bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection timescale of anthropogenic climate change signals in the global ocean
Authors: Tjiputra Jerry , Negrel Jean
Published: March 2022

Robust detection of anthropogenic climate change is a necessary prerequisite in developing reliable climate change mitigation and adaptation plans. Here, we use simulation data from a suite of latest Earth system model projections to establish the detection timescale of anthropogenic signals in the global ocean under a strong future climate change scenario. We focus on projections of temperature, salinity, oxygen, and pH changes from surface to 2000 m depths. Despite lack of direct interaction with anthropogenic forcing, climate changes in the interior ocean are projected to be detectable earlier than on the surface. This general feature is primarily due to the low background natural variability in the subsurface depths. Acidification signals will occur earliest, followed by warming and oxygen changes. Consistent with the global overturning circulation pathway, the interior of the Atlantic basin will experience earlier detectable signals than the Pacific and Indian basins. The model ensemble projects the subsurface tropical Pacific as the domain least susceptible to exposure of anthropogenic climate change signals over the 21st century. Our study suggests earliest detectable anthropogenic exposure can be expected in the Southern Ocean and the North Atlantic. Sustained deployment of monitoring systems, such as ARGO floats equipped with biogeochemical sensors, in these domains would be highly pertinent to timely detect the early emergence of anthropogenic climate change signals.
Multi-instrument observations of polar cap patches and traveling ionospheric disturbances during geomagnetic storms
Authors: Prikryl Paul , Gillies Robert G. , Chakraborty Shibaji , Themens David R. , Thomas Evan G. , Weygand James M.
Published: March 2022

Solar wind Alfvén waves [1] coupling to the magnetosphere-ionosphere-thermosphere (MIT) have been associated with high-intensity long-duration continuous auroral electrojet activity [2] and shown to modulate ionospheric convection in the cusp generating polar cap patches and atmospheric gravity waves [3,4]. The Resolute Bay Incoherent Scatter Radars (RISR-C and RISR-N) [5] are well suited for observing the ionospheric signatures of flux transfer events and subsequent polar patch formation in the cusp.  During minor to moderate geomagnetic storms caused by corotating interaction regions at the leading edge of solar wind high speed streams polar patches were observed as they convected over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN) ionosondes and GPS receivers [6]. The patches were generated by the MIT coupling of Alfvén waves in the upstream solar wind. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including auroral electrojets. The horizontal equivalent ionospheric currents and vertical current amplitudes are estimated from the ground-based magnetometer data using an inversion technique [7].  Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves causing traveling ionospheric disturbances (TIDs) propagating equatorward. TIDs were observed in the SuperDARN HF radar ground scatter [8], in the detrended GPS TEC maps, and in one case, in the altitude profiles of ionospheric electron densities observed by the Poker Flat ISR [9].

[1] Belcher, JW, Davis, L, Jr. 1971. J. Geophys. Res. 76, 3534–3563.

[2] Tsurutani, BT, Gonzalez, WD. 1987. Planet. Space Sci. 35(4), 405–412.

[3] Prikryl, P, et al., 1999. Ann. Geophys. 17, 463–489.

[4] Prikryl, P, et al., 2005. Ann. Geophys. 23, 401–417.

[5] Gillies RG, et al., 2016. Radio Sci., 51(10):1645-1659.

[6] Jayachandran, PT, et al., 2009. Radio Sci., 44, RS0A03.

[7] Weygand, JM, et al., 2011. J. Geophys. Res. 116, A03305.

[8] Chisham, G., et al., 2007. Surv. Geophys. 28, 33–109.

[9] Heinselman, CJ, Nicolls, MJ, 2008. Radio Sci., 43, RS5013.
Implementation of calving processes in large-scale ice sheet models
Authors: Gudmundsson G. Hilmar
Published: March 2022

Concepts and ideas related to implementation of calving in large-scale ice-sheet models are presented and discussed, and new model verification experiments proposed. For unconfined ice shelves, any calving law where the calving rate increases with cliff height (free board) must lead to an unstable advance or retreat. No other solutions are possible and all calving front positions are always unstable. If in contrast, calving rate is a monotonically decreasing function of cliff height, both stable and unstable positions are possible. An example of such a configuration and simple analytical solution for the transient evolution of the calving front is provided, which can be used for numerical verification purposes. It is argued that cliff-height based calving laws are, at least for the case of buttressed ice shelves, arguably unphysical as they can result in a multi-valued function for the calving rate as a function of local state of stress. Implementation of a new variational form of the level-set method, involving forward-and-backward diffusion, for capturing the evolution of calving fronts is discussed and several applications to Pine Island and Thwaites glacier shown.
Aerosol-boundary layer feedbacks triggered by both greenhouse gas and aerosol emissions
Authors: Stjern Camilla Weum , Hodnebrog Øivind , Myhre Gunnar , Pisso Ignacio
Published: March 2022

