Significant wave height (SWH) stems from a combination of locally generated “wind-sea” and remotely generated “swell” waves. In the Northern and Southern Hemispheres, wave heights typically undergo a sinusoidal annual cycle, with larger SWH in winter in response to seasonal changes in high-latitude storm patterns that generate equatorward propagating swell. However, some locations deviate from this hemispheric-scale seasonal pattern in SWH. For example, in the California coastal region, local wind events occur in boreal spring and summer, leading to a wind speed (WSP) annual cycle with a distinct maximum in boreal spring and a corresponding local response in SWH. Here ocean regions with a WSP annual cycle reaching a maximum in late spring, summer, or early fall are designated as seasonal wind anomaly regions (SWARs). Intra-annual variability of surface gravity waves is analyzed globally using two decades of satellite-derived SWH and WSP data. The phasing of the WSP annual cycle is used as a metric to identify SWARs. Global maps of probability of swell based on wave age confirm that during the spring and summer months, locally forced waves are more statistically more likely in SWARs than in surrounding regions. The magnitude of the deviation in the SWH annual cycle is determined by the exposure to swell and characteristics of the wave field within the region. Local winds have a more identifiable impact on Northern Hemisphere SWARs than on Southern Hemisphere SWARs due to the larger seasonality of Northern Hemisphere winds.

Most viscous-plastic sea ice models use the elliptical yield curve. This yield curve has a fundamental flaw: it excludes acute angles between deformation features at high resolution. Conceptually, the teardrop and parabolic lens yield curves offer an attractive alternative. These yield curves feature a non-symmetrical shape, a Coulombic behavior for the low-medium compressive stress, and a continuous transition to the ridging-dominant mode. We show that the current formulation of the teardrop and parabolic lens viscous-plastic yield curves with normal flow rules results in negative or zero bulk and shear viscosities and, consequently, poor numerical convergence and representation of stress states on or within the yield curve. These issues are mainly linked to the assumption that the constitutive equation applicable to the elliptical yield curve also applies to non-symmetrical yield curves and yield curves with tensile strength. We present a new constitutive relation for the teardrop and parabolic lens yield curves that solves the numerical convergence issues naturally. Results from simple uni-axial loading experiments show that we can reduce the residual norm of the numerical solver with a smaller number of total solver iterations, resulting in significant improvements in numerical efficiency and representation of the stress and deformation field. These yield curves lead to smaller angles of failure, in agreement with theoretical predictions, and are good candidates to replace the elliptical yield curve in high-resolution pan-arctic sea ice simulation.

During an earthquake, fault slip weakening is often explained by frictional heating phenomena, generally promoting melt production on the fault surface. Here, we investigate the influence of melt production at the scale of the grains composing a fault gouge. We use a modern version of Discrete Element Modelling (DEM) able to deal with realistic grain shapes, and couple it with a Multibody Meshfree Approach able to provide a satisfactory proxy for the mechanical behaviour of molten grains. Frictional sliding of solid grains and viscous shearing of molten grains are monitored during simulations. Our results confirm the natural tendency of granular gouge to localize deformation in a thin layer, and thus to trigger local melt production. We also show that the appearance of melt is likely to enhance this localization, and might create a positive feedback to its own production. We propose guidelines for the future writing of a friction model inspired by these simulation results.

Ocean Networks Canada (ONC; http://www.oceannetworks.ca/) operates the multidisciplinary NEPTUNE and VENUS cabled ocean observatories off the west coast of Canada and an increasing number of miniature ocean observatories, such as in the Canadian Arctic. All data collected by these observatories are permanently archived and publicly available through ONC’s Oceans 2.0 data portal. Much of the data are related to marine geohazards, such as earthquakes, submarine landslides and tsunamis and are delivered in real-time, including to early warning centers. The NEPTUNE cabled observatory consists of an approximately 800-km long cable loop deployed off the west coast of Vancouver Island that covers the coastal zone, the northern part of the Cascadia subduction zone, Cascadia Basin and the Endeavour Segment of the Juan de Fuca Ridge. The observatory includes several high-precision bottom pressure recorders (BPRs) at each of its five active nodes. On September 30, 2009, just days after the first instruments were installed, six BPRs on the array recorded tsunami waves of 2.5 to 6 cm amplitude originating with the Mw 8.1 Samoa earthquake. The Samoan tsunami was followed by several other events recorded by the network, including those of the 2010 Chilean tsunami, the 2011 Tōhoku-Oki tsunami, and the 2012 Haida Gwaii tsunami. We will review the decade of open-access bottom pressure recorder data, instrument development, and research findings across many disciplines and give an outlook for future developments.

