The domain nesting of the icosahedral non-hydrostatic (ICON) model has been used operationally at Deutscher Wetterdienst for several years. Now it was also made available for the atmospheric part of the ICON Earth system model. With this new climate configuration, regionally higher resolved simulations without the additional use of a separate regional climate model (RCM) are possible. Simulations were performed for the years 1979-2010 at a global resolution of about 80 km and a subdomain over Europe at 40 km resolution. Two simulations with this setup were evaluated and compared: one with a feedback from the regional subdomain to the global domain (two-way nesting) and one without feedback (one-way nesting). The mean atmospheric state of both simulations on the global scale is only slightly different compared to a reference experiment. However, comparisons to reanalyses show regionally distinct biases. The feedback from the subdomain to the global domain has a similar impact over Europe as a globally higher resolution, indicating a stronger North-Atlantic Oscillation at higher horizontal resolution. Over Europe, the skill is higher in the subdomain than in the global domain, but no systematic advantages can be attributed to the feedback. Artifacts at the lateral boundaries of the regional subdomain, as they are known from RCM simulations, also occur strongly in the simulation without feedback and are eliminated by allowing the feedback. A further reduction of resolution dependency of model physics is supposed to improve particularly the simulation with feedback.

Estuarine dams can result in profound changes to estuarine environments. However, their impact on estuarine currents, stratification, and sediment fluxes is not well understood. To develop a general understanding, an idealized modeling study was carried out using the Coupled-Ocean-Atmosphere-Wave-Sediment Transport Modeling System. Idealized estuarine geometry was based on 10 estuaries with estuarine dams. Tide and river forcing were varied to produce strongly stratified, partially mixed, periodically stratified, and well-mixed estuaries. Each model ran for one year. Next, the models were subject to the construction of an estuarine dam and run for another year. Then, the pre- and post-dam conditions were compared. Results showed that estuarine dams amplify the tidal range and reduce the tidal currents. The post-dam estuaries tended to be salt wedge and strongly stratified types during freshwater discharge, but during no freshwater discharge they became fjord, bay, or periodically stratified types based on the estuarine parameter space. For all estuaries, the estuarine turbidity maximum moved seaward, and the suspended sediment concentrations tended to decrease. While the depth changes depended on the estuary type, the surficial sediment texture shifted to being muddier for all types. In terms of sediment flux mechanisms, the estuarine dam reduced the exchange flow and Stokes transport. The estuarine dam also increased the seaward river runoff for cases with strong river, and increased the landward tidal pumping for cases with strong tides. This study is one of the first to generalize the effect of estuarine dams to a range of estuarine types.

We have studied the focal mechanisms of eleven earthquakes with magnitudes of ML ≥ 3.8 on the continental margin of Egypt and the adjacent onshore region from 1951 to 2020 to identify the stress regime and its spatial variations. The uncertainty parameters of each solution are evaluated using HASH software. The stress pattern obtained from focal solutions in the western province matches a compressional stress field with an NNW-SSE orientated compression axis, which corresponds to the direction of movement of the Nubia plate relative to Eurasia. On the other hand, the stress pattern derived from drilling-induced fractures and borehole breakout measurements is not correlated with the identified stress axis. The focal solutions of the recent earthquakes in the eastern-central province of the Nile Deep-Sea Fan indicate the strike-slip stress regime is the prevailing mode of deformation with an almost horizontal ESE-WSW compression axis and an almost horizontal N-S extension axis. Two responsive conjugate strike-slip faults that include both sinistral and dextral faults accommodate this strike-slip deformation style. The stress regime existing in the eastern-central province directly contradicts the northward convergent of the Nubian-Anatolia plates along the Cypriot arc. The stress pattern deflection in the eastern-central province of the Nile Deep-Sea Fan may be attributed to kinematic adaptation resulting from the deformation in and around the Eratosthenes Seamount rigid block as it impinges on the central part of the Cypriot arc. Toward the Egyptian onshore, the extension pattern was behaving differently from the compression stress pattern of the offshore continental margin.

