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A classic conception held by many scientists is that their role is to produce and provide new and reliable information for use by the rest of society (public, decision-makers, media, etc). In the case of the ongoing climate and ecological crisis, this has been the dominant stance of many scientific actors, including the IPCC and IPBES. It has resulted in producing and making available syntheses of scientific results both on the “natural” processes and “societal” impacts. The relevance of this conception has been seriously challenged through decades of mismatch between expected and observed translation of scientific communication regarding the ongoing crisis into policy-relevant mitigation measures. At the same time, the urgency of current climate and ecological crisis calls more than ever for actionable science with a deep and immediate impact on society.Effective communication requires that the recipients of knowledge (i) are able to understand, (ii) want to understand, and (iii) are not distracted by contradictory information (Oreskes, 2022). Most of the effort on science communication has focused on (i), ignoring that conditions (ii) and (iii) are often not met. Other cognitive or psychological issues with important political implications must also be carefully pondered, most notably the fact that popularity or acceptability of a discourse is judged by the public in relation to other discourses, and not in absolute terms, (e.g., Overton window, Simpson et al., 2022) and in relation to the position of the communicator (such as emotional state and personal actions in relation the message, e.g., Attari et al., 2019).Here we contend that scientists joining environmental activist groups, including engaging in direct actions of civil disobedience, have the potential to enhance effective scientific communication on several levels. Indeed, scientists taking their share of discomfort and even breaking the law, is a strong signal of the emotional involvement of the scientists, of the magnitude of the crisis (e.g., the latter largely dwarfs the risk of receiving judiciary sanctions) and of the need to revise the interactions between science, media and politics. In addition to making more acceptable or even legitimizing more moderate ways of communication, such radical propositions of engagement may also raise media attention and therefore audience and support in the general public (Capstick et al., 2022).We review recent non-violent actions involving scientists, and then discuss the complementary/synergistic aspects that such disobedience and related direct actions bring to the spectrum of scientific outreach, as a renewed way of communication and dissemination, especially about urgent challenges. Besides, the question of its complementarity with common ways (process of peer review, consolidation of scientific knowledge before dissemination at the University) is also evaluated. The targeted strategy may not replace the "ancient system" with a new one but rather lead to the development of a new system aimed at reinforcing the efficiency of the existing ones.ReferencesAttari, S. Z., et al., Climatic Change, 154, 529–545, https://doi.org/10.1007/s10584-019-02463-0, 2019. Capstick, S., et al., Nat. Clim. Chang., 12, 773–774, https://doi.org/10.1038/s41558-022-01461-y, 2022. Oreskes, N., Proc.Indian Natl. Sci. Acad., 88, 824–828, https://doi.org/10.1007/s43538-022-00121-1, 2022.

The current state of the climate and environmental crisis calls for science to be able to have a deep impact on society, and to have it quickly. Here we propose to discuss how scientists engaging in climate activism can contribute to educating the general public and press for urgent action, as well as under which conditions such scientific activism can be most effective. The classical way science has been interacting with society has mostly consisted in making scientific results public, without interfering in how politicians, business and the general public would make use of them. Similarly, the role of science educators has been often limited to spreading knowledge to students and broader audiences, independently from how this knowledge affects society. However, such a dynamic is clearly not enough for nowadays climate and environmental science education. Despite an overwhelming scientific consensus about the trajectory of the Earth’s climate and about what is going to happen in the coming decades unless humanity drastically changes its use of natural resources and cuts greenhouse gases emission, too little is still happening. As a result, many scientists, both within and outside academia, have been looking for other ways to communicate the urgency of the climate crisis, including outreach to policy makers and the general public. Notably, communication efforts have been increasingly extending to the public support of environmental action movements and the joining of protests and civil disobedience actions. Since it is good practice to adapt educational methods to both the audience and the message, we argue that activism can be seen as the result of a search for methods that produce viable results and the desired impact on society. Using recent examples of civil disobedience by scientists, including actions we joined and/or supported in national or international groups, we discuss how such activism can be complementary to classical approaches to public education about the urgency of the climate and environmental crisis. We also present the reception and reaction from other actors (politicians, companies) and how such actions are received, supported or criticized by the scientific community. We specifically discuss the relation between activism and the broader scientific community, since we believe that scientific activism can only become an efficient way to communicate science and enhance policy-makingif (i) it finds a way to be accepted and respected within the scientific community, and (ii) it follows some rules allowing such communication to maintain (or ideally increase) scientific reputation and position in the broader society. We also stress the important role of universities and research institutes in making possible, especially for early career scientists, to engage in such activism. Scientific institutions need to make clear that climate activism and advocacy is welcome among both researchers and teachers, that their freedom of speech is protected, and that such activities are recognized as valuable. Finally, we will show some examples of how scientists engaging in climate action can build networks of support, contribute to normalizing such activism in the scientific community, and valorise this form of engagement.

A devastating tsunami struck Palu Bay in the wake of the 28 September 2018 Mw = 7.5 Palu earthquake (Sulawesi, Indonesia). With a predominantly strike-slip mechanism, the question remains whether this unexpected tsunami was generated by the earthquake itself, or rather by earthquake-induced landslides. In this study we examine the tsunami potential of the co-seismic deformation. To this end, we present a novel geodetic data set of Global Positioning System and multiple Synthetic Aperture Radar-derived displacement fields to estimate a 3D co-seismic surface deformation field. The data reveal a number of fault bends, conforming to our interpretation of the tectonic setting as a transtensional basin. Using a Bayesian framework, we provide robust finite fault solutions of the co-seismic slip distribution, incorporating several scenarios of tectonically feasible fault orientations below the bay. These finite fault scenarios involve large co-seismic uplift (>2 m) below the bay due to thrusting on a restraining fault bend that connects the offshore continuation of two parallel onshore fault segments. With the co-seismic displacement estimates as input we simulate a number of tsunami cases. For most locations for which video-derived tsunami waveforms are available our models provide a qualitative fit to leading wave arrival times and polarity. The modeled tsunamis explain most of the observed runup. We conclude that co-seismic deformation was the main driver behind the tsunami that followed the Palu earthquake. Our unique geodetic data set constrains vertical motions of the sea floor, and sheds new light on the tsunamigenesis of strike-slip faults in transtensional basins.

