bluuebunny/crossref_metadata_2025 huggingface dataset:
How long can offshore fresh groundwater support onshore abstractions?
Authors: Cleary Connor , Dempsey David , Morgan Leanne
Published: February 2023

Where onshore and offshore groundwater systems are connected, onshore abstraction may access offshore fresh groundwater (Knight et al., 2018; Post et al., 2013). This draws seawater into the offshore system and may eventually lead to onshore salinization and changes to submarine groundwater discharge. The rate of salinization with respect to changes in onshore conditions is understudied. We analysed the salinization of a range of idealized coastal groundwater systems using numerical models, aiming to identify salinization regimes, characteristic timescales, and tipping points. Our cross-sectional semiconfined aquifer models were simulated using FloPy and SEAWAT. We simulated transient conditions leading to the emplacement of offshore fresh groundwater and post-development salinization. We systematically varied geometric properties like aquifer and aquitard thicknesses and slope, and hydraulic properties like hydraulic conductivities, dispersivity, and anisotropy. Our results show the influence of these properties on salinization rates, under a range of levels of onshore abstraction, and interactions between properties. This provides insight into offshore groundwater systems most at risk of salinization and guidance for parameter analysis during modelling studies.Knight, A. C., Werner, A. D., & Morgan, L. K. (2018). The onshore influence of offshore fresh groundwater. Journal of Hydrology, 561, 724–736. https://doi.org/10.1016/j.jhydrol.2018.03.028Post, V. E. A., Groen, J., Kooi, H., Person, M., Ge, S., & Edmunds, W. M. (2013). Offshore fresh groundwater reserves as a global phenomenon. Nature, 504(7478), 71–78. https://doi.org/10.1038/nature12858
Effect of water on sandstone and limestone, fracture toughness, frictional parameters and brittle strength.
Authors: Violay Marie , Noel Corentin , Baud Patrick
Published: February 2023

The presence of water causes a dramatic reduction of the strength of most rocks. Under compressive stress conditions, fracture mechanics models show the strength of a rock sample is in particular controlled by frictional parameters and the fracture toughness of the material. Previous studies suggested that these parameters could change significantly in the presence of water, but there is a paucity of data quantifying this. Here, we report fracture toughness, frictional and uniaxial compression tests performed on five sandstones and five limestones under dry and water-saturated conditions, that provide new insight into the mechanical influence of water on sedimentary rock strength. Our new data showed that on both sandstones and limestones, the presence of water causes a reduction of both the fracture toughness (from 0 to 50%) and the static friction coefficient (from 0 to 40%), suggesting that water weakening in these sedimentary rocks is mostly due to a reduction of these two parameters under the relatively high strain rate conditions investigated here. While for sandstone we found a reduction of the Uniaxial Compressive Stress between 0 to 35%, it was less variable in limestone, in most cases around 40%. The measured fracture toughness and frictional parameters were then introduced into two well-known micro-mechanical models (the pore-emanating cracks model and the wing crack model), which provide simple theoretical expressions for the Uniaxial Compressive Strength. We found that the predicted water-weakening based on our toughness and friction parameter measurements is in overall agreement with our strength measurements on dry and wet samples.
Growing Terbium Shortage Urges Radical Green Mining of Heavy Rare Earths
Authors: Chen Wei , Wang Peng , Chen Wei-Qiang
Published: February 2023

China’s supply of terbium and other heavy rare earth elements (HREEs) are critical to global sustainable transition. However, their supply chain and corresponding bottlenecks remain unclear. Here we present the first deep-dive analysis of China’s terbium supply chain and trade flows from 1990 to 2018, as well as its future potential trends through 2040. We identify a growing terbium shortage along with its fast-increasing demand to meet various sustainable applications, particularly for electric vehicles (EVs) and wind power (nearly half in 2018). In sharp contrast to previous views, we uncover that the lack of available green mining technology under rigorous environmental regulations, rather than China’s production quota, is currently the main constraint of terbium supply, given only 25% of its quota was exhausted in 2018. Moreover, this supply gap is expected to increase six-fold over the next 20 years to meet China’s EVs and wind power ambitions. Our further analysis reveals the present widely-advocated approaches (including material substitution, reduction, and recycling), will alleviate only around 56% of such shortages, which urges radical green mining breakthroughs to overcome environmental constraints in both China and other HREEs supply countries.
Eco-morphodynamic stability of low-lying coral reef islands in a changing climate
Authors: Fellowes Thomas , Vila-Concejo Ana , Bruce Eleanor , Byrne Maria , Baker Elaine
Published: February 2023