The Quánjí Block (QB) is a sliver of anomalously old and well-preserved continental crust embedded within the Paleozoic-Mesozoic tectonic collage of the northeastern Tibet Plateau. New geological mapping, stratigraphic logging, and geochronological analysis leads to a refined understanding of QB’s history from Paleoproterozoic to present. Deposited atop a largely Paleoproterozoic basement, the Quánjí Group records rifting and epicratonic cover at 1.7-1.6 Ga. The Xiǎogāolú Group preserved black shale, ribbon-shaped fossil and the Ediacaran‐Cambrian glaciation. Ages from Cambrian Olóngbùlǔkè Group samples in open platform deposits are quite different from ages in underlying units, with a subdued age groups in the Neoproterozoic (880-815 Ma) ages. The apparent change in detrital zircon sources coincides with the regionally expressed Great Unconformity during the Precambrian-Cambrian transition. The new mapping, stratigraphy, and U-Pb geochronology of QB suggest the late Paleoproterozoic to Cambrian history of QB has a remarkable similarity to that of North China Block’s (NCB’s) southern margin, and indicate that the QB has been displaced dextrally from an initial location adjacent to NCB. The transform motion occurred in stages between ca. 350 and 200 Ma.

February-March 2020 was marked by highly anomalous large-scale circulations in the Northern extratropical troposphere and stratosphere. The Atlantic jet reached extreme strength, linked to some of the strongest and most persistent positive values of the Arctic Oscillation index on record, which provided conditions for extreme windstorms hitting Europe. Likewise, the stratospheric polar vortex reached extreme strength that persisted for an unusually long period. Past research indicated that such circulation extremes occurring throughout the troposphere-stratosphere system are dynamically coupled, although the nature of this coupling is still not fully understood and generally difficult to quantify. We employ sets of numerical ensemble simulations to provide statistical characterizations of the mutual coupling of the early 2020 circulation extremes. We find an overall robust coupling between tropospheric and stratospheric anomalies: ensemble members with polar vortex exceeding a certain strength tend to exhibit a stronger tropospheric jet and vice versa. Moreover, members exhibiting a breakdown of the stratospheric circulation (associated with a sudden stratospheric warming) tend to lack periods of persistently enhanced tropospheric circulation. A crucial component in determining the stratospheric vortex strength appears to be the vortex geometry, corresponding to states that promote either reflection or dissipation of planetary waves. Despite these lines of evidence for vertical coupling, our simulations underline the role of internal variability within each atmospheric layer. The circulation extremes during early 2020 may be viewed as resulting from a fortuitous alignment of dynamical evolutions within the troposphere and stratosphere, aided by each layer’s modification of the other layer’s boundary condition.

To explore the repeating mud volcanoes influences on the seismicity behaviors, we measured the spatial distribution z and b value changes with the time in the mud volcanoes developing area. We find a weak correlation between the b-z values and the mud volcanoes. Generally, the z-values anomalies of the mud volcanoes area show unchanged negative values and indicate the seismic quiescence before a strong earthquake, while the b-values show the frequently periodicity fluctuations around the value of 0.5. It may indicate the conjunct triggering relationships between the mud volcanoes and earthquakes stuck. We infered that the mud volcanoes eruptions help to partition and release part of the regional stress accumulation from the earthquake seismogenic structures, thus balanced the local stress in the strata. Keywords: Mud volcano; SW Taiwan; coulomb stress change; b-z-value; conjunct triggering relationship

Equatorial Pacific decadal variability (EPDV) modulates global climate. Although EPDV is suggested to be generated by both air-sea thermodynamically coupled slab ocean models (SOM) and fully coupled dynamic ocean models (DOM), the reason of EPDV simulated by the two distinct hierarchies of models remains unclear. This ambiguity arises from a gap in the dynamical framework between SOM and DOM. To fill the gap, we conducted a novel experiment (Clim-tau) that retains only the effects of thermodynamic coupling and mean ocean current on EPDV (without anomalous ocean current). We showed that in Clim-tau, thermodynamic-driven EPDV as in SOM is largely damped by equatorial Pacific mean upwelling; whereas involving anomalous ocean current as in DOM, the damped EPDV will be further amplified. Finally, we discussed the role of ocean dynamics in the observed EPDV. Our study highlights that SOM may misinterpret the physical mechanisms in the regions where ocean dynamics is important.

