While it remains debated if the mineral deposits mined for phosphorus fertilizer are running out, phosphorus insecurity is an emerging global issue. We explore how it is linked to the current linear phosphorus economy (LPE) and the historic and current implications. The problems are multifold: there are geopolitical concerns over phosphorus deposits held only by a few nations, sharply rising costs of phosphorus fertilizers, heavy metal contaminants affecting soil and food, problematic phosphorus mining wastes, and the widespread environmental degradation caused by fertilizer inefficiencies. A new phosphorus economy can resolve these problems. Transitioning to a sustainable use of phosphorus demands a circular phosphorus economy (CPE). A CPE supports several Sustainable Development Goals and enables countries without phosphorus deposits to achieve greater phosphorus autonomy. We illustrate current problems with case studies and outline opportunities for change. The CPE will feature phosphorus recovery facilities, waste valorisation technologies, and improved fertilizer formulations that are customised to crop systems. We highlight examples of the rapidly advancing CPE that forms an integral part of the bioeconomy and the circular economy.

The Blackfoot Reservoir volcanic field (BRVF), Idaho, USA, is a bimodal volcanic field that has hosted explosive silicic eruptions during at least two episodes, as recently as 58 ka. Using newly collected terrestrial and marine gravity data, two large negative anomalies (−16 mGal) are modeled as shallow (<1 km) laccoliths beneath a NE-trending alignment of BRVF rhyolite domes and tuff rings. Given the trade-off between density contrast and model volume, best-fit gravity inversion models yield a total intrusion volume of 50−120 km3; a density contrast of −600 kg m-3 results in model intrusion volume of 63 km3. A distinctive network of 340°−360° trending faults lies directly above and on the margins of the mapped gravity anomalies. Most of these faults have 5−10 m throw; one has throw up to ∼50 m. We suggest that the emplacement of shallow laccoliths produced this fault zone and also created a ENE-trending fault set, indicating widespread ground deformation during intrusion emplacement. The intrusions and silicic domes are located 3−5 km E of a regional, 20 mGal step in gravity. We interpret this step in gravity as a change in the thickness of the Upper Precambrian to lowermost Cambrian quartzites in the Meade thrust sheet, part of the Idaho-Wyoming Thrust Belt. Silicic volcanism in the BRVF is a classic example of volcanotectonic interaction, influenced by regional structure and creating widespread deformation. Exogeneous and endogenous domes are numerous in the region. We suggest volcanic hazard assessments should account for potentially large-volume silicic eruptions in the future.

We conducted dynamic viscoelastic measurements of three clay minerals in a solid–liquid two-phase state: kaolinite, illite, and smectite with water. These constituents of concentrated (dense) suspensions were investigated using a high-temperature and high-pressure rheometer, to understand tectonic and non-tectonic phenomena in the shallow part of a fault system, such as shallow slow slip events in subduction zones, and landslides on fault or bed planes. We observed shear strain rate dependencies of phase angles of both dynamic stress and strain waveforms on the rheometer at varying temperature and pressure. The pressure and temperature dependence of the viscoelastic properties of the system can be qualitatively understood by applying the Zwanzig–Mountain theory. The local packing fraction change owing to dynamic oscillations affects the changing viscoelastic properties in systems such as shallow fault systems.

