Sunlight plays an important role in regulating the nutrient cycle in streams. Throughout the years, more streams are buried to accommodate for residential or commercial facilities. This results in severe impacts on the health of streams due to altered exposure to sunlight, air, and soil; it subsequently affects the growth of aquatic and riparian vegetation, thus impairing the water quality of streams. Although urbanization effects on urban surface streams are well understood, the adverse effects of burying streams on dissolved oxygen (DO), reaeration, photosynthesis and respiration processes have been mainly remained theoretical. This study evaluated the effect of stream piping on DO for two sections of Stroubles Creek in Blacksburg, VA through comparing the water quality prior to entering, and post exiting the buried sections of the Creek. Monitoring DO was conducted through manual readings and continuous measurement for a number of days in Fall 2015 and 2016. The results indicated that the water DO level decreased by approximately 11% as water flowed through the buried sections. The covered section of the stream also caused variability of the water temperature, resulting a possible disturbance to the downstream ecosystem. The buried channels-induced DO variations effects on the Brook Trout (Salvelinus sp.), a sensitive species present at the Stroubles Creek headwaters was also assessed. Further, the photosynthesis rate, reaeration coefficient, and daily respiration rate were computed prior and after one of buried channels through a series of mathematical and empirical approaches to assess the buried channels effect on the aforementioned parameters. The photosynthesis and respiration rates were reduced at the inlet compared to outlet, primarily due to less solar radiation and aquatic vegetation oxygen uptake, however, reaeration rate was increased at the outlet compared to inlet. This study can assist the decision makers and resource planners in taking the appropriate decisions regarding daylighting stream channels to improve water quality or/and accommodate increasing demand for urbanization.

The devastating impacts of the widespread flooding and landsliding in Puerto Rico following the September 2017 landfall of Hurricane Maria highlight the enhanced hazard potential from increasingly extreme storms in mountainous humid-tropical climate zones. Long-standing conceptual models for hydrologically driven hazards in Puerto Rico posit that hillslope soils remain wet throughout the year and antecedent soil wetness imposes a negligible effect on hazard potential. Our post-Maria in situ hillslope hydrologic observations indicate that while some slopes remain wet throughout the year, others exhibit appreciable seasonal and intra-storm subsurface drainage. Therefore, we used receiver-operating characteristic analysis and the Threat Score (TS) skill statistic to evaluate the performance of hydro-meteorological (soil wetness and rainfall) versus intensity-duration (rainfall only) hillslope hydrologic response thresholds that identify the onset of positive pore-water pressure, a predisposing factor for widespread slope instability in this region. We found that the hydro-meteorological thresholds outperformed intensity-duration thresholds for a seasonally wet, coarse-grained soil (TS = 0.8 vs. 0.6, respectively), although they did not outperform intensity-duration thresholds for a perennially wet, fine-grained soil (TS = 0.2 vs. 0.2, respectively). These soils types may also produce radically different stormflow responses, with subsurface flow being more common for the coarse-grained soils underlain by intrusive rocks versus infiltration excess and/or saturation excess for the fine-grained soils underlain by volcaniclastic rocks. We conclude that variability in soil-hydraulic properties, as opposed to the humid-tropical climate zone, is the dominant factor that controls runoff generation and modulates the importance of antecedent soil wetness for our hillslope hydrologic response thresholds. Our findings encourage further deployment of continuous in situ hydrologic monitoring to facilitate the development of empirical hillslope hydrologic response and landslide thresholds for regional-scale hazard warning systems that must account for spatially variable soil types.

