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No abstract is available for this article.

Abstract

Subglacial lakes have been mapped across Antarctica with two methods, radio-echo sounding (RES) and ice-surface deformation. At sites where both are coincident, these methods typically provide conflicting interpretations about the ice-bed interface. With a single exception, active subglacial lakes identified by surface deformation do not display the expected flat, bright, and specular bed reflection in RES data, characteristic of non-active lakes. This observational conundrum suggests that our understanding of Antarctic subglacial hydrology, especially beneath important fast-moving ice streams, remains incomplete. Here, we use an airborne RES campaign that surveyed a well-characterized group of active subglacial lakes on lower Mercer and Whillans ice streams, West Antarctica, to explore inconsistency between the two observational techniques. We test hypotheses of increased scattering and attenuation due to the presence of an active subglacial lake system that could suppress reflected bed-echo power for RES observations in these locations, finding that entrained water is most plausible.

Abstract

The influence of bioturbation induced by bottom-dwelling macrozoobenthos on nitrogen dynamics in lotic stream sediments remains unclear. In this work, we advance the understanding of faunal bioturbation in lotic environments by developing a fully-coupled flow and multicomponent reactive transport model and investigate the influence of sediment reworking and burrow ventilation processes on nitrogenous transformations. The model results indicate that sediment reworking and burrow ventilation significantly increase nitrate (NO3 −) influx, penetration depth, and reaction rates in the streambed. Denitrification rates were observed up to three times higher in beds with U-shaped burrows compared to flatbeds. The ratio of mound height to stream water depth ratio (h/H 0) is a dominant control on determining the relative importance of the sediment reworking and burrow ventilation processes in modulating nitrogenous reactions. A power-law scaling framework is ultimately proposed to predict NO3 − removal efficiency based on the Damköhler number in bioturbated lotic streambeds.

No abstract is available for this article.

Drought in the American West is becoming a persistent reality instead of a periodic emergency due to climate change, and a recent study found that an essential tool used to measure drought can't keep up.

More than 100,000 oil and gas wells across the western U.S. are in areas burned by wildfires in recent decades, a new study has found, and some 3 million people live next to wells that in the future could be in the path of fires worsened by climate change.

A quest for precipitation attractors in weather radar archives
Loris Foresti, Bernat Puigdomènech Treserras, Daniele Nerini, Aitor Atencia, Marco Gabella, Ioannis V. Sideris, Urs Germann, and Isztar Zawadzki
Nonlin. Processes Geophys., 31, 259–286, https://doi.org/10.5194/npg-31-259-2024, 2024
We compared two ways of defining the phase space of low-dimensional attractors describing the evolution of radar precipitation fields. The first defines the phase space by the domain-scale statistics of precipitation fields, such as their mean, spatial and temporal correlations. The second uses principal component analysis to account for the spatial distribution of precipitation. To represent different climates, radar archives over the United States and the Swiss Alpine region were used.

On the relationship between the mesospheric sodium layer and the meteoric input function
Yanlin Li, Tai-Yin Huang, Julio Urbina, Fabio Vargas, and Wuhu Feng
Ann. Geophys., 42, 285–299, https://doi.org/10.5194/angeo-42-285-2024, 2024
This work combines lidar observation data and a new numerical sodium (Na) chemistry model, using data assimilation to study the relation between the mesospheric Na layer and the meteoric input function. Simulation captures the seasonal variability in the Na number density compared with lidar observations over the Colorado State University (CSU) lidar. The estimated global ablated meteoroid material inputs from Andes Lidar Observatory and CSU observations are 83 t d-1 and 53 t d-1, respectively.

Abstract

Electron density irregularities in the ionosphere can give rise to scintillations, affecting radio wave phase and amplitude. While scintillations in the cusp and polar cap regions are commonly associated with mesoscale density inhomogeneities and/or shearing, the auroral regions exhibit a strong correlation between scintillation and density structures generated by electron precipitation (arcs). We aim to examine the impact of electron precipitation on the formation of scintillation-producing density structures using a high-resolution physics-based plasma model, the “Geospace Environment Model of Ion-Neutral Interactions,” coupled with a radio propagation model, the “Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere.” Specifically, we explore the effects of varying spatial and temporal characteristics of the precipitation, including electron total energy flux and their characteristic energies, obtained from the all-sky-imagers and Poker Flat Incoherent Scatter Radar observations, on auroral scintillation. To capture small-scale structures, we incorporate a power-law turbulence spectrum that induces short wavelength features sensitive to scintillation. Finally, we compare our simulated scintillation results with satellite-observed scintillations, along with spectral comparisons.

Abstract

Different from power line harmonic radiation (PLHR) events at high harmonics (∼kHz) in the ionosphere and inner magnetosphere, the wave dynamics of power line emission (PLE) (the fundamental frequency 50/60 Hz or PLHR at low harmonics) can be significantly affected by various ion species. In order to investigate the evolution of the wave properties of PLE from power lines to satellite altitudes in a dipole field, a numerical model is developed to perform full-wave simulations, in which the lithosphere and atmosphere are characterized by electrical conductivity and the ionosphere (inner magnetosphere) is treated as collisional (collisionless) cold plasma consisting of electron, H+, He+, O+, and NO+. Our simulation results show that the spatial distribution and wave properties of PLE are determined by the magnetic latitudes of power lines and plasma densities. PLE from power lines at middle and high magnetic latitudes (|MLAT| > 40°) can propagate to high L shells as whistler waves; PLE from power lines at |MLAT| < 30° usually propagate at low L shells below local He+ cyclotron frequency as left-handedly polarized or right-handedly He+ band electromagnetic ion cyclotron (EMIC) waves. The amplitude of PLE is usually stronger with smaller electron density in the space plasma medium. With power lines at |MLAT| < 30°, the coupling efficiency between different right-handedly polarized EMIC wave modes of PLE decreases significantly with electron density. Wave properties of PLE including Poynting vector direction, wave normal angle and wave polarization obtained from our simulation results are consistent with some of the recent observations using Van Allen Probes.

