To understand the overall features of the history of magmatic activities and surface environment on Mars, I used a numerical model of magmatism in the convecting mantle that is nominally anhydrous and internally heated. Magmatism occurs as an upward permeable flow of basaltic magma generated by decompression melting through matrix. The modeled mantle evolves in four stages. In Stage I, high initial temperature in the uppermost mantle causes an extensive magmatism intensified by two types of positive feedback that operate between magmatism and mantle upwelling flow, the MMUb and MMUc feedback: the buoyancy and volume change of matrix, respectively, caused by migrating magma that a mantle upwelling flow generates intensify the flow itself to generate more magma. The stratification suppresses mantle convection and magmatism for the next tens to hundreds of millions of years, allowing heat to build up in the mantle by internal heating (Stage II). Eventually, magma is generated at depth, and the MMUb feedback operates to cause an episodic plume magmatism that releases water from the interior of Mars (Stage III). The plume magmatism also stirs the mantle to make it more homogeneous and extracts heat producing elements from the deep mantle to let the magmatism itself wane and cease. In the final stage IV, mantle convection becomes more like a thermal convection. The episodic magmatism and water outgassing in Stage III account for the magmatism and clement surface environment observed for early Mars.

A recognized deficiency of ocean models with a constant-depth vertical coordinate is for truncation errors in the advection scheme to result in spurious numerical mixing of tracers, which can be substantial larger than that prescribed by the model’s mixing scheme. The z~ vertical coordinate allows vertical levels to displace in a lagrangian fashion on time scales shorter than a few days, but reverts to fixed levels on longer timescales, and is intended to reduce numerical mixing from transient vertical motions such as internal waves and tides. An assessment of z~ in a ¼° global implementation of the NEMO model is presented. It is shown that, in the presence of near-inertial gravity waves in the North Atlantic, z~ significantly reduces eulerian vertical velocities with respect to those in a control simulation with the default z* vertical coordinate; that the vertical coordinate approaches an isopycnal, or adiabatic, surface on short timescales; and that both tendences are enhanced when the z~ timescale parameters are lengthened with respect to the default settings. Evaluation of an effective diapycnal diffusivity, based on density transformation rates, shows that numerical mixing is consistently reduced as the z~ timescales are lengthened. The realism of the model simulation with different timescale parameters is assessed in the global domain, and it is shown that drifts in temperature and salinity, and the spindown in z*of the Antarctic Circumpolar Current, are reduced with z~, without incurring significant penalties in other metrics such as the strength of the overturning circulation or sea ice cover.

Coronal Holes (CH) are large-scale, low-density regions in the solar atmosphere which may expel high-speed solar wind streams that incite hazardous, geomagnetic storms. Segmentation of CH boundaries may aid in validating predictive coronal and solar wind models but has proved difficult due to similar appearances as filaments and the tendency for dense coronal plasmas to block underlying CHs in Extreme Ultraviolet (EUV) imagery. We propose an automated detection algorithm of CHs which revisits ground-observed, chromospheric He I 10830 Å line imagery and underlying photospheric magnetograms as drivers to circumvent these issues and provide a complementary method to the space-observed, coronal EUV emission-driven methods that have been widely adopted in the community. Classical computer vision techniques are applied to imbue the routine with design variables based in radiative and magnetic properties of CHs, as well as produce an ensemble of boundaries with quantified intra-algorithm uncertainty. This method is science-enabling towards future studies of coronal hole formation and variability from a mid-atmospheric perspective.

A document by Alexander Lipatov. Click on the document to view its contents.

Gibbs free energy, the fundamental thermodynamic potential used to calculate equilibrium mineral assemblages in geological systems, does not apply to non-hydrostatically stressed solids. Consequently, there is debate over the significance of non-hydrostatic stress in petrological and geophysical processes. To help resolve this debate, we consider the effects of non-hydrostatic stress on the polymorph pairs kyanite/sillimanite, graphite/diamond, calcite/aragonite, and quartz/coesite. While these polymorphs are most relevant to metamorphic processes, the concepts developed are applicable to any single-component solid reaction. We quantitatively show how stress variations normal to an interface alter equilibrium temperatures of polymorph pairs by approximately two orders of magnitude more than stress variations parallel to an interface. Thus, normal stress controls polymorph stability to first order. High-pressure polymorphs are expected to preferentially nucleate normal to and grow parallel to the maximum stress and low-pressure polymorphs, the minimum stress. Nonetheless, stress variations parallel to an interface allow for the surprising possibility that a high-pressure polymorph can become more stable relative to a low-pressure polymorph as stress decreases. The effects of non-hydrostatic stress on mineral equilibrium are unlikely to be observed in systems with interconnected, fluid-filled porosity, as fluid-mediated reactions yield mineral assemblages at approximately constant pressures. In dry systems, however, reactions can occur directly between elastic solids, facilitating the direct application of non-hydrostatic thermodynamics. Non-hydrostatic stress is likely to be important to the evolution of metamorphic systems, as preferential orientations of polymorphic reactions can generate seismicity and may influence fundamental rock properties such as porosity and seismic anisotropy.

