Ertel’s potential vorticity theorem is essentially a clever combination of two conservation principles. The result is a conserved scalar q that accurately reflects vorticity values that fluid parcels can possess and acts as a tracer for fluid flow. While true at large horizontal scales in the ocean and atmosphere, at increasingly smaller scales and in sharply curved fronts, its accuracy breaks down. This is because Earth’s rotation imparts angular momentum to fluid parcels and the conservation of absolute angular momentum L restricts the range of centripetal accelerations possible in balanced flow; this correspondingly restricts vorticity. To address this discrepancy, we revisit Ertel’s derivation and obtain a new conserved scalar Lq that more properly reflects the vorticity of fluid parcels at these small horizontal scales. Although limited to flows on the f plane, this theorem nevertheless highlights a fundamental principle applicable to all geophysical fluids: at sufficiently small horizontal scales such that L can appropriately be conserved, centripetal accelerations-or curvature-can modify the vorticity of fluid parcels observed on the sphere.

The precipitation of magnesium oxide (MgO) from the Earth’s core has been proposed as a potential energy source to power the geodynamo prior to the inner core solidification. Yet, the stable phase and exact amount of MgO exsolution remain elusive. Here we utilize an iterative learning scheme to develop a unified deep learning interatomic potential for the Mg-Fe-O system valid over a wide pressure-temperature range. This potential enables direct, large-scale simulations of MgO exsolution processes at the Earth’s core-mantle boundary. Our results suggest that Mg exsolves in the form of crystalline Fe-poor ferropericlase as opposed to a liquid MgO component presumed previously. The solubility of Mg in the core is limited, and the present-day core is nearly Mg-free. The resulting exsolution rate is small yet nonnegligible, suggesting that MgO exsolution can provide a potentially important energy source, although it alone may be difficult to drive an early geodynamo.

The Mars Environmental Dynamics Analyzer (MEDA) instrument, on board the NASA’s Mars 2020 Perseverance rover, includes a number of sensors to characterize the Martian atmosphere. One of this sensors is the Radiation and Dust Sensor (RDS) that measures the solar irradiance at different wavelengths and geometries. We analyzed the RDS observations made during twilight for the period between sol 71 and 492 of the mission (Ls 39◦-262◦) to characterize the clouds over the Perseverance rover site. Using the ratio between the irradiance at zenith at 450 and 750 nm, we inferred that the main constituent of the detected high-altitude aerosol layers was ice from Ls= 39◦ to 150◦ (cloudy period), an dust from Ls 150◦-262◦. A total of 161 twilights were analyzed in the cloudy period using a radiative transfer code and we found: i) signatures of clouds/hazes in the signals in the 58 % of the twilights; ii) most of the clouds had altitudes between 40-50 km, suggesting water ice composition, and had particle sizes between 0.6 and 2 μm; iii) the cloud activity at sunrise is slightly higher that at sunset, likely due to the differences in temperature; iv) the time period with more cloud detections and with the greatest cloud opacities is during Ls 120◦-150◦; and v) a notable decrease in the cloud activity around the aphelion, along with lower cloud altitudes and opacities. This decrease in cloud activity indicates lower concentrations of water vapor or cloud condensation nuclei (dust) around this period in the Martian mesosphere.

The variability of streams in the atmosphere and the ocean, as shown in a number of studies, affects the change in the speed of the Earth’s rotation. However, it can cause a reverse reaction—a change in the Coriolis force; as a result of this, atmospheric and oceanic streams can have some variability. In the following work, a hypothesis is presented and considered: it suggests that a change in the volume of Atlantic water inflow into the Barents Sea is related to the change in the Earth’s rotation speed. The paper presents a methodology for determining representative values of the temperature and salinity of seawater that describe the largest possible volume of the sea, as well as a methodology for calculating the content of Atlantic, river and melt water for the period of 100 years. The change of these parameters, and the length of day values, demonstrates the presence of both linear trends and cyclical fluctuations with a period of about 80 years. As a result, it was shown that a decrease in the Earth’s rotation speed with a linear trend somewhat decreases the observed intensity of the processes of global climate change in the Arctic region (an increase in temperature and salinity). Due to the summation of positive anomalies, both a linear trend and a quasi-80-year cycle, the modern period is characterized by abnormally high values of water temperature, the growth of which has not stopped and will possibly reach its maximum between 2025 and 2030.