Coral reef islands are under threat from warming and rising seas, ocean acidification and increased storminess. These islands are low-lying accumulations of sediment derived from a continual supply of shells and skeletons from calcifying reef organisms. Over 200 million people rely on reefs and their islands for their livelihoods, including Small Island Developing States (SIDS). Coastal States and SIDS commonly use coral islands to support and extend their maritime jurisdictions. Coral islands are morphologically active (e.g., erode, accrete, migrate) across broad spatial-temporal scales and have been extensively studied using historical aerial imagery, satellite imagery and satellite derived bathymetry (SDB). The future of coral islands and the reefs that support them is not certain, and it is unclear what eco-morphological tipping points may cause constructive and destructive impacts. A better understanding of coral island stability and evolution to changing conditions is urgently needed. Here we focus on 31 coral islands on 10 offshore coral reefs that extend Australia’s maritime jurisdictions in the Coral Sea (SW Pacific) and NW continental shelf (Timor Sea). We digitised island morphology (e.g., shoreline positions, island area and shape) from imagery and SDB (1976-2022) and compared this to local ocean and climate data (e.g., cyclone tracks, sea surface temperatures (SST), sea-level rise) to identify potential tipping points and processes. Initial results show that since the 1970s a third of the coral islands were stable (n=9; <3% change in area), half increased in size (n=15) and a fifth decreased in size (n=7). As expected, small (<10 Ha) and unvegetated islands were more active when compared to large and vegetated islands. Meanwhile, we suggest observed increases in island size may be a short-lived response to increasing SST and marine heatwaves that can degrade reefs and produce additional sediment, combined with tropical cyclones that have the capacity to transport additional sediments to islands. The question remains whether islands will survive if reefs continue to degrade, and sediment supply is reduced. Any island loss will have serious social, environmental and geo-political consequences.
Significant drought legacy effects on gross primary productivity detected in terrestrial ecosystems across the globe
Authors: Yu Xin , Orth René , Reichstein Markus , Bahn Michael , Gomarasca Ulisse , Migliavacca Mirco , Papale Dario , Reimers Christian , Bastos Ana
Published: February 2023

The frequency, intensity, and duration of drought are expected to increase in many regions under climate change. A large number of studies have shown that droughts influence terrestrial ecosystems. Yet, assessments of drought impacts on ecosystem carbon cycling usually focus on instantaneous effects during drought, while legacy effects following drought can be important as well. Here, we provide the first synthesis about drought legacy effects on gross primary productivity (GPP) based on 90 long-term (>=7 years) eddy covariance sites across the globe. We predict the ‘potential’ GPP in the 2 years following drought (considered legacy years) based on a random forest model trained by data in non-legacy time periods. Legacy effects are inferred based on the difference between actual and ‘potential’ GPP in legacy periods. Results show widespread drought legacy effects on GPP across the globe. The change in GPP due to legacy effects is of the same order of magnitude as instantaneous effects. Furthermore, using the unconditional dependence test on many different potential factors, we find legacy effects unconditionally depend on aridity, instantaneous impact intensity, and species richness in forests. The conditional dependence test further reveals aridity primarily modulates legacy effects in forests.  These findings highlight the significance of drought legacy effects on ecosystem carbon cycling across the globe. We find a dominant role of climatic controls on drought legacy effects, while species diversity effects did not explain variability in drought legacy effects. 
New observations of climate-relevant properties of atmospheric aerosols in Namibia, southern Africa.
Authors: Hemeret François , Formenti Paola , Di-Biagio Claudia , Language Brigitte , Chevaillier Servanne , Féron Anaïs , Cazaunau Mathieu , Torres-Sánchez Raquel , Piketh Stuart , Engelbrecht François , Moolla Raeesa , Bezuidenhoudt Ulrich , Luyanda Brendan , Marais Eugene , Maggs-Kölling Gillian
Published: February 2023

Southern Africa, and in particular its western part, Namibia, is considered a climate change hotspot by the IPCC and is at risk of severe temperature-related changes. As examples, models projections suggest by the end of the century: 1) Increase of surface temperature of +4 to +7°C; 2) destruction of the stratocumulus cloud deck along the western coast; and 3) decrease of the fog inland. The role of aerosols in this context is still not completely quantified, due to their high spatial and temporal variability, the many sources responsible for the complex mixture and the lack of continuous observations. Most of the past regional climate modelling (RCM) and intensive field campaigns focussed primarily on constraining the radiative effects of the seasonal biomass burning aerosols generally occurring in the end of the austral winter (August to October). However, the aerosol spectral optical properties, aerosol optical depth and the organic fractions are not studied enough to provide a firm understanding of regional aerosol load, interaction with radiation and interplays in relation to particle chemistry.In this work, we present the first analysis of new long-term ground-based aerosol observations conducted since april 2022 at Gobabeb Namib Research Institue (23°33’40‘’S, 15°02’24’’E) in Namibia. Gobabeb is located in the hyperarid Namib desert and it is under the influence of different air masses, transporting maritime and biomass burning aerosols, amongst others. The measurements of optical and physical properties of the aerosol mixtures are analysed to provide with the aerosol single scattering albedo and mass absorption, scattering and extinction efficiencies which are needed to evaluate the first Africa-based Earth system model by the Global Change Institute at the University of Witwatersrand in South Africa. The in situ surface data are complemented by the analysis of pre-existing observations such as those from the AERONET sunphotometers.
Application of an improved snow albedo scheme in the simulation of heavy snow processes over the Tibetan Plateau
Authors: Liu Lian , Ma Yaoming
Published: February 2023