Thermobarometry is a fundamental tool to quantitatively interrogate magma plumbing systems and broaden our appreciation of volcanic processes. Developments in random forest-based machine learning lend themselves to a more data-driven approach to clinopyroxene thermobarometry. This can include allowing users to access and filter large experimental datasets that can be tailored to individual applications in Earth Sciences. Here we present a methodological assessment of random forest thermobarometry, using the R freeware package “extraTrees”, by investigating the model performance, tuning hyperparameters, and evaluating different methods for calculating uncertainties. We determine that deviating from the default hyperparameters used in the “extraTrees” package results in little difference in overall model performance (<0.2 kbar and <3 ⁰C difference in mean SEE). However, accuracy is greatly affected by how the final pressure or temperature (PT) value from the voting distribution of trees in the random forest is selected (mean, median or mode). This thus far has been unapproached in machine learning thermobarometry. Using the mean value leads to a higher residual between experimental and predicted PT, whereas using median values produces smaller residuals. Additionally, this work provides two comprehensive R scripts for users to apply the random forest methodology to natural datasets. The first script permits modification and filtering of the model calibration dataset. The second script contains pre-made models in which users can rapidly input their data to recover pressure and temperature estimates. These scripts are open source and can be accessed at https://github.com/corinjorgenson/RandomForest-cpx-thermobarometer.

The exploration of the surface geology of Venus has been hampered by its inhospitable conditions and thick and opaque atmosphere. Fundamental properties, such as crustal composition and heterogeneity remain poorly constrained. Multiple analytical techniques are required to better understand its geology. A spectroscopy-based study laboratory study of the emissivity properties of Venus-relevant igneous rocks, measured at 440 °C by Dyar et al. (2020b; https://doi.org/10.1029/2020GL090497) shows that the use of multiple atmospheric windows in the 1-μm region can provide strong constraints on the FeO content of Venus-relevant igneous rocks, and by extension, the type of igneous rock. These results will improve our ability to map the surface geology of Venus remotely.

Effective risk assessment can reduce the economic losses and physical damage caused by marine dynamic processes, such as storm surges. Most risk assessments of marine disasters are based on regional parameters and discrete hazard grades. Targeted, multilevel, and multiangle risk assessments are urgently needed. This study focused on specific types of affected infrastructure. We established a sensitivity matrix by considering the effects of different disaster causal factors on different types of affected infrastructure. Through this matrix, hazards, vulnerability, and emergency response and recovery capability were effectively combined in a risk assessment framework. We completed the risk calculation for multiple concurrent effects of disasters in areas with superimposed key infrastructure using complementary risk superposition. The hazard grade, vulnerability grade, and coefficient of emergency response and recovery capability were established based on the means of return period, characteristics of disaster distribution, types of affected infrastructure and disaster relief distance, and were continuous by solving functions, normal cumulative distributions, and analytic functions. On the basis of reasonable MIKE21 numerical simulation and abstract spatial distribution of vulnerable assets, we tested the rationality of the assessment system in the Lekima typhoon storm surge process. The results showed that the assessment system accurately reflected the risk of damage to the important infrastructure. Therefore, this risk assessment framework was suitable for the assessment of marine dynamic disaster process in the lower part of Laizhou Bay. It also provided a reference for disaster prevention and reduction, guided the way for decision-making, and effectively reduced disaster losses.

Geothermal or ground source heat pumps (GSHPs) are among the growing renewable energy technologies used for heating and cooling of buildings. However, little work has been done to investigate their geo-environmental effects within the subsurface, especially in contaminated environments. This research uses FEFLOW software, to simulate heat and mass transport of a vertical closed-loop GSHP system. Transient flow and heat transport results for a multiple borehole system are presented for a hypothetical building located in Toronto, Canada, and shows long-term effects on subsurface temperature. Moreover, the impact of heat exchanged with the subsurface on biodegradation kinetics is examined in a contaminant transport simulation, to evaluate the possibility of utilizing this heat as a remediation strategy. The results revealed that temperature changes caused by GSHP operation can significantly enhance biodegradation of hydrocarbon contaminants. For instance, elevated subsurface temperature resulted in 96% reduction in benzene concentration, after one year of GSHP simulated operation for an office building located in Toronto, Canada.