Pyrrhotites are a class of geologically important nonstoichiometric iron sulfides with the general composition of Fe1-xS (0 ≤ x ≤ 0.125) and are found in a variety of intergrown polytypes, conventionally separated into the antiferromagnetic hexagonal and the ferrimagnetic monoclinic (4C) varieties. Both structures undergo magnetic phase transitions, where antiferromagnetic polytypes display the λ-transition at ~490K and the 4C polytype shows the Besnus transition at ~30K. However, recent studies have shown the relationship between pyrrhotite polytypes and their magnetic behavior to be more complex and new non-monoclinic polytypes (e.g., 3C) have been described that are also capable of retaining a spontaneous magnetization at room temperature. These advances raise the level of detail needed for the characterization of pyrrhotite in rock magnetic and paleomagnetic studies. This study demonstrates the utility of combining X-ray diffraction data collected as a function of temperature with low- and high-temperature magnetic measurements to characterize natural samples. We analyze two natural samples that contain mixtures of 4C, 5C, and 6C polytypes and describe how their polytypes and magnetic properties vary as a function of temperature across the λ-transition and how and when pyrite and greigite form. We also report the effect on natural samples of an annealing protocol commonly used to elevate the concentration of the 4C polytype in synthetic samples and found that annealing instead transformed some antiferromagnetic pyrrhotite into a form whose diffraction pattern most closely resembles the 4C polytype and displays room temperature spontaneous magnetization, but lacks the characteristic Besnus transition.

The lateral erosion of the salt marshes in Galveston Island wetlands was investigated through field UAV surveys. Using a GNSS receiver on the ground and a GNSS receiver attached to the UAV, highly accurate location information for the UAV images was derived through PPK analysis. Based on the collected UAV images with location information, Structure from Motion (SfM) by GNSS-supported aerial triangulation was conducted to generate orthomosaic images of wetlands. Drone surveys have been conducted seven times over a year, and the boundary erosion (represented by boundary retreat) for each period was calculated. The averaged error was less than 2 cm for the horizontal direction in the final orthomosaic images of wetlands. The average wave power, hypothesized to be a significant indicator of potential wetlands erosion, was calculated by investigating the wave climate of the survey area through a simplified numerical model. The relationship between wave power and erosion rate was then summarized. The average amount of erosion from 2019 DEC to 2020 MAR, where winds from north to south were dominant, was higher than from 2020 MAR to 2020 OCT. Much erosion was observed in a protruding part of the wetland. This is caused by waves coming from many different directions surrounding these parts. The erosion of this protrusion had a significant influence on the average erosion rate of the survey areas.

We perform a suite of laboratory friction experiments on saw-cut Westerly Granite surfaces and probe frictional state evolution in response to step changes in normal stress. The experiments are conducted with the objective of illuminating the origin of friction memory effects and the fundamental processes that yield friction rate and state dependence. In contrast to previous works, we measure directly the fault slip rate and account for changes in slip rate caused by normal stress perturbations. Further, we complement mechanical data acquisition by continuously probing the faults with ultrasonic pulses. We conduct the experiments at room temperature and humidity conditions in a servo controlled biaxial testing apparatus in the double direct shear configuration. The normal stress perturbations are carried out during steady shearing over a range of shear velocities, from 0.02 - 100 μm/s. We report observations of a transient shear stress and friction evolution with step increases and decreases in normal stress. Specifically, we show that shear stress evolves in a two-stage fashion – first linear-elastically, then inelastically in response to the normal stress step. We find that the excursions in slip rate resulting from the changes in normal stress must be accounted for in order to accurately predict fault strength evolution. The effects of induced changes in fault slip rate are also apparent in elastic wave properties. Ultrasonic wave amplitudes increase instantly in response to normal stress steps and then gradually decrease to a new steady state value, in part due to changes in fault slip rate. This decrease is strongly related to accelerated creep at the fault interface. We also demonstrate that steady state amplitudes are a reliable proxy for real contact area (RCA) at the fault interface. Previous descriptions of frictional state evolution during normal stress perturbations have not adequately accounted for large slip velocity excursions. Here, we do so by using the measured ultrasonic amplitudes as a proxy for frictional state during transient shear stress evolution. Our work improves understanding of induced seismicity and triggered earthquakes with particular focus on simulating static triggering and stress transfer phenomena using rate-and-state frictional formulations in earthquake rupture models.