Reflection profiles generated using PKPdf as a virtual source show laterally continuous reflections from structures at depths less than 1 km to roughly 200 km beneath the southern Appalachian orogen and Atlantic Coastal Plain. Arrivals interpreted as reflections from the Moho increase in time from ~10 s beneath the Coastal Plain to 17.4 s (~57 km) beneath the Blue Ridge Mountains, providing additional evidence that the southern Appalachians are in rough isostatic equilibrium. Reflections at 32-36 s (120-135 km) are consistent with the depth to the base of the lithosphere found in recent inversions of Ps arrivals and surface waves. Alternatively, these and later reflections at times up to 58 s (~224 km) may be due to layering associated with drag-induced flow in the asthenosphere, suggesting largely horizontal rather than vertical flow for depths less than 225 km beneath the Georgia coastal plain.

Subglacial drainage models represent water flow at the ice--bed interface through coupled distributed and channelized systems to determine water pressure, discharge and drainage system geometry. While they are used to understand processes such as the relationship between surface melt and ice flow, the combination of the number of uncertain model parameters and their computational cost makes it difficult to adequately explore the high-dimensional parameter space and construct robust model predictions. Here, we develop Gaussian Process (GP) emulators that make fast predictions accompanied by uncertainty of subglacial drainage model outputs. Using a truncated principal component basis representation, we construct a GP emulator for daily representation of subglacial water pressure. We also explore emulation of scalar variables describing drainage efficiency and configuration. We train the emulators using ensembles of up to 512 simulations varying eight parameters of the Glacier Drainage System (GlaDS) model on a synthetic domain intended to represent an ice-sheet margin. The emulators make predictions ~1000 times faster than GlaDS simulations, with error <3% for the water pressure field and ~5--9% for drainage efficiency and configuration. We apply the emulators to explore the eight-dimensional input space by computing variance-based parameter-sensitivity indices, finding that three parameters (ice-flow coefficient, bed bump aspect ratio and the subglacial cavity system conductivity) explain 90% of the water pressure variance. The GP emulator approach described here is well-suited to integrate observational data with models to make calibrated, credible predictions of subglacial drainage.

Accurate quantification of the ocean carbon sink and its associated uncertainty is critical for guiding international policy efforts and the accurate monitoring, reporting, and verification (MRV) of marine carbon dioxide removal (mCDR) interventions. Here we use error propagation to break down the uncertainty in air-sea CO$_2$ flux into three primary sources: the gas transfer velocity ($k_w$), the solubility (K$_0$), and the difference in partial pressure of CO$_2$ ($\Delta pCO_2$) between the ocean and atmosphere. These are further decomposed into uncertainties from the underlying variables (e.g., temperature and salinity used to calculate K$_0$). We find regional variability in uncertainty, with $\Delta pCO_2$ being the dominant source in subtropical and eastern boundary upwelling systems; gas transfer being the dominant term in the west equatorial Pacific; and solubility dominating uncertainty near the mouths of large rivers. This methodology provides a foundation for a comprehensive quantification of uncertainty and its underlying drivers. The software used in this study is publicly available on GitHub (\url{https://github.com/lgloege/fluxerror}).

