Conventional engineering measures, such as surge barriers and mobile floodgates, are being adopted in many coastal cities worldwide, threatened by the increasing flooding hazard due to rising sea levels. Famous examples include London, the Netherlands, New Orleans, St. Petersburg and Venice. However, the question of how flood regulation affects the morphodynamic evolution of shallow tidal embayments still lingers. Storm-surge barriers may importantly modify the propagation of tides, surges and wind waves, changing sediment transport and, thus, the morphological evolution of regulated tidal environments, in particular in sediment-starved systems. Combining field data and numerical modelling, we investigate the effect of the Mo.S.E. storm-surge barriers, designed to protect Venice from flooding, on the morphodynamic evolution of the Venice lagoon. Artificial reduction of water levels within the lagoon affects the interaction between tide propagation and wind waves, increasing sediment resuspension on tidal flats. Resuspended sediment hardly accumulates on salt marshes, contributing to their vertical accretion and offsetting the negative effect of relative sea-level rise, owing to the reduction of marsh flooding determined by reduced water levels. Although barrier closures temporarily reduce the sediment export toward the open sea, this does not point to preserve the characteristic lagoonal morphology, hindering salt-marsh accumulation and promoting tidal-flat deepening and channel infilling. We conclude that the operations of flood barriers can promote a significant loss of geomorphological diversity, which will critically impact the ecosystem services provided by the shallow tidal environments they are meant to protect, thus increasing the costs related to their conservation and restoration.

In the paper summarized by this presentation we trace how maps aided the conceptualization and ensuing debate over one of the first inherently spatial and multiscale environmental issues, acid rain. Through interviews with early acid rain ecologists and a critical cartographic analysis of printed maps, we show that mapping was central for constructing this environmental issue. Rather than static representations of a scientific reality, acid rain maps were interconnected and relational processes that operated within political and economic discourses. Accordingly, we suggest that increased critical engagement and participation with the process of mapping can productively aid dialog on many issues, including other current multiscale environmental issues, such as climate change.

There is no consensus on the physical mechanisms controlling the scale at which convective activity organizes near the Equator, where the Coriolis parameter is small. High resolution cloud-permitting simulations of non-rotating convection show the emergence of a dominant length scale, which has been referred to as convective self-aggregation. Furthermore, simulations in an elongated domain of size 12228km x 192km with a 3km horizontal resolution equilibrate to a wave-like pattern in the elongated direction, where the cluster size becomes independent of the domain size. These recent findings suggest that the size of convective aggregation may be regulated by physical mechanisms, rather than artifacts of the model configuration, and thus within the reach of physical understanding. We introduce a diagnostic framework relating the evolution of the length scale of convective aggregation to the net radiative heating, the surface enthalpy flux, and horizontal energy transport. We evaluate these length scale tendencies of convective aggregation in twenty high-resolution cloud-permitting simulations of radiative-convective equilibrium. While both radiative fluxes contribute to convective aggregation, the net longwave radiative flux operates at large scales (1000-5000 km) and stretches the size of moist and dry regions, while the net shortwave flux operates at smaller scales (500-2000 km) and shrinks it. The surface flux length scale tendency is dominated by convective gustiness, which acts to aggregate convective activity at smaller scales (500-3000 km). We further investigate the scale-by-scale radiative tendencies in a suite of nine mechanism denial experiments, in which different aspects of cloud radiation are homogenized or removed across the horizontal domain, and find that liquid and ice cloud radiation can individually aggregate convection. However, only ice cloud radiation can drive the convective cluster to scales exceeding 5000 km, because of the high optical thickness of ice, and the increase in coherence between water vapor and deep convection with horizontal scale. The framework presented here focuses on the length scale tendencies rather than a static aggregated state, which is a step towards diagnosing clustering feedbacks in the real world. Overall, our work underscores the need to observe and simulate surface fluxes, radiative and advective fluxes across the 1km-1000km range of scales to better understand the characteristics of turbulent moist convection.