There is a strong interplay between processes within the planetary boundary layer (PBL) and the number of aerosols within it. Stable weather conditions are conducive to less vertical mixing, a shallower PBL and stronger accumulation of pollutants near the surface. In some cases, this can contribute to episodes of severe haze, with serious health impacts. A change in PBL height, however, may also be driven by changes in anthropogenic emissions and their influence on the atmosphere. In this study, we perform idealized simulation with the earth system model CESM2-CAM6, to investigate the effect of various climate drivers (CO2, black carbon and sulfate) on turbulence, planetary boundary layer height, and ultimately near-surface pollution. We find that while emissions of all three climate drivers influence the number of severe air pollution episodes, only CO2 and black carbon emissions do so through an impact on turbulence and PBL height. While black carbon aerosols are known to cause atmospheric heating, increased boundary layer stability and reduced turbulence, we find CO2 to have a similar albeit opposite effect through surface warming. Our results clearly underline the importance of black carbon mitigation for reducing the most severe exposures to air pollution.
Performances of express mode vs standard mode for d18O, dD and 17O-excess with a Picarro analyzer
Authors: Landais Amaelle , Minster Benedicte , Zuhr Alexandra , Hoffmann Magdalena , Fourré Elise
Published: March 2022

The recent development of optical spectroscopy enabled the development of the use of water isotopes in climate, environment and hydrological studies. An increasing number of studies also includes the most recent parameter 17O-excess as an indicator for kinetic fractionation effects in the water cycle. However, for some applications such as ice core science, the 17O-excess signal to be measured is very small, of the order of 10 – 20 ppm and it is a big analytical challenge to obtain the requested precision.

Here, we present results of performance of the new express mode and the standard mode developed for d18O, dD and now also 17O-excess for a Picarro analyzer. In the standard mode, there is a new injection of water vapor lasting 4.5 minutes every 10 minutes. To get rid of memory effect, the first injections are discarded or a correction is applied which depends on the difference in water isotopic composition between the measured sample and the previous one. For each new sample measured with the express mode, the sequence begins with 6 injections of water vapor in the cavity of 40 secondes each to get rid of the memory effect. It is followed by injections of water vapor lasting 2 minutes every 4 minutes. The advantage of the express mode is to avoid the memory correction and to decrease the measurement time. It thus permits to run more replicates which is important to improve the accuracy of the measurements, especially 17O-excess. We present here results of several series of samples and standards of different water isotopic composition (d18O ranging from -54 to 0 ‰) ran three times with both the standard and the express modes and compare the performances of the two modes.  
The link between downstream river planform changes and upstream changes or processes in high energy mountain rivers 
Authors: Malakar Babita , Ozturk Ugur , Sen Sumit
Published: March 2022

The river morphologies and the associated landscape experience considerable changes in response to landslides and floods. The young and tectonically active Himalayan region is more prone to such natural hazards. The impacts of climate change and anthropogenic activities have further increased the frequency and intensity of such natural disasters in this already active region. These disasters cause vast losses of life, property, infrastructure and disturb the ecological balance. This study explores the geomorphological changes occurring in the downstream river reaches of the Alaknanda River using the Google Earth Engine (GEE) cloud-based computing tool. We extract the active river channel width using Landsat multispectral images. The initial results show considerable changes in width over the years (1990-2021) and the changes start from the knickpoint continuing towards downstream. The changes in the river’s bank line indicate the bank erosion and relocation of sediments along the river, likely supplied by erosion processes at upstream reaches. Here, we try to identify the critical point where the deposition process first starts to highlight the most vulnerable zone geomorphologically. We further check whether there has been an increase in sediment deposition in recent years due to likely increased erosion related to deforestation on higher reaches of the Alakananda catchment. We try to achieve this goal by correlating the river landform changes and land cover changes along riparian areas of the river temporally. Our overall objective is to develop a framework to correlate changes or processes in upstream reaches to depositions or erosions along the downstream sections of a high-energy river.

 

Keywords: Landscape evolution, natural hazards, erosion, deposition, River-line
Space Weather detections with housekeeping sensors onboard Mars Express, Rosetta, BepiColombo and Solar Orbiter
Authors: Sanchez-Cano Beatriz , Witasse Olivier , Knutsen Elise W. , Meggi Dikshita , Lester Mark , Wimmer-Schweingruber Robert F. ,   ESA mission teams
Published: March 2022

While space weather has been a growing field of research and applications over the last 15-20 years, “planetary space weather” is an emerging discipline. In fact, as long as we expand our robotic exploration within the solar system, monitoring planetary space weather is becoming more necessary than ever. Despite this, not every spacecraft is designed for plasma science and only a few of them have the necessary plasma instrumentation for space weather purposes. However, all of them have thousands of housekeeping detectors distributed along the spacecraft. In particular, energetic particles impact detectors and subsystems on a spacecraft and their effects can be identified in selected housekeeping data sets, such as the Error detection and correction (EDAC) counters. In this study, we investigate these engineering datasets for scientific purposes by performing the first feasibility study of solar energetic particle detection using EDAC counters from several available ESA Solar System missions, such as Mars Express, Rosetta, BepiColombo and Solar Orbiter. In order to validate the results, these detections are compared to other observations from scientific instruments on board these missions. Moreover, the potential implications of space weather event detections based on EDAC sensors at Mars and Comet 67P/Churyumov-Gerasimenko is analysed. This study has the potential to provide a good network of solar particle observations at locations where no scientific observations of this kind are available.
Quantifying and understanding very rare climate extremes using ensemble boosting
Authors: Gessner Claudia , Fischer Erich M. , Beyerle Urs , Knutti Reto
Published: March 2022

