The MAVEN mission has measured an electron temperature spike at altitudes where the Martian atmosphere becomes optically thick and changes occur in the atmospheric chemistry. The temperature spike is consistent from orbit to orbit, but changes in location based on solar zenith angle (SZA) and has only been observed for SZA <80o. This letter presents the conditions under which it is observed and discusses possible sources. The electron temperature spike seems to be co-located with a temperature dip in the neutral atmosphere. The observed temperature spike/dip might be indicative of an inversion layer in the Martian atmosphere. The altitude location of the electron temperature spike is in the lower dynamo region where the electrons start to be unmagnetized. The observations are unlikely to be significant for overall Martian plasma dynamics, but are a clear indication that the large-scale Martian atmosphere is still not completely understood.

The Compact Ion Mass Spectrometer (CIMS) is a highly compact ion mass spectrometer capable of high-mass resolution for low-energy space plasma. CIMS is capable of measuring flux, energy, and mass of ions providing unique measurements of the ionospheric outflow and cold plasma in the magnetosphere. Measurements of the ionospheric outflow and cold-magnetospheric ion population will provide the necessary initial conditions of the ion populations that drive some magnetosphere-ionosphere (MI) coupling processes along with magnetospheric ion composition and dynamics. Simultaneous measurements of the cold and hot magnetospheric ion composition in the reconnection region at the magnetotail would provide clues for the outflowing ions as they journey through the plasmasphere and magnetosphere. These data are critical to advancing our current understanding of MI coupling and are required to answer the long-standing questions regarding ionospheric outflow, the source of magnetospheric mass loading, and the subsequent impact on magnetic reconnection. The CIMS utilizes a laminated collimator to define the field-of-view, a laminated electrostatic analyzer to selectively filter ions based on energy-per-charge, a magnetic sector analyzer to separate ions by mass-per-charge, and a microchannel plate with a position sensitive cross-delay anode assembly to detect the location of the ions on the detector plane. This ion mass spectrometer is a simple, compact, and robust instrument ideal for obtaining low-energy (0.1 eV to 500 eV) ion composition measurements of ionospheric and cold magnetospheric ions. The instrument design has significant mass and volume savings when compared to current state-of-the-art ion mass spectrometers and has the additional advantage of being able to simultaneously measure multiple ion species at given energy-per-charge at 100% duty cycle, thus providing a full energy spectra for individual ion species. The concept and operation are intrinsically simple, and enable ultrafast (<0.1 s) measurement of plasma ion composition to provide an improved understanding of the physical processes that drive the complex ion dynamics in the magnetosphere.

The Mercury’s magnetic fields are known to be weaker than that predicted by conventional dynamo models. In order to explain the Mercury’s weak magnetic field, several models are proposed (Stanley and Glatzmaier, 2010). One of them is the thermoelectric dynamo, which drive the dynamo via the thermoelectric force (Stevenson, 1987). The field strength is proportional to the relative Seebeck coefficient between the core and the mantle. Because the Seebeck coefficient of insulators is more than one order larger than that of metals, the Seebeck coefficient of Mercury’s mantle is the central parameter. Therefore, we investigated the Seebeck coefficient of mantle minerals from the first-principles calculations. The structure relaxation and band structure calculations were conducted by using the Quantum ESPRESSO package. The bandgap energy was calibrated by means of the quasiparticles self-consistent GW (QSGW) approximation adopted in the ecalj package. The Seebeck coefficient was calculated via the Boltzmann equation implemented in the BoltzTraP package. The results indicate that the Seebeck coefficient of forsterite with a small amount of dopant exhibit comparable to that previously thought (|S| ~ 1000 μV/K). This value may constrain the upper limit. The Mercury’s mantle may contain ~3wt% FeO (Robinson and Taylor, 2001). The Fe substitution and O vacancy act as donor, which is predicted to reduce the Seebeck coefficient, significantly. The field strength also depends on the electrical conductivity of the mangle. Recent high pressure experiments suggest that the electrical conductivity of the Earth’s mantle is ~ 10^-2 Sm. Considering the both of the Seebeck coefficient and the electrical conductivity of mantle material, the field strength is calculated to be ~ 0.1 nT, which is significantly weaker than the observed value of 300 nT. Therefore, we conclude that the thermoelectric dynamo cannot generate the Mercury’s magnetic fields.

