Climate models still need to be improved in their capability of reproducing the present climate at both global and regional scale. The assessment of their performance depends on the datasets used as comparators. Reanalysis and gridded (homogenized or not homogenized) observational datasets have been frequently used for this purpose. However, none of these can be considered a reference dataset. Here, for the first time, using in-situ measurements from NOAA U.S. Climate Reference Network (USCRN), a network of 139 stations with high-quality instruments deployed across the continental U.S, daily temperature, and precipitation from a suite of dynamically downscaled regional climate models (RCMs; driven by ERA-Interim) involved in NA-CORDEX are assessed. The assessment is extended also to the most recent and modern widely used reanalysis (ERA5, ERA-Interim, MERRA2, NARR) and gridded observational datasets (Daymet, PRISM, Livneh, CPC). Results show that biases for the different datasets are mainly seasonal and subregional dependent. On average, reanalysis and in-situ-based datasets are generally warmer than USCRN year-round, while models are colder (warmer) in winter (summer). In-situ-based datasets provide the best performance in most of the CONUS regions compared to reanalysis and models, but still have biases in regions such as the Midwest mountains and the Northwestern Pacific. Results also highlight that reanalysis does not outperform RCMs in most of the U.S. subregions. Likewise, for both reanalysis and models, temperature and precipitation biases are also significantly depending on the orography, with larger temperature biases for coarser model resolutions and precipitation biases for reanalysis.

The Main Ethiopian Rift (MER) is accompanied by extensive volcanism and the formation of geothermal systems, both having an imminent impact on lives of millions of local inhabitants. Although previous studies from the region found evidence that asthenospheric upwelling and associated decompression melting provide melt to magmatic mush systems that feed the tectono-volcanic segments in the rift valley, no geophysical model imaged these regional and local scale transcrustal structures within a single comprehensive 3-D model. To fill this gap, we combined regional and local magnetotelluric data sets to obtain the first multi-scale 3-D electrical conductivity model of the central MER. The model clearly images a magma ponding zone with up to 7 vol.% melt at the base of the crust in the western part of the rift, its connection to Aluto volcano via a tectonically controlled transcrustal magmatic mush system and how the melt, stored at shallow crustal depths, supplies heat for Aluto’s geothermal system. Our model provides evidence that different volcano-tectonic lineaments in the rift valley share a common melt source, which has been debated in the past. The presented multi-scale model provides new constraints as well as geologic insights into the melt distribution below the rift and will facilitate future geothermal developments and volcanic hazard assessments in the MER.

The prevalence of mixing vs. precipitation processes in biomass burning aerosol (BBA) laden air over the southeast Atlantic is assessed during three intensive observation periods during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign. Air in the lower free troposphere (FT) and marine boundary layer (MBL) are treated as separate analyses, although connections are made where relevant. The study, centering on aircraft in-situ measurements of total water heavy isotope ratios, has two main objectives. The first is to gauge whether the atmospheric hydrology, and in particular precipitation, can be constrained primarily through visual assessment of the aircraft isotope ratio data plotted against total water concentration, similarly to several previous studies. However, regression of the data onto a simple model of convective detrainment is also used and alludes to the possibility of a precipitation data product derived from isotope ratios. The second objective is to connect variations in aerosol concentrations to the hydrology as diagnosed by the isotope ratio measurements, and determine whether aerosol variations are attributable to wet scavenging. First, joint water concentration (q) and H2O/HDO isotope measurements (δD) in the lower FT are combined with satellite and MERRA-2 data into simple analytical models to constrain hydrologic histories of BBA-laden air originating over Africa and flowing over the southeast Atlantic. We find that even simple models are capable of detecting and constraining the primary processes at play. Further, a strong correlation between isotopic evidence of precipitation in lower FT air masses and an in-situ indicator of wet scavenging of black carbon – the ratio of black carbon to carbon monoxide (BC/CO) – is shown. In comparison, the correlation between BC/CO and the water concentration itself is low. Since wet scavenging is the primary removal mechanism of black carbon, these findings suggest that isotope measurements could support studies constraining the lifetime of black carbon in the FT. Next, the ability of measurements interpreted with simple analytical models in (q, δD) space to distinguish cloud-top entrainment vs. precipitation signals in the MBL is tested. This proves more difficult than the lower FT analysis since signals are smaller. We find that the largest obstacle to this goal is the (q, δD) values of the entrained airmass at cloud-top. We also compare cloud condensation nuclei (CCN) concentrations in the sub-cloud layer to the isotopic measurements. In 2016 and 2018 IOPs, lower CCN concentrations coincide with isotope ratio evidence of precipitation, indicating aerosol scavenging. However, a more complex model simulating water, isotope ratios, and aerosols would be necessary to achieve more definitive conclusions. For the 2017 IOP, with the highest sub-cloud CCN concentrations, there is no connection between precipitation signals and CCN concentrations.