In recent years, unprecedented temperature and precipitation extremes have been observed across the world. With further global warming, climate models project extreme events to get even more intense and likely break observational records by large margins. It is challenging to estimate how extreme climate events could get and to quantify the contribution of physical drivers in the future or even in the present climate? To address these questions, we introduce the ensemble boosting method, a model-based method that generates large samples of re-initialized extreme events in climate simulations. In doing so, the method provides physically consistent storylines of climate extremes that can be used to analyse the driving factors and estimate the very high return levels for the event type beyond observational records. We apply ensemble boosting to heat waves in the millennial pre-industrial control run, made with CESM1 and to heavy precipitation in the large ensemble near future simulations, carried out with CESM2. We find that individual members of the boosted ensembles can substantially exceed the most extreme heat and precipitation events over Europe and North America in the respective climatology. Furthermore, we show that estimated upper bounds of heat correspond to the statistical estimates by the generalized extreme value (GEV) distribution and regression models. Therefore, the framework of ensemble boosting might ultimately contribute to adaption and the stress testing of ecosystems or socioeconomic systems, increasing the resilience to extreme climate stressors.
Characteristics of microscopic pore throat changes in shale reservoir after CO2 fracturing
Authors: He Mengqing , Li Tiantai , Huang Xing , Li Xiang , Wu Ke
Published: March 2022

The interaction of CO2 with the shale reservoir in the process of CO2 fracturing can change the pore-throat structure characteristics of the rock. In order to determine the microscopic pore throat change characteristics in shale reservoir after CO2 fracturing , typical shale core samples before and after fracturing were selected, combined with casting thin slice(CST), field emission scanning electron microscope(FESEM), CT scan, high pressure mercury injection(HPMI), and nuclear magnetic resonance(NMR) test results, and quantitatively evaluate the change characteristics of micro pore throats in shale  reservoir after CO2 fracturing. The results show that various storage spaces such as intergranular pores, intragranular pores, organic pores, and microfractures can be observed in shale reservoirs before CO2 fracturing, which are with poor pore throat connectivity, and most of them are distributed in a dispersed and isolated state. The discharge pressure is low, 0.89Mpa on average, the mercury removal efficiency is low, and the maximum mercury saturation difference is large. Movable fluid saturation ranges from 2.72% to 41.24%, with an average of 26.78%. After CO2 fracturing the shale reservoir, FE-SEM photos often show dissolved pores. The proportion of micro-cracks increased, and the number of cracks observed for a single sample ranged from 1 to 11, with an average of 4. The average length, opening and spacing of micro-cracks are 27.75μm, 286.63μm, and 3.70μm. The average porosity and permeability of micro-cracks are 9.03% and 1.74×10-3μm2. The pore throat connectivity of the shale samples becomes better, the degree of development is higher, the displacement pressure is increased to 3.05MPa, and the mercury removal efficiency and the maximum mercury saturation are both increased. NMR results showed that the movable fluid saturation of shale core samples increased significantly after CO2 fracturing, and the movable fluid saturation was between 1.57% and 50.25%, with an average of 38.14%. CO2 fracturing shale reservoirs will not only produce secondary fractures, but also easily form complex fracture networks. In addition, it will also improve the dense micro-pore throat structure of the shale reservoir itself, increase fluid seepage capacity, and increase oil and gas recovery.
Dual-frequency spectral radar retrieval of snowfall microphysics: a deep-learning based approach
Authors: Billault–Roux Anne-Claire , Ghiggi Gionata , Berne Alexis
Published: March 2022

Better understanding and modeling snowfall microphysical properties and processes is a key challenge in atmospheric science, crucial for snowfall quantification, remote sensing, and weather prediction in general.

The use of meteorological radars for this intent has become quite popular, in particular through two techniques: the use of multi-frequency radar variables on the one hand, and of radar Doppler spectra on the other. Combining both techniques is however a challenging task, complicated by the variability of ice crystals properties and atmospheric conditions, in addition to measurement errors and artifacts such as radars' imperfect calibration and beam matching. We propose a novel approach to retrieve snowfall microphysical properties, by making the most of dual-frequency Doppler spectrograms while relaxing some assumptions on beam-matching and non-turbulent atmosphere.

The technique is based on a two-step deep-learning framework inspired from auto-encoder models, which are generally used for dimension reduction purposes: an encoder maps high-dimensional data to a lower-dimensional “latent” space, while the decoder tries to recover the original signal from this latent space. In the proposed framework, dual-frequency Doppler spectrograms constitute the high-dimensional input, while the dimensions of the latent space are constrained to represent the snowfall properties which we seek to retrieve.

