector. A recurrent type of debris gathered in waters of the Canary Islands are the identification tags employed at lobster traps deployed at the north-eastern coast of North America. Since 2016 to the present, these debris have been routinely collected and classified by the EOMAR group (MICROTROFIC Project) through coastal sampling focused on the eastern part of the Canary archipelago. In order to address this problem, a further understanding of the distribution and dynamics of these debris in the ocean is demanding. In this work, a pre-existing tool in Matlab has been upgraded to produce Lagrangian trajectories based on Marine Copernicus surface current velocity (GLORYS12V1). The main goal is to assess the trajectories that floating particles might follow in the North Atlantic subtropical gyre when released over a grid in the north-eastern coast of North America (Gulf of Maine). Our results provide a quantitative basis about the link between the North American north-eastern coast and the Canary Islands, where the presence of these and other debris is of increasing concern.
On convective memory
Authors: Becker Thorsten
Published: February 2023

Plate tectonics is the surface expression of mantle convection, but many aspects of our present-day tectonic setting depend on how the solid Earth system has evolved over time. I touch on work across a range of spatio-temporal scales addressing how convective memory can be used to validate tectonic scenarios to better understand plate boundary evolution. Seismic anisotropy in the upper mantle is one recorder of convective deformation, and the duration over which textures are reworked controls the lifespan of memory. This means that the lithosphere may allow distinguishing between different plate tectonic scenarios over the last ~50 Ma. Uncertainties about those scenarios and slab rheology imply that our understanding of subduction mass transport remains incomplete, leading to ambiguities about the deep mantle record of subduction. One particular issue is how slabs are deformed upon bending in the trench. I discuss results from convection models with rheological memory which affects subduction dynamics and plume-slab interactions. Within global, plate generating convection models, reactivation of damage zones increases the frequency of plate reorganizations, and hence reduces the dominant periods of surface heat loss fluctuations. Inheritance of lithospheric damage dominates surface tectonics over any local boundary stabilizing effects of rheological weakening. Progressive generation of weak zones may counteract any effects of reduced convective vigor throughout planetary cooling, with implications for the frequency of orogeny throughout Wilson cycles. I close by a consideration of the effects of local rheological damage weakening vs. the longest recorder of geological history of all, the continental lithosphere.
Energy budget of quasi-dynamic earthquake cycle
Authors: Kheirdast Navid , Almakari Michelle , Villafuerte Carlos , Thomas Marion Y. , Bhat Harsha S.
Published: February 2023

The elastic medium that hosts several, multi-scale, faults could be regarded as an energy reservoir that is charged by the far field stress rate and discharged by friction dissipation during earthquake slips on the faults.  In this study, we carefully analyze the energy budget variations that occur throughout a synthetic, 2D plane-strain, earthquake cycle on a fault system comprising of a main fault surrounded by a hierarchy of off-fault slip planes/fractures. We evaluate the rate of kinetic energy variation, stress power across the continuum, far field power supply, and the dissipation due to the rate-and-state friction on the faults given a spectrum of slips ranging from slow-slip to rapid ruptures. We study how the medium's energy budget evolves after these components have been determined.  Additionally, we compute the dissipation rate for a variety of slip rates to determine the contributions of so-called slow-slip events, low-frequency earthquakes (LFEs), and tremors to this budget. We also evaluate the share of off-fault fractures to determine their energetic role during earthquake cycles.
Effects of Inhomogeneity and Anisotropy on THM Simulations
Authors: Chaudhry Aqeel Afzal , Zhang Chao , Ernst Oliver , Nagel Thomas
Published: February 2023