Dynamic stress evolution during earthquake rupture contains information of fault frictional behavior that governs dynamic rupture propagation. Most of earthquake stress drop and evolution studies are based on kinematic slip inversions. Several dynamic inversion methods in the literature require dynamic rupture modeling that makes them cumbersome with limited applicability. In this study, we develop a fault-stress model of earthquake sources in the framework of the representation theorem. We then propose a dynamic stress inversion method based on the fault-stress model to directly invert for dynamic stress evolution process on the fault plane by fitting seismic data. In this inversion method, we calculate numerical Green’s function once only, using an explicit finite element method EQdyna with a unit change of shear or normal stress on each subfault patch. A linear least-squares procedure is used to invert for stress evolution history on the fault. To stabilize the inversion process, we apply several constraints including zero normal slip (no separation or penetration of the fault), non-negative shear slip, and moment constraint. The method performs well and reliably on a synthetic model, a checkerboard model and the 2016 Mw 5.0 Cushing (Oklahoma) earthquake. The proposed fault-stress model of earthquake sources with inversion techniques such as one presented in this study provides a new paradigm for earthquake source studies using seismic data, with a potential of deciphering more physics from seismic recordings of earthquakes.

We show the first achievement of inferring the electron temperature in ionospheric conditions from synthetic data using fixed-bias Langmuir probes operating in the electron saturation region. This was done by using machine learning and altering the probe geometry. The electron temperature is inferred at the same rate as the currents are sampled by the probes. For inferring the electron temperature along with the electron density and the floating potential, a minimum number of three probes is required. Furthermore does one probe geometry need to be distinct from the other two, since otherwise the probe setup may be insensitive to temperature. This can be achieved by having either one shorter probe or a probe of a different geometry, e.g. two longer and a shorter cylindrical probe or two cylindrical probes and a spherical probe. We use synthetic plasma parameter data and calculate the synthetic collected probe currents to train a neural network and verify the results with a test set. We additionally verify the validity of the inferred temperature in altitudes ranging from about 100 km-500 km, using data from the International Reference Ionosphere model. Even minor changes in the probe sizing enable the temperature inference and result in root mean square relative errors between inferred and ground truth data of under 3%. When limiting the temperature inference to 120-450 km altitude an RMSRE of under 0.7% is achieved for all probe setups. In future, the multi-needle Langmuir Probe instrument dimensions can be adapted for higher temperature inference accuracy.

