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Publication date: Available online 28 May 2024

Source: Advances in Space Research

Author(s): Alessio Pignalberi, Dieter Bilitza, Pierdavide Coïsson, Haris Haralambous, Bruno Nava, Michael Pezzopane, Fabricio Prol, Artem Smirnov, David R. Themens, Chao Xiong

Off the coasts of southern British Columbia, Washington, Oregon and northern California lies a 600 mile-long strip where the Pacific Ocean floor is slowly diving eastward under North America. This area, called the Cascadia Subduction Zone, hosts a megathrust fault, a place where tectonic plates move against each other in a highly dangerous way.

Researchers around the globe are sounding the alarm: ocean temperatures are the warmest ever recorded. In 2023, the North Sea also experienced dramatic record highs, as readings taken by the Alfred Wegener Institute's Biological Institute Helgoland indicate. As data from the time series Helgoland Reede also reveal: It's not the first year in which the German Bight experienced marine heat waves. The high temperatures and extreme weather events are a product of climate change and could have substantial impacts on the ecosystem.

The South China Karst, the world's most concentrated karst area, has reduced rocky desertification through extensive conservation and restoration over the past two decades, making it a global "greening" hotspot. However, the sustainability of this trend remains uncertain due to challenges related to afforestation site selection, forest productivity, ecosystem services, and balancing "greening" with economic benefits.

Where there's smoke, there's not necessarily fire. Wildfire smoke, sometimes drifting from hundreds of miles away, touched nearly every lake in North America for at least one day per year from 2019 to 2021, according to a study from the University of California, Davis.

Though it was the site of active tectonics 140 million years ago, today, the coast of West Africa is a passive margin, far from an active tectonic plate boundary and thought to be seismically quiet. So scientists don't fully understand why the region is experiencing a growing number of earthquakes between magnitudes 2 and 5. The lack of widespread seismic monitoring stations across the region presents a major challenge.

The phenomenon of regular pulse bursts in lightning research is characterized by continuous pulses occurring at regular intervals, resulting in intermittent rapid changes in the electric field at ground level. The individual pulses last for microseconds, while the entire sequence can last for milliseconds. The mechanism behind their occurrence has long puzzled scientists.

Abstract

Recent observations beneath Kanto, Japan have shown that seismic activity and seismic attenuation within the overlying continental plate change with time due to drainage caused by slow-slip events (SSEs) along the upper boundary of the Philippine Sea plate. However, associated changes in rock properties have not been investigated. In this study, we estimate frequency-dependent shear-wave anisotropy to provide a detailed insight into the structural change associated with drainage. We perform shear-wave splitting analysis in frequency ranges of 1–4, 2–6, and 4–8 Hz for 306 earthquakes that occur during September 2009–August 2021 and recorded at the Metropolitan Seismic Observation network. Obtained time differences between fast and slow S waves (delay time) range from almost zero to 0.16–0.18 s, exhibiting spatio-temporal variation and frequency dependence. The fast S-wave polarization directions are generally consistent with the direction of the maximum horizontal compressional axis in the study region, which suggests that the observed anisotropy is probably caused by the NE–SW-oriented fractures developed under the regional stress field. The temporal variation in delay times is correlated with SSEs activity with a lag time of 0.0–0.1 year. Furthermore, comparisons between observed frequency-dependent delay times and numerical calculation of fracture-induced anisotropy suggest that the average fracture radius is almost constant (0.30–0.35 m) over time but fracture density temporally varies from 0.025 to 0.035. We infer that the fracture density is probably enhanced by opening of the NE–SW-oriented fractures during the upward migration of fluids that are expelled from the plate interface.

Abstract

To gain a deeper understanding of the extensive and varied lithospheric deformations beneath northern Oman, we examine seismic anisotropy in this region using splitting analysis of teleseismic shear wave data. Our study utilizes data from a dense network consisting of 13 permanent and 45 temporary seismic stations, which were operational for approximately 2.5 years starting from October 2013. By examining the azimuthal distribution of shear wave splitting (SWS) parameters, we were able to divide the study area into three sub-regions. The stations located to the west of the Hawasina window exhibit relatively azimuthally invariant SWS parameters suggesting a single anisotropic layer. On the other hand, most of the stations located in the central and eastern regions display variations versus back-azimuth, indicating the potential presence of depth-dependent anisotropy. The General NW-SE trend of the Fast Polarization Directions (FPDs) of the one-layer anisotropy in the west and FPDs of the upper layers in the east is concordant with the strike of the structures resulting from the collision between the continental and oceanic plates. A clear contrast in SWS parameters is observed in the Semail Gap Fault Zone (SGFZ), suggesting that the SGFZ can be a lithospheric-scale structure that hampers the intrusion of mafic magma from the southeast. Furthermore, the FPDs of the lower layer in the east exhibit an NE-SW trend, which may be indicative of the large-scale mantle flow resulting from the present-day plate motion.