As a first step, a decoder neural network is trained to generate Doppler spectra from a given set of microphysical variables, using simulations from the radiative transfer model PAMTRA as training data. In a second step, the encoder network learns the inverse mapping, from dual-frequency spectrograms to the microphysical latent space. It is trained on real data, and outputs values in the latent space which, when passed as input to the decoder – whose parameters are now frozen – yield reconstructed spectrograms that should match the original data.

In comparison with classical methods, which provide a direct gate-to-gate inversion of the problem, the proposed framework allows to take into account the spatial continuity of the microphysical variables by using convolutions in the architecture of the models, thereby reducing the ill-posedness of the problem.

The method was implemented on X- and W-band data from the ICE GENESIS campaign that took place in January 2021 in the Swiss Jura, and showed promising results. Comparisons with in-situ airborne data also collected during the campaign allow for in-depth assessments of the performance of the algorithm.
Investigating Greenhouse climate control on coal-bearing cycles in the Tethyan Upper Cretaceous Gosau Group (Northern Calcareous Alps, Austria）
Authors: Xiang Xinxuan , Wagreich Michael , Draganits Erich
Published: March 2022

Climate-controlled sea-level rise and fall have important effects on the depositional processes of strata. During periods of widespread glaciation, climate cycles influence sea-level rise and fall by controlling ice sheet growth and melting. The Late Cretaceous period was characterized by a typical greenhouse climate, and evidence for the presence of ice is strongly debated. However, the sedimentary record shows short-term larger sea-level fluctuations, and there is growing evidence for aquifer-eustasy (Sames et al. 2020) as an additional mechanism controlling sea-level rise and fall during this period. Field observations, microscopic observations, and analytical studies on upper Santonian to lower Campanian coal-bearing strata of the Gosau Group in the Northern Calcareous Alps (Hofer et al. 2011) have led to the identification of marginal marine mixed carbonate-siliciclastic cycles. Coal layers and lacustrine fine-grained sediments are present and attest to continental sedimentation with raised groundwater table, whereas intermittent marine strata with foraminifera and calcareous nannoplankton give evidence for marine incursions and high sea-level intervals. In a frame of a University of Vienna project, such Upper Cretaceous coal-bearing cycles in European basins will be investigated in detail to infer regional and Tethyan-wide controlling processes on sea-level and groundwater-table.
Glacier runoff variation since 1981 in the upper Naryn river catchments, Central Tien Shan
Authors: Saks Tomas , Pohl Eric , Machguth Horst , Dehecq Amaury , Barandun Martina , Kenzhebaev Ruslan , Kalashnikova Olga , Hoelzle Martin
Published: March 2022

Water resources in Central Asia strongly depend on glaciers, which in turn adjust their size in response to climate variations. We investigate glacier runoff in the period 1981–2019 in the upper Naryn basin, Kyrgyzstan. The basins contain more than 1000 glaciers, which cover a total area of 776 km2. We model the mass balance and runoff contribution of all glaciers with a simplified energy balance melt model and distributed accumulation model driven by ERA5 LAND re-analysis data for the time period of 1981 - 2019. The results are evaluated against discharge records, satellite-derived snow cover, stake readings from individual glaciers, and geodetic mass balances. Modelled glacier volume decreased by approximately 6.7 km3 or 14%, and the majority of the mass loss took place from 1996 until 2019. The decreasing trend is the result of increasingly negative summer mass balances whereas winter mass balances show no substantial trend. Analysis of the discharge data suggests an increasing runoff for the past two decades, which is, however only partly reflected in an increase of glacier melt. Moreover, the strongest increase in discharge is observed in winter, suggesting either a prolonged melting period and/or increased groundwater discharge. The average runoff from the glacierized areas in summer months (June to August) constitutes approximately 23% of the total contributions to the basin's runoff. The results highlight the strong regional variability in glacier-climate interactions in Central Asia.
Testing nonlinearity and nonstationarity of the connection between Palmer drought indices and Danube discharge in the lower basin
Authors: Mares Ileana , Mares Constantin , Dobrica Venera , Demetrescu Crisan
Published: March 2022

The aim of the study is to reduce the uncertainty of the influence of Palmer-type drought indices in estimating seasonal discharge in the lower Danube basin. For this, four indices were considered: Palmer Drought Severity Index (PDSI), Palmer Hydrological Drought Index (PHDI), Weighted PDSI (WPLM) and Palmer Z-index (ZIND). These indices were quantified by PC1 of EOF decomposition, obtained from 15 stations located along the Danube basin.

The influences of these indices on the Danube discharge were tested, both simultaneously and with certain lags, by linear and nonlinear methods applying the elements of information theory. Nonstationarity was tested by wavelet analysis. The results differ depending on the season and the Palmer index.

The linear connections are generally obtained for synchronous links, and the nonlinear and nonstationary ones for the predictors considered with certain lags (in advance) compared to the discharge predictand. This result is useful for estimating the discharge, as Palmer indices can be estimated from the simulated data by the General Circulation Models or Regional Climate Models.