The Advanced Topographic Laser Altimeter System (ATLAS) on ICESat-2 offers a new remote sensing capability to measure complex sea ice surface topography. We demonstrate the retrieval of six sea ice parameters from ICESat-2/ATLAS data: surface roughness, ridge height, ridge frequency, melt pond depth, floe size distribution and lead frequency. Our results establish that these properties can be observed in high fidelity, across broad geographic regions and ice conditions. We resolve features as narrow as 7 m, and achieve a vertical height precision of 0.01 m, representing a significant advance in resolution over previous satellite altimeters. ICESat-2 employs a year-round observation strategy spanning all seasons, across both the Arctic and Southern Oceans. Because of its higher resolution, coupled with the spatial and temporal extent of data acquisition, ICESat-2 observations may be used to investigate time-varying, dynamic and thermodynamic sea ice processes.

Lightning is a magnificent natural experiment of dielectric breakdown on a vast scale, providing us rare opportunities to explore this powerful and dangerous phenomenon hidden deeply in the thunderclouds. Specifically, how lightning is initiated in the insulating air is still poorly understood. Using the radio-imaging technique, scientists remotely sensed the very-high frequency (VHF) radiation of lightning and found that a system of positive polarity streamers, named fast positive breakdown (FPB), could be the initiating discharges of some lightning. Streamers are potential plasma waves composed of ionized air molecules, which can gradually transition the insulating air into hot, high conductivity lightning plasma channels. Recently, lighting has also been reported to be initiated by a burst of negative polarity streamers, called fast negative breakdown (FNB). However, the laboratory experiments and simulations of dielectric breakdown suggest that FPB should be more readily produced compared with FNB. Here, we use our high bandwidth (>200 MHz) and fast time resolution (<0.5 microseconds) VHF radio-imaging system, reporting the first observational evidence of FPB preceding FNB and of simultaneous development of positive and negative polarity streamers in lightning initiation. These observations represent a significant addition to our current physical understanding of natural dielectric breakdown in thunderstorms.

Leveraging aerosol data from multiple airborne and surface-based field campaigns encompassing diverse environmental conditions, we calculate statistics of the oxalate-sulfate mass ratio (median: 0.0217; 95% confidence interval: 0.0154 – 0.0296; R = 0.76; N = 2948). Ground-based measurements of the oxalate-sulfate ratio fall within our 95% confidence interval, suggesting the range is robust within the mixed layer for the submicrometer particle size range. We demonstrate that dust and biomass burning emissions can separately bias this ratio towards higher values by at least one order of magnitude. In the absence of these confounding factors, the 95% confidence interval of the ratio may be used to estimate the relative extent of aqueous processing by comparing inferred oxalate concentrations between air masses, with the assumption that sulfate primarily originates from aqueous processing.

Solar Radiation Management (SRM) geoengineering is a proposed response to anthropogenic global warming (AGW)1. Stratospheric aerosol injection (SAI) is one proposed method, reliant on lofting particles into the stratosphere. Engineering reviews related to this technology approach have been sparse, with most major primary analyses now at least five years old. We attempt to bridge this gap – with a short, mainly qualitative review of recent developments in fields of engineering with potential applicability to stratospheric aerosol injection. Our analysis shows that a new conventional aircraft design is still likely to be the most dependable and affordable technology solution, with hybrid airships a potential challenger. Rockets, gas guns and MAGLEV/coilguns show some potential, although they lack the level flight capability preferred for direct aerosol distribution, without substantial additional engineering. Should very high-altitude access be required, rockets, hybrid rockets, and light-gas guns offer the required capability. Costs and performance for tethered balloons remain highly uncertain. No other methods are found to be promising. Nevertheless, the extreme accessibility of disposable balloons suggests that this method may be used primarily for reasons of political leverage, as opposed to being an optimal engineering solution.