Snow albedo is an essential factor in the land surface energy balance and the water cycle. It is usually parameterized as functions of snow-related variables in land surface models (LSMs). However, comparing with albedo schemes in the CLM and Noah-MP LSMs, the default snow albedo scheme in the widely used Noah LSM shows evident drawbacks in land-atmosphere interactions simulations during an extreme snow process on the complex topographic Tibetan Plateau (TP). We firstly demonstrate that the improved Noah snow albedo scheme includes MODIS albedo products and explicit considers snow depth as an additional factor. It performs well in relation to near-surface meteorological elements estimates during an extreme snow process. Then, we comprehensively evaluate the performance of the improved snow albedo scheme in WRF coupled with Noah LSM in simulating the additional eight heavy snow events on the TP. It reveals that the improved snow albedo scheme significantly outperforms the default Noah scheme in relation to air temperature, albedo and sensible heat flux estimates, by alleviating cold bias estimates, albedo overestimates and sensible heat flux underestimates, respectively. This in turn contributes to more accurate reproductions of snow event evolution. The averaged RMSE relative reductions (and relative increase in correlation coefficients) for air temperature, albedo, sensible heat flux and snow depth reach 27% (5%), 32% (69%), 13% (17%) and 21% (108%) respectively. These results demonstrate the strong potential of the improved snow albedo parameterization scheme for heavy snow events simulations on the TP.
Isotopic Simulation of Combustion-derived Vapor Emission in Urban Areas Using Regional Spectral Model
Authors: Yang Yan , Yoshimura Kei
Published: February 2023

Vapor from anthropogenic emissions accounted for a significant proportion of the urban atmospheric water due to the process of urbanization. Fossil fuel combustion-derived vapor (CDV) is one of the main sources of anthropogenic water. Due to the extremely low d-excess (δD - 8*δ18O) value of CDV (-206.7‰ weighted average from different kinds of fossil fuels), stable hydrogen and oxygen isotope can be a promising method to partition CDV from other natural sources. Considering several limitations of long-term in-situ measurement of water isotopes in the urban area, this study explored the possibility to use IsoRSM, an isotopic-enable regional spectral model to simulate the emission situation of CDV.Two experiments were made respectively in Salt Lake City, USA for one month and in Beijing, China for one year. A fixed emitting rate of CDV with a fixed isotopic ratio was added to the evaporation process of the model in the urban domains (2°×2°) of these two cities, and the result indicated that the addition of CDV could significantly decrease the d-excess of water vapor, especially when the boundary layer was stable. The modified d-excess fitted better with the time series and diurnal variation of in-situ observation than the simulation without CDV in Salt Lake City and in the summer monsoon season of Beijing. Furthermore, the addition of CDV also resulted in an obvious negative correlation between vapor d-excess and specific humidity.  In the simulations, the fraction of CDV in the total atmospheric water in January of Salt Lake City reached more than 20% with an average value of 3.4%, and the peak values mainly occurred when the stability of the atmosphere was relatively high. The mean CDV fraction in the monsoon season of Beijing would also be 2.3%. The CDV fraction calculated from vapor d-excess was slightly lower than moisture tracer method. In summary, the bias of d-excess simulation from IsoRSM in the stable boundary layer periods could be improved by adding CDV emission into the local evaporation process.
An ongoing triggered slow slip event after the 2006 Pingtung offshore earthquake in Hengchun Peninsula, Taiwan
Authors: Hsiao Shih-Han , Ching Kuo-En , Chang Wu-Lung , Tsai Pei-Ching , Giletycz Slawomir , Chen Chien-Liang
Published: February 2023

    An ongoing triggered slow slip event (SSE) on the inland Hengchun fault after the 2006 ML 7.0 Pingtung offshore earthquake in Taiwan is proposed in this study by analyzing the coordinate time series of 13 continuous GNSS stations, 37 campaign-mode GNSS stations and 3 precise leveling routes in Hengchun Peninsula from 2002 to 2022. Four surface velocity patterns have been determined based on these geodetic data: (1) the interseismic period from 2002 to the 2006 Pingtung offshore earthquake; (2) the 2nd period after the earthquake to April 2010; (3) the 3rd period from April 2010 to 2016; (4) the 4th period from 2016 till 2022. In general, a velocity discontinuity is discovered approximately located at 1-2 km east of the currently known Hengchun fault trace. Then we evaluate the slip deficit rate and slip rate distributions of the Hengchun fault through baseline inversion model and coseismic fault model, respectively. The modeling results shows that Hengchun fault is a reverse fault with a minor left-lateral component. Two asperities are shown in the southern and northern segments, respectively. Furthermore, the energy on the asperities has been gradually released from south to north after the 2006 earthquake, even though the postseismic deformation has faded. On the other hand, the geological investigation results also indicate that surface ruptures were generated on the Hengchun fault until 2017. Therefore, we infer that (1) the temporal pattern changes of surface velocity in Hengchun Peninsula are driven by the 2006 ML 7.0 Pingtung offshore earthquake; (2) the Hengchun fault ought to be relocated at 1-2 km to the east; (3) a SSE occurs on the Hengchun fault after the 2006 ML 7.0 Pingtung offshore earthquake. (4) the energy keeps releasing through the SSE after the earthquake and decrease the earthquake potential in Hengchun Peninsula.
Research on the effect of periodic wide atmospheric pressure change on CO emission in closed goaf
Authors: Shao Zhuangzhuang , Tan Bo
Published: February 2023