 
Amerasia Basin: new data and new geological model
Authors: Nikishin Anatoly , Petrov Eugene , Rodina Elizaveta , Startseva Ksenia , Chernykh Andrey , Cloetingh Sierd , Foulger Gillian , Posamentier Henry
Published: March 2022

We present an interpretation of the regional seismic lines for the Amerasia Basin, and new data from analyses of rocks from the Alpha-Mendeleev Rise. This report is based primarily on interpretation of 2D seismic lines and analysis of magnetic and gravity field anomalies, from data acquired through the Russian Arktika-2011, Arktika-2012, Arktika -2014, and Arktika-2020 projects. We use also open Canadian seismic data (Shimeld et al., 2021) and published data. We propose that the Alpha-Mendeleev Rise is a Eurasian aborted double-sided volcanic passive continental margin with stretched and hyper-extended continental crust intruded by basalts. This rise has a number of SDR-like seismic units. The age of volcanism is ~125-100 Ma. The Podvodnikov, Toll, Mendeleev, Nautilus, Stefansson basins have SDR-like seismic units. The top of SDR-like units has a similar age in all basins. The Alpha-Mendeleev Rise has an axis of symmetry. The East North Chukchi, Toll, Mendeleev, Nautilus, Stefansson basins are coeval basins with very stretched continental crust. They are connected by a long united axial line of hyperextension, subsidence and volcanism.  The Makarov, Podvodnikov, West North Chukchi basins are coeval basins with very stretched continental crust. They are connected by a long united axial line of hyperextension, subsidence and volcanism.  The Alpha-Mendeleev Rise and all mentioned basins originated simultaneously in the same geodynamic environment during the HALIP magmatic epoch at nearly 125-100 Ma. This study was supported by the Russian Science Foundation (Grant 22-27-00160).
The influence of temperature on soil complex dielectric permittivity in the 0.02 – 3 GHz frequency range
Authors: Szypłowska Agnieszka , Lewandowski Arkadiusz , Kafarski Marcin , Szerement Justyna , Wilczek Andrzej , Majcher Jacek , Skierucha Wojciech
Published: March 2022

Dielectric properties of soil are often utilized for the purpose of soil moisture measurement. However, the relations between soil complex dielectric permittivity and volumetric water content depend also on other factors, such as the operating frequency of the sensor, soil texture, and temperature. The goal of the presented work is to examine the impact of temperature in the 0.5 – 40°C range on the complex dielectric permittivity spectrum of two soils of silt loam and loamy sand textures. The permittivity spectra were measured in a coaxial transmission-line cell system with the use of a Copper Mountain R60 one-port vector-network-analyzer in the frequency range from 20 MHz to 3 GHz. The relations between the real part of dielectric permittivity and soil volumetric water content were modeled at each examined frequency and the temperature dependence of the applied model parameters was determined. In the future research steps, the obtained relations will be applied and tested with the use of a prototype field soil moisture probe operating in a broadband frequency range.

 

The research has been supported by the Polish National Agency for Academic Exchange under Grant No. PPI/APM/2018/1/00048/U/001. The soil dielectric spectra have been obtained in the scope of the project No. 2014/15/D/ST10/04000 financed by the Polish National Science Centre (NCN).
Identifying taxa from highly degraded shell micro-fragments in anthropogenic soils from Waterfall Bluff, South Africa
Authors: Oertle Annette , Szabó Katherine , Gaqa Sibongiseni , Cawthra Hayley , Esteban Irene , Pargeter Justin , Fisher Erich
Published: March 2022

Archaeomalacological analysis is generally undertaken on recovered macro-remains to characterize the overall composition of faunal remains in a deposit. Given the susceptibility of shell middens to a variety of taphonomic processes, it is assumed that the prior presence of shell in deposits may therefore occasionally be missed. Deteriorated micro-remains can mix indistinguishably into surrounding sediments and make their analyses and identification difficult, particularly in older deposits and in environments that experience rapid rates of weathering. This paper explores whether microscopic remains of deteriorated molluscs can be distinguished from other microscopic remains at the coastal rock shelter site of Waterfall Bluff in Mpondoland, South Africa. The methodology uses a multi-scalar approach integrating shell mineralogy and microstructure using the taxonomic distinctiveness of these features. The diagnostic features (e.g. morphology, hinges, spires, and apertures) used for identifying macro-remains are absent in micro-remains, therefore unique methods of identification are needed to identify these microscopic mollusc fragments. Through mineralogical analyses and scanning electron microscope (SEM) imaging, the nacreous remains of mussel shell were identified from previously unidentified degraded shell remains as well as sediment samples from Waterfall Bluff. These highly degraded remains were located under the dripline in the oldest deposits (LBCS) which are sharply comparable to the more well-preserved macro mollusc evidence in the younger (SRCS) deposits. These methods recovered ‘invisible’ evidence of shellfish remains, which led to additional and clearer evidence of continued coastal foraging from Marine Isotope Stage 3 to the early Holocene (40 ka to 10 ka) on the South African coast.
Towards a morphology diagram for terrestrial carbonates: Evaluating the impact of carbonate supersaturation and alginic acid in calcite precipitate morphology
Authors: Rogerson Mike , Mercedes-Martín Ramon , Prior Timothy , Brasier Alexander , Reijmer John , Billing Ian , Matthews Anna , Love Tracy , Lepley Scott , Pedley Martyn
Published: March 2022