When modeling the material properties of host rocks for THM simulations for the purpose of barrier integrity investigations in deep geological disposal of radioactive waste, there are numerous modeling aspects to consider. We consider the simple case of stationary Darcy flow in a two-dimensional medium to convey the basic phenomena when constructing a suitable model for host rock permeability with a special focus on the treatment of anisotropy occurring at different spatial scales and the associated uncertainty. If complete information were available, permeability would be a known function of space, and hydrological features such as inhomogeneity (spatial variability) and anisotropy (direction-dependence) can be expressed by spatially varying and tensor-valued permeability coefficients. In reality, uncertainty is present and needs to be considered. One approach is to model the rock medium as piecewise homogeneous in such a way that the permeability values in each homogeneous subregion (e.g. geological layer) are modeled as random variables. The permeability values at any two locations of the same subregion are then completely correlated. Randomness with a more general structure can be modeled by random fields, the realizations of which are functions of space which are not necessarily constant. A common modeling choice is that of a Gaussian random field for log permeability, which is completely determined by its mean and two-point correlation function. Anisotropy can now occur both in the statistical covariance structure, resulting in different correlation lengths along principal axes, and in the hydraulic properties, leading to tensor-valued random fields the realizations of which are anisotropic tensors for which the underlying covariance structure may, in addition, display statistical anisotropy.In this work we present a number of simulations designed to illustrate the effects of inhomogeneity, randomness as well as statistical and hydraulic anisotropy.
Vulnerability of Firn to Hydrofracture, Part I: Poromechanical Modeling
Authors: Meng Yue , Culberg Riley , Lai Ching-Yao
Published: February 2023

Ice slabs are multi-meter thick layers of solid reforzen ice that form on top of the porous firn layer in Greenland’s wet snow zone. Recent observations in Northwest Greenland highlight the ability of this relict firn layer to store meltwater in its pores after surface meltwater drains rapidly through cracks in the overlying ice slab. Current fracture mechanics (i.e., LEFM) assumes that the stored elastic energy in an impermeable solid matrix is instantaneously dissipated by creating new crack surfaces, which only holds for impermeable solid media. To better understand the fate of meltwater in the porous firn layer beneath ice slabs, we develop a two-dimensional, poroelastic continuum model to quantify the stress and pressure changes in the porous firn during meltwater penetration.We extend Biot’s poroelastic theory to two-phase immiscible flow by introducing meltwater saturation as an extra variable. By coupling the fluid continuity and force balance equations, we resolve the spatiotemporal evolution of 1) matrix deformations and effective stresses, 2) the water saturation field, and 3) the water pressure field. We adopt a fracture criterion for the cohesive porous firn layer: the maximum tensile effective stress should exceed the material tensile strength to generate fractures. We study the maximum tensile effective stress induced by water injection as a function of firn’s mechanical and hydraulic properties (bulk modulus, porosity, and permeability), and the infiltration conditions (constant infiltration pressure or flow rate). Our results show that the maximum tensile effective stress in the firn layer is no more than a quarter of that predicted for an equivalent solid ice column, because the imposed load is mostly transmitted into the pore pressure. Therefore our model predicts that surface-to-bed hydrofracture is unlikely to form if meltwater can leak into the firn layer. In “Vulnerability of Firn to Hydrofracture, Part II: Greenland’s Ice Slab Regions”, we apply this model to assess the vulnerability of Greenland’s ice slab regions.
Changes in Mangrove Carbon Stocks and Exposure to Sea Level Rise (SLR) under Future Climate Scenarios
Authors: Singh Minerva
Published: February 2023

Various anthropogenic changes, including climate change, threaten mangrove ecosystems. The main aim of this research is to quantify the spatial variation in the different mangrove carbon stocks, aboveground carbon (AGC), belowground carbon (BGC), and soil carbon (SOC), under future climate scenarios and sea-level rise (SLR). Different representative concentration pathways (RCPs) ranging from the most optimistic (RCP 2.6) to medium emissions (RCP 4.5) and the most pessimistic (RCP 8.5) were considered for 2070. Marine Ecoregions of the World (MEOW), a biogeographical classification of coastal ecosystems, was used to quantify the variation in future carbon stocks and identify regions of potential carbon stock losses and gains. Mangroves of Central and Western Indo-Pacific islands (Andamans, Papua New Guinea, and Vanuatu) and north-eastern South America are projected to lose all three carbon stocks in future scenarios. Andaman ecoregion is projected to have an 11–25% decline in SOC accumulation. In contrast, the Western Indo-Pacific realm is projected to undergo the sharpest declines, ranging from 10% to 12% under all three scenarios. These ecoregions should be prioritised for conservation.
Size distributions reveal regime transition of dominant driving force in lake systems
Authors: Hu Shengjie , Yang Zhenlei , Torres Sergio , Wang Zipeng , Li Ling
Published: February 2023