Impact cratering is an important geological process that affects all planetary bodies in our solar system. As rock breakdown plays a vital role in the evolution of landforms and sediments on a planetary scale, it is crucial to assess the role of inheritance in the subsequent breakdown of impactites (impact rocks). The shock pressure of several gigapascals generated during the impact can exceed the effective strength of target lithology by three to four orders of magnitude and is responsible for melting, vaporisation, shock metamorphism, pore collapse, vesiculation fracturing and fragmentation of rocks. Environmental conditions and heterogeneities in rock properties exert an important control in rock breakdown. Similar to other subaerial rocks, impactites are affected by a range of rock breakdown processes. In order to better understand the role of low-shock inheritance on rock breakdown, a rock breakdown experiment was conducted in a simulated environmental cabinet under conditions similar to terrestrial semi-arid conditions. We cycled temperature (-2 to 35°C) and relative humidity (13-45%) through 39 accelerated diurnal cycles (each of 8 hours duration). We used 41 impactite samples in the experiment that included low shocked sedimentary and crystalline rocks, impact melt rocks and impact breccias. Mechanical (Equotip and weighing), photographic (photographic monitoring), microscopic and solid-state methods (petrographic microscopy, powder X-ray diffraction, scanning electron microscopy, X-ray computed tomography) were used to characterise the rock samples relative to unshocked rocks, and to assess the shock related changes before and after the experiments. The low shocked sedimentary rocks showed a decrease in porosity by 38% (Coconino Sandstone) and 88% (Moenkopi Sandstone) compared to unshocked counterparts. Macrofractures of 0.1-0.2 mm and microfractures 0.1-5 µm in aperture were observed in all types of impactites. The results showed that impactites exhibited an accelerated decline in strength compared to non-impacted control samples. However, rock type and impact deformation history were key parameters controlling the rate of deterioration.

The 25-27 August geomagnetic storm was the third largest storm in 24th solar cycle, which was a surprising space event that generated in the background of very low solar activity. This study presents an overview of temporal-spatial behaviors of ionospheric plasma irregularities as functions of geographic longitude, latitude and altitude by ground-based (GNSS receivers and ionosonde) instruments and space-borne (Swarm-A and Swarm-B) satellites. The results not only reveal the enhanced equatorial ionization anomaly (EIA) and hemispheric asymmetry over the Asian-Australian and American sectors in a particular time, but also discover the development of hemispheric asymmetric features of global ROTI in the main and recovery phases. In addition, this storm also triggered positive plasma irregularities in altitudes of 100 to 150km near Auroral zone, and the changed ratio of bottom-side plasma irregularities exceeded 250%, which has been cross validated by multiple instrument and TIE-GCM’s simulation. Furthermore, the thermospheric density ratio O/N2, equatorial electrojet and vertical E×B drifts suffered from the storm largely, the equatorial and mid-latitude plasma irregularities may be a combined action of thermospheric composition change, equatorial electrojet and vertical E×B drifts. Finally, the storm also induced positive Joule heating irregularities in Auroral ionosphere in altitudes of 100 to 400km with a maximum changed ratio of >200%, as well as the cross Polar voltage enhanced to ~90kv. The Polar ionospheric irregularities may be associated with the additional energy input through the ways of particle precipitation, Joule heating and ionospheric currents intensification.

Sulfate (SO42-) reduction is a major SO42- output flux from Earth’s oceans, but an imbalance between recent estimates of this flux and corresponding input fluxes suggests inaccuracy in our understanding. Here, we combine global geographic trends in aqueous and dissolved-phase sedimentary data to resolve this inaccuracy. [SO42-] profiles from 700+ sites partition into geographically-distinct k-means clusters based on net sulfate reduction rate (nSRR). Pairing nSRRs with literature-derived pyrite accumulation rates confirms that shelf and slope pyrite burial dominate burial globally. Our results also suggest that sampling and measurement biases have led to erroneously high prior global output estimates and can account for the flux imbalance. Disparate mean d34S values for shelf versus deeper ocean pyrite indicate that sea level change may be an overlooked mechanism for forcing past changes in seawater d34S.