Mare Humboldtianum is a Nectarian-aged basin on the northeast limb of the Moon, whose inner ring was flooded by basalt billions of years ago. The topography of Mare Humbold is rather complex, which makes it difficult to define the basaltic units only by the spectral data. To improve understanding of the geological units in Mare Humbold-28 tianum and provide new interpretations of the formation process, we use the brightness temperature (TB) data obtained by the Chang’E-2 (CE-2) mission, which is proved to have a good penetration feature. The TB difference (dTB) maps at multichannels are created to analyze the TB variations. The Backpropagation Neural Network (BPNN) model is first used to provide a statistical interpretation of the relation between dTB distributions and surface parameters. Our results show that, most of the dTB performances are strongly affected by the topography. Several abnormally dTB performances are observed on dTB maps. This observation indicates that there exists two different mare units in the eastern and western parts in the basin floor. These TB variations are interpreted that most of the dTB anomalies are strongly related to the special tectonic features. The statistical results based on BPNN method indicate that multichannel TB variations reflect different topographic features. Most of the topographic effects related to dTB variations are found in the regions controlled by the small craters and topographic bulges in the basin floor.

Climate change may cause profound changes in the regional water cycle causing negative impacts in many sectors, such as agriculture or water resources. In this study, projected changes of the terrestrial water cycle are investigated based on the simulations from 47 regional climate model ensemble members of the COordinated Regional Downscaling EXperiment (CORDEX) project’s EURO-CORDEX initiative, which downscale different global climate models of the CMIP5 experiment over a 12km resolution pan-European model domain. We analyze climate change impacts on the terrestrial water budget through changes in the long-term annual and seasonal cycles of precipitation, evapotranspiration, and runoff over 20 major European river catchments (Guadalquivir, Guadiana, Tagus, Douro, Ebro, Garonne, Rhone, Po, Seine, Rhine, Loire, Maas, Weser, Elbe, Oder, Vistuala, Danube, Dniester, Dnieper, and Neman) for near (2021-2050) and far future (2070-2099) time spans with reference to a historical period (1971-2000) for three Representative Concentration Pathways (RCPs), RCP2.6, RCP4.5, and RCP8.5. The analysis shows substantial differences between the projected changes in precipitation, evapotranspiration, and runoff for the twenty European catchments. For the near future RCP8.5 scenario, the long-term average of the annual sum precipitation increases over most of Europe by up to 10% in the ensemble mean over central European catchments; but also decreases up to 10 % are found, e.g. over the Iberian Peninsula. For the far future, the long-term average ensemble means of the annual precipitation sum increases from 30% for eastern, 15% for central to 7% for western European catchments, and further decreases up to 25% over the Iberian Peninsula, which will likely cause water stress situations. These first order changes in precipitation lead to ensuing changes in evapotranspiration and runoff, that cause altered hydrological regimes and feedback processes in the water cycle in the catchments.

We conducted high‐temperature and high-pressure deformation experiments on hot-pressed aggregates of olivine + 9 wt% dolomite at 1 GPa and 1100ºC in a Griggs-type apparatus. At run conditions, the dolomite decomposed to produce ~7 vol% CO2 as a supercritical fluid. Microstructural observations show that CO2 is distributed at triple junctions and as isolated “bubbles” along grain boundaries in the hot-pressed samples. After deformation, the CO2 is redistributed to form CO2-rich bands and CO2-depleted bands. Compared to experiments with the basaltic melt, CO2 does not reduce olivine viscosity as much. The CPOs of CO2-bearing samples are much stronger than the CPO of melt-bearing samples, although [100] and [001] axes girdles are found in both types of samples. Olivine is much more soluble in basaltic melt than CO2, which enhances diffusion accommodated deformation mechanisms more in melt-bearing samples. Our mechanical and microstructural data support the hypothesis that the kinetic effect of a fluid or melt phase depends on the chemistry and fluid topology.

To understand the movement of subglacial water in Antarctica, we present an updated inventory of active subglacial lakes using ICESat-2 laser altimetry data. The ICESat-2/ATLAS instrument’s six-beam laser array captures denser point measurements than the previous generation ICESat and Cryosat-2 satellites, allowing us to examine the spatial and temporal variability of active subglacial lakes with unprecedented detail. Active subglacial lakes are classified directly from the high density ATL11 land ice time-series (60 m along track spatial resolution) point cloud data using an unsupervised density-based clustering algorithm. The key finding we show is how subglacial lake shorelines can migrate spatially over time through fill-drain cycles. In addition, we examine subglacial water connectivity from coupled fill-drain cycles over lakes at the Whillans Ice Stream on the Siple Coast. This study yields new insights into the dynamic nature of the subglacial water system in Antarctica, and will be of interest to biologists quantifying biogeochemical cycle processes and glaciologists studying the influence of subglacial hydrology on ice dynamics.