On this poster we explore how well global HYbrid Coordinate Ocean Model (HYCOM) simulations predict (semidiurnal) internal tides and their decay. We explore two important factors that govern the internal tide predictability: model resolution (8 km vs. 4 km) and wave drag. We validate these simulations with internal-tide sea-surface height amplitudes from altimetry, surface-tide dissipation rates estimated from an altimetry-constrained model, finestructure and microstructure dissipation rates, and modal-conversion rates computed from analytical models. To compare HYCOM to various altimetry data sets, we derive a spatially varying correction factor that accounts for the effect of time series duration on non-stationarity. We perform tidal energy balances and decompose the M2 internal tides into vertical modes.

Estuaries in the northern California current system (NCCS) experience seasonally reversing wind stress, which is expected to impact the origin and properties of shelf water which enters NCCS estuaries (’shelf inflow’). Wind stress has been shown to affect the source of shelf inflow by driving alongshelf currents. However, the effects of wind-driven Ekman dynamics and shelf currents from larger-scale forcing on shelf inflow have yet to be explored. Variations in shelf inflow to the Salish Sea and the Columbia River estuary, two large NCCS estuarine systems, were studied using a realistic hydrodynamic model. The paths and source of shelf water were identified using particles released on the shelf. Particles were released every two weeks of 2017 and tracked for sixty days. Shelf inflow was identified as particles that crossed the estuary mouths. Mean wind stress during each release was compared with initial horizontal and vertical positions and physical properties of shelf inflow particles. For both the Salish Sea and the Columbia River estuary, upwelling-favorable wind stress was correlated with a shelf inflow source north of the estuary mouth. Depth was not correlated with wind stress for either estuary, but relative depth (depth scaled by isobath) increased during upwelling-favorable winds for both. Properties of inflow changed from cold and fresh during upwelling to warm and salty during downwelling, reflecting seasonal changes in NCCS shelf waters. These results may be extended to predict the source and properties of shelf inflow to estuaries in other regions with known wind or shelf current patterns.

The North American Monsoon occurs July-September bringing significant rainfall to Colorado River headwater basins. This rain may buffer streamflow deficiencies caused by reductions in snow accumulation. Using a data-modeling framework, we explore the importance of monsoon rain in streamflow generation over historic conditions in an alpine basin. Annually, monsoon rain contributes 18{plus minus}7% water inputs, generates 10{plus minus}6% streamflow and increases water yield 3{plus minus}2% the following year. The bulk of rain supports evapotranspiration in lower subalpine forests. However, rains have the potential to produce appreciable streamflow at higher elevations where soil storage, forest cover and aridity are low; and rebounds late season streamflow 64{plus minus}13% from simulated reductions in snowpack as a function of monsoon strength. Interannual variability in monsoon efficiency to generate streamflow declines with low snowpack and high aridity, implying the ability of monsoons to replenish streamflow in a warmer future with less snow accumulation will diminish.

Recent developments in ocean-bottom pressure gauge (OBP) networks have enabled us to continuously monitor various waves in the ocean. On 1 July, 2020, an OBP network, S-net, recorded tsunami-like pressure changes, although no earthquake was reported. These waves were well explained by a numerical simulation supposing a northward-moving atmospheric low pressure system with a maximum pressure depression of −0.5 ± 0.1 hPa and an apparent speed of 100–110 m/s. This simulation suggested that these waves were meteotsunamis. The simulation also suggested that the maximum amplitudes of the sea-surface height of ~ 2 cm were up to ~30% larger than those expected from the observed pressure if we do not consider the effect of the atmospheric pressure change. Our study showed that the S-net can detect the generation and propagation of meteotsunamis, which could not be achieved in the past when OBP networks with only a few stations were available.