Ancient and recent terrestrial carbonate-precipitating systems are characterised by a heterogeneous array of deposits volumetrically dominated by calcite. In these environments, calcite precipitates display an extraordinary morphological diversity, from single crystal rhombohedral prisms, to blocky crystalline encrustations, or spherulitic to dendritic aggregates. Despite many decades of thorough descriptive and interpretative work on these fabrics, relating calcite micro-morphology with sedimentary hydrogeochemical conditions remains a challenge. Environmental interpretations have been hampered by the fact that calcite morphogenesis results from the complex interaction between different physico-chemical parameters which often act simultaneously (e.g., carbonate mineral supersaturation, Mg/Ca ratio of the parental fluid, organic and inorganic additives). To try to experimentally address the sedimentological causes of calcite morphogenesis, an experimental approach yielding a first attempt at a calcite growth-form phase diagram is presented here. The initial aim was to account for the carbonate products experimentally nucleated in alkaline, saline lake settings. These are the result of at least two competing calcite precipitation ‘driving forces’ that affect morphogenesis: the calcite supersaturation level of the parental fluid, and the concentration of microbial-derived organic molecules (alginic acid). A key finding of this study is that common naturally-occurring calcite products such as calcite floating rafts, rhombohedral prismatic forms, di-pyramid calcite crystals, spherulitic calcite grains, or vertically stacked spheroidal calcite aggregates, can be related to specific hydrogeochemical contexts, and their physical transitions pinpointed in a phase diagram. By exploring binary or ternary responses to forcing in morphological phase-space, links between calcite growth forms and (palaeo)environmental conditions can be determined. This provides a truly process-oriented means of navigating questions around carbonate precipitate morphogenesis for the future.
Volume balance of frontally confined submarine landslides - a case study of the Ana Slide, Eivissa Channel, western Mediterranean Sea
Authors: Sager Thore , Urlaub Morelia , Geersen Jacob , Berndt Christian
Published: March 2022

Submarine landslides can cause devastating tsunamis and inundate surrounding coastal areas or directly compromise offshore infrastructure. A landslides’ ability to generate a tsunami is expressed as the tsunamigenic potential controlled, amongst other parameters, by the amount of landslide material mobilized during failure. The Ana Slide, located in the Eivissa Channel on the Balearic Promontory, western Mediterranean Sea, developed as a frontally confined landslide. This means that the mobilized mass is frontally buttressed against unaffected strata. Unique to the Ana Slide is that it is completely covered by high-resolution 2D, 3D reflection seismic and bathymetric data. Steady hemipelagic sedimentation prevailed in the study area way before the occurrence of the Ana Slide. Strata outside the perimeter of the Ana Slide shows predictable thicknesses that can be interpolated from outside to inside the landslide.

Within this study, we reconstruct the pre-failure seafloor morphology of the Ana Slide. We use a published GIS-tool for the source area and facilitate predictive sedimentary thicknesses as an interpretational basis for the sink area. These methods allow the actual volume of mobilized landslide material from the evacuational source into the accumulational sink area to be determined. In addition, we can calculate the ratio between actually mobilized landslide and affected material that was not directly involved in the landslide motion. Results of the volume balance calculation expose that the Ana Slide represents a “closed system” landslide because all evacuated landslide material from the source area has completely accumulated within the sink area with an uncertainty of < 5%.

Based on a detailed kinematic analysis previously performed for the Ana Slide, we show that the volume of actually mobilized landslide material is significantly smaller than that of the affected material that was not directly involved in the landslide motion. We show that mobilized landslide material can affect strata to significant depths beneath the deposit, while being relatively thin itself. This could potentially lead to erroneous or excessive landslide volume estimations. Our findings may therefore be critical for tsunamigenic potential assessment and geological hazard predictions.
Towards Urban Flood Susceptibility Mapping Using Data-Driven Models
Authors: Seleem Omar , Ayzel Georgy , Costa Tomaz de Souza Arthur , Bronstert Axel , Heistermann Maik
Published: March 2022