Stall-Induced Vibrations (SIV) are an important design consideration for wind turbine blade design, especially for large, modern, wind turbines with highly flexible blades. Their severity depends on both the inflow and the structural characteristics of the blades. Studying SIV has a high computational cost, because it requires high-fidelity aeroelastic simulations, and potentially a large number of input variables. In an effort to reduce the computational cost of the domain exploration, in this work we have adopted a Surrogate-Based Optimization (SBO) framework. This way, the combination of input variables that lead to SIV can be explored with the minimum number of aeroelastic simulations. The proposed SBO framework can use any type of surrogate model, and leverages Delaunay triangulation to iteratively select samples to refine the surrogate model. The occurrence and severity of SIV on the IEA 10MW turbine is studied in a five variables space consisting of: wind speed, yaw angle, vertical wind shear, wind veer, and atmospheric temperature. A well-trained surrogate model is developed and used to predict the damping ratio of the first blade edgewise mode in the entire inflow space at a reduced computational cost. Sensitivity analysis of the predicted damping ratio shows that yaw angle is the most influential variable, while temperature is the least influential variable in terms of inflow conditions that can lead to the occurrence of SIV. Inflow conditions with a moderate yaw angle (around 10–25 deg), high wind speeds, and moderate to high negative veer are found to lead to severe SIV. This study should serve as a guiding tool to decide the scope of the more computationally expensive simulations such as high-fidelity CFD-based aeroelastic simulations which can provide a more accurate description of SIV.

Land ice discharge from the Antarctic continent into the ocean is restrained by ice shelves, floating extensions of grounded ice that buttress the glacier outflow. The ongoing thinning of these ice shelves – largely due to enhanced melting at their base in response to global warming – is known to accelerate the release of glacier meltwater into the world oceans, augmenting global sea level. Mechanisms of ocean heat intrusion under the ice base are therefore crucial to project the future of Antarctic ice shelves. Furthermore, ice shelves are weakened by the presence of kilometer-wide full-thickness ice rifts, which are observed all around Antarctica. However, their impact on ocean circulation around and below ice shelves has been largely unexplored as ocean models are commonly characterized by resolutions that are too coarse to resolve their presence. Here, we apply the Massachusetts Institute of Technology general circulation model at high resolution to investigate the sensitivity of sub-shelf ocean dynamics and ice-shelf melting to the presence of a kilometer-wide rift in proximity of the ice front. We find that (a) the rift curtails water and heat intrusion beneath the ice-shelf base and (b) the basal melting of a rifted ice shelf is on average 20 % lower than for an intact ice shelf under identical forcing. Notably, we calculate a significant reduction in melting rates of up to 30 % near the grounding line of a rifted ice shelf. We therefore posit that rifts and their impact on the sub-shelf dynamics are important to consider in order to accurately reproduce and project pathways of heat intrusion into the ice-shelf cavity.

Stall Induced Vibrations (SIV) are an important design consideration for wind turbine blade design, especially for large, modern wind turbines which require long and flexible blades. Their severity depends on the inflow conditions, and structural characteristics of the blade, and the study of the parameter space that leads to SIV has a high computational cost due to the aeroelastic simulations involved, and the cost increases drastically with increasing number of variables to be studied. Given the computationally expensive nature of the problem, in this work, a Surrogate-Based Optimization (SBO) framework which uses surrogate models as an alternative to the high fidelity simulations is proposed to explore the behaviour of SIV. The proposed framework is not specific to any type of surrogate model and uses Delaunay Triangulation to iteratively select samples to refine the surrogate model. The framework is demonstrated to study the occurrence and severity of SIV on the IEA 10MW turbine in a five variable inflow space consisting of wind speed, yaw angle, vertical wind shear, wind veer, and atmospheric temperature. Using the proposed framework, a well-trained surrogate model is developed and used to predict the damping ratio of the first blade edgewise mode in the entire inflow space at a reduced computational cost. Sensitivity analysis of the predicted damping ratio shows that yaw angle is the most influential variable, while temperature is the least influential variable in terms of inflow conditions that can lead to occurrence of SIV. Inflow conditions with a moderate yaw angle (around 15–20 deg), high wind speeds, and moderate to high negative veer are found to lead to severe SIV. This framework is expected to serve as a guiding tool to decide the scope of the more computationally expensive simulations such as high fidelity CFD-based aeroelastic simulations which can provide a more accurate description of SIV.

Illumination estimation is the essential step of computational color constancy, one of the core parts of various image processing pipelines of modern digital cameras. Having an accurate and reliable illumination estimation is important for reducing the illumination influence on the image colors. To motivate the generation of new ideas and the development of new algorithms in this field, two challenges on illumination estimation were conducted. The main advantage of testing a method on a challenge over testing it on some of the known datasets is the fact that the ground- truth illuminations for the challenge test images are unknown up until the results have been submitted, which prevents any potential hyperparameter tuning that may be biased. The First illumination estimation challenge (IEC#1) had only a single task, global illumination estimation. The second illumination estimation challenge (IEC#2) was enriched with two additional tracks that encompassed indoor and two-illuminant illumination estimation. Other main features of it are a new large dataset of images (about 5000) taken with the same camera sensor model, a manual markup accompanying each image, diverse content with scenes taken in numerous countries under a huge variety of illuminations extracted by using the SpyderCube calibration object, and a contest- like markup for the images from the Cube++ dataset. This article focuses on the description of the past two challenges, algorithms which won in each track, and the conclusions that were drawn based on the results obtained during the first and second challenge that can be useful for similar future developments.