Abstract

We developed an enhanced Kalman-based approach to quantify abrupt changes and significant non-linearity in vertical land motion (VLM) along the coast of Chile and the Antarctic Peninsula using a combination of multi-mission satellite altimetry (ALT), tide gauge (TG), and GPS data starting from the early 1990s. The data reveal the spatial variability of co-seismic and post-seismic subsidence at TGs along the Chilean subduction zone in response to the Mw8.8 Maule 2010, Mw8.1 Iquique 2014, and Mw8.3 Illapel 2015 earthquakes that are not retrievable from the interpolation of sparse GPS observations across space and time. In the Antarctic Peninsula, where continuous GPS data do not commence until ∼1998, the approach provides new insight into the ∼2002 change in VLM at the TGs of +5.3 ± 2.2 mm/yr (Palmer) and +3.5 ± 2.8 mm/yr (Vernadsky) due to the onset of ice-mass loss following the Larsen-B Ice Shelf breakup. We used these data to constrain viscoelastic Earth model parameters for the northern Antarctic Peninsula, obtaining a preferred lithosphere thickness of 115 km and upper mantle viscosity of 0.9 × 1018 Pa s. Our estimates of regionally-correlated ALT systematic errors are small, typically between ∼±0.5–2.5 mm/yr over single-mission time scales. These are consistent with competing orbit differences and the relative errors apparent in ALT crossovers. This study demonstrates that, with careful tuning, the ALT-TG technique can provide improved temporal and spatial sampling of VLM, yielding new constraints on geodynamic models and assisting sea-level change studies in otherwise data sparse regions and periods.

Quantum data assimilation: a new approach to solving data assimilation on quantum annealers
Shunji Kotsuki, Fumitoshi Kawasaki, and Masanao Ohashi
Nonlin. Processes Geophys., 31, 237–245, https://doi.org/10.5194/npg-31-237-2024, 2024
In Earth science, data assimilation plays an important role in integrating real-world observations with numerical simulations for improving subsequent predictions. To overcome the time-consuming computations of conventional data assimilation methods, this paper proposes using quantum annealing machines. Using the D-Wave quantum annealer, the proposed method found solutions with comparable accuracy to conventional approaches and significantly reduced computational time.

Abstract

In this paper, we study the ionization-recombination processes in the lower ionosphere during solar flares of various classes in June 2014 and September 2017. For the first time, ionization and recombination rates of the ionospheric D-region were estimated using the experimental data on variations in the amplitude and phase characteristics of very low frequencies (VLF) signals and two-channel data from the GOES satellite (0.05–0.4 nm and 0.1–0.8 nm). The empirical two-parameter Wait-Ferguson model was used to calculate temporal changes in the electron concentration Ne during solar flares of different classes. GOES satellite data and black body model were used to estimate the X-ray fluxes in the wavelength spectral range λ ≤ 0.3 nm. Joint analysis of the temporal evolution of the Ne vertical profile in the lower ionosphere and X-ray fluxes in different wavelength ranges was carried out. As a result, the values of the ionization and recombination rate coefficients were obtained, and the spectral ranges of radiation that have the greatest impact on Ne at given heights were determined. Calculated ionization and recombination rate coefficients and ranges were successfully verified using VLF data during different solar flares. The results obtained in this work can be used in future studies for a more accurate assessment of the response of lower ionosphere to solar flares of various classes.

Author(s): Sumesh P. Thampi, Kevin Stratford, and Oliver Henrich

Anisotropic particles are often encountered in different fields of soft matter and complex fluids. In this work, we present an implementation of the coupled hydrodynamics of solid ellipsoidal particles and the surrounding fluid using the lattice Boltzmann method. A standard link-based mechanism is u…