The effective stress coefficient α determines the effective stress, which dominating the permeability of rocks. However, the documented value of α for rocks shows a high scatter (0.3-5.5), based on the laboratory measurement. The well know Clay Shell Model (CSM) successfully explain why the α of the clayey sandstone can well above 1 theoretically. However, CSM cannot account for the stress dependency of α observed experimentally. In this study, a modification of CSM was proposed. This proposed Discretized Clay Shell Model (DCSM) discretizes multi-layers clay domain to account for the stress dependent elastic modulus of clay and calculates the pore radius of DCSM model under different confining stress σc and pore pressure Pp. Iso-pore radius curves under different σc and Pp was used to determine the α. The parametric study illustrates the superior features of the proposed DCSM to the traditional CSM. Critical findings include: (1) The predicted α form a concaving upward surface in the pore pressure-confining stress space using DCSM. (2) The influence of Pp on α will be stronger than the influence of σc especially under low Pp. (3) The predicted α is not necessary positively or negatively correlated to σc under constant Pp. (4) The predicted α for soft, high stress dependent deformability of clay coating on the pores of sandstones could be far higher than 1. Two synthetic cases (laboratory and in-situ scale) illustrate the importance of stress dependent (σc and Pp) effective stress coefficient α for determining the effective stress and permeability.

Reusing produced water for hydraulic fracturing simultaneously satisfies challenges of fresh water sourcing and the design/operation of an extensive disposal well infrastructure. This presentation provides an overview of a reuse program from concept through implementation including qualification of advanced water recycling technologies. We target the most prolific unconventional reservoir play in the United States – the Permian Basin. Sourcing water for full-field development therein represents a significant problem since it is in short supply in (semi)arid regions of West Texas and Southeastern New Mexico. We report results from a synergistic industry-academia collaboration wherein desalination pretreatment was first evaluated at lab scale to (i) systematically evaluate partial softening (i.e. “floc-and-drop”) versus neutral pH oxidation for iron removal (ii) investigate synergistic effects of FeCl3 and polymer addition to destabilize colloids (including particulate iron) and induce high-rate sedimentation and (iii) develop and implement robust techniques using video and image analysis to characterize process performance and floc properties (e.g. morphology, size, and settling velocity). Jar tests and associated measurements were completed in the range 4 - 44 ºC covering the range of temperatures measured in the Permian. FeCl3 in conjunction with an anionic polymer dramatically improved colloid destabilization and floc growth via enmeshment of primary colloids by amorphous iron precipitates and inter-particle bridging by the adsorbed polymer. Larger, stronger, and denser flocs thus formed settled extremely rapidly without breakage (i.e. high rate sedimentation). Bench-scale results were integrated in the design and testing a 5,000 BPD pilot scale high-rate clarifier. Pilot scale results show that the neutral pH method of clean-brine generation produced 5-10 times less sludge while achieving 15-20% higher throughput over the alternative floc-and-drop method. Both bench- and pilot-scale findings were incorporated in design and operation of a 50,000 BPD full-scale reuse facility in the Permian Basin. This presentation will share lessons learned from operating a large-scale reuse facility and how academic research can inform and be motivated by industrial practices (and vice versa).

We report on a laboratory study of wave-swash interactions, which occur in the very nearshore environment of a beach when the shallow swash flow of a breaking wave interacts with a subsequent wave. Wave-swash interactions have been observed in the field, hypothesized to be important for nearshore transport processes, and categorized into different qualitative types, but quantitative descriptions of their dynamics have remained elusive. Using consecutive solitary waves with different wave heights and separations, we are able to reliably and repeatably generate a wide variety of wave-swash interactions with large flow velocities and vertical accelerations. We find that wave-swash interactions can be quantitatively characterized in terms of two dimensionless parameters: H2/H1 and Tsep/Tswash, where the first is the wave height ratio for consecutive waves and the second is a dimensionless measure of the time separation between consecutive wave crests. We find that wave-swash interactions commonly involve three main stages and that the cross-shore location of these stages is dependent on the interaction type. Using measurements of bed pressure and free-surface displacement, we estimate the total vertical accelerations and focus on the peak upward-directed acceleration. We find that wave-swash interactions can generate vertical accelerations that can easily exceed gravity, despite occurring in very shallow water depths. The vertical velocities during large vertical accelerations are upward-directed and are quickly followed by onshore-directed horizontal velocities. Together, our findings suggest that wave-swash interactions are capable of inducing large material suspension events of sediment or solutes in sediment pores, and transporting them onshore.