Abstract: Atmospheric pressure fluctuation is one of the most important factors affecting the climate environment and gas emission in the fire area. In order to obtain the influence rule of the surface atmospheric pressure change on the gas sampling and abnormal emission in the mine closed goaf, the No. 1 coal mine in Dananhu, Xinjiang was taken as the research object. Using Fourier transform and Fisher harmonic analysis and other methods, the influence of the periodic variation of atmospheric pressure on the gas leakage and outflow in the closed goaf was studied. The results showed that there were three atmospheric pressure periods of 15.2d, 1d and 182.2d, and the probability was greater than 95%. The time period with the highest number of atmospheric pressure peaks was 7:00-8:00, which accounted for 20.2% of total occurrence number in a day. And the time periods with the highest number of atmospheric pressure trough were 2:00, 15:00 and 16:00, accounting for 27.4%. The peak-to-trough transition time was mainly concentrated around 6h, and the diurnal variation curve of atmospheric pressure was mainly bimodal. The atmospheric pressure change rate was mostly concentrated in 10~50 Pa/h. It was determined that the distance that the gas sampling pipe was pre-laid into the inner side of the closed wall should be greater than 44.4m, and the CO concentration and atmospheric pressure in the closed goaf were both periodic and negative with atmospheric pressure. The research results have important guiding significance for the disaster warning and environmental protection of the goaf.
Hysteresis of European Summer Mean and Extreme Precipitation in a CO2 Removal Experiment
Authors: Im Nari , Kim Daehyun , An Soon-Il , Shin Jongsoo
Published: February 2023

This study investigates the changes in the mean and extreme summer precipitation over Europe in a CO2-removal experiment, in which CO2 concentration is quadrupled and reduced back to the current climate level symmetrically over a 280-year period. Due to the pronounced summertime drying caused by greenhouse gas-induced warming, the mean and extreme precipitation decrease and bounce back during the CO2 ramp-up (RU) and ramp-down (RD) period, respectively. Interestingly, the degree of reduction in the mean precipitation is two times that of extreme precipitation. Also, the mean precipitation shows hysteresis with respect to CO2 forcing, which is absent in extreme precipitation. We show that the changes in the mean precipitation, in which convective precipitation is the dominant component, are tightly associated with those of the mean moist convective instability (MCI). Compared to the RU period, the mean MCI is lower during the RD period with a drier lower troposphere which is due to lower soil moisture and weaker surface evaporation. In contrast, the changes in extreme precipitation, whose major component is large-scale precipitation, closely follow those of the mean column relative humidity. Our results suggest that the partitioning of total precipitation into convective and large-scale components in models needs to be considered when analyzing model-simulated future projections of regional precipitation changes.
Geographical distribution and spatio-temporal scale dependence of air-sea coupling via the vertical mixing mechanism
Authors: Putrasahan Dian , von Storch Jin-Song
Published: February 2023

Reanalysis and current generation global coupled climate models have shown a dominant role of atmospheric forcing for the ocean such as stronger winds that increase turbulent heat flux and consequently cools sea surface temperatures (SSTs) . While satellite observations and eddy-resolving global coupled climate models have additionally shown clear imprints of mesoscale ocean forcing on the atmosphere, such as warm SST anomalies that can destabilise the overlying atmosphere and enhance surface winds by transferring momentum from aloft to the surface (vertical mixing mechanism; VMM). With winds blowing along downwind or crosswind SST gradients, this can subsequently induce wind stress divergence or curl respectively, particularly over mesoscale ocean features. The dominance of forcing from either atmosphere or ocean indicate a spatial scale dependency for the coupling variability of air-sea interactions. Using a global coupled 5-km ICON-ESM simulation, we derive a global distribution map of the air-sea coupling associated with the VMM, and investigate the spatial and temporal scale dependency of the vertical mixing mechanism. Choosing various regions over the ocean, we evaluate the frequency-wavenumber cross-spectra between downwind SST gradients and windstress divergence in order to identify the dominant temporal and spatial scales between them. For example, we found that over the tropical Pacific, such interactions are prevalent on spatial scales of about 300-3000km and longer than 10-days timescale, while over the Gulf stream region, they are dominant at scales of roughly 100-1000km and longer than 5-days timescale. This is the first time that the dominant spatial and temporal scales for the vertical mixing mechanism in various regions of the world's ocean is quantified. 
Assessment of agricultural drought effects on groundwater system using the standardized groundwater level index (SGI) in S. Korea
Authors: Song Sung-Ho , Lee Byungsun , Lee Jaenam
Published: February 2023