Landcover information is of relevance for a range of applications in Arctic environments including up-scaling of in situ measurements, permafrost monitoring and modelling and climate change impact assessment. But not only natural landcover types, also the identification of human impacted areas is required. A wide range of satellite records are available, but often there are coverage and resolution limitations. Due to the spatial heterogeneity typical for the Arctic, an as high as possible spatial resolution is needed. Sentinel-1 as well as Sentinel-2 offer 10m nominal resolution for specific bands and modes and are freely available across the entire Arctic. The multi-spectral information from Sentinel-2 is specifically of value for discrimination of tundra types. The Synthetic Aperture Radar mission Sentinel-1 provides added value through representation of land surface structure features. A combination of both allows significantly improved characterization of landcover over larger areas. Here, we review recent progress in monitoring the land surface close to Arctic coasts (focus region of HORIZON2020 Nunataryuk), specifically the distribution of human impacted areas beyond of what is represented in databases such as OpenStreetMap or global settlement maps. The added value of machine learning techniques will be discussed and results based on Sentinel-1 und Sentinel-2 presented. Further on, permafrost change information provided through the ESA CCI+ Permafrost project is combined with the novel maps. The CCI+ Permafrost datasets cover 1997-2018 for ground temperature, active layer thickness and permafrost fraction with 1 km gridding (partially derived from MODIS LST, https://climate.esa.int/en/projects/permafrost/data/) and therefore allow detailed assessment of areas with human presence over permafrost.

Papers published in Science of Climate Change by Harde and Salby (2021), and by Berry (2021) contend that the well documented growth of atmospheric CO2 in recent decades is predominantly a natural phenomenon rather than human caused. Both papers are wrong on two counts. First, they focus only on their own (suspect) calculations of anthropogenic atmospheric carbon levels, rather than on measured total carbon levels. The present concentration of anthropogenic carbon in the atmosphere, even correctly calculated, does not establish the human contribution to the rise in total atmospheric carbon. Second, the models these authors develop for determining present anthropogenic atmospheric carbon levels are incompatible with 14C data. The sources of background “anomalous 14C” postulated by Harde and Salby fall well short of being large enough to salvage their model. A highly questionable assumption built into Harde and Salby’s model is explicitly identified.

This is the second half of a two-part study. In the first part, we had used the World Wide Lightning Location Network’s recorded signal amplitudes to test a model of Very Low Frequency signal transmission from the lightning to each sensor. The model predicts a dramatic worsening of transmission at low magnetic latitudes, for nighttime propagation (compared to daytime propagation) toward magnetic West. However, we found that the use of amplitudes was ill-adapted for testing the model under conditions of a deep outage of transmission. Since the relative weakening of nighttime transmission is rather counter-intuitive, we have now developed an alternative approach to testing that model prediction. This alternative approach highlights the patterns of detection/non-detection of several low-magnetic-latitude WWLLN stations and compares those patterns with the appropriate patterns of the model transmission.

Astrobiology as a field is not well known by the public, and is a difficult topic to introduce to the those who have never heard of it before. This presentation will showcase projects and experiences from a museum setting to explore how to best bring up such a complex field of science, and how astrobiologists can make their work as digestible as possible to the general public.

The Indian Ocean (IO) is witnessing acidification as a direct consequence of the continuous rising of atmospheric CO2 concentration and indirectly due to the rapid ocean warming, which disrupts the pH of the surface waters. This study investigates the pH seasonality and trends over various bio-provinces of the IO and regionally assesses the contribution of each of its controlling factors. Simulations from a global and a regional ocean model coupled with biogeochemical modules were validated with pH measurements over the basin, and used to discern the regional response of pH seasonality (1990-2010) and trend (1961-2010) in response to changes in Sea Surface Temperature (SST), Dissolved Inorganic Carbon (DIC), Total Alkalinity (ALK) and Salinity (S). DIC and SST are significant contributors to the seasonal variability of pH in almost all bio-provinces. Total acidification in the IO basin was 0.0675 units from 1961 to 2010, with 69.3% contribution from DIC followed by 13.8% contribution from SST. For most of the bio-provinces, DIC remains a dominant contributor to changing trends in pH except for the Northern Bay of Bengal and Around India (NBoB-AI) region, wherein the pH trend is dominated by ALK (55.6%) and SST (16.8%). Interdependence of SST and S over ALK is significant in modifying the carbonate chemistry and biogeochemical dynamics of NBoB-AI and a part of tropical, subtropical IO bio-provinces. A strong correlation between SST and pH trends infers an increasing risk of acidification in the bio-provinces with rising SST and points out the need for sustained monitoring of IO pH in such hotspots.