Meter-scale AUV mapping of 85-km of the summit and rift zones of Axial Seamount shows systematic variation in morphology of the lava flows with depth and distance from the caldera. ROV sampling reveals flow age and chemistry variations. Each rift zone has a steady downward slope of ~2° outside the caldera. In the caldera and first few km down the rift zones, flows are predominantly channelized sheet flows with collapses along the channels. Mid-rift, drained inflated hummocky flows consisting of complex mounds with tumuli and lava lakes, and narrow ridges of hummocky mounds become common. On the axis of the south rift, the first cones with craters occur 3.2 km from the caldera at 1600 m depth, and broad inflated hummocky flows emplaced through complex lava tubes first appear 6 km down-rift at 1715 m. On the north rift, similar cones and complex flows appear at 10.5 km down-rift at 1725 m depth. The historical flows exemplify this variation: on the upper south rift as channelized sheet flows in 1998 and 2011 erupted from fissures that extended 6.5 km down-rift; on the middle north rift, inflated hummocky flows up to 126 m thick erupted in 2015 from fissures 17.5 km from the caldera; and on the distal south rift, a narrow ridge of coalesced hummocks 160 m tall formed during the 2011 eruption. Older and older lavas remain exposed at greater distances from the more active summit and upper rift zones. Deep on the rift zones, stellate and steep cones with smooth talus slopes occur that did not feed expansive flows, despite being constructed of hotter, less viscous, near-primary magmas. These cones are first observed on both rift zones at 1800 m depth and 18 km from the caldera. Deeper still, emanating from both distal rift axes beginning ~30 km from the caldera, lie voluminous inflated sheet and inflated hummocky flows 30 to 135 m thick with combined area of over 150 km2. The plagioclase-phyric voluminous flows on the south rift erupted ~1250 years ago, and the aphyric ones on the north rift ~13,000 years ago. Eruption rate is the most likely cause of the flow morphology changes since estimated magma viscosity does not correlate with flow morphology. Lateral transport through long dikes would slow magma delivery unless dike widths are large. The near-primary magmas may have risen through narrow conduits from the mantle to the distal rifts.

CO2 geological storage is a promising method to dispose excess CO2 in the atmosphere, and the existence of brine in deep saline aquifer and below oil reservoir may lead to salt precipitation in pore space for dry-out formation. Water diffusion coefficient is helpful to evaluate salt precipitation. However, limited previous data cant satisfy the need of CO2 geological storage. Raman quantitative spectroscopy is used to observe water diffusion in CO2 in a high-pressure capillary cell and corresponding diffusion coefficients are obtained at 10-50 MPa and 353.15-433.15 K. Diffusion coefficient is temperature and pressure dependent, and also increases linearly with the reciprocal of CO2 density. Free volume theory and PC-SAFT EOS are utilized to establish a thermodynamic model for water diffusion in CO2, and it predicts diffusion coefficient accurately at 10-50 MPa and 353.15-433.15 K. Besides, diffusion coefficient is used to evaluate when salt precipitation occurs and salt precipitation process is observed in a one-dimensional capillary tube and a two-dimensional micromodel respectively.

To manage potential risks due to H2 leaks into the near-surface geosphere from H2 underground storages (e.g. salt caverns, aquifer), reliable monitoring methods along with a precise knowledge of the geochemical environmental impacts are necessary. Thus, the evolution of some prominent parameters in soil and aquifers can be determined: gas concentrations, redox potential, ionic balance and trace elements. As part of the ROSTOCK’H project, Ineris simulated H2 leakage by injection of dissolved H2 into a shallow aquifer (~20 m deep) in an experimental site within the Paris basin. This experiment aimed to testing advanced monitoring techniques and studying hydrogeochemical impacts at shallow depths. The aquifer water has calcium-bicarbonate facies and a neutral pH. Eight piezometers were aligned over 80 m according to the aquifer main flow (west-east). Hydrogeochemical monitoring devices were set up. One of the piezometers was equipped with a completion connected to a Raman probe and a specific Mid-IR cell for continuous measurement of aqueous gases. At the experiment outset, 5 m3 of water were extracted from the aquifer to be saturated with H2 under atmospheric conditions, before being reinjected through the injection well. About 100 LSTP of dissolved H2 (concentration of 1,8 mg/L) was injected in the aquifer. The H2 injection was preceded by the injection of underground water containing tracers (He(aq), uranine and LiCl) in order to warn the H2 plume arrival in the piezometers located downstream of the injection well. The concentrations of aqueous gases (He, H2, N2, O2, CO2, H2S and CH4) were measured in a control piezometer (20 m upstream) and in six piezometers up to 60 m downstream. Thus, the maximum H2 contents were detected up to 20 m downstream of the injection well: 0.6 mg/L at 5 m, 0.17 mg/L at 7 m then 1.8 µg/L of H2 at 10 and 20 m during the first week. Following the H2(aq) addition, the aquifer physico-chemistry has been modified: low increase in pH, high decrease in redox potential and O2(aq). These results confirm the feasibility of detecting and monitoring H2 in shallow aquifers in very low concentration conditions and highlight the potential impacts. This is of first importance for establishing the surveillance and security aspects related to with H2 storage.