Export of sinking particles from the surface ocean is critical for carbon sequestration and to provide energy to the deep biosphere. The magnitude and spatial patterns of this export have been estimated in the past by \emph{in situ} particle flux observations, satellite-based algorithms, and ocean biogeochemical models; however, these estimates remain uncertain. Here, we use a recent machine learning reconstruction of global ocean particle size distributions from Underwater Vision Profiler 5 (UVP5) measurements to estimate carbon fluxes by sinking particles (35 $\mu$m - 5 mm equivalent spherical diameter) from the surface ocean. We combine global maps of particle size distribution properties with empirical relationships constrained against \emph{in situ} flux observations to calculate particulate carbon export from the euphotic zone and wintertime mixed layer depths. The new flux reconstructions suggest a less variable seasonal cycle in the tropical ocean, and a more persistent export in the Southern Ocean than previously recognized. Smaller particles (less than 420 $\mu$m) contribute most of the flux globally, while larger particles become more important at high latitudes and in tropical upwelling regions. Export from the wintertime mixed layer globally exceeds that from the euphotic zone, suggesting shallow particle recycling and net heterotrophy in the deep euphotic zone. These estimates open the way to fully three-dimensional global reconstructions of particle fluxes in the ocean, supported by the growing database of \emph{in situ} optical observations.

Recent research in real-time tsunami early warning can be broadly classified into two approaches. The first involves the use of seismic and regional geodetic data to calculate the tsunami wavefield indirectly through the estimation of earthquake source parameters. The second directly reconstructs the tsunami wavefield using data assimilation of ocean-bottom pressure sensor data such as those from DONET and S-NET (Maeda et al. 2015, Gusman et al. 2016). Data assimilation interpolates between the numerical solution and the observations to make the forecast more consistent with real data. Currently, the most popular method for forecasting the waveform is optimal interpolation, which uses a Kalman filter (KF) like approach, but holds the Kalman gain matrix fixed to reduce the runtime. This approach, coupled with tsunami Green’s functions, is very efficient and generates useful predictions. Here, we demonstrate that more accurate and stable forecasts can be obtained using the ensemble KF (enKF), a more computationally efficient variant of KF, in which the gain matrix is updated according to the physical model and the evolution of the error covariance matrix. The ensemble representation is a form of dimensionality reduction, in that only a small ensemble is propagated, instead of the joint distribution including the full covariance matrix. This method also provides a means to obtain the probability distribution of the forecast at each grid point location. We use a scenario tsunami in the Cascadia subduction zone, generated from a 2D fully-coupled dynamic rupture simulation (Lotto et al., submitted 2018). Randomly perturbed tsunami wave height data is used in the assimilation process, as we propagate the wave using a 1D linear shallow water code on a staggered grid. Better waveform agreement is achieved even in the early stages of assimilation, with much less fluctuation compared to optimal interpolation. We also explore spatial and temporal aliasing effects, in terms of the relation between observation station spacing and wavelength, as well as between assimilation and forecast time intervals. Although enKF is computationally more expensive, we are working on a fast, parallelized GPU implementation, which will significantly reduce the runtime, taking us a step closer to reliable real-time tsunami early warning.

Fluids influence fault zone strength and the occurrence of earthquakes, slow slip events, and aseismic slip. We introduce an earthquake sequence model with fault zone fluid transport, accounting for elastic, viscous, and plastic porosity evolution, with permeability having a power-law dependence on porosity. Fluids, sourced at a constant rate below the seismogenic zone, ascend along the fault. While the modeling is done for a vertical strike-slip fault with 2D antiplane shear deformation, the general behavior and processes are anticipated to apply also to subduction zones. The model produces large earthquakes in the seismogenic zone, whose recurrence interval is controlled in part by compaction-driven pressurization and weakening. The model also produces a complex sequence of slow slip events (SSEs) beneath the seismogenic zone. The SSEs are initiated by compaction-driven pressurization and weakening and stalled by dilatant suctions. Modeled SSE sequences include long-term events lasting from a few months to years and very rapid short-term events lasting for only a few days; slip is ~1-10 cm. Despite ~1-10 MPa pore pressure changes, porosity and permeability changes are small and hence fluid flux is relatively constant except in the immediate vicinity of slip fronts. This contrasts with alternative fault valving models that feature much larger changes in permeability from the evolution of pore connectivity. Our model demonstrates the important role that compaction and dilatancy have on fluid pressure and fault slip, with possible relevance to slow slip events in subduction zones and elsewhere.