The uncertainty afflicting modal parameter estimates stems from e.g., the finite data length, unknown, or partly measured inputs and the choice of the identification algorithm. Quantification of the related errors with the statistical Delta method is a recent tool, useful in many modern modal analysis applications e.g., damage diagnosis, reliability analysis, model calibration. In this paper, the Delta method-based uncertainty quantification methodology is validated for obtaining the uncertainty of the modal parameter and the modal indicator estimates in the context of several well-known subspace identification algorithms. The focus of this study is to validate the quality of each Delta method-based approximation with respect to the experimental Monte Carlo distributions of parameter estimates using a statistical distance measure. On top of that, the accuracy in obtaining the related confidence intervals is empirically assessed. The case study is based on data obtained from an extensive experimental campaign of a large scale wind turbine blade tested in a laboratory environment. The results confirm that the Delta method is, on average, adequate to characterize the distribution of the considered estimates solely based on the quantities obtained from one data set, validating the use of this statistical framework for uncertainty quantification in practice.

Secular GNSS velocities on the overriding plate have been observed to change after several megathrust earthquakes (2003 Tokachi-oki, 2007 Bengkulu, 2010 Maule, 2011 Tohoku-oki, 2012 Oaxaca, 2014 Iquique). In particular, landward velocities are larger than before the earthquake in regions laterally adjacent to the ruptured zone, as close as 300–500 km along-trench from the centroid. Previous explanations of this enhanced landward motion invoked either increased slip deficit accumulation or overriding plate bending during postseismic relaxation; the mechanism is relevant for seismic hazard. We investigate whether plate bending alone – driven by afterslip and/or viscous relaxation – is likely to occur and can reproduce the observed patterns of velocity changes. We use 3D quasi-dynamic finite element models with periodic earthquakes.We find that rapid afterslip in the shear zone downdip of the brittle megathrust, at depths greater than 40 km, produces only enhanced trenchward surface motion in the overriding plate. Bulk viscous relaxation in the mantle wedge does produce enhanced landward motion, although only when afterslip in the deep shear zone is spatially restricted by imposing a constant shear rate beyond a certain depth (75–150 km in our models). This landward motion indeed is a consequence of in-plane bending and shortening of the overriding plate. However, this modeled landward velocity change is one order of magnitude lower than observed, decays , and , resulting in no net enhanced landward motion. These findings are robust with respect to variations in mantle viscosity, plate elasticity, maximum afterslip depth and earthquake size. We thus conclude that plate bending probably occurs, but cannot explain the observed lateral landward velocity changes. The observed enhanced landward motion in the laterally adjacent regions of the subduction zone consequently reflect true local slip deficit accumulation at a faster rate than before the earthquake, whether because of transient slab acceleration or because of frictional changes on the megathrust. The implication is a greater seismic hazard in those lateral regions.

The Celebes Sea subducts beneath the North Arm of Sulawesi, Indonesia, at the Minahassa trench. Over the past three decades, only a few Mw>7 earthquakes ruptured this plate interface, despite a 40 mm/yr convergence rate. The left-lateral Palu-Koro fault delineates the extent of the overriding plate at the western termination of the Minahassa subduction zone and hosted a Mw7.5 earthquake in September 2018. Observations of post-seismic surface motion following the 2018 event were interpreted in a previous study to result from afterslip that extended underneath the co-seismic rupture plane. A mismatch between observed post-seismic surface motions and predictions from afterslip distributions remained at the North Arm of Sulawesi. In this study we revisit and reprocess the GNSS observations in NW Sulawesi. We analyse the post-2018 time series to determine whether the post-seismic signal can be ascribed to a single source. This is not the case, as we detect another, yet smaller amplitude signal. We take a Bayesian approach and find that this smaller magnitude signal corresponds to slow slip on the Minahassa subduction interface. This delayed-triggered, (apparently aseismic) slow slip event occurred just east of the 1996 Mw7.9 megathrust rupture. The 20-year long time series is characterized by four additional periods of transient surface motion. Three of these periods are likely the result of distinct slow slip events and one is a post-seismic signal from the 2008 subduction Mw7.4 earthquake. The presumed slow slip events generally take more than 300 days to quiet down again with a recurrence interval of about five years.

Global mean sea-level rise (SLR) has accelerated since 1900 from less than 2 mm/year during most of the century to more than 3 mm/year since 1993. At the regional scale, detection of an acceleration in SLR is difficult, because the long-term sea-level signal is obscured by large inter-annual variations with multi-year trends that are easily one order of magnitude larger than global mean values. Here, we developed a time series approach to determine whether regional SLR is accelerating based on tide gauge data. We applied the approach to eight 100-year records in the southern North Sea and detected, for the first time, a common breakpoint in the early 1990s. The mean SLR rate at the eight stations increases from 1.7±0.3 mm/year before the breakpoint to 2.7±0.4 mm/year after the breakpoint (95% confidence interval), which is unprecedented in the regional instrumental record. These findings are robust provided that the record starts before 1970 and ends after 2015.

GIA is a global process, because of gravitational effects, its interplay with earth rotation, and the large spatial extent of ice-sheet and ocean loading. However, mainly due to the presence of heterogeneities in the structure of crust and upper mantle, modelling of GIA signals often requires a regional approach. This is particularly true in the light of continuous advances in earth observation techniques, that allow increasingly accurate determination of land deformation, coastal sea level change, and mass balance of glaciers and ice sheets.This talk will address a number of open issues related to regional GIA models, such as the effect of transient and non-linear rheologies, and the complementary role of forward and semi-empirical approaches, with an eye on the needs of the geodetic, sea level and cryosphere communities.