Mechanisms of fluid flow localization and pockmark formation remain an open question. Many conceptual models have been proposed, but very few predictive models exist. We propose a model based on erosive fluidization where seepage induced erosion, fluidization, and transport of granular material leads the formation of fluid escape structures (FES) like pipes, chimneys and pockmarks. The model predicts: 1) formation of conical focused flow conduits with brecciated core and annular gas channels encased within a halo of low permeability sediment, 2) pockmarks of diverse shapes and sizes, including W-, U-, and ring-shapes, and 3) pulsed gas release. Results show that the morphology of FES depends on properties related to sediment-fluid interactions (like erodibility and flow anisotropy), not on intrinsic sediment properties (like permeability). Although the study is theoretical, we show that our predicted FES have many real world analogs, highlighting the broad scope of the predictive capability of our model.

The São Francisco Craton (SFC) and its marginal Araçuaí and Brasília orogens exhibit a significant diversity in their lithospheric architecture. These orogens were shaped during the Neoproterozoic–Cambrian amalgamation of West Gondwana. The rigid cratonic lithosphere of the SFC and the relatively weak lithosphere of the Araçuaí Orogen were disrupted during the Cretaceous opening of the South Atlantic Ocean, whereas the Brasília Orogen remained in the continental hinterland. In earlier research, the thermal effects of the Phanerozoic reactivations in the shallow crust of the Araçuaí Orogen have been revealed by low-temperature thermochronology, mainly by apatite fission track (AFT) analysis. However, analyses from the continental interior are scarce. We present new AFT data from forty-three samples from the Brasília Orogen, the SFC and the Araçuaí Orogen, far from the passive margin of the Atlantic coast (~150 to 800 km). Three main periods of basement exhumation were identified: (i) Paleozoic, recorded both by samples from the SFC and Brasília Orogen; (ii) Early Cretaceous to Cenomanian, recorded by samples from the Araçuaí Orogen; and (iii) Late Cretaceous to Paleocene, inferred in samples from all domains. We compare the differential exhumation pattern of the different geotectonic provinces with their lithospheric strengths. We suggest that the SFC likely concentrated the Meso-Cenozoic reactivations in narrow weak zones while the Araçuaí Orogen displayed a far-reaching Meso-Cenozoic deformation. The Brasília Orogen seems to be an example of a stronger orogenic lithosphere, inhibiting reworking, confirmed by our new AFT data. Understanding the role of the lithosphere rigidity may be decisive to comprehend the processes of differential denudation and the tectonic–morphological evolution over Phanerozoic events.

Large alluvial rivers transport water and sediment across continents and shape lowland landscapes. Repeated glacial cycles have dominated Earth's recent climate, but it is unclear whether these rivers are sensitive to such rapid changes. The Amazon River system, the largest and highest-discharge in the world, features extensive young terraces that demonstrate geologically rapid change temporally correlated with changes in runoff from Quaternary climate cycles. To test the plausibility of a causal relationship, we use a simple model to estimate from empirical measurements how quickly a river profile responds to changes in discharge or sediment supply. Applying this model to data from 30 gauging stations along alluvial rivers throughout the Brazilian Amazon, we find that many rivers of the Amazon basin can respond faster than glacially induced changes in runoff or sediment flux. The Amazon basin is unusually responsive compared to other large river systems due to its high discharge and sediment flux, narrow floodplains, and low slopes. As a result, we predict that the Amazon basin has been highly dynamic during Quaternary glacial cycles, with cyclical aggradation and incision of lowland rivers driving repeated habitat and environmental change throughout the region. This dynamic landscape may have contributed to the exceptional biodiversity of the region and patterns of ancient human settlement.