Based on the object-based tracking algorithm, the precipitation simulation ability of the convection-permitting (CP) regional climate models (RCMs) is evaluated from the viewpoints of the precipitation systems in this work. The characteristics of precipitation systems over eastern China during 1998-2007 derived from the Weather Research and Forecasting model (WRF) with the horizontal grid spacing of ~ 4 km are compared with CMORPH. On the whole, CP RCMs can capture the average duration and eccentricity of all precipitation systems reasonably. However, precipitation systems tend to be stronger but with smaller coverage area in CP RCMs, which leads to the wet biases and dry biases of accumulated precipitation amount in the longer-duration (>= 48 hr) and shorter-duration (< 48 hr) systems, respectively. Such deficiencies in accumulated precipitation amount of precipitation systems with various durations can be made up by employing spectral nudging technique in CP RCMs to a certain degree. This work further indicates that, to improve the capability of precipitation simulation in CP RCMs, the relationship between intensity and coverage area of precipitation systems should be described properly in CP RCMs, especially for those with shorter-duration.

Lava domes form by the effusive eruption of viscous lava and are inherently unstable and prone to collapse. Dome collapses can generate pyroclastic flows and trigger explosive eruptions and thus represent a significant natural hazard. Many processes may contribute to the instability and collapse of lava domes, including advance of the dome margins, overtopping of confining topography, internal gas overpressure, and gravitational instability of the dome structure. Collapses that result from these processes can generally be grouped into two types: active and passive. Active collapses are driven by processes associated with active lava effusion, (e.g. dome growth or gas pressurization), while passive collapses are not directly associated with eruptive activity and can be triggered by overtopping of topographic obstacles or weakening of the dome structure. We use data collected by uncrewed aerial systems (UAS, commonly called ‘drones’) and a slope stability model to both identify and assess the stability of potential collapse sites for both passive and active processes. We collected visual and thermal infrared images by UAS and used structure-from-motion photogrammetry to generate thermal maps and digital elevation models (DEMs) of two example lava domes at Sinabung Volcano (Sumatra, Indonesia) and Merapi Volcano (Java, Indonesia). We evaluate the stability of erupted lava using the Scoops3D numerical model to assess the risk of passive and active collapses, including an assessment of the effect of lava material properties and internal pore pressure on the dome stability. We compare the collapse risk from Scoops3D with UAS-derived temperature maps and DEM differencing to evaluate the stability, size, and location of observed or potential collapses. We test whether Scoops3D can hindcast the sites and magnitudes of passive collapses at Sinabung that occurred in 2014 and 2015 and assess the stability of the remaining lava dome (growth has ended in spring 2018). For both volcanoes. Through application of these techniques, we are able to evaluate the collapse risk due to multiple processes that may act contemporaneously to generate dome instability. This study demonstrates how identification and classification of individual collapse mechanisms can be used to assess hazards at dome-forming volcanoes.

The isotope tracer technique plays a key role in identifying the sources and atmospheric processes affecting pollution. The sources of brown carbon (BrC) at Guangzhou during 2017-2018 was characterized by positive matrix factorization with carbon isotope constraints and multiple linear regression analysis. The primary emission factors of fossil fuel combustion (FF) and biomass burning (BB) accounted for 34% and 27% of dissolved BrC absorption at λ = 365 nm, respectively. The total mean light absorption contributed by secondary sources was 39%. The absorption of FF-origin BrC was relatively stable and dominant in the summer monsoon period, whereas the absorption of BrC from BB and secondary nitrate formation increased and contributed larger fractions during the winter monsoon period. Transported BrC was estimated using an index of 7 Be/(7 Be+n 210 Pb). Higher values were generally accompanied by lower BrC absorption, whereas lower values were associated with higher BrC absorption, indicating that BrC absorption of aerosols transported from the upper-atmosphere is lower than that of aerosols transported near the surface. Based on the positive correlations between 210 Pb and BrC absorption and non-fossil dissolved organic carbon in the winter monsoon period, we estimated that the contribution of invasive BrC (include ground and upper-atmosphere level) to total absorption during the period of elevated BrC was approximately 50%, which was likely related to BB organic aerosols and secondary nitrate formation processes. This study supports radionuclides as a novel method for characterizing the sources and transport of BrC that can be applied in future atmospheric research.