MHD wave phenomena have been readily observed in recent years in various magnetic elements found within the solar atmosphere. They are often touted as a possible mechanism in channeling energy to the outer layers of the solar atmosphere. Recent advances in both observational techniques and instrumentation has gradually bridged the gap between observations and theory of these phenomena, as various wave modes have been identified and their properties studied across a wide range of structures. For example, numerous contemporary studies have identified and studied the properties associated with compressible sausage modes in different bandpasses, often employing magnetic pores as a test bed. However, the spatial structuring of the mode within the flux tube, that is, the surface and body characteristics, has thus far been ignored in observational studies. We employed high spatial and temporal resolution observations from a combination of both ground- (ROSA) and space-based (SDO) instrumentation to study several pore datasets, which were observed to support sausage modes. Using a range of techniques, we observed and were able to classify, for the first time, the surface and body characteristics for the wave modes observed within the pores. The most frequently occurring oscillation period in our observations was found to be ~300s, which is consistent with the p-mode spectrum. We find surface modes more frequently in the data. We find frequencies in the range of ~2–12 mHz, with body modes as high as 11 mHz, but we do not find surface modes above 10 mHz. Estimates made for the energetics of these wave modes will also be discussed within the context of our results.

Both high-power large aperture (HPLA) radars and smaller meteor radars readily observe the dense head plasma produced as a meteoroid ablates. However, determining the mass of such meteors based on the information returned by the radar is challenging. We present a new method for deriving meteor masses from single-frequency radar measurements, using a physics-based plasma model and finite-difference time-domain (FDTD) simulations. The head plasma model derived in~\citeA{dimopp17} depends on the meteoroids altitude, speed, and size. We use FDTD simulations of a radar pulse interacting with such head plasmas to determine the radar cross section (RCS) that a radar system would observe for a meteor with a given set of physical properties. By performing simulations over the observed parameter space, we construct tables relating meteor size, velocity, and altitude to RCS. We then use these tables to map a set of observations from the MAARSY radar (53.5 MHz) to fully-defined plasma distributions, from which masses are calculated. To validate these results, we repeat the analysis using observations of the same meteors by the EISCAT radar (929 MHz). The resulting masses are strongly linearly correlated; however, the masses derived from EISCAT measurements are on average 1.33 times larger than those derived from MAARSY measurements. Since this method does not require dual-frequency measurements for mass determination, only validation, it can be applied in the future to observations made by many single-frequency radar systems.

Millisecond Pulsars (MSPs) are likely to be or to become a timing, navigation, and metadata communication standard across the galaxy. Regarding timing, they provide a parallel clock to terrestrial ones, are based on macroscopic neutron stars behavior instead of quantum processes, and they will remain ticking longer than any clock we can construct on Earth. Regarding navigation, X-ray MSPs provide all the necessary ingredients for a Pulsar Positioning System that has many similarities with GPS. In astronautics, X-ray pulsar-based navigation (XNAV) uses a time-of-arrival navigation method comparable to GPS, accurate down to about 100 meters. Regarding metadata communication, MSPs would be a natural metadata coding choice for any galactic communication effort. On Earth, any letter or email contains metadata information about where it comes from, where it goes, and when it was written. We can expect that similar conventions exist for any potential galactic communication. Most messages are likely to be galacto-tagged and pulsar-time-stamped by reference to MSPs. This simple remark opens a simplified SETI search. Given any suspicious message we want to decode, the first step becomes to attempt to decode not the message itself, but its metadata (Vidal 2017). GPS is a technological breakthrough that enables many others: one needs only to think about all the location-based services (LBS) that it has unlocked in our modern societies. The realm of potential galactic LBS is an area totally unexplored, and may well be a key to find technosignatures of many kinds. Is GPS a technology? The answer is an obvious yes. Now imagine that we would find around an exoplanet’s orbit well-distributed timekeeping devices with an accuracy comparable with atomic clocks, beaming timing information that can be used as a positioning system, just like GPS. Would not we be compelled to check if it is a technosignature? This is exactly the current situation with MSPs, but on a galactic scale. This is why I have proposed ways to test whether the pulsar positioning system is actually an instance of galactic engineering (Vidal 2019). Seeking such a galactic technosignature proof is actually searching for a distributed signal, instead of searching for a localized signal around one particular star or planet. If the search program succeeds, it would lead to the discovery of extraterrestrial intelligence, through their engineered timing and navigation system. References: Vidal, C. 2017. “Millisecond Pulsars as Standards: Timing, Positioning and Communication.” Proceedings of the International Astronomical Union 13 (S337): 418–19. doi:10.1017/S1743921317008596. https://arxiv.org/abs/1711.06036. (where this poster was first presented) Vidal, C. 2019. “Pulsar Positioning System: A Quest for Evidence of Extraterrestrial Engineering.” International Journal of Astrobiology 18 (3): 213–34. doi:10.1017/S147355041700043X. https://arxiv.org/abs/1704.03316.