The Chalk Group deposited on the Schill Grund Platform in Dutch offshore comprises a near complete early Danian to late Cenomanian chalk succession. Such a long record (~30 Myrs) allows for the study of long period (>1 Myr) astronomical cycles providing insights into amplitude modulation of astronomical cycles. A 405kyr eccentricity-based tuning was created for one gamma-ray log and one thorium well-logs which go through the Chalk Group. These results were tuned to astronomical solution La2010d, which were then be used to study aspects of long period astronomical cycles. Firstly, the amplitude modulation of the 405 kyr eccentricity by long period astronomical cycles was studied, which indicates that secular resonance transitions took place at ~85 Ma and ~92 Ma. The secular resonance transition at ~92Ma shifted the duration of the 2.4 Myr eccentricity cycle to a 1.2 Myr period while the resonance transition at ~85 Ma shifted the period shifted back 2.4 Myr. The amplitude modulation records were also compared to the amplitude modulation records of astronomical solutions. None of the astronomical solutions accurately model the observed resonance transition. The second result is related to Ocean Anoxic Event II (OAEII). The 2.4 Myr cycle is at a maximum ~ 400kyr before the onset of OAEII and progressively transitions towards a minimum during OAEII, as the 1.2 Myr obliquity cycle peaks during OAEII. This phase relationship between these astronomical cycles leads to a progressive increase in the contribution of the obliquity to the astronomical-insolation signal during OAEII.

We observed temperature variations over 10 months within a Kuroko ore (hydrothermal sulfide) cultivation apparatus installed atop a 50-m-deep borehole drilled in the Noho hydrothermal system in the mid-Okinawa Trough, southwestern Japan, for monitoring of hydrothermal fluids and in situ mineral precipitation experiments. Temperature and pressure in the apparatus fluctuated with the tidal period immediately after its installation. Initially, the average temperature was 75–76 °C and the amplitude of the semi-diurnal tidal temperature modulation was ~0.3 °C. Four months later, the amplitude of tidal temperature modulation had gradually increased to 4 °C in synchrony with an average temperature decrease to ~40 °C. Numerical modeling showed that both the increase in tidal amplitude and the decrease in average temperature were attributable to a gradual decrease in inflow to the apparatus, which promoted conductive cooling through the pipe wall. The reduced inflow was probably caused by clogging inside the apparatus, but we cannot rule out a natural cause, because the drilling would have significantly decreased the volume of hot fluid in the reservoir. The temperature fluctuation phase lagged the pressure fluctuation phase by ~150°. Assuming that the fluctuations originated from inflow from the reservoir, we conducted 2-D numerical hydrothermal modeling for a poroelastic medium. To generate the 150° phase lag, the permeability in the reservoir needed to exceed that in the ambient formation by ~3 orders of magnitude. The tidal variation phase can be a useful tool for assessing the hydrological state and response of a hydrothermal system.

Fault zones are usually composed of a granular gouge, coming from the wear material of previous slips, which contributes to friction stability. Once considering a mature enough fault zone that has already been sheared, different types of infill materials can be observed, from mineral cementation to matrix particles that can fill remaining pore spaces between clasts and change the rheological and frictional behaviors of the gouge. We aim to understand and reproduce the influence of grain-scale characteristics on slip mechanisms and gouge rheology (Riedel bands) by employing the Discrete Element Method. A 2D-direct shear model is considered with a dense assembly of small polygonal cells of matrix particles. A variation of gouge characteristics such as interparticle friction, gouge shear modulus or the number of particles within the gouge thickness leads to different Riedel shear bands formation and orientation that has been identified as an indicator of a change in slip stability (Byerlee et al., 1978). Interpreting results with slip weakening theory, our simulated gouge materials with high interparticle friction or a high bulk shear modulus, increase the possible occurrence of dynamic slip instabilities (small nucleation length and high breakdown energy). They may give rise to faster earthquake ruptures.