Urban water systems are composed of subsystems (gully pots, storm sewers and surface water), each with its own system dynamics. Engineers balance the functioning of the systems based on storage and discharge capacity of the subsystems. The load on, and capacity are influenced by e.g. ageing, urbanization, climate change. Consequently, the performance of and demand put on subsystems varies over time, potentially resulting in disturbances in the balance between the storage and discharge capacity of the subsystems. The Graph Based Weakest Link Method (GBWLM) is developed to analyse the behaviour of urban water systems to identify potential limitations due to deterioration, and/or changes in load. The proposed GBWLM is based on the structure of the networks. In addition, Graph theory is applied as alternative for series of hydraulic calculations. The GBWLM allows for an integrated performance assessments of urban water systems using multi-decades rainfall series. The results are sufficiently accurate to be able to determine the extent and frequency of urban flooding in order to compare the performance of the subsystems for various degrees of available discharge capacity. Keywords Criticality, flow paths analysis, Graph theory, linearised hydrodynamics, urban water systems, Weakest Link Method Highlights 1. Method for the analysis of urban water systems based on Graph theory 2. The use of linearised hydrodynamics in flow path analyses

During the last ice age, the western United States was covered by large lakes, sustained partly by higher levels of precipitation. Increased rainfall was driven by the atmospheric circulation associated with the presence of large North American ice sheets, yet Pleistocene lakes generally reached their highstands not at glacial maximum but during deglaciation. Prior modeling studies, however, showed nearly monotonic drying since the last glacial maximum. Here I show that iTraCE, a transient climate simulation of the last deglaciation, run at higher resolution and with updated boundary conditions, reproduces a robust peak in winter rainfall over the Great Basin near 16 ka. I further demonstrate that the simulated peak is driven by a transient southward shift of the midlatitude jet. The causes for the southward shift of the jet are multifactorial, with meltwater forcing, changing orbital conditions, and rising atmospheric CO2 all playing a role.

In global applications and data sparse regions, which comprise most of the earth, hydrologic model-based flood monitoring relies on precipitation data from satellite multisensor precipitation products or numerical weather forecasts. However, these products often exhibit substantial errors during the meteorological conditions that lead to flooding, including extreme rainfall. The propagation of precipitation forcing errors to predicted runoff and streamflow is scale-dependent and requires an understanding of the autocorrelation structure of precipitation errors, since error autocorrelation impacts the accumulation of precipitation errors over space and time in hydrologic models. Previous efforts to account for satellite precipitation uncertainty in hydrologic models have demonstrated the potential for improving streamflow estimates; however, these efforts use satellite precipitation error models that rely heavily on ground reference data such as rain gages or weather radar and do not characterize the nonstationarity of precipitation error autocorrelation structures. This work evaluates a new method, the Space-Time Rainfall Error and Autocorrelation Model (STREAM), which stochastically generates possible true precipitation fields, as input to the Hillslope Link Model to generate ensemble streamflow estimates. Unlike previous error models, STREAM represents the nonstationary and anisotropic autocorrelation structure of satellite 2 precipitation error and does not use any ground reference to do so. Ensemble streamflow predictions are compared with streamflow generated using satellite precipitation fields as well as a radar-gage precipitation dataset during peak flow events. Results demonstrate that this approach to accounting for precipitation uncertainty effectively characterizes the uncertainty in streamflow estimates and reduces the error of predicted streamflow. Streamflow ensembles forced by STREAM improve streamflow prediction nearly to the level obtained using ground-reference forcing data across basin sizes.