Landslide force history inverted from long-period seismic records for a landslide has been used to extract its physical parameters. An important precondition is that the inverted landslide force histories are reasonable approximations. We first discuss how to estimate the accuracy of the inverted force histories and then propose an approach to determine the proper frequency band used in the inversion. We perform a long-period seismic waveform inversion for the 2003 Qianjiangping landslide to obtain its force-time history and estimate its movement parameters. Based on the results, we build a simple model to study the effects of the portion of the initial sliding mass and the location of the mass entrainment on the seismically estimated mass, which shows that if the entrainment occurs at the slow-down phase the seismically estimated mass is a closer approximation of the initial sliding mass.

This study presents the novel application of tidal gravimetric data in the determination of phase-velocity dispersion curves of Rayleigh surface waves. Tidal gravimeters are capable to detect surface waves of periods even up to 500−600 s, while a typical broad-band seismic sensor can detect them up to the periods of 200−300 s due to its mechanical limitation. The capability of using tidal gravimeters as long period seismometers has already been analyzed since the late ’90s. These researches were mainly focused on the comparison of the power spectral density of noise level of gravimeters and seismometers and the analysis of normal modes of the largest earthquakes recorded by gravimeters. The first steps in the calculation of group velocity dispersion curves of Rayleigh surface waves were carried out lately. The Wiener deconvolution technique was used to calculate the phase-velocity dispersion curve by a two-stations method, from two pre-processed traces recorded in two different stations, located at the same great circle that the epicentre. The Incorporated Research Institutions for Seismology (IRIS) database were searched in terms of availability of at least 1 Hz data recorded by a co-located broad-band seismometer and tidal gravimeter. Additionally, the IRIS database provides the information about the transfer function of instruments, what is necessary in the two-stations method. Only, three sites met the above conditions: Black Forest, Membach and Rochfort, all located in Western and Central Europe. The compatibility of gravimetric and seismic data in the period range of 20-100 s are shown. Tidal gravimeters, because of their higher sensitivity, can better detect weaker earthquakes, which results in a higher number of recordings. However, to explore all advantages of gravimetric recordings of earthquakes, especially up to the periods of 500-600 s, above analysis must be applied to tidal gravimeters with higher inter-station distances and evaluated transfer functions. This work was done in the research project No. 2017/27/B/ST10/01600 financed from the funds of the Polish National Science Centre.

Since the 1970s, agricultural production in central Argentina has shifted away from perennial crops and grasses towards annual crops, largely soy. In this work we use observations and modeling to understand how this shift in land cover has affected the sub-surface, surface and atmospheric fluxes of moisture and energy in a flat agricultural area. We analyze the flux tower data from a paired site at Marcos Juarez in central Argentina during the period of the RELAMPAGO field campaign (2018-2019). When compared to perennial alfalfa, the observations over soy show lower evapotranspiration and specific humidity, higher sensible heat, higher outgoing shortwave radiation and soil temperature. Furthermore, water table depth is shallower below the soy than the alfalfa sites. To better understand the long-term temporal behavior from 1970s to present, the Noah-MP land surface model was calibrated at both soy and alfalfa sites based on RELAMPAGO data. Long-term simulation of the calibrated model suggests that ~95% of precipitation is evaporated in the alfalfa site with negligible recharge and runoff. In the case of soy, ET is about 68% of precipitation, leaving nearly 28% for recharge and 4% for runoff. Observed increases in streamflow and decreases in water table depth over time are likely linked to shifts in land cover. The changes in water table depth are enhanced in El Nino years. Furthermore, the partitioning of net radiation shifts from latent heat to sensible heat resulting in a 250% increase in Bowen ratio (from 0.2 to 0.7).

Marine boundary layer clouds tend to organize into closed or open mesoscale cellular convection (MCC). Here, two-dimensional wavelet analysis is applied for the first time to passive microwave retrievals of cloud water path (CWP), water vapor path (WVP), and rain rate from AMSR-E in 2008 over the Northeast and Southeast Pacific, and the Southeast Atlantic subtropical stratocumulus to cumulus transition regions. The (co-)variability between CWP, WVP, and rain rate in 160x160 km2 analysis boxes is partitioned between four mesoscale wavelength octaves (20, 40, 80, and 160 km). The cell scale is identified as the wavelength of the peak CWP variance. Together with a machine-learning classification of cell type, this allows the statistical characteristics of open and closed MCC of various scales, and its relation to WVP, rain rate and potential environmental controlling factors to be analyzed across a very large set of cases. The results show that the cell wavelength is most commonly 40-80 km. Cell-scale CWP perturbations are good predictors of the WVP and rain rate perturbations. A universal cubic dependence of rain rate on CWP is found in closed and open cells of all scales. This suggests that aerosol control on precipitation susceptibility is not as important for open cell formation as are processes that cause increases in cloud water. For cells larger than 20 km, there is no obvious dependence of cell scale on the environmental controlling factors tested, suggesting that the cell scale may depend more on its historical evolution than the current environmental conditions.