The current study aimed at assessing the capabilities of five machine learning models in term of mapping tungsten polymetallic prospectivity in the Gannan region of China. The five models include logistic regression (LR), support vector machine (SVM), random forest (RF), convolutional neural network (CNN), and light gradient boosting machine (LGBM) models. Geochemical, lithostratigraphic, and structural datasets were used to generate 16 evidential maps, which were integrated into the machine learning models. Tungsten polymetallic deposits were randomly separated into two parts: 80% for training and 20% for validating. Performances of the models were evaluated through receiver operating characteristic (ROC) and K-fold cross validation, with an emphasis on the variable influence within different machine learning methods. The results show that the models are especially sensitive to the chemical elements: Be, Bi, Pb and Cd, implying that these are closely related to tungsten polymetallic mineralization. Compared to other models, the LGBM and CNN models performed best, while the LR model was the most stable. The results also indicated that the CNN model can predict maximum known deposits within a minimum area, based on the prediction-area plot analysis of the five models, while the RF model can capture the most well-known deposits within the smallest study area. Finally, eighteen prospective areas were delineated according to the predicting results of the machine learning models, which will provide important guidance for further tungsten polymetallic exploration and associated studies.

This study discovers various geothermal prospects in the Great Basin, USA based on shallow groundwater chemical (geochemical) data. The geochemical data are expected to include hidden (latent) information that is a proxy for geothermal prospectivity. We processed the sparse geochemical data in the Great Basin at 14,341 locations including 18 attributes. Next, a non-negative matrix factorization with customized k-means clustering (NMFk) is applied to the geochemical data matrix. NMFk automatically finds three hidden geothermal signatures representing modestly, moderately, and highly confident geothermal prospects. The algorithm also evaluated the probability of occurrence of these types of resources through the studied region. There is a consistency between regional geothermal prospectivity as estimated by our ML methodology and the traditional play fairway analysis conducted over a portion of the study area. We also identify the dominant data attributes associated with each signature. Finally, our ML analyses allow us to reconstruct attributes from sparse into continuous over the study domain. The predicted continuous attributes can be used for future detailed geothermal explorations in the Great Basin.

Equatorial Guinea’s Bioko Island is located in the Atlantic Ocean off the west coast of Cameroon. Bioko is a volcanic island and the first off-shore expression of the Cameroon Volcanic Line. It is home to three shield volcanoes: Pico de Basile, Pico Biao, and San Carlos. Eruptive histories are not known for Pico Biao or San Carlos. Pico de Basile erupted within the past 100 years, and steam vents were observed as recently as 2012. Malabo, the capital city of Equatorial Guinea, sits in the shadow of Pico de Basile. There is no permanent seismic monitoring; the closest seismic stations are in Cameroon and have not reported data since 2015. In November 2017 Drexel University researchers, supported by the Bioko Biodiversity Protection Program (BBPP) and the Universidad Nacional de Guinea Ecuatorial (UNGE), installed 4 broadband seismometers. In February 2018, the data were retrieved, and stations serviced. Preliminary earthquake detection and location was completed using an automated STA/LTA algorithm. S wave arrivals were added manually. The initial locations use the global IASP91 model and events were relocated using a local model. The events detected cluster into two areas: those near Bioko Island and those near Cameroon. Between 12-Dec-2017 and 17-Feb-2018, 77 events were recorded. Local magnitudes range between 0.16 and 2.61. Of these events, 49 are located near Cameroon and 28 are near Bioko. Most of the depths are crustal, mostly upper to mid crust. Our preliminary results show there is seismicity associated with Bioko Island as well as Cameroon. The locations match well with events recorded by a local network installed in Cameroon in 2007. The four stations were serviced again in November 2018. One station failed due to water infiltration and one was vandalized within a week of the previous service. One station was still operational at service with only a few days down and the last station was operational until the height of the rainy season when power failed.