On December 04, 2021, a total solar eclipse occurred over west Antarctica. Nearly an hour beforehand, a geomagnetic substorm onset was observed in the northern hemisphere. Eclipses are suggested to influence magnetosphere-ionosphere (MI) coupling dynamics by altering the conductivity structure of the ionosphere by reducing photoionization. This sudden and dramatic change in conductivity is not only likely to alter global MI coupling, but it may also introduce a variety of localized instabilities that appear in both hemispheres. Global navigation satellite system (GNSS) based observations of the total electron content (TEC) in the southern high latitude ionosphere during the December 2021 eclipse show signs of wave activity coincident with the eclipse peak totality. Ground magnetic observations in the same region show similar activity, and our analysis suggest that these observations are due to an “eclipse effect” rather than the prior substorm. We present the first multi-point interhemispheric study of a total south polar eclipse with local TEC observational context in support of this conclusion.

We test the application of a rare event simulation algorithm to accelerate the sampling of extreme winter rainfall over Europe in a climate model. The genealogical particle analysis algorithm, an ensemble method that interrupts the simulation at intermediate times to clone realizations in which an extreme event is developing, is applied to the intermediate complexity general circulation model PlaSim. We show that the algorithm strongly reduces the numerical effort required to estimate probabilities of extremes, demonstrating the potential of rare event simulation of seasonal precipitation extremes.

Our longest, stable record of cloud-top pressure (CTP) and cloud-top height (CTH) are derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-Angle Imaging Spectroradiometer (MISR) on Terra. Because of single cloud-layer assumptions in their standard algorithms, they provide only single CTP/CTH retrievals in multi-layered situations. In the predominant multi-layered regime of thin cirrus over low clouds, MODIS significantly overestimates cirrus CTP and emissivity, while MISR accurately retrieves low-cloud CTH. Utilizing these complementary capabilities, we develop a retrieval algorithm for accurately determining both-layer CTP and cirrus emissivity for such 2-layered clouds, by applying the MISR low-cloud CTH as a boundary condition to a modified MODIS CO2-slicing retrieval. We evaluate our 2-layered retrievals against collocated Cloud-Aerosol Transport System (CATS) lidar observations. Relative to CATS, the mean bias of the upper cloud CTP and emissivity are reduced by ~90% and ~75% respectively in the new technique, compared to standard MODIS products. We develop an error model for the 2-layered retrieval accounting for systematic and random errors. We find up to 88% of all residuals lie within modeled 95% confidence intervals, indicating a near-closure of error budget. This reduction in error leads to a reduction in modeled atmospheric longwave radiative flux biases ranging between 5-40 Wm-2, depending on the position and optical properties of the layers. Given this large radiative impact, we recommend that the pixel-level 2-layered MODIS+MISR fusion algorithm be applied over the entire MISR swath for the 22-year Terra record, leading to a first-of-its-kind 2-layered cloud climatology from Terra’s morning orbit.

Based on the long-term climatological data from Ny Alesund, Svalbard Airport – Longyearbyen and Hornsund Polish Polar Station, we undertook an analysis of drought indices on West Spitsbergen Island, Svalbard for the period 1979-2019. The features and causes of spatio-temporal variability of atmospheric drought on Svalbard were identified, as expressed by the Standardised Precipitation Evapotranspiration Index (SPEI). It was possible to indicate several-years long periods with the SPEI indicating a domination of drought or wet conditions. Long-term variability of annual and half-year (May-October) values of SPEI showed a prevalence of droughts in the 80-ties and in the first decade of the 21st century while wet seasons were frequent in the 90-ties and in the second decade of the 21st century. Seasonal SPEIs were characteristic of great inter-annual variability. In MAM and JJA droughts were more frequent after 2000; in the same period in SON and DJF, the frequency of wet seasons increased. The most remarkable changes in the scale of the entire research period were estimated for autumn where negative values of SPEI occur more often in the first part of the period and positive values dominate in the last 20 years. The long-term course of the variables in subsequent seasons between 1979-2019 indicates strong relationships between the SPEI drought index and anomalies of precipitable water and somewhat weaker relationships with anomalies of sea level pressure.