Spectra of small-scale sprite structures, downward and upward propagating streamers, glow, and beads, were recorded with a slit-less spectrograph at 10,000 frames per second (fps) from aircraft missions in 2009 and 2013. The spectra are dominated by emissions from molecular nitrogen, the 1 positive band in the red, and in the blue the 2 positive band plus the 1 negative band of molecular nitrogen ions. The excitation threshold for the blue emissions is higher than for the red emissions so the blue/red ratio can, in principle, be used as a proxy for the electron energy leading to the emissions. We extracted for analysis time series of spectra from 11 sprites: 18 time series from downwards propagating streamers, 6 from upward propagating streamers, 14 from glow and 12 from beads. The total number of spectra in the 50 time series is 953. Blue emissions are almost exclusively associated with streamers indicating the more energetic nature of streamers compared with glow and beads. Both downward and upward propagating streamers start and end with low blue emissions indicating time variations in the associated processes. Because the red and blue nitrogen emissions are significantly affected by quenching, which is altitude dependent, and we do not have sufficiently accurate altitudes, the observed spectral blue/red ratios cannot be directly applied to sprite models.

This article explores the impact that SSP 1-2.6 and 5-8.5 have on near surface temperature across Canada. This is achieved through the use of model ensembles, made up of CMIP5 data, to establish both the historic record of near surface temperature across Canada, as well as how this is predicted to change in the future given the two SSP emission scenarios. The conclusions drawn from this modelling and analysis is valuable in the context of sustainable development and both climate mitigation and climate adaptation discussions. Specifically, an understanding of the spatial extent of warming trends, across Canada, will allow for a more specific and tailored approach to be taken towards adaptation and can ensure appropriate measures are taken in good time.

We present the first 3-D images of P-wave radial anisotropy (RAN) and azimuthal anisotropy (AAN) down to 750-km depth beneath Greenland and surrounding regions. The results are obtained by applying a regional tomographic method to simultaneously invert P wave arrival times of 1,309 local events and P wave relative traveltime residuals of 7,202 teleseismic events, which were recorded mainly by the latest GLISN network. A high-velocity body located beneath northeast Greenland (NEG) to its offshore exhibits a strong negative RAN and a strong AAN with N-S to NE-SW oriented fast-velocity directions (FVDs). The FVDs are generally consistent with the direction of the fold axis of the Caledonian fold belt, which is considered as an outcrop of the NEG body on land. Beneath the Iceland, Jan Mayen, and Svalbard hotspots, a strong positive RAN and a negligible or weak AAN are revealed, which may reflect effects of upwelling mantle plumes. Among the three regions, a weak AAN with a constant FVD is only revealed beneath Iceland, which may reflect the existence of background mantle flow. The RAN and AAN features beneath the Labrador Sea, Davis Strait, and Baffin Bay suggest the following scenario on breakup between Greenland and Canada: the breakup was initiated at the Labrador Sea due to local mantle upwelling, but the northward propagation of the breakup was blocked by a strong high-velocity anomaly beneath Davis Strait; the opening of Baffin Bay might be caused passively by far-field plate forces.

Mixing state of black carbon (BC) with secondary species has been highlighted as a major uncertainty in assessing its radiative forcing. While recent laboratory simulation has demonstrated that BC could serve as a catalyst to enhance the formation of sulfate, its role in the formation and evolution of secondary aerosols in the real atmosphere remains poorly understood. In the present study, the mixing of BC with sulfate/nitrate in the atmosphere of Guangzhou (China) was directly investigated with a single particle aerosol mass spectrometer (SPAMS). The peak area ratios of sulfate to nitrate (SNRs) for the BC-containing particles are constantly higher than those of the BC-free particles (with negligible BC signals). Furthermore, the seasonal SNR peak is observed in summer and autumn, and the diurnal peak is found in the afternoon, consistent with the trends of radiation-related parameters (i.e., solar radiation and temperature), pointing to the BC-induced photochemical production of sulfate. Such hypothesis is further supported by the multilinear regression and random forest analysis, showing that the variation of SNRs associated with the BC-containing particles could be well explained (R2 = ~0.7-0.8) by the radiation-related parameters (> 30% of the variance) and the relative BC content (~20%) in individual particles, but with limited influence of precursors (SO2/NOx: < 5%). Differently, the radiation-related factors only explain < 10% of the SNR variation for the BC-free particles. These results provide ambient observational evidence pointing to a unique role of BC on the photochemical formation and evolution of sulfate, which merits further quantitative evaluations.

A document by Sydney JN Baratta. Click on the document to view its contents.