It has been known for many decades that the lunar tidal influence in the equatorial electrojet (EEJ) is noticeably enhanced during northern hemisphere winters. Recent literature has discussed the role of stratospheric sudden warming (SSW) events behind the enhancement of lunar tides and their findings suggest a positive correlation between the lunar tidal amplitude and lower stratospheric parameters (zonal mean air temperature and zonal mean zonal wind) during SSW events. The positive correlation raises the question whether an inverse approach could also be developed which makes it possible to deduce the occurrence of SSW events before their direct observations(before 1952) from the amplitude of the lunar tides. This study presents an analysis technique based on the phase of the semi-monthly lunar tide to determine the lunar tidal modulation of the equatorial electrojet (EEJ). A statistical approach using the superposed epoch analysis is also carried out to formulate a relation between the EEJ tidal amplitude and lower stratospheric parameters. Using these results, we have estimated a threshold value for the tidal wave power that could be used to identify years with SSW events from magnetic field observations.

River deltas and enclosed lagoons represent a zone where fluvial and littoral processes interacts through a redistribution, erosion, and deposition of sediment, with a huge impact on coastal management and engineering. The focus of the study is to understand the correct balance between strategies to maintain the navigational efficiency of tidal inlets and the respect of the ecological and economical function in coastal lagoons. We applied an integrated modeling system which will link multiple hydrodynamic and morphodynamic models to understand how coastal processes and the associated sediment transport can influence the functioning of the southern inlet of the Barbamarco lagoon in the Po River Delta, Italy. Furthermore, our study provides engineering solutions aimed at the inlet functioning efficiency with a proposal for the monitoring plan. Our results highlight the importance of the seasonal effects of wave climate on the littoral sediment transport. Model outcomes show that the dredging volume is approximately 15,000 cubic meter/year for the southern inlet that might vary with wave climate. However, shaping a wider tidal channel seaward will reduce the dredging activities with a longer interval than the actual sediment removal. A design of a deeper and wider channel will deflect the along shore current seaward with a sediment bypass of the inlet. Therefore, the sediment will reach the erosional side of the inlet enhancing the redistribution of the sediment which might reduce the over-wash during storms and high-water levels. Our results display the ephemeral equilibrium of tidal inlets and coastal lagoons in deltaic systems impacted by large riverine sediment delivery. Shore management scenario and decision relies on hydro-morphodyanmic numerical model to predict the best practice for coastal sustainability.

Whistler-mode waves have often been proposed as a plausible mechanism for pitch angle scattering and energization of electron populations in the solar wind. Recent studies reported observations of obliquely propagating and narrowband waves consistent with the whistler mode at 1 AU. Close to 0.3 AU, similar waves have also been observed in PSP data, where evidence of strong scattering of strahl electrons indicates that these waves regulate the electron heat flux. At both radial distances, the wave amplitude can be as high as 10% of the ambient magnetic field. The oblique propagation angle enables resonant interactions without requiring that the electrons counter-stream with the waves. Self-consistent PIC simulations by Roberg-Clark et al (2019) and Micera et al (2020) studied the strahl scattering and subsequent halo formation due to anomalous resonant interactions enabled by oblique whistlers generated from the heat flux fan instability. Observational studies of whistlers near the Sun have also concluded that they are connected to this instability. Cattell and Vo (2021) also demonstrated the same features of the scattering from a particle tracing simulation, one advantage of which is the ability to calculate kinetic quantities such as the diffusion coefficients. Also, the tracing code includes variational calculations to ensure energy conservation in the presence of highly chaotic dynamics. In this study, we investigate in more detail the resonant interactions of electrons with these high amplitude and oblique whistlers. We will show that these waves at 0.3 AU may exceed the stochasticity condition where resonance overlap occurs. Furthermore, the stochastic width around the primary islands might be large enough that diffusion is enabled even before they overlap. In simulations with 1 AU parameters, the particle motion is strongly stochastic where all harmonics significantly overlap, leading to an isotropic pitch angle diffusion which forms the halo population. Our calculations also indicate the presence of higher-order effects, allowing for sub- and super-harmonic resonant interactions.