Coastal aquifers act as a major host of seawater-groundwater interaction and play an important role in modulating the marine elemental budget. Calcium stable isotopes (δ44/40Ca) have been used to identify mass dependent isotope fractionation processes such as carbonate dissolution and precipitation in a range of geological reservoirs that has major implications in constraining global geochemical cycles. However, there is limited Ca isotope data from coastal aquifers globally. Here we report δ44/40Ca values of groundwater collected in 2017-18 from multiple locations and depths from the Bakkhali delta front, Sundarbans, India. The sampling depth varied between 14 m below ground level (m bgl) and 333 m bgl and the salinity of the groundwater samples range from 1-25 ppt. The salinity of the water samples decreases with increasing depth indicating greater seawater incursion from the Bay of Bengal at shallower depths. Variable amounts of mixing of freshwater and seawater is also supported by Sr and Ca concentrations which vary between 1.6-62.8 μmol/l and 0.29-8.92 mmol/l, respectively, and show progressively lower concentrations with depth. The δ44/40Ca values of dissolved phase in groundwater samples (relative to NIST SRM 915a) were measured using a 43Ca-48Ca Double Spike TIMS technique at Centre for Earth Sciences, Indian Institute Science, Bangalore. The δ44/40Ca values of the groundwater samples show significant variability between 1.52-2.28‰ (2SD ~0.1‰) with several samples showing δ44/40Ca values higher than modern seawater (~1.88‰). Low δ44/40Ca values, mostly in deeper groundwater samples, is consistent with higher proportions of freshwater input. Samples showing high δ44/40Ca values are mostly from shallower depths and likely reflect carbonate precipitation which is consistent with high Sr/Ca (~8.13-12.26) in samples from 30-42 m depth. The high δ44/40Ca in groundwater samples from the Ganges-Brahmaputra delta could explain the high δ44/40Ca values reported in water samples from the Bay of Bengal1. [1] Chakrabarti et al., Goldschmidt Boston, 2018 Abstract.

Carbon dioxide is a greenhouse gas that has a strong absorption in the 4.2– 4.3 micrometers region of the infrared spectrum. Consequently, non-dispersive infrared (NDIR) spectroscopy using interference optical filters tuned in this spectral band can be utilized to provide reliable, high resolution and fast response measurements of atmospheric CO2 concentrations. As part of eddy covariance systems, open-path gas analyzers based on this principle are widely used in remote locations around the world because of their low-power consumption, fast frequency response, and ease of operation. One of the challenges of the open-path design is that the in-situ optical beam is exposed to the rapid fluctuations in ambient temperature. Besides gas composition and pressure being the two major spectroscopic line broadening mechanisms that affect the absorption of infrared light, air temperature also can influence the broadened half-width and the intensity of the spectral lines. Consequently, the fast temperature fluctuations of the air parcels in the optical path of such a sensor can produce changes in the amount of absorbed light and cause errors in the gas concentration measurement that can propagate into the flux calculations. The temperature dependence of the infrared absorption has not been quantified in the context of the CO2 NDIR gas analyzer methodology. The study will evaluate the temperature effects on absorption spectra of CO2-air-mixtures across the 4.2–4.3 micrometers infrared active region, typically used by NDIR gas analyzers. Infrared spectra will be modeled line-by-line from spectral-line parameters obtained from the high-resolution transmission molecular spectroscopic database (HITRAN). HITRAN-predicted molecular cross sections, the product of component spectral line intensity and spectral line shape at different wavelength, will be used to generate absorption spectra of CO2 air mixtures at ambient pressure using different concentrations and temperatures. The temperature dependence of CO2 absorption will be inferred from the integrated area under the absorptivity curve. Results interpreted in the context of the Beer-Lambert law will further characterize the temperature related spectroscopic effects on CO2 concentration calculations.