To evaluate the effects of drought on groundwater system in rural areas, the standardized groundwater level index (SGI) was applied to groundwater monitoring wells over S. Korea. Moreover, accumulation period (AP), representing the month with the highest correlation coefficient between SGI and the standardized precipitation index (SPI), was calculated for monitoring wells. In this case, correlation analysis was performed to investigate differences in the response of precipitation and groundwater level to drought using SPI. Groundwater level data from 68 monitoring wells were used for the analysis. The response time of groundwater level to precipitation appeared to be very short, but the groundwater level did not go with SPI during the long-term drought. Results of correlation analysis between reservoir level and SPI show high correlation on the relatively long AP. The results of analysis between SGI and SPI appeared that the AP values ranged from 1 to 3 months for most of the wells indicating that the total amount of groundwater will not decrease significantly in long-term drought periods unlikely it of reservoirs with the high AP values. The nationwide maximum AP values between SGI and SPI were around 4 in the central part of S. Korea, while the minimum AP values were around 2 in the eastern and western part of S. Korea. Consequently, it could be concluded that the wells with low AP value tend to respond to short-term drought, but it has little effect on groundwater system when the long drought occurs. Acknowledgement: This research was supported by the Institute of Planning and Evaluation for Technology in Food, Agriculture, and Forestry (IPET) [Grant number 320046053HD020].
Drivers and barriers of drought risk adaptation decisions by agro-pastoralists in Kenya
Authors: Schrieks Teun , Botzen Wouter , Haer Toon , Wasonga Oliver , Aerts Jeroen
Published: February 2023

The Horn of Africa Drylands are increasingly experiencing severe droughts, which imposes a thread on traditional livelihood strategies of pastoralist communities. Understanding adaptation behaviour in rural communities is essential to help reducing the impact of these droughts. In this study, we identify drivers and barriers of drought risk adaptation decisions in pastoralist communities, by analysing household survey data from 502 Kenyan households. To provide theoretically sound insights into adaptive behaviour, we have grounded our empirical research in four established economic and psychological theories on decision-making under risk: Expected Utility Theory (EUT), Rank Dependent Utility Theory (RDU), Protection Motivation Theory (PMT) and Theory of Planned Behaviour (PMT). The variables of all theories are measured by multiple survey questions and we have included an economic experiment in the survey to measure the risk aversion parameters of Expected Utility Theory and Rank Dependent Utility theory. With regression models, we analyse the relation between the theory variables and adaptation behaviour. To measure adaptation behaviour, we have selected 15 different adaptation measures for which we asked about current uptake and the intention to adopt these measures in the future. Regression analyses show that important factors in adaptation decisions are risk attitudes, financial constraints, perceives self-efficacy and adaptation by family and friends.  An analysis of adaptation intention for each adaptation measure separately shows that drivers and barriers of adaptation are different for different types of adaptation measures. Risk-averse pastoralists are more likely to implement adaptation measures that are adjustments to current pastoral practices, and less likely to implement adaptation measures that require a (partial) shift to other livelihood activities. A person’s belief in their own ability to implement an adaptation measure (perceived self-efficacy) is an important factor in explaining which measure people are going to adopt. Furthermore, we find that some measures are more likely to be taken by women and others more likely to be taken by men and we find significant effects for differences in education levels. Our analysis can help to gain more knowledge on the drivers of individual adaptation decisions of pastoralists, which can enhance policies promoting adaptation of dryland communities. Our results indicate that drivers and barriers of adaptation can be quite different for different groups, which suggests that policies should be carefully targeted at specific groups.
The Evolution of Paleo-Porosity in Basalts: Reversing Pore-Filling Mechanisms Using X-Ray Computed Tomography
Authors: Macente Alice , Dobson Katherine J. , MacDonald John , Wadsworth Fabian B. , Vasseur Jeremie
Published: February 2023

Basaltic rocks are considered excellent candidates for CO2 storage by in situ mineral trapping, due to their large presence on Earth’ surface and their higher reactivity with CO2 to form calcium-rich minerals. Often carrying a high-volume fraction of vesicles, basaltic rocks can be an important reservoir horizon in petroleum systems. When the vesicle network has been filled by earlier mineralization the basalts can act as impermeable seals and traps. Characterizing the spatial and temporal evolution of the porosity and permeability is critical to understand the CO2 storage potential of basalts. We exploited X-ray computed tomography (XCT) to investigate the precipitation history of an amygdaloidal basalt containing a pore-connecting micro-fracture network now partially filled by calcite as an analogue for CO2 mineral trapping in a vesicular basalt. The fracture network likely represents a preferential pathway for CO2-rich fluids during mineralisation. We quantified the evolution of basalt porosity and permeability during pore-filling calcite precipitation by applying novel numerical erosion techniques to “back-strip” the calcite from the amygdales and fracture networks. We found that permeability evolution is dependent on the precipitation mechanism and rates, as well as on the presence of micro-fracture networks, and that once the precipitation is sufficient to close off all pores, permeability reaches values that are controlled by the micro-fracture network. These results prompt further studies to determine CO2 mineral trapping mechanisms in amygdaloidal basalts as analogues for CO2 injections in basalt formations.
Ammonia oxidation as the engine to induce denitrification to produce N2O in alkaline agricultural soils
Authors: Ju Xiaotang , Song Xiaotong
Published: February 2023