In 2013, the Office of Science and Technology Policy (OSTP) issued a memorandum directing Federal agencies with over $100 million in annual research and development expenditures to develop a plan to support increased access to federally funded research results. In response, the US Geological Survey developed a Public Access Plan and published four new data management policies. The policies focus on review and approval of scientific data supporting scholarly conclusions, requirements for metadata, preservation, and data management planning. The new policies, in conjunction with the Public Access Plan, represent a shift in culture in how the USGS manages and provides access to its science data. The USGS recognizes that successful implementation of these new policies requires multiple pillars of support, from USGS leadership and staff buy-in, to effective tools. Active community engagement in the Bureau is stimulated through the Community for Data Integration (CDI), an open forum for community discussion and engagement, and an important component creating buy-in and contributing to the success of the new policies. Also critical are a suite of tools available to scientists to ensure their ability to implement the policies. Finally, support from leadership that manifests in the Fundamental Science Practices Advisory Council (FSPAC), a committee of representatives from across the Bureau who preside over policies and guidance is a critical component. While far from complete, the USGS has shifted its approach to science data management by engaging the community, offering tools to support policy, and providing leadership support for the quality and scientific integrity of USGS science data.

For many years, rainfall has been measured in Brazil on a daily basis only; hence it is unusual to find studies considering a better temporal resolution for the whole country. However, since 2013, the National Centre for Monitoring and Early Warning of Natural Disasters (CEMADEN) has started to monitor rainfall in a sub hourly basis at more than 3,000 gauges. This study is the first to analyze sub-daily characteristics of rainfall in Brazil on national scale. Raw data from 3 years (2015-2017) was downloaded from CEMADEN’s home page and then quality control procedures were applied to select the high-quality rain gauges. Then, two rainfall properties were calculated: (i) Number of Wet Days – NWD, which is the number of rainy days per year; and (ii) Number of Effective Wet Days – NEWD, which is the number of rainy hours per year divided by 24 hours. Both NWD and NEWD were grouped according to NEWD values and spatially analyzed. About 1,100 rain gauges were used in this study: 824 (2015), 1,288 (2016), and 1,385 (2017). NWD ranges from 26 to 226 days (average: 151 days), while NEWD ranges from 1.2 to 47.8 days (average: 14.3 days). Results showed that group A (NEWD < 10.3 days) contains gauges located in the Brazilian Mid-western and northeastern semiarid regions. Group B (10.3 ≤ NEWD < 13.2 days) occurs in parts of the coastal region of Northeast and highlands of Southeast. Groups C (13.2 ≤ NEWD < 17.4 days) and D (NEWD ≥17.45 days) are found in South and part of the Southeastern coastal region. The region with the most concentrated rainfall rates (group A) is the one with the lowest annual rainfall. Orographic effects seem to cause reduction in NEWD, from 15.2 days to 11.8 days (group B). Groups C and D comprehend the rainiest region, preceded by the Amazon region. Finally, we highlight that spatial distribution of NWD and NEWD did not change abruptly annually, with an overall ratio between them of ~10 times. Although in some regions rainfall occurs in four months, it effectively falls from 10 to 13 days. This study is important to understand how concentrated the rainfall is in the different Brazilian regions.