Objectives: Evidences from either small series or spontaneous reporting are accumulating that SARS-CoV-2 involves the Nervous Systems. The aim of this study is to provide an extensive overview on the major neurological complications in a large cohort of COVID-19 patients. Methods: Retrospective, observational analysis on all COVID-19 patients admitted from February 23rd to April 30th, 2020 to ASST Papa Giovanni XXIII, Bergamo, Italy for whom a neurological consultation/neurophysiological assessment/neuroradiologic investigation was requested. Each identified neurologic complication was then classified into main neurologic categories. Results: Of 1760 COVID-19 patients, 137 presented neurologic manifestations that manifested after COVID-19 symptoms in 98 pts and was the presenting symptom in 39. Neurological manifestations were classified as: (a) cerebrovascular disease [53 pts (38.7%)] including 37 ischemic and 11 haemorrhagic strokes, 4 transient ischemic attacks, 1 cerebral venous thrombosis; (b) peripheral nervous system diseases [31 (22.6%)] including 17 Guillain–Barrè syndromes; (c) altered mental status [49 (35.8%)] including one necrotizing encephalitis and 2 cases with RT-PCR detection of SARS-Cov-2 RNA in CSF; (d) miscellaneous disorders, among whom 2 patients with myelopathy associated with Ab anti-SARS-CoV-2 in CSF. Patients with peripheral nervous system involvement had more frequently severe ARDS compared to patients with cerebrovascular disease (87.1% vs 42%; difference = 45.1% 95% CI 42.0–48.2; χ2= 14.306; p < 0.0002) and with altered mental status (87.1% vs 55.6%; difference = 31.5% 95% CI 27.5–37.5%; χ2= 7.055; p < 0.01). Conclusion: This study confirms that involvement of nervous system is common in SARS-CoV-2 infection and offers clinicians useful information for prevention and prompt identification in order to set the adequate therapeutic strategies.

The effect of glacial isostatic adjustment (GIA) on the shape and gravity of the Earth is usually described by numerical models that solve for both glacial evolution and Earth's rheology, being mainly constrained by the geological evidence of local ice extent and globally distributed sea level data, as well as by geodetic observations of Earth's rotation. In recent years, GPS and GRACE observations have often been used to improve those models, especially in the context of regional studies. However, consistency issues between different regional models limit their ability to answer questions from global-scale geodesy. Examples are the closure of the sea level budget, the explanation of observed changes in Earth's rotation, and the determination of the origin of the Earth's reference frame. Here, we present a global empirical model of present-day GIA, solely based on GRACE data and on geoid fingerprints of mass redistribution. We will show how the use of observations from a single space-borne platform, together with GIA fingerprints based on different viscosity profiles, allows us to tackle the questions from global-scale geodesy mentioned above. We find that, in the GRACE era (2003–2016), freshwater exchange between land and oceans has caused global mean sea level to rise by 1.2±0.2 mm yr−1, the geocentre to move by 0.4±0.1 mm yr−1, and the Earth's dynamic oblateness (J2) to increase by 6.0±0.4×10-11 yr−1.

Ocean mass change is one of the main drivers of present-day sea-level change (SLC). Also known as barystatic SLC, it is driven by the exchange of freshwater between the land and the ocean, such as melting of continental ice from glaciers and ice sheets, and variations in land water storage. While many studies have quantified the present-day barystatic contribution to global mean SLC, fewer works have looked into regional changes. This study provides a comprehensive analysis of regional barystatic SLC trends since 1993 (the satellite altimetry era), with a focus on the uncertainty budget. We consider three types of uncertainties: intrinsic (the uncertainty from the data/model itself); temporal (related to the temporal variability in the time series); and spatial-structural (related to the location/distribution of the mass change sources). We collect a range of estimates for the individual freshwater sources, which are used to compute regional patterns (fingerprints) of barystatic SLC and analyse the different types of uncertainty. When all the contributions are combined, we find that the barystatic sea-level trends regionally ranges from −0.43 to 2.55 mm year−1 for 2003–2016, and from −0.39 to 2.00 mm year−1 for 1993–2016, depending on the choice of dataset. When all types of uncertainties from all contributions are combined, the total barystatic uncertainties regionally range from 0.62 to 1.29 mm year−1 for 2003–2016, and from 0.35 to 0.90 mm year−1 for 1993–2016, also depending on the dataset choice. We find that the temporal uncertainty dominates the budget, although the spatial-structural also has a significant contribution. On average, the intrinsic uncertainty is almost negligible. The main source of uncertainty is the temporal uncertainty from the land water storage contribution, which is responsible for at least 50 % of the total uncertainty, depending on the region of interest. The second main contributions come from the spatial-structural uncertainty from Antarctica and land water storage, which show that different locations of mass change can lead to trend deviations larger than 20 %. As the barystatic SLC contribution and its uncertainty vary significantly from region to region, better insights into regional SLC are important for local management and adaptation planning.

In the future of Ancillary Services for the HV grid, Demand Side Response (DSR) will play an increasingly important role to ensure grid stability and promote Renewable Energy Sources integration in the electrical system. A particular use case of the Italian Demo of the H2020 project “Optimal System-Mix Of flexibility Solutions for European electricity” (OSMOSE) is to demonstrate multiple grid services provision based on DSR by seven industrial plants distributed in a HV grid area between Apulia and Basilicata. Sites have been managed by three Balance Service Providers (BSPs). On each industrial plant, project partners first have performed an energy audit and then they have installed all the electric and TLC equipment needed to test and manage the flexibilities identified. The main result of these activities was that the hardware required for DSR comes at a relatively small price compared to the magnitude of loads that could be controlled. Purpose of this work is to provide an analysis of possible benefits and limits of DSR for the grid as well as to direct a possible new future market strategy for these resources.