Predicting stress changes in the subsurface leading to failure or seismicity remains challenging. Developing a robust monitoring method can help the prediction and thus mitigation of natural hazards. Ultrasonic transmission experiments were performed on Red Pfaelzer sandstones to investigate the forecasting potential to failure at different confining pressures. The forecasting potential for failure of the energy of the direct and coda wave, the transmissivity, Q-factor, coda wave decorrelation coefficient, and velocity change by coda wave interferometry are investigated and compared. Our results show the failure of the tested samples can be forecasted from 40 to 70% of the failure point. Small differences are visible in the precursors between the tested confining pressures, but as the trends are very similar, a robust prediction of failure can be made by combining the various analyses techniques. In this paper, we propose a traffic light forecasting system using active acoustic monitoring which is applicable for forecasting failure at various depths and or stress conditions, for a better prediction of small stress-induced changes in the subsurface and thus mitigation of failure (and seismicity) in the subsurface.

A typhoon (hurricane) is a very strong local disturbance that can affect ocean water as deep as 1000 m. According to observations and numerical simulations, the decrease in ocean temperature is believed to be caused by inertial pumping, entrainment, upwelling, and a pressure-gradient force; however, these assumptions are mostly based on modeling and do not have a clear dynamic mechanism. Therefore, in this study, the dynamic mechanism of ocean water in a highly-idealized ocean and wind field was calculated. Within the maximum wind range, upwelling in the ocean surface is caused as per the classical Ekman layer theory. Then, a pressure-gradient force drives a cyclo-geostrophic current. Because it provides centripetal force, the pressure-gradient force decreases with increasing depth. These different currents generate friction that is similar to bottom Ekman pumping, leading to upwelling. In the actual ocean, the pressure-gradient force is not only balanced by centripetal force but also baroclinic force. When these forces are balanced, the pressure-gradient force disappears, and the dynamic motion of the ocean water stops. Thus, upwelling no longer occurs. The depth at which this balance occurs is considered to be the maximum depth that a typhoon can impact. Therefore, the pressure-gradient force, caused by typhoons and then offset by centripetal and baroclinic forces, is the original dynamic of upwelling in deep ocean water.

Aseismic slip may occur during a long preparatory phase preceding earthquakes, and what controls it remains poorly understood. In this study, we explored the potential dependencies of the slow slip during the preparatory stage prior to stick-slip instabilities on two main factors, namely the loading rate and surface roughness. To that end, we conducted shear stress-driven friction experiments by imposing varying loading rates on sawcut granite samples with different surface roughness at confining pressure of 35 MPa. We measured the average slip along the fault using far-field displacements and strain changes, while using acoustic emission sensors and local strain gages to capture local slip variations. We found that the average aseismic slip during preparatory stage increases with roughness, whereas its duration decreases with increased loading rate. These results also evidence a complex slip pattern on rough faults which leads to dynamic ruptures at high loading rates.

The Krafla area in north Iceland hosts a high-temperature geothermal system within a volcanic caldera. Temperature measurements from boreholes drilled for power generation reveal enigmatic contrasts throughout the drilled area. While wells in the western part of the production field indicate a 0.5-1 km thick near-isothermal (~210 °C) liquid-dominated reservoir underlain by a deeper boiling reservoir, wells in the east indicate boiling conditions extending from the surface to the maximum depth of drilled wells (~2 km). Understanding these systematic temperature contrasts in terms of the subsurface permeability structure and overall dynamics of fluid flow has remained challenging. Here, we present a new numerical model of the natural, pre-exploitation state of the Krafla system, incorporating a new geologic/conceptual model and a version of TOUGH2 extending to supercritical conditions. The model shows how the characteristic temperature distribution results from structural partitioning of the system by a rift-parallel eruptive fissure and an aquitard at the transition between deeper basement intrusions and high-permeability extrusive volcanic rocks. As model calibration is performed using a Bayesian framework, the posterior results reveal significant uncertainty in the inferred permeability values for the different rock types, often exceeding two orders of magnitude. While the model shows how zones of single-phase vapor develop above the deep intrusive heat source, more data from deep wells is needed to better constrain the extent and temperature of the deep vapor zones. However, the model suggests the presence of a significant untapped resource at Krafla.