A number of insitu and passive microwave satellite sensors have observed Arctic sea ice and Greenland Ice Sheet (GrIS) mass loss trends over recent decades. Along with sea and land ice declines, above-freezing, near-surface air temperatures are observed earlier in boreal spring and later in autumn thus extending periods of melt beyond the core of summer (JJA). Little is known about whether lengthening periods of open ocean proximate to the ice sheet, for instance, demonstrably effect unseasonal GrIS melt events. Here, a new Baffin Bay sea ice advance dataset is utilized to determine dates of sea ice growth along Greenland’s west coast for the 2011-2015 period. Preceding, multi-scale ocean-atmospheric conditions, including at the Baffin-GrIS interface, are analyzed and linked to unseasonal melt events observed at a series of on-ice automatic weather stations (AWS) along the K-transect in southwest Greenland. The local marine versus synoptic influence on the above and below freezing surface air temperature events is assessed through analyses involving AWS winds, pressure, and humidity observations. These surface observations are further compared against Modele Atmospherique Regional (MAR), Regional Atmospheric Climate Model (RACMO), and ERA-Interim reanalysis fields to understand the airmass origins and (thermo)dynamic drivers of the melt events. Results suggest that the K-transect transition season melt events, primarily in the ablation zone, are strongly affected by ridging atmospheric circulation patterns that transport warm, moist air from lower latitude land-ocean areas toward west Greenland. While local conduction of oceanic surface heat appears to impact coastal air temperatures, consistent with previous studies, marine air incursions from Baffin waters onto the ice sheet are likely obstructed by barrier flows and the pressure gradient-driven katabatic regime off of central Greenland.

In airborne or model data, clouds are often defined using information about Liquid Water Content (LWC). Unfortunately LWC is not enough to retrieve information about the dynamical boundary of the cloud, i.e. volume of turbulent air around the cloud. In this work, we propose an algorithmic approach to this problem based on a method used in time series analysis of variables in dynamic systems, namely Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA). By studying RP’s constructed with turbulence kinetic energy, vertical velocity and temperature fluctuations and quantifying appropriate time series of laminarity (LAM) calculated using the plots, we distinguish between turbulent and non-turbulent segments along a horizontal flight leg.

We consider the transient electrokinetic response of an aquifer-aquitard system to groundwater abstraction from the aquifer. The system was instrumented with 18 non-polarizable copper/copper sulphate electrodes installed at three different depths in the aquitard above the aquifer. The sensing electrodes were installed at depth of 1, 2, and 4 m below ground surface along three overlapping transects. The differential voltages relative to a single permanent electrode were measured with a Campbell Scientific CR1000 datalogger with a single multiplexer. Additionally, six piezometers screened in the top 1.5 m of the confined aquifer, were installed by direct-push. All the piezometers were instrumented with pressure transducers to measure directly the hydraulic response of the aquifer. The vertical variation of resistivity in the aquitard was measured on sediment cores recovered from one of the boreholes used to install the deepest piezometer. The resistivity distribution at antecedent sediment wetness (moisture content) was measured using the MC Miller resistivity boxes and meter, with wetness measured gravimetrically. Previous exploratory drilling and sampling activities at the site indicate that the aquifer is fractured greywacke sandstone overlain with clayey aquitard of semi-consolidated alluvial sediment, with the aquifer-aquitard contact at a depth of 10.3 m below the ground surface. We report the results of the site instrumentation, monitoring, characterization, hydraulic testing, and compare the results of parameter estimation using streaming potential and hydraulic data separately and jointly. We explore the effect of depth of installation of the electrodes in the aquitard on signal strength and quality and compare this to model predicted behavior using semi-analytical models from the literature. The results suggest the need for deep sensing of electrokinetic signals generated by groundwater flow to improve signal-to-noise ratios and the usefulness of self-potential data for hydrogeophysical characterization of aquifer-aquitard systems.