Satellite radar altimetry has been providing estimates of global mean sea level (GMSL) since 1992. The early TOPEX record originates from two identical instruments, which requires the estimation of an intermission bias and careful handling of the problematic first part of the record. Calibration of TOPEX is crucial to obtain a continuous and consistent record, which is needed to quantify any recent acceleration. We propose a novel approach to calibrate TOPEX altimeter data using sea surface height differences at crossovers of TOPEX and ERS. Tide gauges are only used to determine a drift in one of the two datasets. We provide a new and more accurate estimate of the intra-mission bias, which leads to a much reduced GMSL acceleration over the whole record. Hence, the conundrum of an uncertain GMSL acceleration from altimetry is still unsolved, in spite of recent opposite claims, and in contrast to the expected effect of ocean warming and continental freshwater fluxes.

We present a new approach to estimate time variations in J2. Those variations are represented as the sum of contributions from individual sources. This approach uses solely Gravity Recovery And Climate Experiment (GRACE) data and the geoid fingerprints of mass redistributions that take place both at the surface and in the interior of the solid Earth. The results agree remarkably well with those based on satellite laser ranging, while estimates of the sources explain the observed variations in J2. Seasonal variations are dominated by terrestrial water storage and by mass redistribution in the atmosphere and ocean. Trends, however, are primarily controlled by the Greenland and Antarctic ice sheets and by glacial isostatic adjustment. The positive trend from surface mass variations is larger than the negative trend due to glacial isostatic adjustment and leads to an overall rising trend during the GRACE period (2002–2017).

A parked wind turbine can be subjected to large yaw angles, which causes vortex shedding. Under some particular inflow conditions, the interaction between the shed vorticity and the blade structure could lead to Vortex-Induced Vibrations (VIV). VIV are an instability where the response grows until it reaches a limit cycle oscillation. In this paper, we will focus on this last part of the response. We will see that the shedding makes the aeroelastic system linear time-periodic, and study its stability with Floquet theory. We will use high-fidelity simulations of different inflow conditions, and quantify the stability of the system using a model-free approach.

Stall Induced Vibrations (SIV) are an aeroelastic instability that might happen when large portions of the wind turbine blade operate in moderate stall, which leads to high internal loads that can damage the structure. Exploring the inflow space that cause SIV has a high computational cost, which quickly increases with the number of input variables, since it involves high-fidelity aeroelastic simulations. In this work, a surrogate model is used to effectively explore the behavior of SIV in a five variable inflow space consisting of wind speed, yaw angle, vertical wind shear, wind veer, and atmospheric temperature. The surrogate model, trained from the results of a few aeroelastic simulations, predicts the severity of SIV for a given inflow condition. The surrogate model is chosen by comparing the performance of a few common model types, and Artificial Neural Networks (ANN) are found to provide a good balance between accuracy and computational time. Using the ANN, the occurrence and severity of SIV in the inflow space is studied. The analysis shows that for the turbine studied, yaw angle is the most influential variable, while temperature is the least influential variable in terms of conditions that lead to occurrence of SIV. Inflow conditions with a moderate yaw angle (around 10-25 deg), high wind speeds, and high negative veer are found to be the most critical in terms of severity of SIV. The current work is expected to serve as a helping tool to decide the focus of computationally expensive simulations such as high fidelity CFD based aeroelastic simulations.

This study focusses on improved constraint of the millennial time-scale glacial isostatic adjustment (GIA) signal at present-day, and its role as a contributor to present-day sea-level budgets. The study area extends from the coastal regions of northern Europe to Scandinavia. Both Holocene relative sea level (RSL) data as well as vertical land motion (VLM) data are incorporated as constraints in a semi-empirical GIA model. Specifically, 71 geological rates of GIA-driven RSL change are inferred from Holocene proxy data. Rates of vertical land motion from GNSS at 108 sites provide an additional measure of regional GIA deformation; within the study area, the geological RSL data complement the spatial gaps of the VLM data and vice versa. Both datasets are inverted in a semi-empirical GIA model to yield updated estimates of regional present-day GIA deformations. A regional validation is presented for the North Sea, where the GIA signal may be complicated by lateral variations in Earth structure and existing predictions of regional and global GIA models show discrepancies. The model validation in the North Sea region suggests that geological data are needed to fit independent estimates of GIA-related RSL change inferred from tide gauge rates, indicating that geological rates from Holocene data can provide an important additional constraint for data-driven approaches to GIA estimation. The geological proxy rates therefore provide a unique dataset with which to complement or validate existing data-driven approaches that use satellite era rates of change.

In Southeast Alaska, extreme uplift rates are primarily caused by glacial isostatic adjustment (GIA), as a result of ice load changes from the Little Ice Age to the present combined with a low viscosity asthenosphere. Current GIA models adopt a one-dimensional (1-D) stratified Earth structure. However, the actual (3-D) structure is more complex due to the presence of a subduction zone and the transition from a continental to an oceanic plate. A simplified 1-D Earth structure may not be an accurate representation in this region and therefore affect the GIA predictions. In this study we will investigate the effect of 3-D variations in the shallow upper mantle viscosity on GIA in Southeast Alaska. In addition, investigation of 3-D variations also gives new insight into the most suitable 1-D viscosity profile.We test a number of models using the finite element software ABAQUS. We use shear wave tomography and mineral physics to constrain the shallow upper mantle viscosity structure. We investigate the contribution of thermal effects on seismic velocity anomalies in the upper mantle using an adjustable scaling factor, which determines what fraction of the seismic velocity variations are due to temperature changes, as opposed to non-thermal causes. We search for the combination of the scaling factor and background viscosity that best fits the GPS data. Results show that relatively small lateral variations improve the fit with a best fit background viscosity of 5.0×1019 Pa s, resulting in viscosities at ~80 km depth that range from 1.8×1019 to 4.5×1019 Pa s.