Power law size distribution, associated with important system behaviors including scale-invariance, critical tipping and self-organization, has been observed in many complex systems. Such distribution also emerges from natural lakes, with potentially important links to the dynamics of lake systems. But the driving mechanism that generates and shapes this feature in lake systems remains unclear. Moreover, the power law itself was found inadequate for fully describing the size distribution of lakes, due to deviations at the two ends of size range. Based on observed and simulated lakes in China’s 11 hydro-climatic zones, we established a conceptual model for lake systems, which covers the whole size range of lake size distribution and reveals the underlying driving mechanism. The full lake size distribution is composed of three components featured by exponential, stretched-exponential and power law distribution. These three distributions are referred to as three phases which represent system (size) states with successively increasing degrees of heterogeneity and orderliness, and more importantly, indicate the dominance of exogenic and endogenic forces in lake systems, respectively. As the dominant driving force changes from endogenic to exogenic, a phase transition occurs with lake size distribution shifted from power law to stretched-exponential and further to exponential distribution. Apart from compressing the power law phase, exogenic force also increases its scaling exponent, driving the corresponding lake size power spectrum into the regime of “blue noise” with reduced system resilience. Besides, the change may also lead to a rising proportion of small lakes in the whole size distribution, which would increase the overall greenhouse gas emissions from natural lakes.
Charting the solar cycle variation of the climate of space weather and its impacts
Authors: Chapman Sandra
Published: February 2023

Sunspot records reveal that whilst the sun has an approximately 11 year cycle of activity, no two cycles are of the same duration. Since this activity is a direct driver of space weather at earth, this presents an operational challenge to quantifying space weather risk. We recently showed [1,2] that the Hilbert transform of the sunspot record can be used to map the variable cycle length onto a regular 'clock' where each cycle has the same duration in Hilbert analytic phase.  Extreme geomagnetic storms rarely occur within the quiet part of the cycle which is a fixed interval of analytic phase on the clock; there is a clear active-quiet switch-off and quiet-active switch-on of activity. Some of the most extreme geomagnetic storms have occurred just at the switch-on time, rather than at solar maximum, so that determining when this will occur could provide guidance on planning and preparedness which necessarily must balance resilience against cost. Here [3] we show how the times of the switch-on/off can be determined directly from the sunspot time-series, without requiring a Hilbert transform.  We propose a method- charting- that can be used to combine observations, and both historical and current reports of societal impacts, to improve our understanding of space weather risk.[1] S. C. Chapman, S. W. McIntosh, R. J. Leamon, N. W. Watkins, Quantifying the solar cycle modulation of extreme space weather, Geophysical Research Letters, (2020) doi:10.1029/2020GL087795[2] S. C. Chapman, S. W. McIntosh, R. J. Leamon, N. W. Watkins, The Sun's magnetic (Hale) cycle and 27 day recurrences in the aa geomagnetic index. Ap. J. (2021) doi: 10.3847/1538-4357/ac069e[3] S. C. Chapman, Charting the Solar Cycle, Front. Astron. Space Sci. - Space Physics, in press (2022) doi: 10.3389/fspas.2022.103709
Observational studies of water surface Evaporation on inland lake over the classical Tibetan Plateau
Authors: Ma Weiqiang , Ma Yaoming , wang Binbin , Su Rongmingzhu , Ma Weiyao , Xie Zhipeng , Hu Wei , He Jianan , Yao Nan , Ma Longtengfei , Bai Ling
Published: February 2023

To understand how the changing process of lake water level and area in Tibetan Plateau effects on the dynamic process of water resources in the surrounding area is very important. This project intends to focus on the study of surface evaporation observation of typical inland lake in Tibetan plateau and makes full use of the "water - ice - atmosphere -biology " multi-spheres comprehensive observation and various professional networks on the Tibetan plateau and surrounding regions which were establish by the leading of institute of the Tibetan plateau research, CAS, to carry out the research of synchronous comprehensive observation. Meanwhile, it collects the existing comprehensive observation data combined with the inversion method of satellite remote sensing to carry out multi-disciplinary comprehensive analysis and research. The aim is to reveal the longer time scale change of lake level by the lake expansion and withdrawal process in different areas of Tibetan plateau. By improving the method of remote sensing and observation, it will get the hourly and daily long-term data of the water level of inland lakes in different areas of Tibetan plateau which is lacking in previous studies. And by combining the analysis of meteorological factors and flow data in lake regions to research daily water cycle, it will help us to clearly understand the change rule of lake water level in different areas of Tibetan plateau. This time some general in-situ observation and model results will be show here.