Recent, record-breaking discharge in the Yenisei River, Siberia, is part of a larger trend of increasing river flow in the Arctic driven by Arctic amplification. These changes in magnitude and timing of discharge can lead to increased risk of extreme flood events, with implications for infrastructure, ecosystems, and climate. To better understand the changes taking place, it is useful to have records that help place recent hydrological changes in context. In addition to an existing network of river gauges, extreme flood events can be captured in the wood anatomical features of riparian trees, which help identify the most extreme flood events. Along the Yenisei River, Siberia we collected willow (Salix spp.) samples from a low terrace that occasionally floods when water levels are extremely high. Using these samples, we use an approach known as quantitative wood anatomy to measure variation in radial cell dimensions, including vessel area, wood fiber size and cell wall thickness. We then compare these measurements to observed records of flood stage. We hypothesize that (1) characteristic patterns of wood fiber size and cell wall thickness in Salix rings are present during flood years, (2) these patterns can be quantified by measuring wood fiber size and cell wall thickness, and (3) quantified variations in cell anatomical properties can be related to flood magnitude and duration. Understanding how riparian vegetation responds to extreme flood events can help us better manage riparian ecosystems and understand changes to the Arctic hydrological regime.

Expansion of unplanned agriculture and urbanization increases the danger of extreme flood and sedimentation. The Upper Awash basin has been under tremendous influence of human activities in the last five decades. The historical land use/land cover (LULC) change analysis was made by processing multi-temporal Landsat images and the future LULC was predicted using the Land Change Modeler. The LULC transition between a pair of classified LULC maps and driver variables were combined to predict the future LULC scenario. The five different LULC change and future land management scenarios are LULC 1974, LULC 2014, increase in the urban area, riparian and steep slope afforestation, and predicted future LULC 2045. The LULC change scenarios together with other spatial and climate data were used to simulate the hydrology, and sedimentation at four main subbasins using the calibrated soil and water assessment tool (SWAT) model. The mean monthly change in the water balance components and sedimentation have indicated higher rates of fluctuation due to LULC change. The riparian and steep slope reforestation scenario has reduced the mean annual surface runoff volume by 9.3% and sedimentation yield by 6.1% from the baseline LULC 2014. Moreover, the frequency of estimated 100-year annual extreme daily discharge reveals significant variation among the LULC scenarios. Notably, the future LULC 2045 has indicated a higher increase of extreme daily discharge by 23.5% at Homole subbasin. The study outlined the impact of land management on the flood events and sedimentation in the large basin, and spatial variation of LULC change impact has been presented. It suggests that the increase in deforestation due expansion of cropland and urbanization will intensify floods, whereas, riparian and steep slope reforestation has significantly reduced the peak discharge and sedimentation. Therefore, the future land management plans should consider appropriate vegetative conservation measures in the upland areas.

The orbital history of Triton, coupled to its thermal evolution, and the role played from obliquity tides [1, 2], together with the ongoing geological activity [3] suggest a differentiated interior, with an outer ice shell, a possible sub-surface ocean, and a deep-rocky interior. Triton’s deep interior could be hydrated, as suggested for other icy satellites, such as Titan [4, 5]. Antigorite (density: 2.5-2.6 g/cm3) is the most evocated mineral to explain the low estimated average density of the deep interior of icy moons [5]. Nevertheless, a model of a hydrated deep interior must consider the chemical environment, the lithostatic pressure, and the internal temperature, which define by their own the resulting mineral assemblages. Methods We adopt the algorithm Perple_X [6] to produce a pseudosection (Fig.1), modelling the stability fields of several mineral phases at thermodynamical equilibrium, in the function of pressure (P) and temperature (T). We select as the initial bulk composition of a proto-Triton a chondritic material. Results Figure 1 shows an Orgueil-like bulk composition simulating the rocky deep interior composition in a hydrated scenario. In addition to antigorite, we found that the mineralogy of hydrated deep interior should be characterized by the primary phases: amphibole, chlorite, antigorite, and talc, for the expected temperature and pressure of Triton’s deep interior and at a temperature lower than 980 K. For higher temperature we found that hydrated phases dehydrate in olivine and pyroxenes, as main phases. We plan to investigate the role of volatiles and ices in modelling the mineralogy of the deep interior. Acknowledgments G.M. and C.C., acknowledge support from the Italian Space Agency (2020-13-HH.0). References [1] McKinnon, W. B. (1984). Nature, 311(5984), 355-358. [2] Nimmo, F., & Spencer, J. R. (2015). Icarus, 246, 2-10. [3] Hansen C.J., & Kirk R. (2015), 46th LPSC, 2423. [4] Fortes, A. D., et al. (2007). Icarus, 188(1), 139-153. [5] Castillo-Rogez J.C., Lunine J.I. (2010). Geophys. Res. Lett.37(20). [6] Connolly, J. A. D. (2005). Earth Planet Sci Lett, 236.1-2:524-541.