Ocean mass variation is one of the main drivers of present-day sea-level change (SLC). Also known as barystatic SLC, those fluctuations are due to the melting of continental ice from glaciers and ice sheets, and variations in landwater storage. While a large number of studies have quantified the contribution of barystatic SLC to global mean SLC, fewer works have looked into how much ocean mass has contributed to regional SLC. Besides, most of the regional studies have focused only on the effect of one of the components (e.g., melt from Antarctica), or on the period and results of the GRACE satellite mission (since 2002). This work aims at providing a comprehensive analysis of global and regional barystatic SLC since 1993. For that, we collect a suite of estimates of the individual freshwater sources, namely the Antarctic and Greenland ice sheets, glaciers and terrestrial water storage. We then use them as input on the sea-level equation to obtain regional patters (fingerprints) of barystatic SLC, and validate our results by comparing the individual estimates with the values obtained from GRACE products. We finalize our analysis by looking into trend uncertainty patterns related to each contribution.

The 2018 Mw 7.5 Palu earthquake is a remarkable strike-slip event due to its nature as a shallow supershear fault rupture across several segments and a destructive tsunami that followed co-seismic deformation. GPS offsets in the wake of the 2018 earthquake display a transient in the surface motions of northwest Sulawesi. A Bayesian approach identifies (predominantly a-seismic) deep afterslip on and below the co-seismic rupture plane as the dominant physical mechanism causing the cumulative, post-seismic, surface displacements whereas viscous relaxation of the lower crust and poro-elastic rebound contribute negligibly. We confirm a correlation between shallow supershear rupture and post-seismic surface transients with afterslip activity in the zone below an inter-seismically locked fault plane where the slip rate tapers from zero to creeping.

We present a method for illuminant estimation that exploits a generative adversarial network architecture to generate a spatially-varying illuminant map. This map is then transformed by consensus into a global illuminant estimation, in the form of a single RGB triplet. To this end, different consensus strategies are designed and compared in this paper. The best solution won second place in the 2nd International Illumination Estimation Challenge, specifically for the indoor track.

SUMMARYIn this study, we focus on improved constraint of the glacial isostatic adjustment (GIA) signal at present-day, and its role as a contributor to present-day sea level budgets. The main study area extends from the coastal regions of northwestern Europe to northern Europe. Both Holocene relative sea level (RSL) data as well as vertical land motion (VLM) data are incorporated as constraints in a semi-empirical GIA model. 71 geological rates of GIA-driven RSL change are inferred from Holocene proxy data and 108 rates of vertical land motion from GNSS provide an additional measure of regional GIA deformation. Within the study area, the geological RSL data complement the spatial gaps of the VLM data and vice versa. Both data sets are inverted in a semi-empirical GIA model to yield updated estimates of regional present-day GIA deformations. A regional validation using tide gauges is presented for the North Sea, where the GIA signal may be complicated by lateral variations in Earth structure and existing predictions of regional and global GIA models show discrepancies. The model validation in the North Sea region suggests that geological data are needed to fit independent estimates of GIA-related RSL change inferred from tide gauge rates, indicating that geological rates from Holocene data do provide an important additional constraint for data-driven approaches to GIA estimation.

The 2018 (Formula presented.) Palu earthquake is a remarkable strike-slip event due to its nature as a shallow supershear fault rupture across several segments and a destructive tsunami that followed coseismic deformation. GPS offsets in the wake of the 2018 earthquake display a transient in the surface motions of northwest Sulawesi. A Bayesian approach identifies (predominantly aseismic) deep afterslip on and below the coseismic rupture plane as the dominant physical mechanism causing the cumulative, postseismic, surface displacements whereas viscous relaxation of the lower crust and poro-elastic rebound contribute negligibly. We confirm a correlation between shallow supershear rupture and postseismic surface transients with afterslip activity in the zone below an interseismically locked fault plane where the slip rate tapers from zero to creeping.

Recent studies disagree about the contribution of variations in temperature and salinity of the oceans—steric change—to the observed sea-level change. This article explores two sources of uncertainty to both global mean and regional steric sea-level trends. First, we analyze the influence of different temperature and salinity data sets on the estimated steric sea-level change. Next, we investigate the impact of different stochastic noise models on the estimation of trends and their uncertainties. By varying both the data sets and noise models, the global mean steric sea-level trend and uncertainty can vary from 0.69 to 2.40 and 0.02 to 1.56 mm/year, respectively, for 1993–2017. This range is even larger on regional scales, reaching up to 30 mm/year. Our results show that a first-order autoregressive model is the most appropriate choice to describe the residual behavior of the ensemble mean of all data sets for the global mean steric sea-level change over the last 25 years, which consequently leads to the most representative uncertainty. Using the ensemble mean and the first-order autoregressive noise model, we find a global mean steric sea-level change of 1.36 ± 0.10 mm/year for 1993–2017 and 1.08 ± 0.07 mm/year for 2005–2015. Regionally, a combination of different noise models is the best descriptor of the steric sea-level change and its uncertainty. The spatial coherence in the noise model preference indicates clusters that may be best suited to investigate the regional sea-level budget.

PyWake isan AEP calculator for wind farms implemented in Python including a collection of wake models.

The break-up of large ice shelves and the associated loss of ice are thought to play a destabilizing role in the ice sheet dynamics. Although ice shelves are a substantial buttressing source in the stability of continental ice sheets, the propagation of large rifts eventually leads to the break-up of icebergs into the ocean. As consequence, this loss of ice would trigger further glacier acceleration and ice sheets retreat, destabilizing the ice cap. Retreat and collapse of ice sheets are also thought to be related to regional climate warming. Indeed, satellite observations suggest that a warming surrounding would induce the ice sheet to progressive thinning and weakening.The prolongation of un-grounded ice into the ocean is often interrupted by the propagation of fractures that eventually separates large icebergs from the ice shelf. These fractures are called rifts and range from dimensions of 10 to 100 km. A recent example of such phenomena is the massive break-up of the Larsen C in July, 2017 which followed the disintegration of Larsen A in 1995 and the partial break-up of Larsen B in 2002. The tabular iceberg formed by Larsen C was limited by the propagation of a large rift that began in summer 2016, although the ice shelf had already been thinning since 1992.Rift initiation and propagation are thought to be the result of glaciological and oceanographic sources that trigger ice to break. Nonetheless, exact mechanisms remain elusive. The on-going project focuses on ice-ocean interactions in ice shelves that accommodate rifts by using oceanographic models. The goal is to couple rift propagation and ocean circulation underneath ice cavities in order to infer how basal melting affects the development of rifts. The numerical framework is developed within the capabilities of the MITgcm. We aim to identify the sensitivity of propagation rate and opening rate of rifts to variations in the ocean circulation that have occurred during the separation of part of the ice shelf.On a larger scale, we are interested in the role of rifting in the stability of Antarctic shelves. Therefore, we work toward a better understanding of which processes are involved in the triggering of rift propagation.