Ionospheric convection patterns from the Super Dual Auroral Radar Network are used to determine the trajectories, transit times and decay rates of three polar cap patches from their creation in the dayside polar cap ionosphere to their end of life on the nightside. The first two polar cap patches were created within 12 minutes of each other and travelled through the dayside convection throat, before entering the nightside auroral oval after 104 and 92 minutes, respectively. When the patches approached the nightside auroral oval, an intensification in the poleward auroral boundary occurred close to their exit point, followed by a decrease in the transit velocity. The airglow decay rates of patches 1 and 2 were found to be ≈0.6% and ≈0.9% per minute, respectively. The third patch decayed completely within the polar cap and had a lifetime of only 78 minutes. After a change in drift direction, patch 3 had a radar backscatter power half-life of 4.23 minutes, which reduced to 1.80 minutes after a stagnation, indicating a variable decay rate. 28 minutes after the change in direction, and 16 minutes after stagnation, patch 3 completely disintegrated. We relate this rapid decay to increased frictional heating, which speeds up the recombination rate. Therefore, we suggest that the stagnation of a polar cap patch is a main determinant to whether or not a polar cap patch can exit through the nightside auroral oval.

Environmental justice and equity should include access to clean water for all. It is expensive to drill borehole wells, typically over $10,000 US dollars, and so organizations working to provide wells in developing countries have typically installed community wells at some common gathering place. This requires that many users must walk long distances to access these water sources. This limits the quantity of water available to a family, and also creates vulnerabilities for the family member, usually a woman or child, sent for the water since the journey is often made early in the morning or at night in the dark. I have been drilling wells with a Kenyan team since 2010 using a simple, manual percussion hydraulic method developed by WaterForAllinternational.org whereby we can install a well generally for less than $200 US dollars excluding labor. Through their own participation in the drilling process, this low-cost enables families to pay for and drill their own well. In this way, they gain access to a much larger supply of water at or close to home, and eliminate the need and vulnerability associated with walking long distances to procure water for their family. Both the drilling apparatus and the cased well, including the pump, is constructed from materials available off-the-shelf at local hardware stores. Over the years I have made several modifications to the pump design, other infrastructure, and manufacturing process to improve the longevity, simplicity, and interchangeability of the final product. The drilling method is primarily applicable to aquifers lying above bedrock and it is feasible to drill wells to a depth of several hundred feet. The greatest challenge in the endeavor is earning the trust and cultivating the participation of the local community. This presentation will address the drilling process, the well infrastructure, and some socio-cultural aspects of the project.

Many chemical processes depend non-linearly on temperature. Gravity-wave-induced temperature perturbations have been previously shown to affect atmospheric chemistry, but accounting for this process in chemistry-climate models has been a challenge because many gravity waves have scales smaller than the typical model resolution. Here, we present a method to account for subgrid-scale orographic gravity-wave-induced temperature perturbations on the global scale for the Whole Atmosphere Community Climate Model (WACCM). The method consists of deriving the temperature perturbation amplitude $\hat{T}$ consistent with the model’s subgrid-scale gravity wave parametrization, and imposing $\hat{T}$ as a sinusiodal temperature perturbation in the model’s chemistry solver. Because of limitations in the gravity wave parameterization, scaling factors may be necessary to maintain a realistic wave amplitude. We explore scaling factors between 0.6 and 1 based on comparisons to altitude-dependent $\hat{T}$ distributions in two observational datasets. We probe the impact on the chemistry from the grid-point to global scales, and show that the parametrization is able to represent mountain wave events as reported by previous literature. The gravity waves for example lead to increased surface area densities of stratospheric aerosols. This in turn increases chlorine activation, with impacts on the associated chemical composition. We obtain large local changes in some chemical species (e.g., active chlorine, NOx, N2O5) which are likely to be important for comparisons to airborne or satellite observations, but find that the changes to ozone loss are more modest. This approach enables the chemistry-climate modeling community to account for subgrid-scale gravity wave temperature perturbations in a consistent way.