We present a labeled machine learning (ML) training dataset derived from Sentinel 1 C-band synthetic aperture radar (SAR) data for flood events. In this paper, we detail the steps to collect, pre-process, label, curate, and catalog the training dataset. Development of benchmark ML models and usage of the training datasets for a data science competition are also presented.

The importance of regional air pollutant transport modulated by large-scale synoptic circulation has been poorly understood for air pollution. In the present study of 5-year (2015-2019) observation, we targeted the Twain-Hu Basin (THB), a region of heavy PM2.5 pollution over central China to investigate the regulation of synoptic circulation governing regional PM2.5 transport for heavy air pollution. It was found that regional transport of PM2.5 predominated 65.2% of the heavy pollution events (HPEs) over the THB based on the statistics of observational environment and meteorology. By employing the FLEXPART-WRF model, the regional transport of PM2.5 from upwind source areas in central and eastern China (CEC) to receptor region in the THB was identified with three prominent pathways in the northerly, northeasterly, and easterly directions respectively. Based on T-mode principal component analysis in conjunction with the K-means cluster method, it was recognized that three regional PM2.5 transport pathways for the HPEs over central China were determined respectively by three patterns of synoptic circulation over CEC with 1) weak high air pressure to the north, 2) strong high air pressure to the northeast, and 3) weak high air pressure to the east, governing the cold air invasions southwards to the THB region in central China with the large contributions of 76.0%, 56.7%, and 53.9% to the THB- PM2.5 concentrations in the HPEs, revealing a significant modulation of large-scale synoptic circulation for regional transport of air pollutants in environmental change.

To confirm whether the uplift in Jigokudani valley between 2007 and 2010 detected by Interferometric Synthetic Aperture Radar has continued to the present, we conducted leveling survey since 2015. Most bench marks showed subsidence up to 5.6 cm from October 2016 to September 2020, while a bench mark locates at the center of the leveling route uniquely showed uplift. A crack with a length of 350 m, a width of 100 m, a dip of 61° and striking parallel to the old explosion craters is identified at a depth of 50 m near the center of Jigokudani valley. The estimated crack is located at a similar position of the gas chamber identified from the audio-frequency magnetotelluric survey. Opening of the crack turned to closing between 2017 and 2020 probably because of the increase in emission of volcanic fluid or gas with a formation of a new crater.

Laboratory experiments were performed to study the impact of the relative particle protrusion P/D (P is the protrusion height and D is the diameter of the target particle) on the mechanism of entrainment of sediment particles from a spherical rough bed. The target particle to be entrained was instrumented with electronic sensors, which can measure the tri-axis linear acceleration, and consequently the inertial hydrodynamic forces, during the entrainment process. The velocity field was obtained using the two-dimensional Particle Image Velocimetry (PTV) technique and the velocity data were synchronised with the force data relative to the entrainment time. Experimental results show that the magnitudes of inertial drag force and lift force have a decreasing trend as particle protrusion increases. The ratio of inertial lift force to drag force reveal that drag force slightly dominates the entrainment process at P/D > 0.7 while lift force slightly dominates at P/D < 0.62. Also, the inertial drag and lift coefficients were computed by the force data and velocity data. The inertial drag coefficient was found to be independent of P/D when P/D < 0.62 but declined with increasing P/D for P/D > 0.62. Similarly, the variation of inertial lift coefficient with P/D reversed at P/D = 0.7. This variation of force coefficients with P/D is consistent with the independence of inertial forces with respect to P/D when P/D > 0.62-0.7. In summary, the inertial forces demonstrate that the impact of protrusion on the particle entrainment becomes less important when P/D > 0.62-0.7.