In this study, we focus on better constraint of the long term glacial isostatic adjustment (GIA) signal at present-day, and its role as a contributor to total present-day rates of change. The main study area extends from the coastal regions of northern Europe to Scandinavia. Both Holocene relative sea level (RSL) data as well as vertical land motion (VLM) data are incorporated as constraints in a semi-empirical GIA model. Specifically, 70 geological rates of GIA-driven RSL change are inferred from Holocene data; peak RSL fall is indicated in central Scandinavia and the northern British Isles where past ice sheets were thickest, RSL rise is indicated in the southern British Isles and along the northern European coastline. Rates of vertical land motion from GPS at 108 sites provide an additional measure of regional GIA deformation. Within the study area, the geological RSL data complement the spatial gaps of the VLM data and vice versa; both datasets are inverted in a semi-empirical GIA model to yield updated estimates of regional present-day GIA deformations. A regional validation is presented for the North Sea, where the GIA signal may be complicated by lateral variations in Earth structure and existing predictions of regional and global GIA models are discrepant. The model validation in the North Sea region indicates that geological data are needed to fit independent estimates of GIA-related RSL change inferred from tide gauge rates, suggesting that the geological rates provide an important additional constraint of present-day GIA.

Two major fault systems host Mw>7 earthquakes in Central and Northern Sulawesi, Indonesia: the Minahassa subduction interface and the Palu-Koro strike-slip fault. The Celebes Sea oceanic lithosphere subducts beneath the north arm of Sulawesi at the Minahassa subduction zone. At the western termination of the Minahassa subduction zone, it connects to the left-lateral Palu-Koro strike-slip fault zone. This fault strikes onshore at Palu Bay and then crosses Sulawesi. Interseismic GNSS velocities indicate that the Palu-Koro fault zone accommodates about 4 cm/yr of relative motion in the Palu Bay area, with a ~10 km locking depth. This shallowly locked segment of the Palu-Koro fault around the Palu Bay area ruptured during the devastating, tsunami-generating, 2018 Mw7.5 Palu earthquake. This complex event highlights the high seismic hazard for the island of Sulawesi.We have a >20-year record of GNSS velocities on Sulawesi, where the densest cluster of monument sites surrounds the Palu-Koro fault, specifically around Palu Bay, whereas the rest of the island is less densely covered. High quality estimates of interseismic velocities reveal second-order complex patterns of transient deformation in the wake of major earthquakes: the velocities in northern Sulawesi and around the Palu-Koro fault do not follow their interseismic trends after a major subduction earthquake has occurred, for several years after the event. This effect of transient deformation reaches more than 400km away from the epicentre of the major earthquakes. Surprisingly, a deviation from the background slip rate on the Palu-Koro fault is not accompanied by a deviation from the background (micro)seismic activity.We construct a 3D numerical model based on the structural and seismological data in the Sulawesi region. We investigate the post-seismic relaxation pattern from a subduction earthquake and determine whether the slip rate on the Palu-Koro fault changes due to this earthquake through forward model calculations. With a modelling focus on the 1996 Mw7.9 and 2008 Mw7.4 earthquakes that ruptured the Minahassa subduction interface, this study outlines the triggering of transient deformation and continual interaction between the Minahassa subduction interface and the Palu-Koro strike-slip fault.

Tide gauges are the main source of information about sea-level changes in the Industrial Age. When looking at global mean values, century-long reconstructions produce rates between 1-2 mm/yr, while estimates over the last three decades reveal a much faster rise of about 3 mm/yr, as also indicated by satellite altimetry observations. In spite of this evidence for a recent acceleration, its quantification remains a challenging and relevant task, because results are highly dependent on the length of the record and on the reconstruction technique, whereas decision makers require clear proof to legitimise action.While global mean results are very important to understand climate change, regional to local variations are more relevant for the purpose of planning mitigation and adaptation measures. However, mainly due to natural variability, looking at individual tide gauge stations hampers the accurate determination of linear and non-linear trends.We analyse tide gauge records along the Dutch coast by means of advanced statistical techniques, with the main objective of determining whether and under which conditions it is possible to detect departures from secular trends. We particularly focus on how to handle noise in the natural system, which for the Dutch coast is mainly represented by local atmospheric effects and by variability in ocean dynamics in the NE Atlantic.

The steric component of sea-level change comprises variations in the temperature (thermosteric) and salinity (halosteric) of the oceans, which alter the water’s density, leading to volumetric variations of the water column. Although its importance is unarguable, throughout the literature there is a disagreement on how much the steric component actually contributes to sea-level change.Here, we investigate two sources of uncertainty to steric trends, both at global and regional scale. First, we look at how the use of different temperature and salinity datasets influences the estimated steric height. For that, we analyzed 15 datasets, combining different techniques (hydrographic profiles, Argo floats and ocean reanalyses). Second, since the estimation of uncertainties for linear and quadratic trends requires the adoption of a noise model, we compared the performance of several different noise models. We find that by varying both the dataset and noise-model, the global mean trend and uncertainty from 2005 to 2015 can vary from 0.566 to 2.334 mm/yr and 0.022 to 1.646 mm/yr, respectively. This range becomes even larger at regional scales. At a global scale, the selection of datasets has a larger influence on the trend, while at a regional scale the choice of the noise model dominates the spread in steric sea-level trends. Our results emphasize the need to use an ensemble of datasets to infer steric changes, and to carefully choose a noise model.