California’s Central Valley is responsible for $17 billion of annual agricultural output, producing 1/4 of the nation’s food. However, land in the Central Valley is sinking at a rapid rate (as much as 20 cm per year) due to continued groundwater pumping. Land subsidence has a significant impact on infrastructure resilience and groundwater sustainability. It is important to understand subsidence and groundwater depletion in a consistent framework using improved models capable of simulating in-situ well observations and observed subsidence. Currently, groundwater well data is sparse and sampled irregularly, compromising our understanding of groundwater changes. Moreover, groundwater pumping data is a major missing piece of the puzzle. Limited data availability and spatial/temporal uncertainty in the available data have hampered understanding the complex dynamics of groundwater and subsidence. To address this limitation, we first integrated multimodal data including InSAR, groundwater, precipitation, and soil composition by interpolating data with the same spatial and temporal resolutions. We then identified regions with different temporal dynamics of land displacement, groundwater depth, and precipitation. Some areas (e.g., Helm) with coarser grain soil compositions exhibited potentially reversible land transformations (elastic land compaction). Finally, we fed the integrated data into the deep neural network of a gated recurrent unit-based sequence-to-sequence generation model. We found that the combination of InSAR, groundwater depth, and precipitation data had predictive power for soil composition using deep neural networks (correlation coefficient R=0.83, normalized Nash-Sutcliffe model efficiency NNSE=0.84). A random forest model was tested as baseline (R=0.65, NNSE=0.69). We also achieved significant accuracy with only 40% of the training data (NNSE=0.8), suggesting that the model can be generalized to other regions for indirect estimation of soil composition. Our results indicate that soil composition can be estimated using InSAR, groundwater depth and precipitation data. In-situ measurements of soil composition can be expensive and time consuming and may be impractical in some areas. The generalizability of the model sheds light on high spatial resolution soil composition estimation utilizing existing measurements.

Microplastic (MP) contamination of freshwaters and soils has become one of the major challenges within the Anthropocene. MP is transported in large quantities through river systems from land to sea. However, the question is whether there is transport only or also deposition within the system? Floodplains and their soils as part of the river system are known for their sink function for sediments, nutrients, and pollutants. The present case study analyzes the spatial distribution of large (L-MP, 2,000–1,000 μm) and medium (M-MP, 1,000–500 μm) MP particles in floodplain soils of the Lahn River (Germany). Based on a geospatial sampling concept, the MP contents in floodplain soils are investigated down to a depth of 2 meters through a holistic method approach. The analysis of the plastic particles is carried out by density separation, visual fluorescence identification, and additional ATR-FTIR analysis. In addition, grain size analyses and 210Pb/137Cs dating was performed to reconstruct the MP deposition conditions in floodplains. The results prove a spatial frequent accumulation of MP in upper floodplain soils (0–50 cm) deposited by flood dynamics since the 1960s. MP detection over the entire soil column to a depth of 2 meters and below recent (>1960) sediment accumulation indicates MP relocation and in-situ vertical transfer of mobile MP particles through natural processes (e.g., preferential flow, bioturbation). Furthermore, the role of MP as a potential marker of the Anthropocene is assessed based on the findings. This study advances our understanding of the deposition and relocation of MP at the aquatic-terrestrial interface.

Distributed Acoustic Sensing (DAS) was originally intended to measure oscillatory strain at frequencies of 1 Hertz or more on a fiber optic cable. Recently, measurements at much lower frequencies have opened the possibility of using DAS as a dynamic strain sensor in boreholes. A fiber optic cable mechanically coupled to a geologic formation will strain in response to hydraulic stresses in pores and fractures. A DAS interrogator can measure dynamic strain in the borehole which can be related to fluid pressure through the mechanical compliance properties of the formation. Because DAS makes distributed measurements, it is capable of both locating hydraulically active features and quantifying the fluid pressure in the formation. We present field experiments in which a fiber optic cable was mechanically coupled to two crystalline rock boreholes. The formation was stressed hydraulically at another well using alternating injection and pumping. The DAS instrument measured oscillating strain at the location of a fracture zone known to be hydraulically active. Rock displacements of less than one nanometer were measured. Laboratory experiments confirm that displacement is measured correctly. These results suggest that fiber optic cable embedded in geologic formations may be used to map hydraulic connections in three dimensional fracture networks. A great advantage of this approach is that strain, an indirect measure of hydraulic stress, can be measured without beforehand knowledge of flowing fractures that intersect boreholes. The technology has obvious applications in water resources, geothermal energy, CO sequestration, and remediation of groundwater in fractured bedrock.