Both frequency and severity of urban pluvial floods have been increasing due to rapid urbanization and climate change. Hydrological and two dimensional (2D) hydrodynamic models are still too computationally demanding to be used for real-time applications for large urban areas (i.e. flood management scale). As an alternative, data-driven models could be used for flood susceptibility mapping. This study evaluated and compared the performance of image-based models represented by a convolutional neural network (CNN) and point-based models represented by an artificial neural network (ANN), a random forest (RF) and a support vector machine (SVM) with regard to the spatial resolution of the input data. We also examined model transferability. Eleven variables representing topography, anthropogenic aspects and precipitation were selected to predict flood susceptibility mapping. The results showed that: (1) all models were skilful with a minimum area under the curve AUC = 0.87. (2) The RF models outperformed the other models for all spatial resolutions. (3) The CNN models were superior in terms of transferability. (4) Aspect and elevation were the most important factors for flood susceptibility mapping for image-based and point-based models respectively.
Retreat of the Northeast Greenland ice stream during the last glacial termination - a case study from Norske Trough
Authors: López-Quirós Adrián , Andresen Katrine J. , Davies Joanna , Junna Tuomas , Nielsen Tove , Pearce Christof , Seidenkrantz Marit-Solveig
Published: March 2022

The Greenland Ice Sheet (GIS), the second largest ice sheet on Earth, has experienced a dramatic ice mass reduction during the last decades, coincident with global warming and an increase in atmospheric CO2. About 16% of the GIS is currently drained via marine terminating glaciers, mostly through the Northeast Greenland Ice Stream (NEGIS; with ~12%). Two cross-shelf troughs (Norske and Westwind troughs) served as drainage pathways of the NEGIS. According to numerical ice-sheet models, a whole meltdown of the GIS may cause a global sea−level rise of >7 m, causing permanent damage to the environment and countless economic impacts on our coastal society. In order to better understand the processes driving these present changes, studies of the development of glaciers/glacial troughs and ice sheets in response to past climate changes are required for testing numerical models that seek to predict ice-sheet response to anthropogenic climate change.

In this study, high-resolution INNOMAR sediment subbottom profiler data combined to multi-proxy analyses of gravity core DA17-NG-ST10-117G, obtained from Norske Trough during the NorthGreen17 expedition, are investigated. Multi-proxy data derived from the sediment gravity core include 14C-derived ages, descriptions of sedimentary units, compositional variability of ice-rafted debris, and continuous logging of magnetic susceptibility and micro-XRF core scanning. In Norske Trough, submarine glacial landforms indicate that ice sheet retreat to the outer middle shelf after the Last Glacial Maximum (LGM) was stepwise, with phases of grounding line stabilization, while ice sheet retreat from the middle shelf to the coastline during deglaciation was fast. Sedimentological evidence at our recorded coring site captures the transition from sub–ice stream (subglacial) environments to proximal (proglacial)/distal glaciomarine conditions during the LGM to Holocene recession. In addition, preliminary foraminifera analysis indicates warmer recirculating Atlantic Water on the middle Norske Trough immediately on deglaciation, suggesting that oceanic forcing very likely played a significant role during the retreat of the ice margin. This presentation will include a comprehensive comparison of the spatio-temporal sedimentation patterns across the Norske Trough.
Diurnal Dips and Forbush Decreases in Galactic Cosmic Rays Observed at High Cutoff Rigidity
Authors: Banglieng Chanoknan , Ruffolo David , Sáiz Alejandro , Mitthumsiri Warit , Nutaro Tanin , Duldig Marc L. , Humble John E.
Published: March 2022

A Forbush decrease (FD) is the decrease in Galactic cosmic ray (GCR) flux, e.g., as observed by a neutron monitor count rate, in association with a coronal mass ejection (CME) and/or its shock. The FD amplitude is known to decrease at higher cutoff rigidity. During Solar Cycle 24, the Mawson neutron monitor in Antarctica, with a low (atmosphere-limited) cutoff rigidity of ~1 GV, observed numerous FDs, while the Princess Sirindhorn Neutron Monitor (PSNM) located near the Earth's equator at Doi Inthanon, Thailand, with the world’s highest geomagnetic cutoff rigidity (17 GV), observed only a fraction of these as FDs.  Instead, we find that the shock arrival is often followed by repeated dips in the PSNM count rate at only certain times of day, while the GCR flux from other directions remains near the pre-shock level.  We refer to decreases of this type as diurnal dips.  In this work, we have surveyed FDs and diurnal dip events observed by PSNM and the dependence of their maximum amplitude on the solar wind speed, ICME speed, and interplanetary magnetic field.  We acknowledge logistical support from Australia's Antarctic Program for operating the Mawson NM and support from the National Astronomical Research Institute of Thailand and grant RTA6280002 from Thailand Science Research and Innovation.
Diverse manifestations of the impact of astronomical forcing and CO2 on climate and vegetation changes during MIS-11 and MIS-13
Authors: Su Qianqian , Lyu Anqi , Wu Zhipeng , Yin Qiuzhen
Published: March 2022