The conventional sea level budget (SLB) equates changes in sea surface height with the sum of ocean mass and steric change, where solid‐Earth movements are included as corrections but limited to the impact of glacial isostatic adjustment. However, changes in ocean mass load also deform the ocean bottom elastically. Until the early 2000s, ocean mass change was relatively small, translating into negligible elastic ocean bottom deformation (OBD), hence neglected in the SLB equation. However, recently ocean mass has increased rapidly; hence, OBD is no longer negligible and likely of similar magnitude to the deep steric sea level contribution. Here, we use a mass‐volume framework, which allows the ocean bottom to respond to mass load, to derive a SLB equation that includes OBD. We discuss the theoretical appearance of OBD in the SLB equation and its implications for the global SLB., Key Points The conventional sea level budget equation does not include elastic ocean bottom deformation, implicitly assuming it is negligibleRecent increases in ocean mass yield global‐mean ocean bottom deformation of similar magnitude to the deep steric sea level contributionWe use a mass‐volume approach to derive and update the sea level budget equation to include ocean bottom deformation as a process

This work provides a comparison of four approaches that can be used to describe uncertainty in models of the long-term glacial isostatic adjustment (GIA) process. The four methods range from pessimistic to optimistic representations of GIA uncertainty. Each estimation method is applied to selected one dimensional GIA model predictions and compared with vertical land motion data from Global Positioning System (GPS) measurements across Fennoscandia and North America. The methods are evaluated relative to two main properties: (1) their expected ability to separate non-GIA from GIA signals and (2) their estimated statistical appropriateness given a specific GIA model and data set. For the first point, non-GIA signals are considered isolated from the long-term (millennial time scale) GIA signal at sites where measurement and model uncertainties do not overlap. Across methods, the frequency and accuracy with which non-GIA signals are separated from GIA signals in GPS data display both consistent similarities and disparities. For the second point, we compare model predictions with rates of vertical land motion and relative sea level change that have been cleaned of non-GIA signals to determine the most appropriate value of model uncertainty and relate the findings to the four approaches. Best fit inferences suggest that within deglaciation centers, GIA model uncertainty is up to ~2 mm/yr (vertical land motion). Likewise, away from the former ice sheet centers, GIA uncertainty for relative sea level change is inferred to be ~0.3–0.5 mm/yr along the U.S. East Coast and ~0.6–0.8 mm/yr in the North Sea.

Tide gauge (TG) records are affected by vertical land motion (VLM), causing them to observe relative instead of geocentric sea level. VLM can be estimated from global navigation satellite system (GNSS) time series, but only a few TGs are equipped with a GNSS receiver. Hence, (multiple) neighboring GNSS stations can be used to estimate VLM at the TG. This study compares eight approaches to estimate VLM trends at 570 TG stations using GNSS by taking into account all GNSS trends with an uncertainty smaller than 1mm yr-1 within 50km. The range between the methods is comparable with the formal uncertainties of the GNSS trends. Taking the median of the surrounding GNSS trends shows the best agreement with differenced altimetry-tide gauge (ALT-TG) trends. An attempt is also made to improve VLM trends from ALT-TG time series. Only using highly correlated along-track altimetry and TG time series reduces the SD of ALT-TG time series by up to 10%. As a result, there are spatially coherent changes in the trends, but the reduction in the root mean square (RMS) of differences between ALT-TG and GNSS trends is insignificant. However, setting correlation thresholds also acts like a filter to remove problematic TG time series. This results in sets of ALT-TG VLM trends at 344-663 TG locations, depending on the correlation threshold. Compared to other studies, we decrease the RMS of differences between GNSS and ALT-TG trends (from 1.47 to 1.22mm yr-1), while we increase the number of locations (from 109 to 155), Depending on the methods the mean of differences between ALT-TG and GNSS trends vary between 0.1 and 0.2mm yr-1. We reduce the mean of the differences by taking into account the effect of elastic deformation due to present-day mass redistribution. At varying ALT-TG correlation thresholds, we provide new sets of trends for 759 to 939 different TG stations. If both GNSS and ALT-TG trend estimates are available, we recommend using the GNSS trend estimates because residual ocean signals might correlate over long distances. However, if large discrepancies ( > 3mm yr-1) between the two methods are present, local VLM differences between the TG and the GNSS station are likely the culprit and therefore it is better to take the ALT-TG trend estimate. GNSS estimates for which only a single GNSS station and no ALT-TG estimate are available might still require some inspection before they are used in sea level studies.

The mass and steric components of sea level changes have been separated in the Tropical Asian Seas (TAS) using a statistically optimal combination of Jason satellite altimetry, GRACE satellite gravimetry and ocean reanalyses. Using observational uncertainties, statistically optimally weighted time series for both components have been obtained in four regions within the TAS over the period January 2005 - December 2012. The mass and steric sea level variability is regressed with the first two principal components (PC1&2) of Pacific equatorial wind stress and the Dipole Mode Index (DMI). Sea level in the the South China Sea is not affected by any of the indices. Steric variability in the TAS is largest in the deep Banda and Celebes seas and is affected by both PCs and the DMI. Mass variability is largest on the continental shelves, which is primarily controlled by PC1. We argue that a water flux from the Western Tropical Pacific Ocean is the cause for mass variability in the TAS. The steric trends are about 2 mm yr−1 larger than the mass trends in the TAS. A signifcant part of the mass trend can be explained by the aforementioned indices and the nodal cycle. Trends obtained from fingerprints of mass redistribution are statistically equal to mass trends after subtracting the nodal cycle and the indices. Ultimately, the effect of omitting the TAS in global sea level budgets is estimated to be 0.3 mm yr−1.