Venus today is inhospitable at the surface, its average temperature of 750 K being incompatible to the existence of life as we know it. However, the potential for past surface habitability and upper atmosphere (cloud) habitability at the present day is hotly debated, as the ongoing discussion regarding a possible phosphine signature coming from the clouds shows. We review current understanding about the evolution of Venus with special attention to scenarios where the planet may have been capable of hosting microbial life. We compare the possibility of past habitability on Venus to the case of Earth by reviewing the various hypotheses put forth concerning the origin of habitable conditions and the emergence and evolution of plate tectonics on both planets. Life emerged on Earth during the Hadean when the planet was dominated by higher mantle temperatures (by about 200$^\circ$C), an uncertain tectonic regime that likely included squishy lid/plume-lid and plate tectonics, and proto continents. Despite the lack of well-preserved crust dating from the Hadean-Paleoarchean eons, we attempt to resume current understanding of the environmental conditions during this critical period based on zircon crystals and geochemical signatures from this period, as well as studies of younger, relatively well-preserved rocks from the Paleoarchean. For these early, primitive life forms, the tectonic regime was not critical but it became an important means of nutrient recycling, with possible consequences to the global environment on the long-term, that was essential to the continuation of habitability and the evolution of life. For early Venus, the question of stable surface water is closely related to tectonics. We discuss potential transitions between stagnant lid and (episodic) tectonics with crustal recycling, as well as consequences for volatile cycling between Venus’ interior and atmosphere. In particular, we review insights into Venus’ early climate and examine critical questions about early rotation speed, reflective clouds, and silicate weathering, and summarize implications for Venus’ long-term habitability. Finally, the state of knowledge of the venusian clouds and the proposed detection of phosphine is covered.

SPICAM-IR, an AOTF spectrometer onboard Mars Express spacecraft with a resolving power of 2,000 covering the spectral range 1-1.7 μm has been observing Mars since 2004. In this wavelength range, it is possible to distinguish between CO2 and H2O ices and measure their band depths. We obtained about 200,000 high-fidelity spectra of CO2 ice in different seasons and locations over the Martian polar caps. The spectra have been associated with slab ice, fine-grained ice, permanent caps, and dark and dirty ice at the cryptic region of the south polar cap. Also, we observed more than 200,000 water ice spectra, specifically its broad feature around 1.5 μm. Water ice is present at the surface or in the atmosphere resulting in a variety of different band depths, often in combination with the CO2 ice. We mapped the equivalent width of 1.43 μm CO2 ice band and the depth of 1.5 μm water ice band, which are the proxies for grain size, and followed their seasonal evolution. From the maps, we produced the edge (outer crocus line) of the CO2 south and north caps for nine Martian Years. The cap edges evolve similarly through all years and are in good agreement with previous OMEGA/Mars Express observations. We also discuss the impact of the global dust storms on the cap edges. Lastly, we interpret some of the water ice observations as water ice clouds in the aphelion cloud belt and the polar hoods.

Metamorphic core complexes in the western North American Cordillera are commonly interpreted as the result of a single phase of large-magnitude extension during the middle to late Cenozoic. We present evidence that mylonitic shear zones inthe Harcuvar and Buckskin-Rawhide core complexes in west-central Arizona also accommodated an earlier phase of extension during the Late Cretaceous to early Paleocene. Microstructural data indicate substantial top-NE mylonitization occurred at amphibolite-facies, and 40Ar/39Ar thermochronology documents post-tectonic footwall cooling to <500°C by the Paleocene to mid-Eocene. Amphibolite-facies mylonites are spatially associated with voluminous and variably deformed footwall leucogranites that were emplaced from ca. 74-64 Ma, and a late kinematic ca. 63 Ma dike indicates this phase of mylonitization had waned by the early Paleogene. Reconstruction of the footwall architecture indicates that this latest Cretaceous – early Paleocene deformation occurred within a NE-dipping extensional shear zone. The leucogranites were likely the result of crustal melting due to orogenic thickening, implying a model whereby crustal heating triggered gravitational collapse of overthickened crust. Other tectonic processes, such as the Laramide underplating of Orocopia Schist or mantle delamination, may have also contributed to this episode of orogenic extension. Miocene large-magnitude extension was superimposed on this older shear zone and had similar kinematics, suggesting that the location and geometry of Miocene extension was strongly influenced by tectonic inheritance. We speculate that other Cordilleran core complexes also experienced a more complex and polyphase extensional history than previously recognized, but in many cases the evidence may be obscured by later Miocene overprinting.