Ammonia oxidation contributes to global N2O emissions both by direct production and by fueling denitrification (provision of nitrite or nitrate to denitrifiers). Urea or ammonia-based fertilizers account for approximately 70% of annual nitrogen fertilizer inputs globally. This means that the subsequent coupling processes driven by ammonia oxidation are of great significance to N2O emissions. However, for this important source of N2O production, direct evidence at the process- and microorganism- level is highly lacking, leading to that the systematic mechanism of the coupling processes and microbial activities in response to environmental changes (especially O2 changes) remains unknown. Here, we investigated ammonia oxidation, other soil N transformation processes, N2O emissions and related environmental changes (e.g., O2 consumption) and microbial activities in a calcareous upland soil in Northern China, which has a strong ammonia oxidizing rate and is a global N2O hotspot, by combining field observations, microcosm, molecular and isotope techniques. The results showed that the soil has a far (5-30 times) higher nitrification potential and gross nitrification rate than other cropland soils in the world. The strong ammonia oxidation led to rapid O2 consumption and NO2- accumulation in soil matrix, causing strong emission peaks of N2O, which was in line with the N2O yield from denitrifiers. The N2O 15N site preference and 15N labeling data further revealed a major role of nitrification-induced denitrification in high N2O emissions. A higher AOB/AOA gene abundance ratio correlated the higher nitrification potential, higher NO2- transition and higher N2O emissions. A coupling expression of nitrifying and denitrifying genes (amoA, narG, nirS, nirK, nosZ) and a significant structural alteration of the soil microbiota along with the O2 consumption driven by ammonia oxidation linked to higher N2O emissions. All the evidence points to ammonia oxidation-linked denitrification being the major process generating N2O. In consequence, reducing N surplus, slowing down nitrification rate using nitrification inhibitors, and avoiding high ammonium microzones using slow-release or organic fertilizers are main measures to reduce N2O emissions per unit of urea or NH4+-based N input in intensively managed alkaline soils globally.
Thermal Convection in Vesta’s Core from Experimentally-Based Conductive Heat Flow Estimates
Authors: Orole Oluwasanmi , Yong Wenjun , Secco Richard
Published: February 2023

Electrical resistivity measurements of Fe-5wt%Ni were made in-situ under pressures of 2-5 GPa and temperatures up to 2000 K in a cubic-anvil press. The thermal conductivity was calculated from the measured electrical resistivity data using the Wiedemann–Franz law. Comparison of these data with previous studies on pure Fe and Fe-10wt%Ni shows that a change in the Ni content within the range 0-10wt% Ni has no significant effect on electrical resistivity of Fe alloys.The thermal conductivity values of Fe-5wt%Ni from this study, was used to calculate the adiabatic heat flux in Vesta’s core. Vesta is of interest because the remnant magnetism in eucrites dated at 3.69Ga, reveals it possessed an internally generated dynamo (Fu et al., 2012). Comparing the estimated adiabatic core heat flux of ~331 MW at the top of Vesta’s core to the range of estimated heat flux through the CMB of 1.5–78 GW, we infer that the mechanism stirring Vesta’s liquid outer core to generate its surface magnetic field tens of millions of years in its early history was thermal convection.
Effects of sea spray on large-scale climatic features over the Southern Ocean
Authors: Song Yajuan
Published: February 2023

The Southern Ocean, characterized by strong westerly winds and a rough sea state, exhibits the most pronounced
sea spray effects. Sea spray ejected by ocean surface waves enhances heat and water exchange at the air–sea interface.
However, this process has not been considered in current climate models, and the influence of sea spray on the
coupled air–sea system remains largely unknown. This study incorporated a parameterization of the sea spray influence on
latent and sensible heat fluxes into the First Institute of Oceanography Earth System Model version 2.0 (FIO-ESM v2.0), a
climate model coupled with an ocean surface waves component. The results indicate that the spray-mediated enthalpy flux
accounted for over 20%–50% of the total value. Sea spray promoted ocean evaporation and heat transport, resulting in air
and ocean surface cooling and strengthened westerly winds. Furthermore, a moist and stable atmosphere favored an
increase in cloud fraction over the Southern Ocean, particularly low-level clouds. Increased clouds reflected downward
shortwave radiation and reduced solar radiation absorption at the surface. At present, the climate models participating in
phase 6 of the Coupled Model Intercomparison Project (CMIP6) still suffer notable deficiencies in reasonably reproducing
the climatological features of the Southern Ocean, including warm SST and underestimated clouds biases with more
absorbed shortwave radiation. Our results suggest that consideration of sea spray effects is a feasible solution to mitigate
these common biases and enhance the confidence in simulations and predictions with climate models.
Waveform similarity reveals the relationship among pressure, acceleration and velocity in shallow water: a study based on seismic records from different sensors
Authors: Jin Zhen , Cai HuiTeng
Published: February 2023