Bedload movement is fundamentally probabilistic. Our quantitative understanding of gravel transport is particularly limited when flow conditions just exceed thresholds of motion, in part because of difficulties in measuring transport statistics during floods. We used accelerometer-embedded tracer clasts to precisely measure the timing of grain motions and rests during snowmelt floods in Halfmoon Creek, a gravel-bed mountain stream in Colorado, USA. These new data let us explore how probabilities of tracer movement vary with snowmelt discharge. Bedload hysteresis occurred over both daily and seasonal timescales, and included clockwise, counter-clockwise, and figure-eight patterns. We quantitatively explain these observations in terms of how thresholds of motion progressively evolved over 22 days during a seasonal snowmelt flood. Our results suggest that thresholds of motion are functions of both (a) cumulative shear stress and (b) temporal changes in shear stress during floods.

Subglacial models represent moulins as cylinders or cones, but field observations suggest the upper part of moulins in the Greenland Ice Sheet have more complex shapes. These more complex shapes should cause englacial water storage within moulins to vary as a function of depth, a relationship not currently accounted for in models. Here, we use a coupled englacial--subglacial conduit model to explore how moulin shape affects depth-dependent moulin water storage and water pressure dynamics within a subglacial channel. We simulate seven different moulin shapes across a range of moulin sizes. We find that the englacial storage capacity at the water level is the main control over the daily water level oscillation range and that depth-varying changes in englacial water storage control the temporal shape of this oscillation. Further, the cross-sectional area of the moulin within the daily oscillation range, but not above or below this range, controls pressures within the connected subglacial channel. Specifically, large cross-sectional areas can dampen daily to weekly oscillations that occur in the surface meltwater supply. Our findings suggest that further knowledge of the shape of moulins around the equilibrium water level would improve englacial storage parameterization in subglacial hydrological models and aid predictions of hydro-dynamic coupling.

Continued global warming is expected to result in drying of Central America, with projections suggesting a decrease in precipitation. Poor hindcasting of precipitation, however, due in part to spatial and temporal limitations in instrumental data, subjects these projections to considerable uncertainty. Paleoclimate proxy data are therefore critical for understanding regional climate responses during times of global climate reorganization. Here we present two lake-sediment based records of precipitation variability in Guatemala along with a synthesis of Central American hydroclimate records spanning the last millennium (800-2000 CE). The synthesis reveals that regional climate responses have been strikingly heterogeneous, even over relatively short distances. Our analysis further suggests that shifts in the mean position of the Intertropical Convergence Zone, which have been invoked by numerous studies to explain variability in Central American and circum-Caribbean proxy records, cannot alone explain the observed pattern of hydroclimate variability. Instead, interactions between several ocean-atmosphere processes and their disparate influences across variable topography have resulted in complex precipitation responses. These complexities highlight the difficulty of reconstructing past precipitation changes across Central America and point to the need for additional paleo-record development and analysis before the relationships between external forcing and hydroclimate change can be robustly determined. Such efforts should help anchor model-based predictions of future responses to continued global warming.