Marine wildlife ingest plastic pollution, making them a reservoir for plastic debris and an important part of the “where is all the plastic” puzzle. To date, we lack estimates of how much plastic pollution resides within marine animals globally, making it difficult to reconcile the fate of plastic pollution in the global ocean. To help fill this knowledge gap, we collected data on amount of plastic debris found in sea turtles necropsy studies from the scientific literature up until January 1, 2020. We used this data along with predictor variables in a regression model to quantify how much plastic resides within green turtles (Chelonia mydas) globally for a snapshot in time. We found that geographic, socio-economic, and ecological indicators significantly correlate with how much plastic pollution is found in sea turtle gastrointestinal tracts. Our model suggests that leatherback turtles (Dermochelys coriacea) contain the most plastic in their gastrointestinal tracts, and loggerhead turtles (Caretta caretta) contain the least. This presents one of the first attempts to understand which sea turtle species has the highest propensity for plastic ingestion. We also provide the first estimate of a global marine animal reservoir of plastic pollution – we estimate that at any given time, green turtles carry 7.5-8.2 tonnes of plastic globally in their gastrointestinal tracts.

Land scarcity is increasing over time, driven by complex multi-sector dynamics. The impacts of land scarcity on the economy and environment are multi-faceted and regional, so any action to convert land will contain inherent tradeoffs. These impacts are complicated by the deeply uncertain evolution of the various sectors influencing land scarcity. A need therefore exists to provide multi-metric and multi-sector assessments that are robust to myriad uncertainties. Land conservation effectively limits the supply of productive land, while biofuel consumption increases the demand and competition for that land, and how these dynamics individually and jointly propagate to economic and environmental impacts is an important open question. To address this, we adopt the Global Change Analysis Model (GCAM) that has representations of various important sectors including the climate, land-use economy, energy systems, agriculture, and water resources. Scenarios of increased land demand (from biofuels) and decreased land supply (from conservation) under various socioeconomic pathways drawn from the SSPs were simulated using GCAM. We find that while biofuel consumption and land conservation reduce carbon emissions, this comes at the cost of higher food prices, reduced crop production, and increased water withdrawals. Additionally, some regions experience these tradeoffs more severely than others and are more heavily impacted from the same biofuel mandate or by an additional percent of protected land. These and other findings highlight the importance of multi-sector modeling frameworks that capture many cross-sector linkages, and acknowledge the important uncertainties confronting the human-Earth system when making any analysis of the land scarcity impacts.

Malaria poses a great challenge for the maintenance of good public health and sustenance of human wellbeing in many parts of the world. Apparently, the anthropogenic global warming has expanded the spatio-temporal extent of the disease; incidences are now reported beyond tropics and in non-endemic seasons. This emerging trend of climate change has increased the malaria risk factor for millions more across the globe. While global warming remains a key factor to address the future adaptations and mitigation measures, the existing association between climate and malaria prevalence needs careful observations and analyses besides the non-climatic factors. Such a climate association is investigated here with the available malaria case counts in the northeastern districts of South Africa. It is found that the regional variations in seasonal rainfall and temperature, that primarily control mosquito population and thereby infection rates, are linked with a basin-scale climate phenomenon manifested as a dipole pattern in the interannual anomalies of sea surface temperature (SST) of southwestern Indian Ocean. In addition to the year-to-year variations, partly related to the basin warming, a decadal shift in the SST dipole pattern, and associated decrease in seasonal rainfall, leads to decreasing number of case counts in recent years as indicated by the malaria records.