Globally, countries along oceans attach great importance to research involving oceanic observations. In the past 60 years, the United States and Canada, Japan, and the European Community have continued to promote development of ocean Seafloor seismic observations. The first Seafloor seismic station in China was built in Fujian in 2018,  the Wuyu Island Seafloor seismic station, has recorded more than 100 earthquakes since it began operations more than a year ago. A far-field spherical wave incidence, which can be approximately considered a plane wave, and the sound pressure and vibration velocity are in phase; In the low frequency range (0.1-10Hz), The theory of "forced oscillation" describes that the change of water pressure is proportional to the vertical component of ground acceleration. We demonstrate the equivalence of the acceleration, velocity in shallow water and water-pressure signals for a set of local earthquakes .The cross spectrum method is used to analyze the similarity characteristics of velocity and acceleration with pressure signals at different frequencies. In addition, The similarity relationship between sound pressure and velocity acceleration in different frequency ranges is visually displayed through similarity probability distribution. The results show that with the decrease of frequency, the influence of hydrostatic pressure on the pressure detector gradually increases, and the pressure detector gradually changes from high-velocity correlation to high-acceleration correlation. Our work is not only to prove the existence of "forced oscillation" frequency, but also to explain the reason for high similarity of different types of waveforms by using formulas. Finally, we analyze the position of conversion frequency points through probability density distribution. This work can put forward a new design idea for the future research and development of hydrophone type Seafloor seismometer.
Variability of wave heights in marginal seas around Korea analyzed using ERA5 Reanalysis data
Authors: Bayhaqi Ahmad , Yoo Jeseon , Son Donghwi , Bang Min-Seon , Park Sung-Hwan
Published: February 2023

Ocean Wave conditions play a crucial role in the coastal region, influencing coastal communities and human activities. In this study, a 42-year data with the period of 1980-2021 from ERA-5 Reanalysis has been employed to investigate the various temporal scale of significant wave height (Hs) variability in the surrounding seas of Korean Peninsula. The signal decomposition of long-term data has been done using Empirical Mode Decomposition (EMD). In the seasonal scale, the highest (lowest) Hs occurs in the winter (summer) season with the averaged value of 1.1 (0.4) meter. These variations were related to monsoonal winds, with the stronger winds during winter season leading to the higher Hs. Year-to-year variation displays the contribution of ENSO events; the appearance of El Nino could significantly reduce the Hs by weakening the magnitude of winter monsoon in which are statistically found in the East Sea and East China Sea. The long-term changes of Hs in the region show a clear trend in which summer (winter) season have increased (decreased) trend, owing to the enhanced typhoon activities and weakened winter monsoon respectively.
Separation of climate models and observations based on daily output using two machine learning classifiers
Authors: Brunner Lukas , Sippel Sebastian , Voigt Aiko
Published: February 2023

Climate models are primary tools to investigate processes in the climate system, to project future changes, and to inform decision makers. The latest generation of models provides increasingly complex and realistic representations of the real climate system while there is also growing awareness that not all models produce equally plausible or independent simulations. Therefore, many recent studies have investigated how models differ from observed climate and how model dependence affects model output similarity, typically drawing on climatological averages over several decades.Here, we show that temperature maps from individual days from climate models from the CMIP6 archive can be robustly identified as “observation” or “model” even after removing the global mean. An important exception is a prototype high-resolution simulation from the ICON model family that can not be so  unambiguously classified into one category. These results highlight that persistent differences between observed and simulated climate emerge at very short time scales already, but very high resolution modelling efforts may be able to overcome some of these shortcomings.We use two different machine learning classifiers: (1) logistic regression, which allows easy insights into the learned coefficients but has the limitation of being a linear method and (2) a convolutional neural network (CNN) which represents rather the other end of the complexity spectrum, allowing to learn nonlinear spatial relations between features but lacking the easy interpretability logistic regression allows. For CMIP6 both methods perform comparably, while the CNN is also able to recognize about 75% of samples from ICON as coming from a model, while linear regression does not have any skill for this case.Overall, we demonstrate that the use of machine learning classifiers, once trained, can overcome the need for multiple decades of data to investigate a given model. This opens up novel avenues to test model performance on much shorter times scales.
Hydraulic control of the submarine glacier melt in Greenlandic sill fjords
Authors: Wiskandt Jonathan , Koszalka Inga Monika , Nilsson Johan
Published: February 2023