In-situ measurements from the Magnetospheric Multiscale (MMS) mission are used to estimate electron density from spacecraft potential and investigate compressive turbulence in the Earth’s magnetosheath. During the MMS Solar Wind Turbulence Campaign in February 2019, the four MMS spacecraft were arranged in a logarithmic line constellation enabling the study of measurements from multiple spacecraft at varying distances. We estimate the electron density from spacecraft potential for a time interval in which the ion emitters actively control the potential. The derived electron density data product has a higher temporal resolution than the plasma instruments, enabling the examination of fluctuation for scales down to the sub-ion range. The inter-spacecraft separations range from 132 km to 916 km; this corresponds to scales of 3.5 to 24.1 ion inertial lengths. The derived density and magnetic field data are used to study fluctuations in the magnetosheath through time lags on a single spacecraft and spatial lags between pairs of spacecraft over almost one decade in scale. The results show an increase in anisotropy as the scale decreases.

Ice sheets such as Pine Island and Thwaites Glaciers which terminate at their ice shelves in the eastern Amundsen Sea, West Antarctica, are losing mass faster than most others about the continent. The mass loss is due to basal melting, this affected by a deep current thought to be guided by bottom bathymetry that transports warm Circumpolar Deep Water (CDW) from the continental shelf break towards the ice shelves. This current and associated heat transport are controlled by the near-surface winds that vary on a range of timescales due to both anthropogenic and natural effects. In this study we use idealised models to reproduce essential features of the Amundsen Sea circulation and heat transport. The aim is to elucidate the role of bathymetric features in shaping the circulation and in enabling heat transport from the deep ocean onto the continental shelf. Bathymetric variations along the continental slope enhance on-shelf heat transport by inducing breaks in the Antarctic Slope Front that separates off-shelf CDW from the colder, fresher shelf waters. The idealised model results imply that a ridge that blocks deep westward inflow from the Bellingshausen Sea leads to the existence of a deep cyclonic circulation on the shelf. Part of this circulation is an eastward undercurrent that flows along the continental shelf break. The broader cyclonic circulation transports heat that has been recently fluxed onto the shelf towards the south. These fundamental investigations will help refine the aims of future fieldwork and modelling.

Deforestation alters the exchange of heat, moisture, and momentum between the Earth's surface and the atmosphere, which can significantly affect the surface energy balance and water budget. However, changes in surface heat fluxes in response to deforestation are diverse among multi-model simulations. Changes in surface heat fluxes may lead to further energy partitioning and different land-atmosphere interactions. This study explores factors that might cause different changes in surface fluxes under tropical deforestation. The mediating effect of the Bowen ratio on changes in turbulent surface fluxes in response to the removal of tropical rainforests is examined with the Community Earth System Model of the National Center for Atmospheric Research. Different flux partitioning in the mean state of the Bowen ratio is associated with various flux changes under deforestation. When the mean Bowen ratio is smaller, deforestation tends to increase sensible heat fluxes and reduce latent heat fluxes. Our research further indicates that the simulated mean-state Bowen ratios in the Land Use Model Intercomparison Project model archive might modulate changes in surface heat fluxes that provide some clues for the land surface model developments.