Topographic features are commonly interpreted to represent interactions between tectonic and climate-driven processes. However, recent work has highlighted how drainage reorganization from river capture may produce landscapes that resemble those generated by changing tectonic conditions and emphasized the importance of developing tools and metrics to identify the source of landscape transience (Yang et al., 2015; Whipple et al., 2017). While few studies have sought to estimate the rates and magnitudes of increased transient incision resulting from river capture (e.g. Prince et al., 2011, Yanites et al., 2013), the ability to quantify river capture-related incision is vital to improve our characterization of landscape responses to transience. This work tests the hypothesis that the observed incision and distribution of knickpoints in the Sutlej river network of the western Himalaya is the result of an ongoing transient response to a large-scale river capture event that occurred in the late Pleistocene. A combination of topographic analyses using digital elevation models, knickpoint propagation modeling, 1-D numerical incision modeling, and landscape evolution modeling are used in conjunction with new and existing field-derived data (e.g. cosmogenic radionuclide-derived erosion rates and (U-Th)/He and fission track thermochronology) to quantify the magnitude and timing of the transient landscape response. Redistribution of drainage area and the subsequent enhancement of incision along the Sutlej may explain the increased amounts of Himalayan detritus delivered to the Indus fan since 5 Ma (Clift and Blusztajn, 2005). Similar large-scale river capture events proposed throughout the Himalaya (e.g. Garzione et al., 2003; Van Der Beek et al., 2018), suggest that capture events may be a regional phenomenon inherent to the Himalayan orogen and imply that river capture may be an important contributor to the distribution of sediment along collisional margins.

Water ice clouds form in the mesospheres of terrestrial planets in the solar system (and most likely elsewhere) by vapor deposition at low pressures and temperatures. Under these conditions a range of crystalline and amorphous phases of ice might form. The phase is important because it influences nucleation kinetics, density, vapor pressure over the solid, growth rates and particle shape. In the past the temperature range over which these different phases exist has been defined on the basis of depositing ice at low temperature and warming it while observing phase changes. However, the direct deposition of ice at a range of temperatures relevant for the terrestrial planets has not been systematically investigated. Here we present X-ray Diffraction (XRD) measurements of water ice deposited at temperature intervals between 88 and 145 K in a vacuum chamber. XRD patterns showed that low density amorphous ice was formed at ≤ 120 K, stacking disordered ice I formed from 121 – 135 K and hexagonal ice I formed at 140 and 145 K. Direct deposition results in the stable hexagonal phase at much lower temperatures than when warming stacking disordered ice. All three phases of water ice observed here are possible in clouds in the mesospheres of Earth and Mars, while on Venus only amorphous ice is likely to form.

Seismic-frequency torsional forced-oscillation measurements of shear modulus dispersion and associated strain-energy dissipation under conditions of simultaneously high temperature and pressure in our laboratory require the specimen to be enclosed within a thin-walled metal sleeve – typically of mild steel. However, the well-known transition between the austenite and ferrite phases on cooling across the interval 900-700ºC complicates its mechanical behaviour. The resulting uncertainty tends to mask the seismologically important onset, within this temperature range, of appreciably anelastic behaviour of polycrystalline olivine. In order to more closely document this important transition in mechanical behaviour, we have conducted an unpublished study in which of a specimen of polycrystalline olivine is jacketed within a copper sleeve which retains its face-centred-cubic (fcc) structure throughout the range of the measurements limited to 1050ºC by the proximity of the melting point. Here we report measurements to higher temperature (1200ºC) in which we employ austenitic (fcc) stainless steel (SS) as an alternative jacket material. Two parallel reference experiments with a SS-jacketed SS specimen and a SS-jacketed sapphire specimen were also conducted to obtain the mechanical properties of the jacket material. Such information concerning the viscoelastic behaviour of SS is used to subtract the torsional stiffness of the SS jacket from the properties of SS-jacketed olivine and thereby isolate the mechanical behaviour of olivine. The resulting dissipation spectrum for the olivine specimen consists of a monotonic background dissipation with a superimposed peak located within the 1-1000 s period range for temperatures between 900 and 1050ºC. The dissipation peak and associated shear modulus dispersion, potentially attributable to elastically accommodated grain boundary sliding, display an Arrhenius dependence upon temperature - moving systematically to shorter periods with increasing temperature. Comparison of the results obtained for sol-gel Fo90 olivine specimens enclosed within the alternative mild-steel, copper, and stainless-steel jackets will provide new insight into the nature of the seismologically important transition between the elastic and anelastic regimes.