Numerous studies have been made on paleoclimate and paleovegetation reconstructions and simulations of the past interglacials. However, systematical analysis of the global patterns of the correlation between vegetation pattern and astronomical forcing as well as CO2 between different interglacials is rare. Given the distinct differences in orbital configurations and climate/vegetation variations between MIS-11 and MIS-13, we performed two sets of transient simulations using LOVECLIM 1.3, one driven by insolation change only, and another one by changes in both insolation and CO2. These simulations allow us to investigate the relative effect of astronomical forcing and CO2 on global and regional vegetation changes during these two interglacials. Our results show that the effects of precession and obliquity on vegetation depend strongly on regions, and the simulated results are in good agreement with vegetation reconstructions at key regions. The vegetation response differs widely between MIS-11and MIS-13, which is mainly caused by the difference in their astronomical configurations, and the difference in CO2 concentration between these two interglacials plays a minor role. In addition to the effect of precession and obliquity, our simulations are also able to capture the half precession signal (~ 10 ka) in the climate and vegetation changes in the tropical regions in response to the tropical insolation.
Eddy advection and the evolution of Mixed layer properties: a case study at Southeast Tropical Indian Ocean
Authors: Azaneu Marina , Matthews Adrian , Baranowski Dariusz
Published: March 2022

The Southeast Tropical Indian Ocean region has a complex background current system whose instabilities lead to eddy generation through energy cascade. Many studies have documented the eddy activity in the region. More recently the generation of these features were investigated, being ocean shear velocity and tropical Pacific winds identified as important forcings of these westward-southwestward propagating features. By mixing and advecting anomalous waters, eddies not only have act on fertilizing the ocean surface layer but also have effect on the properties of the mixed layer. As a consequence, eddy activity may have a significant impact on the ocean-atmospheric fluxes of this highly dynamic region. Here we present a case study focused on a 2.5 months high temporal and vertical resolution data from 2 gliders deployed between Christmas Island and Java Island, in which we explore the temporal evolution and the effects of eddy advection and atmospheric forcing on the ML properties. Spatial information was complemented by using the Nemo global analysis forecast product (1/12 degree). Nemo forecast of changes in the average temperature, salinity and depth of the mixed layer caused by the advection of eddies closely fits the glider data close to Java and the Sunda and Lombok Straits. It’s capability decays as we move away from the coast, a main source of the eddies, as the mesoscale features acquire a more filament nature, and thus becoming more challenging of closely reproduction. Nevertheless, Nemo constituted as a useful tool for defining the oceanic basic state previous to the deployment and estimate horizontal shear and eddy advection time. Nemo and glider data showed the expected thermodynamical response associated with intraseasonal atmospheric systems, such as the decrease/increase in SST during active/suppressed phases of MJO, Convectively coupled Kelvin waves and Equatorial Kelvin waves observed during the deployment and identified in filtered GPM precipitation and ERA5 wind data. Besides the atmospheric forcing, eddy activity also varied throughout the mission, as well as the role of temperature and salinity in setting the mixed layer depth. We identified initially that the effect of eddy advection on SST can differ depending on the presence or intensity of the atmospheric forcing. As future work, we intend to combine this environmental information with Nemo and the high vertical resolution data from the glider to explore the role of eddy advection, ocean background state and atmospheric forcing on setting the ML properties during the glider deployment and the effect of the ocean-atmospheric fluxes.
Linkage among different compound drought-hot events at a global scale
Authors: Feng Sifang , Hao Zengchao , Hao Fanghua , Zhang Xuan
Published: March 2022

Droughts manifest in different forms, such as meteorological droughts, agricultural droughts, and hydrological droughts. Due to common forcing factors or land-atmosphere interactions, droughts may co-occur with high-temperature extremes over global land areas. The concurrence of droughts and hot extremes (or CDHEs) has received increased attention in the past decade, owing to their amplified impacts on society and ecosystems. Changes in different forms of CDHEs under global warming have been evaluated at different regional scales. However, the investigation of linkages among different CDHEs is rather rare. In this study, we assessed the variation and connection among different CDHEs during the warm period at the global scale based on the Global Land Data Assimilation System (GLDAS). We found an increased frequency of different CDHEs in the past half-century over most regions. In addition, we also investigated their connection in the variability at different climate regimes. Results on the linkage among different compound events can provide valuable information for water resources management under global warming.
Long-Lasting Marine Heatwaves Instigated by Ocean Planetary Waves in the Tropical Indian Ocean During 2015–2016 and 2019–2020
Authors: Zhang Ying , Du Yan , Feng Ming , Hu Shijian
Published: March 2022

Marine heatwaves (MHWs) in the tropical Indian Ocean (TIO) showed remarkable increases in duration and frequency during the satellite observing era, responding to rising sea surface temperature. Long-lasting MHWs were found in three upwelling regions of the TIO in 2015–2016 and 2019–2020, closely related to persistent downwelling oceanic planetary waves. In 2015, a prolonged MHW (149 days) in the western TIO was initiated by the downwelling Rossby waves associated with the co-occurring super El Niño and positive Indian Ocean dipole (IOD) events. In the following year, the negative IOD sustained the longest MHW (372 days) in the southeastern TIO, prompted by the eastward-propagating equatorial Kelvin waves. In 2019–2020, the two longest MHWs recorded in the southwestern TIO (275 days in 2019 and 149 days in 2020) were maintained by the downwelling Rossby waves associated with the 2019 extreme IOD. This study revealed the importance of ocean dynamics in long-lasting MHWs in the TIO.