Water resources management is a non-trivial process requiring a holistic understanding of the factors driving the dynamics of human-water systems. Policy-induced or autonomous behavioral changes in human systems may affect water and land management, which may affect water systems and feedback to human systems, further impacting water and land management. Currently, hydro-economic models lack the ability to describe such dynamics either because they do not account for the multi-factor/multi-output nature of these systems, and/or are not designed to operate at a river basin scale. This paper presents a flexible and replicable methodological framework for integrating a microeconomic multi-factor/multi-output Positive Multi-Attribute Utility Programming (PMAUP) model with an eco-hydrologic model, the Soil and Water Assessment Tool (SWAT). The connection between the models occurs in a sequential modular approach through a common spatial unit, the “Hydrologic-Economic Representative Units” (HERUs), derived from the boundaries of decision-making entities and hydrologic responsive units. The resulting SWAT-PMAUP model aims to provide the means for exploring the dynamics between the behavior of socio-economic agents and their connection with the water system through water and land management. The integrated model is illustrated by simulating the impacts of irrigation restriction policies on the Río Mundo sub-basin in south-eastern Spain. The results suggest that agents’ adaptation strategies in response to the irrigation restrictions have broad economic impacts and subsequent consequences on surface and groundwater resources. We suggest that the integrated modeling framework can be a valuable tool to support decision-making in water resources management across a wide range of scales.

There are potential benefits from the addition of 3-C rotational motions to traditional 3-C translational displacements for moment tensor (MT) inversions. The rotational radiation pattern is orthogonal to the shear radiation pattern, thus incorporating rotations is equivalent to gaining another observation point on the focal sphere. We demonstrate this by simulating the curl and displacement wavefields in a half-space for a regional distance station. We also demonstrate the effect of velocity gradients beneath a station on rotational motions compared to displacements. Further investigation is needed to study how this affects the MT inversion. We added rotational Greens functions to regional long-period MT inversion computing spatial gradients from f- reflectivity synthetics. We used array derived rotational motions from the Piñon Flats Observatory Array in California and Golay arrays deployed during the IRIS Community Wavefield Demonstration Experiment in Oklahoma. Well-constrained MT solutions were estimated for three earthquakes using long-period regional waves with and without rotational ground motions as test cases. Prepared by LLNL under Contract DE-AC52-07NA27344. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number LLNL-ABS-781439. Index Terms: 7215 Earthquake source observations, 7290 Computational seismology Plain-Language Summary Scientists have traditionally used seismometers to record earthquake generated translational ground motions using three-dimensional axes typically oriented in a vertical, north-south and east-west directions in other words a “Cartesian coordinate system”. Recent advancements in seismometer development for recording rotational or twisting ground motions about the same three-axes provide additional information, which, in addition to translational seismometers can help resolve the radiation patterns of quakes. In cases where physical access is limited, the sparse distribution of seismometers caused by, for example, ocean coasts, islands, Lunar, and Mars surfaces can prevent the complete observation of the quake radiation pattern. The combination of these two types of seismometers at a single point are useful to infer faulting mechanisms of quakes or other seismic source types than using just one seismometer. Submitted to American Geophysical Union Fall Meeting, San Francisco, CA 9-13 December 2019. S032 – Rotation and Strain in Seismology – Applications, Instrumentation and Theory S21G-0589