Six conceptually different models of steady groundwater flow and conservative transport are applied to the heterogeneous MADE aquifer. Their predictive capability is assessed by comparing the modelled and observed longitudinal mass distributions at different times of the plume in the MADE-1 experiment, as well as at a later time. The models differ in their conceptualization of the heterogeneous aquifer structure, computational complexity, and use of permeability data obtained from various observation methods (DPIL, Grain Size Analysis, Pumping Tests and Flowmeter). Models depend solely on aquifer structural and flow data, without calibration by transport observations. Comparison of model results by various measures, i.e. peak location, bulk mass and leading tail, reveals that the predictions of the solute plume agree reasonably well with observations if the models are underlined by a few parameters of close values: mean velocity, a parameter reflecting log-conductivity variability and a horizontal length scale related to conductivity spatial correlation. From practitioners perspective the robustness of the models is an important and useful property. The model comparison provides insight into relevant features of transport in heterogeneous aquifers. After further validation by additional field experiments or by numerical simulations, the results can be used to provide guidelines for users in selecting conceptual aquifer models, characterization strategies, quantitative models and implementation for particular goals.

Amazon Basin deforestation has been driven by agricultural expansion and other developments. Interactions between deforestation, fire, climate, and drought have led to changes in precipitation patterns and river discharge. Previous work suggests that these changes are amplified by land use. Therefore, it is important to understand the degree of change in precipitation patterns and rainy season characteristics. We used long term daily gauge measurements and remote sensing data to analyze the variability and seasonality of rainfall patterns over the Amazon Basin. We focused on the PERSIANN-CDR and CHIRPS precipitation datasets from 1983 to 2018 to quantify trends in predefined indices. The indices that were analyzed to assess variability of precipitation are NDD (Number of dry days); NXE (number of extreme events) during both wet and dry seasons; ORS (Onset of Rainy Season); and ERS (End of Rainy Season). We analyzed the trends for statistical significance and spatial similarity to identify hot spots of change. To connect pattern to process, we also simulated the land-atmosphere system using WRF to assess coupling strength and causality. We are running the simulation using CFSR 2010, with grid resolution of 16 km with the convection scheme active to capture small scale convective rainfall. Previous evidence has suggested an increasing trend on NDD during the dry season, a shift to a later onset and later cessation of the rainy season window, and an increasing trend in the NXE during both wet and dry seasons. The significance and spatial distribution of changes may vary over the region, but we anticipate that in the area with the largest percent of deforestation we will see the highest amount of changes in precipitation.

Chapter 27 of the 4th U.S. National Climate Assessment, Volume 2, assesses climate impacts, future risks, and adaptation in Hawai‘i and the U.S.-Affiliated Pacific Islands. The author team collaboratively developed the chapter’s Key Messages and narrative. Webinars and an informal survey of stakeholders informed the selection of focal sectors. To be inclusive of the vast region and expertise, the authors convened six half-day workshops on key sectors, including remote participation from experts in the U.S. Affiliated Pacific Islands. In all, the chapter involved more than 60 technical contributors. Authors reviewed major areas of risk and new understanding since the last national assessment, including on issues such as: (1) reliable and safe water supplies, (2) marine and terrestrial ecosystem health, (3) sea level rise and coastal impacts, (4) impacts on community livelihoods and well-being, including Indigenous peoples. Under these climate-related challenges to island sustainability, diverse groups are coming together to combine forward-looking policies with adaptation strategies. An integrated theme throughout the chapter is that early intervention can lower the economic, environmental, and social and cultural costs from a changing climate.