Geothermal systems consisting of fractures in impermeable rocks are difficult to characterize by in situ methods. In an effort to link characteristics of small-scale and large-scale fractures, this study investigated possible relations between their geophysical parameters. We upscaled the relationship between fracture permeability and formation factor in a laboratory specimen to larger fracture dimensions. Microscopic flow characteristics indicate that this relationship is related to the tortuosity of flow paths. We derived an empirical formula that directly predicts changes in fracture permeability from changes in formation factor. This relation may make it possible to monitor subsurface hydraulic activities through resistivity observations.

Subduction zone earthquakes show varying energy release patterns and frequency content, based on their tectonic settings and hypocentral depths. Resolving these features from the nonlinear and non-stationary seismograms is a challenge. Our work in the Japan Trench follows studies by Huang et al. (1998, 2001) and Zhang et al. (2003), who demonstrated the use of empirical mode decomposition to separate records into multiple timescales, or intrinsic mode functions (IMFs). Zhang et al. observed that IMFs 2-5 represented the source rupture process for the 1994 Northridge earthquake. Chauhan (master’s thesis, 2019) used time-frequency distributions, short-time Fourier and continuous wavelet transforms, of IMFs of strong-motion data for a pair of interplate-intraslab earthquakes to identify the dominant, short duration, low-frequency energy release for the intraslab event. He found a high correlation between the original signal and a linear combination of IMFs 3 and 4, possibly representing the source. Chatterjee et al. (AGU, 2018) observed an association between time-frequency-energy distributions of certain IMFs and moment rate functions (MRFs) from teleseismic waveform models, for five earthquakes. Chatterjee et al. (AGU, 2019) and Mache et al. (AGU, 2019) used Hilbert spectral analysis (Huang et al., 1998) of IMFs selected based on their frequency and energy and observed better match between the two. This new function, which they regard as the Energy Rate Function (ERF), can reproduce the MRF’s essential elements, i.e., its duration and shape, but Mache (master’s thesis, 2020) observed that results depended on the selection of stations. As the next step, Mache and Rajendran (JpGU-AGU, 2020) based the selection criteria on the slip distribution, strike, and JMA intensity distribution maps (JMA 1996) and applied the method to 7 earthquakes from various tectonic settings of the Japan Trench. Here we present an overview of the various methods for analyzing KiK-net strong-motion data for selected earthquakes to extract information on their time-frequency-energy distributions. The ERF generated through this analysis is a physically compatible expression of the MRF and, therefore, more useful in predicting the shaking effects of earthquakes.

Nuclear and coal power use in the United States are projected to decline over the coming decades. Here, we explore how simultaneous phase-outs of these energy sources could affect air pollution and distributional health risk with existing grid infrastructure. We develop an energy grid dispatch model to estimate the emissions of CO2, NOx and SO2 from each U.S. electricity generating unit. We couple the emissions from this model with a chemical transport model to calculate impacts on ground-level ozone and fine particulate matter (PM2.5). Our yearlong scenario removing nuclear power results in compensation by coal, gas and oil, leading to increased emissions that impact climate and air quality nationwide. We estimate that changes in PM2.5 and ozone lead to an additional 9,200 yearly mortalities, and that changes in CO2 emissions over that period lead to an order of magnitude higher mortalities throughout the 21st century. Together, air quality and climate impacts incur between \$80.7-\$126.1 billion of annual costs. In a scenario where nuclear and coal power are shut down simultaneously, air quality impacts due to PM2.5 are larger and those due to ozone are smaller, because of more reliance on high emitting gas and oil, and climate impacts are substantially smaller than that of nuclear power shutdowns. With current reliance on non-coal fossil fuels, closures of nuclear and coal plants shift the distribution of health risks, exemplifying the importance of multi-system analysis and unit-level regulations when making energy decisions.