The oceanic forcing of basal melt remains a major source of uncertainty in climate ice sheet modelling.Several factors such as ice and fjord geometry, ambient water properties and subglacial discharge in-fluence the submarine melt processes. We use a high resolution, non-hydrostatic configuration of theMassachusetts Institute of Technology general circulation model (MITgcm, see Wiskandt et al., 2022)to investigate the dependence of basal melt rates and melt driven circulation in the Sherard OsbornFjord (SOF) under the floating ice tongue of Ryder Glacier (RG), northwest Greenland, on the fjordsbathymetry in connection with variable subglacial discharge. In SOF, a sill in front of the floating iceshields the cavity underneath the ice from warm Atlantic water (AW) penetrating towards the groundingline, providing an effective shielding of the glacier from oceanic thermal forcing. The volume flux of theAW inflow is controlled by the sill height and the melt water outflow. The outflow volume flux is in turndependent on basal melting, subglacial discharge and the mixing of the two with the AW. For sufficientlystrong outflow, hydraulic control at the sill crest can limit the available glacier–ward flux and thereforethe available oceanic thermal forcing for basal melting creating a stabilizing feedback. In this studywe investigate the sensitivity of the AW inflow into an idealized fjord to the presence of a sill, variablesill height and seasonal forcing from subglacial discharge. The model results are compared to theory ofhydraulic control (Nilsson et al., 2022).ReferencesNilsson, J., van Dongen, E., Jakobsson, M., O’Regan, M., and Stranne, C. (2022).Hydraulic suppression of basal glacier melt in sill fjords. EGUsphere, 2022:1–33.Wiskandt, J., Koszalka, I. M., and Nilsson, J. (2022). Basal melt rates and oceancirculation under the Ryder Glacier ice tongue and their response to climate warming: a high resolutionmodelling study. EGUsphere, 2022:1–29.
Modeling fuel- and vehicle- type specific CO2 emissions from global on-road vehicles during 1970-202
Authors: Yan Liu , Zhang Qiang , He Kebin
Published: February 2023

Vehicles are one of the most important contributors to global anthropogenic CO2 emissions. However, lack of fuel- and vehicle- type specific information about global on-road CO2 emissions from existing datasets, which are only available at sector level, makes it insufficient to support establishment of emission mitigation strategies. Thus, a fleet model is developed in this study and CO2 emissions from global on-road vehicles during 1970-2020 are estimated at vehicle level. Here we access the fuel- and vehicle- type specific characteristics of both vehicular CO2 emissions and vehicle ownership, and highlight the trend in the intensity of CO2 emissions and ownership of on-road vehicles in hotspot regions. We find that, heavy-duty trucks and buses which account for less than 10% of global vehicle ownership but represent over 30% of on-road CO2 emissions. Contribution of diesel vehicles to global on-road CO2 emissions has doubled during 1970-2020, driven by the shift in fuel-type distribution of vehicle ownership. As the top four vehicle markets, vehicles per thousand people in the United States, European Union, China and India all increased significantly from 1970 to 2020 while vehicle intensity China and India was still lower than global average level, which indicates that developing countries have to face great challenges in vehicular decarbonization in the future. CO2 emissions per vehicle in these regions generally decreased for the last 50 years, but vehicular CO2 emission intensity in the United States and European Union were relatively higher, meaning that there're still large potentials for developed countries in vehicular CO2 emission mitigation. These findings provide better understanding of trends of historical CO2 emissions from on-road vehicles, as well as insights into the effective governance of CO2 emissions in the future.
Radiocarbon constraints on lake succession and sedimentation processes in a small mountainous lake in NE Taiwan
Authors: Hsu Kuan-Yi , Löwemark Ludvig
Published: February 2023

    Monsoon rainfall in East Asia is a subsystem of the global monsoon system and affects nearly one-quarter of the world's population. Taiwan, an island in the subtropical East Asian monsoon system, provides the unique opportunity to study monsoon and typhoon variability over the western subtropical Pacific on both historical and geological time scales. However, the Holocene paleoclimate records retrieved from various lakes in Taiwan have shown discrepancies in their recorded climate variability. This could partly be caused by the lack of modern sedimentological observations, limiting our understanding of the mechanisms controlling lake sedimentation and thus introducing uncertainty in the interpretation of lake records. To understand the paleoclimate records archived in lacustrine sediments, a robust age model is essential. The aim of this study is to understand the complex processes that led to the formation of a small wetland (24°30' N, 121°35' E, 2095 meters above sea level), which is located in the Taiping Mountains, Yilan County, NE Taiwan.    In this study, we use several cores from different parts of the wetland, including wooded swamps, fens, and the open pond, to construct a robust model for lake formation and succession. However, cores from different parts of the wetland display puzzling differences in both maximum ages and sedimentation rates. Moreover, one core displays a major age reversal. Multiple radiocarbon dates corroborate that this reversal is not a sampling or analytical artifact but actually reflects an inversion of the sediment sequence. Possible hypotheses explaining this age reversal include typhoons, landslides, and overturned floating fens. Examples from other mountain lakes in Taiwan demonstrate that floating islands consisting of a mixture of aquatic plants, bryophytes, helophytes, and sediment can move hundreds of meters during typhoons. If a floating island is blown by typhoon winds, it may become turned upside down, resulting in an inverse age sequence.