The seismic low-velocity zone (LVZ) of the upper mantle is generally associated with a low-viscosity asthenosphere that has a key role in decoupling tectonic plates from the mantle. However, the origin of the LVZ remains unclear. Some studies attribute its low seismic velocities to a small amount of partial melt of minerals in the mantle, whereas others attribute them to solid-state mechanisms near the solidus, or the effect of its volatile contents. Observations of shear attenuation provide additional constraints on the origin of the LVZ. On the basis of the interpretation of global three-dimensional shear attenuation and velocity models, here we report partial melt occurring within the LVZ. We observe that partial melting down to 150–200 kilometres beneath mid-ocean ridges, major hotspots and back-arc regions feeds the asthenosphere. A small part of this melt (less than 0.30 per cent) remains trapped within the oceanic LVZ. Melt is mostly absent under continental regions. The amount of melt increases with plate velocity, increasing substantially for plate velocities of between 3 centimetres per year and 5 centimetres per year. This finding is consistent with previous observations of mantle crystal alignment underneath tectonic plates. Our observations suggest that by reducing viscosity, melt facilitates plate motion and large-scale crystal alignment in the asthenosphere.

Peatland soils are of great interest for study and management because of their high carbon contents and known role in the global carbon cycle. However, carbon stocks have yet to be constrained in many wetland ecosystems. Relative to bogs, fens and saline coastal ecosystems, less is known about carbon stocks in freshwater marsh soils despite their global prevalence, and it is not well understood how disturbance of freshwater marshes may affect carbon-climate dynamics. To better understand the potential for freshwater marshes to be net carbon sinks, we review how freshwater marshes and associated soils are classified, and synthesize available data on short- and long-term rates of carbon accumulation in freshwater marsh soils in temperate North America. Although often described as mineral-based, our findings suggest that freshwater marshes are not restricted to mineral substrates, and that inconsistencies in classification may underestimate presumed carbon stocks. Organic carbon contents and bulk density measurements are highly variable, and can range between 1-45% and 0.04-1.5 g cm-3, respectively. Moreover, rates of carbon accumulation in freshwater marshes are often measured over recent time scales (50-100 years; on average 155 +/- 74 g C m-2 yr-1), while long-term rates (measured over centuries and millennia; on average 51 +/- 38 g C m-2 yr-1) are much more scarce. We suspect that short-term rates are markedly greater than long-term rates of carbon accumulation because they do not account for long-term carbon loss and may reflect large increases in sedimentation since European settlement in North America. However, we also suspect that long-term carbon storage in freshwater marsh soils is underestimated, and that freshwater marshes can have long-term rates of carbon accumulation similar to those reported for temperate peatlands. In this presentation, we will show that variability of rates of carbon accumulation, rates of sediment accretion, bulk density and organic carbon content in freshwater marshes needs to be better constrained in order to accurately quantify their regional and global carbon pools. We will discuss the importance for scientists to specify timeframes over which they are measuring rates of carbon accumulation so that the capacity for wetlands to be net carbon sinks can be correctly understood.

Insights from the RAPID–MOCHA observation network in the North Atlantic have motivated a recent focus on the South Atlantic, where water masses are exchanged with the neighboring Indian and Pacific ocean basins. Moreover, the South Atlantic meridional overturning circulation basin-wide array (SAMBA) was recently launched to monitor variability in the South Atlantic MOC (SAMOC) at 34.5ºS. In this study, we are interested in understanding the processes which generate volume transport variability that would be observed at this latitude band. To perform this attribution, we compute sensitivities of the SAMOC at 34ºS to atmospheric state variables (e.g. wind stress, precipitation) using the adjoint of a global ocean model which is fit to a vast number of ocean observations over the past 20 years. These sensitivities isolate the impact from each atmospheric variable, and highlight the oceanic mechanisms, such as Kelvin and Rossby waves, which carry atmospheric forcing perturbations to the SAMOC. The domain of influence for the SAMOC is shown to be quite broad, covering neighboring ocean basins even on short time scales. This result differs from what has previously been shown in the North Atlantic, where Atlantic meridional overturning circulation (AMOC) variability is largely governed by dynamics confined to that basin. We convolve historical forcing variability from ERA-Interim with the computed sensitivities in order to attribute seasonal to interannual SAMOC variability to each atmospheric component. The seasonal cycle of the SAMOC is therefore shown to be largely driven by local zonal wind forcing. Interannual variability, however, is shown to have originated from remote locations across the globe, including a nontrivial component originating from the tropical Pacific. We conclude with preliminary results which employ both modeling results and an analysis of modern altimetry observations to show how El Niño Southern Oscillation variability might influence the South Atlantic.