Two models are compared for Darcian flows in a vadose zone and shallow unconfined aquifer with an intensive evapotranspiration, common for hyperarid climates. An analytical 2-D Dupuit-Forchheimer approximation, in which the vadose zone is considered as a “distributed sink” (similar to a standard “distributed source” which models recharge to the water table in humid climates), is collated with HYDRUS3D. In a planar domain, a vertically-averaged flow from a constant piezometric head contour (seepage from ditches or trenches) is studied and integral criteria (the volume of the saturated zone and the area of unsaturated lacuna) are either evaluated or estimated by the Pòlya and Szegö isoperimetric inequalities. Mixed BVPs for Richards’ equation in cylindrical domains are numerically solved and give the pressure head, moisture content, and velocity fields, streamlines and criteria. Implicaitons for urban hydrology and ecohydrology of water logged drylands are discussed.

Research on bedrock rivers primarily focused on bedrock incision and, to the best of our knowledge, morphodynamic models have not yet considered the variability of sediment grain size and the presence of small scale bedforms in low-slope (slope < 0.005) bedrock reaches. Further, very few models can quantify spatial and temporal changes in the fraction of channel bed covered with alluvium (alluvial cover) within these reaches. Here we present a novel formulation of alluvial morphodynamics of low-slope bedrock reaches transporting non-uniform bed material. The formulation is implemented in a one-dimensional model and validated against laboratory experiments on bedrock reaches downstream of stable alluvial-bedrock transitions, where the flow accelerates in space. The validated model is used to study the alluvial morphodynamics of bedrock reaches upstream of stable bedrock-alluvial transitions. Equilibrium results show that the interactions between flow, sediment transport and non-erodible bedrock surface result in a flow decelerating in the streamwise direction. The effects of this spatial flow deceleration are 1) a streamwise increase in alluvial cover, and 2) the formation of a pattern of downstream coarsening of bed surface sediment. We then investigated the effects of sea level rise/fall on the location of alluvial-bedrock and bedrock-alluvial transitions. In the case of sea level rise, alluvial-bedrock transitions migrate downstream and bedrock-alluvial transitions migrate upstream. Opposite migration directions are expected in the case of sea level fall.

We consider particle flux enhancements occurred during Winter months on Aragats. We demonstrate that these events are originated from Rodon and Thoron chain isotopes gamma radiation only. The relativistic runaway electron avalanche is possible on Aragats only in Spring-Autumn seasons. We measure with precise spectrometer the lines of most isotopes participated in the flux enhancement and use multidetector measurements for proving the origin of the particle flux.

Wet-surface evaporation equations related to the Penman equation can be represented graphically on vapor pressure () versus temperature () graphs (Qualls & Crago, 2020). Here, actual regional evaporation is represented graphically on (, ) graphs using the Complementary Relationship (CR) between actual and apparent potential evaporation. The CR proposed by the authors can be represented in a simple and intuitive geometric form, in which lines representing the regional latent heat flux, , and the wet surface (Priestley & Taylor, 1972) evaporation rate, , intersect at =0. This approach allows a graphical estimate of (or the corresponding mathematical formulation) without the need to know either the wet surface or the apparent potential evaporation rates. The wet surface temperature is needed, and a calculation method for it is provided. The formulation works well using monthly data from seven sites in Australia, even when the same value of the Priestley & Taylor parameter α is used for all sites.

The Negribreen Glacier System on the east coast of Spitsbergen, Svalbard, has been actively surging since 2016, i.e., during the entire lifetime of ICESat-2 (launched in September 2018). The progression of Negribreen's surge throughout the glacier system has resulted in large-scale elevation changes and wide-spread crevassing, which is ideally mapped and analyzed using ICESat-2 measurements processed by the Density Dimension Algorithm for Ice (DDA-ice) (see Herzfeld et al. 2016, IEEE TGRS, and Herzfeld et al., 2022, Science of Remote Sensing).    In this analysis, we quantify how Negribreen has been evolving in its mature surge phase over the course of 2019 and 2020. Using ICESat-2 data, together with airborne field data and Sentinel-1-derived velocity data, we quantify large-scale effects such as elevation-change and mass transfer through the system, as well as smaller-scale effects afforded by high-resolution data products of the DDA-ice such as crevasse characterization, surface roughness and changes thereof.     Results show the expansion of the surge in upper Negribreen where increased crevassing has occurred along with height change rates nearing 30 m/year. In addition, fresh surge crevasses formed along the margin between the surging ice of Negribreen and non-surging ice of neighboring Ordonnansbreen. Finally, increased surge activity found on inflowing glaciers from the Filchnerfonna accumulation zone suggest that surge effects may continue to expand up glacier leading to further disintegration of the ice system with continued mass loss.