[Phys. Rev. E 109, 065302] Published Fri Jun 07, 2024

Abstract

In this study, the Extreme Hourly Precipitation Areas (EHPAs) of three extreme levels (i.e., between the 95th and 99th percentiles, between the 99th and 99.9th percentiles, beyond the 99.9th percentile) in the Pearl River Delta over South China are identified; then the related events and associated Convective Cores (CCs) are tracked, and their macro-and-microphysical characteristics are analyzed using multi-year dual-polarization radar observations. Results show that >90% of EHPAs are smaller than 10 km2, and 65%–75% of EHPA events last only one hour. They tend to be more localized and persist longer with increasing hourly-precipitation extremity. The EHPAs overlap with the CCs during 50%–64% of the EHPAs' life span. Their occurrence frequencies are nearly quadrupled after the monsoon onset over South China Sea (SCS), with a major (secondary) peak at about 1400 LST (0600 LST) in the diurnal variations. The CCs are non-linear shaped with about 65% being meso-γ-scale and embedded within mostly meso-β or α-scale 20 dBZ regions. The CCs generally contain active warm-rain processes and about 70% possess moderate-to-intense mixed-phase microphysical processes. The ratios of ice water path to liquid water path are about 0.37, and coalescence dominates (about 68%) the liquid-phase processes. The average size of raindrop is slightly larger than the “maritime-like” regime and the average concentration is much higher than the “continental-like” regime. These CCs' characteristics roughly resemble those of the convection producing extreme instantaneous precipitation, except for a larger horizontal scale and less evident variations with the increasing hourly-precipitation extremity.

Abstract

The question of stratospheric aerosol type following the Raikoke eruption is revisited. Raman lidar measurements suggest the aerosols are predominately smoke, while Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) results indicate the aerosols are predominately sulfate aerosols. The suggested mechanism of smoke particles self-lofting into the stratosphere is inconsistent with observations in 2020, when more severe Siberian fires failed to invoke a response even vaguely similar to 2019. A side-by side comparison of the Sarychev and Raikoke eruptions invalidates model calculations that suggest sulfate aerosols should be at levels too low to explain the observed aerosol loading. Structure in infrared absorption spectra provides conclusive evidence of composition, a unique fingerprint for identifying aerosol type. Such information cannot be misinterpreted so long as there is sufficient resolution and spectral coverage. ACE-FTS infrared aerosol spectra often have an order of magnitude stronger absorption than that of background sulfate aerosols. These spectra can be accurately reproduced by laboratory measured sulfate aerosol spectroscopic information, providing unambiguous identification of the aerosols as sulfate. Visual inspection of thousands of infrared aerosol spectra from the period following the Raikoke eruption indicates the aerosols in the lower stratosphere are predominately sulfate, with no indication of smoke. The lidar study's identification of the aerosols as smoke was based primarily on observed lidar ratios that were more consistent with a material that absorbed significantly at the lidar wavelengths, inconsistent with expectations for sulfate aerosols. However, this could indicate the presence of a substance dissolved in the sulfate aerosols absorbing at those wavelengths rather than smoke particles.

Abstract

Based on satellite observations in the Arctic stratosphere at latitudes from 61° to 66°N in the second half of 2019, Boone et al. (2022, https://doi.org/10.1029/2022jd036600) provide the impression that the aerosol in the upper troposphere and lower stratosphere (UTLS) over the entire Arctic consisted of sulfate aerosol originating from the Raikoke volcanic eruption in the summer of 2019. Here, we show that this was most probably not the case and the aerosol layering conditions were much more complex. By combining the stratospheric aerosol typing results of Boone et al. (2022, https://doi.org/10.1029/2022jd036600) with lidar observations at 85°–86°N of Ohneiser et al. (2021, https://doi.org/10.5194/acp-21-15783-2021) of a dominating wildfire smoke layer in the UTLS height range, we demonstrate that the Arctic UTLS aerosol most likely consisted of Siberian wildfire smoke in the lower part and sulfate aerosol in the upper part of the aerosol layer which extended from 7 to 19 km height and was well observable until May 2020. The smoke- and sulfate-related aerosol optical thickness (AOT) fractions were about 0.7–0.8 and 0.2–0.3, respectively, according to our analysis. The sulfate AOT is in good agreement with model-based predictions of the Raikoke sulfate AOT.

Abstract

The South Atlantic Ocean hosts several well-studied volcanic ridges and seamount chains, but the origin of their associated mantle plumes is debated. Reduced seismicity on the southern Mid-Atlantic Ridge (MAR) suggests anomalously ductile thermomechanical conditions at 52°S and 47.5°S. These low seismicity patches extend 120–560 km along-axis, and correspond with axial high spreading ridge morphology, geochemical anomalies, and mantle wave speed patterns likely associated with the Shona and Discovery plumes. Bathymetric data show that the northern extent of the Shona swell is associated with increased volcanism, elevated axial bathymetry, and a series of northward-propagating rifts, with the overall swell geometry suggesting a buoyancy flux of 0.4–0.5 Mg s−1. The nearby Bouvet Island may be a product of a branch of the larger Shona plume swell, which has influenced crustal accretion on the southern MAR for the past 24 million years.

Science, Volume 384, Issue 6700, June 2024.

Science, Volume 384, Issue 6700, June 2024.

Science, Volume 384, Issue 6700, June 2024.