Few of the large Southern peri-alpine lakes have been studied with a sedimentological approach in their deep basin to understand the dynamics of their long-term sedimentation due, among other factors, to the high complexity of the coring in such deep lakes. In 2018, a 15.5 m-long sediment section was retrieved from the deep basin of Lake Iseo (Italy) at 251 m of water depth. Seismic survey associated to a multi-proxy approach with sedimentological and geochemical analyses, reveals a high number of event layers that corresponds to 61.4 % of the total sedimentation during the last 2000 years. The great heterogeneity of textures, colours, and grain-size distribution between the different types of event layers can be explained by the high number of potential sources of sediment inputs in this large lake system. By combining proxies for sediment source with transport processes, we were able to distinguish: i) flood events, and ii) destabilisations of slopes and deltas due to an increase of the sediment load and/or to seismic shaking. From a thorough comparison with both, the regional climatic fluctuations, and the human activity in the watershed, it appears that periods of high sediment remobilization can be linked to a previous increase in Critical Zone erosion in the watershed mainly under human forcing. Hence, even in large catchments, human activities play a key role on erosion processes and on sediment availability, disrupting the recording of the Critical Zone functioning in such lacustrine archive.

Benthic oxygen fluxes consist of advective and diffusive terms. Both terms in the south-eastern North Sea exhibit a prominent annual cycle but with opposite variation patterns. To understand the driving mechanisms quantitatively, a novel 3-D benthic-pelagic coupled model resolving interactions among macrobenthos, bioturbation, oxygen consumption and carbon early diagenesis was applied to reconstruct the benthic states. Simulation results show a satisfactory agreement with field data and reveal that the benthic oxygen flux is determined by not only pelagic drivers but also by internal dynamics associated with the interaction between organic carbon and macrobenthos, and bedform morphodynamics. Variation of advective flux, characterized by summer-low and winter-high, is mainly driven by hydrodynamics and bedform morphodynamics, while variation of diffusive flux, featured by summer-high and winter-low, is a compound effect of pelagic and benthic drivers with a dominant control by macrobenthos through bioturbation. The role of bioturbation in benthic oxygen consumption is twofold: (i) on the one hand, it alters the particulate organic carbon (POC) distribution in surface sediments, thereby changing the availability of POC to oxygen consumption; (ii) on the other hand, it mixes oxygen down into sediments, thereby facilitating oxygen consumption. Our results indicate that the first role prevails in sandy seafloor characterized by energetic hydrodynamics, while the second role becomes increasingly important along with a weakening of bottom currents. We found that bioturbation-induced oxygen consumption contributes to more than 85% and 52% of the total benthic oxygen fluxes in muddy seabed and at a regional scale, respectively.

Since 1973 micro-erosion meters (MEM) have been used at Kaikōura Peninsula to determine lowering rates on inter-tidal shore platforms. Rates measured over two, two year periods (1973-1975 and 1994-1996) and at decadal scales (20-30 years) demonstrate that platform surface lowering is on average 1.1 mm/yr. The 14 November 2016 Kaikōura magnitude 7.8 (Mw) earthquake caused an instantaneous uplift of 0.8-1.0 m of the peninsula. The uplift offers the rare opportunity to examine how such an event alters processes and rates of erosion on these shore platforms, since these are now partially marine terraces as the inner margins of some platforms are now above high tidal levels (but perhaps not storm surge). Since the earthquake, 42 MEM sites have been measured seven times at 3 monthly intervals. Most recently in September 2018. MEM sites show widely varying responses to the uplift. Erosion rates are at some MEM sites three times the previous annual rate while other sites show significant amounts of rock swelling (3-4 mm in 6 months), or aggradation as weathered rock fragments are no longer removed by wave action. The coseismic uplift has fundamentally changed the process regime operating on these platforms. Zones of maximum wetting and drying have migrated seaward causing previously slow eroding (< 1 mm/yr) MEM sites to accelerate to twice the pre-earthquake rates. Erosion rates demonstrate rapid adjustment of the platform surface to this disturbance and illustrate how uplifted marine terraces can be rapidly eroded despite being above sea level. The preservation of the new marine terrace is probably dependent on further uplift within the next 300-400 years, otherwise erosion by lowering and backwear will likely remove the new surface. This scenario has significant implications for marine terrace preservation and the recording of coseismic events in the landscape.