We describe a three-dimensional discrete fracture hybrid model (DFHM) that returns forecasts of both induced seismicity and of power generation in an Enhanced Geothermal System (EGS). Our model considers pore-pressure increase as the mechanism driving induced seismicity, similarly to other hybrid models, but it employs discrete fracture modelling for flow and heat that allows accurate and realistic transient solutions of pore pressure and temperature in fractured reservoirs. Earthquakes and flow are thus considered as closely coupled processes. In the DFHM model, the creation phase of an EGS is described as a Markovian process with a transitional probability that encapsulates the irreducible uncertainty with regards to induced seismicity. We conditioned this transitional probability on field observations from the 2006 EGS project in Basel, achieving a good match with observations of seismicity evolution. Specifically, our model effectively reproduces and explains the observed long-term exponential decay of seismicity after the well was shut in, suggesting that pore pressure diffusion in a critically stressed fractured reservoir is sufficient to explain long-lasting post-injection seismic activity as observed in Basel. We then investigate alternative injection scenarios, using Monte Carlo simulations to capture the uncertainties in fault locations and stressing conditions. We show that the number of induced events depends not only on the total injected volume but also on the injection strategy. We demonstrate that multi-stage injection schemes are superior to single-stage ones, since the former are associated with less seismic risk and can generate at least the same revenue in the long term.

FSO is a symbolic regression method that allows for automatic estimation of the structure and parameterization of transfer functions from catchment data. The FSO method transforms the search for an optimal transfer function into a continuous optimization problem using a text generating neural network (variational autoencoder). mHM is a widely applied distributed hydrological model, which uses transfer functions for all its parameters. For this study, we estimate transfer functions for the parameters saturated hydraulic conductivity and field capacity. To avoid the influence of parameter equifinality, the remaining mHM parameter values are optimized simultaneously. The study domain consists of 229 basins, including 7 major basins for Training and 222 smaller basins for validation, distributed across Germany. 5 years of data are used for training und 35 years for validation. By validating the estimated transfer functions in a set of validation basins in a different time period, we can examine the FSO estimated transfer functions influence on model performance, scalability and transferability. We find that transfer functions estimated by FSO lead to a robust performance when being applied in an ungauged setting. The median KGE of the validation basins in the validation time period is 0.73, while the median KGE of the 7 training basins in training time is 0.8. These results look promising, especially since we are only using 5 years of training data, and show the general applicability of FSO for distributed hydrological models.

The process of primary migration, which controls the transfer of hydrocarbons from source to reservoir rocks, necessitates the existence of fluid pathways in formations with inherently low permeability. Primary migration starts with the maturation of organic matter that produces fluids which increase the effective stress locally. The interactions between local fluid production, microfracturing, stress conditions, and transport remain difficult to apprehend in shale source rocks. Here, we analyze these interactions using a coupled hydro-mechanical model based on the discrete element method. The model is used to simulate the effects of fluid production emanating from kerogen patches contained within a shale rock alternating kerogen-poor and kerogen-rich layers. We identify two microfracturing mechanisms that control fluid migration: i) propagation of hydraulically driven fractures induced by kerogen maturation in kerogen-rich layers, and ii) compression induced fracturing in kerogen-poor layers caused by fluid overpressurization of the surrounding kerogen-rich layers. The relative importance of these two mechanisms is discussed considering different elastic properties contrasts between the rock layers, as well as various stress conditions encountered in sedimentary basins, from normal to reverse faulting regimes. Results show that the layering causes local stress redistribution that controls the prevalence of each mechanism over the other. When the vertical stress is higher than the horizontal stress in kerogen-rich layers, microfractures propagate from kerogen patches and rotate toward a direction perpendicular to the layers. Microfracturing in kerogen-poor layers is more pronounced when the confinement in these layers is higher. Those mechanisms were shown to be representative of Draupne formation.

Sea ice is a porous mushy layer composed of ice crystals and interstitial brine. The dense brine tends to sink through the ice, driving convection. Downwelling at the edge of convective cells leads to the development of narrow, entirely liquid brine channels. The channels provide an efficient pathway for drainage of the cold, saline brine into the underlying ocean. This brine rejection provides an important buoyancy forcing on the ocean, and causes variation of the internal structure and properties of sea ice on seasonal and shorter timescales. This process is inherently multiscale, with simulations requiring resolution from O(mm) brine-channel scales to O(m) mushy-layer dynamic scales. We present new, fully 3-dimensional numerical simulations of ice formation and convective brine rejection that model flow through a reactive porous ice matrix with evolving porosity. To accurately resolve the wide range of dynamical scales, our simulations exploit Adaptive Mesh Refinement using the Chombo framework. This allows us to integrate over several months of ice growth, providing insights into mushy-layer dynamics throughout the winter season. The convective desalination of sea ice promotes increased internal solidification, and we find that convective brine drainage is restricted to a narrow porous layer at the ice-ocean interface. This layer evolves as the ice grows thicker over time. Away from this interface, stagnant sea ice consists of a network of previously active brine channels that retain higher solute concentrations than the surrounding ice. We investigate the response of ice growth and brine drainage to varying atmospheric cooling conditions, and consider the potential implications for ice-ocean brine fluxes, nutrient transport, and sea ice ecology.

Previous studies indicate significant intraseasonal (20-90 days) variability on the Indonesian Throughflow (ITF) transport produced by the Madden-Julian Oscillation (MJO). These studies, however, mostly focus on the transport through each individual strait, especially Makassar strait, and overall impacts of the MJO on ITF transport are not well understood. This study examines the intraseasonal variability of ITF transport associated with the MJO, including the transport through multiple major straits (Makassar, Lombok, Ombai, Timor) in the Indonesian Seas using a new 1/12° global HYbrid Coordinate Ocean Model (HYCOM) reanalysis. The composite analyses of oceanic and atmospheric variables are performed for the period January 2004-December 2015, in which eighteen well-defined MJO events were identified. Consistent with previous studies, large intraseasonal variability of the Makassar Strait Throughflow is identified from the analysis. In addition, the contribution of anomalous ITF transport through other straits during both active and suppressed phase of the MJO for the total transport is quantified based on the composite analysis.

To better understand the mechanisms of crustal exhumation related to tectonic extension, we report on the progressive doming and detachment faulting of the Cretaceous Liaonan metamorphic core complex (MCC). The detachment fault zone of Liaonan MCC is comprised of two branches, i.e., the Jinzhou detachment fault zone (JDFZ) and the poorly-researched Dongjiagou shear zone (DSZ). Thus, integrated structural, microstructural, quartz c-axis fabrics, and fluid inclusion analysis, and U-Pb on zircon dating were performed on mylonites along the DSZ. In contrast with the JDFZ that possesses characteristics of detachment fault zone, the DSZ encompasses Archean gneisses and Neoproterozoic meta-sedimentary rocks, between which exists an obvious metamorphic contrast forming a tectonic discontinuity contact (TDC). However, rocks from both sides of the TDC possess structures and fabrics for identical geometries and kinematics that are consistent with those along the JDFZ. Thermometric analysis of fluid inclusions from syn-tectonic quartz veins (630 °C, 470 °C, 350 °C) and quartz c-axis fabric from mylonites along the DSZ show that the shearing penetrates throughout the Archean to Neoproterozoic rocks. Dating of zircons from syn-kinematic granitic dikes from DSZ yields an age ca. 134 Ma, which is similar to the ages of early shearing along the JDFZ (ca. 133~134 Ma). The results imply that the shearing initiated in both JDFZ and DSZ at an early stage, then progressive shearing continued, and finally developed the detachment faulting along the JDFZ. Based on the timing and processes of the regional extension, a geodynamic model of MCC’s is proposed.

Open water evaporation from reservoirs and lakes is becoming increasingly important for water management under a changing climate and increasing demands from growing populations. Remotely sensed evapotranspiration (ET) data have significantly advanced from MODIS to Landsat to ECOSTRESS. Here, we evaluate remotely sensed open water evaporation from NASA JPL’s ET data production team (e.g., ECOSTRESS) against in situ measurements of evaporation from multiple sites around the world.