SummaryAirborne magnetics have found few applications in investigating basalt-trapped areas because anomaly interferences from deep and shallow sources prevent clear identification of subjacent dyke systems. The structural positioning of dykes is of major importance in basin studies due to their role as a heat source for maturing organic matter and plumbing capacity to feed intrusive bodies and surface lava flows. Aeromagnetic data in such a scenario can outline faults and the basin framework but faces difficulties in identifying the distribution of dykes seated at different depth levels. We present a procedure that sequentially combines conventional processing techniques to identify and retrieve the magnetic anomaly content with two-dimensional (2D) properties, as expected from tabular dykes with contrasting magnetic properties with respect to the background medium. The mean direction of 2D anomalies is quantitatively evaluated by tracking the directions in which the horizontal component of the transformed anomaly mostly vanishes. The observed field is then cosine-direction filtered to retain the anomaly content along this mean direction. Once isolated, the filtered 2D content of the anomaly is interpreted with multiple thin-sheet models to determine the dyke distribution and their respective depths to the top. The inferred depths are interpreted concerning basin stratigraphic markers to recognize dykes possibly serving as a heat source for geothermal or petroleum and gas maturation, acting as compartments to aquifer systems, or determining the location of former conduits once feeding the lava flow volcanism. The developed procedure is applied to the Ponta Grossa Dyke Swarm, along its North-western continuation beneath the basalt-capped sedimentary sequences of the Palaeozoic Paraná Basin. The distribution of the dykes recognizes a sequence confined to the bottom Paleozoic formations with petroleum and gas potential, a sequence intercepting the upper layers forming the Guarani aquifer system (GAS), and dykes at different depth levels within the basalt Serra Geral traps, indicative of at least two feeding events supplying the Mesozoic surface lava flows.

SummaryDistributed acoustic sensing (DAS) enables high-density sampling of seismic wavefields at low cost compared to conventional geophones. This capability facilitates structural detection of a municipal solid waste (MSW) landfill, which is important for protecting the surrounding ecosystem. However, processing the vast amount of data from DAS array for ambient noise imaging can be computationally intensive. To address this, we employed the common-midpoint two-station (CMP-TS) analysis to enhance the efficiency of ambient noise imaging in the MSW landfill. CMP-TS analysis involves selecting pairs of traces at equal distances on both sides with the subarray midpoint as symmetry, which reduces the number of DAS array recordings for cross-correlation calculations. After positioning the DAS arrays linearly on top of the MSW landfill to automatically collect ambient noise, we used the CMP-TS analysis in the cross-correlation calculations to speed up the measurement of dispersion. The S-wave velocity structure of the study region was obtained quickly by inverting the extracted dispersion curves using the gradient optimization method. Ambient noise imaging based on CMP-TS analysis with DAS was applied to a test of an area-type MSW landfill. The resulting S-wave velocity section revealed a discontinuous low-velocity zone, validated by the high-density resistivity method. This low-velocity zone was interpreted as containing leachate from waste decomposition, and its discontinuity may be caused by excessive differences in the waste residues settling rates under compaction. Employing CMP-TS analysis in ambient noise data collected by DAS offers more cost-effective monitoring and a reliable basis for environmental pollution prevention and control.

SummaryA regional approach is developed for high-resolution gravity anomaly recovery from the full airborne gravity gradient tensor (GGT) based on the radial basis function (RBF) technique. The analytical expressions that link the full GGT to the gravity anomaly based on Poisson wavelets are developed, where the closed formulas of the associated derivatives of Poisson wavelets are deduced. Based on this approach, the gravity anomalies at a mean resolution of ∼ 0.15 km over the Kauring Test Range in Australia are recovered by using the local airborne GGT. The results show that the solution computed from the vertical component provides the best quality when a single component is used, whereas the model computed from the curvature component performs the worst. Moreover, the incorporation of two components magnifies the gravity anomalies and further improves the fit with the terrestrial and airborne gravity data, compared with the solutions computed from individual components. However, the solutions calculated by additionally merging one or more components provide comparable qualities with the models calculated by fusing two components only. Finally, the solution is computed by merging the full airborne GGT, and the standard deviation of the misfits against the terrestrial gravity data is 0.788 mGal. Further comparisons with the Fourier transformation and equivalent source method demonstrate that the proposed approach has slightly better performance. The proposed method is numerically efficient and offers a better data adaptation, which is useful for high-resolution gravity data recovery in managing huge number of gravity gradient data.

After the 2011 Tohoku-oki earthquake, a seafloor observation system observed rapid landward deformation. These seafloor observation data are potentially explicable via modeling of a low-viscosity zone under th...

A team at Los Alamos National Laboratory has used machine learning—an application of artificial intelligence—to detect the hidden signals that precede an earthquake. The findings at the Kīlauea volcano in Hawaii are part of a years-long research effort pioneered at Los Alamos, and this latest study represents the first time scientists were able to detect these warning signals in a stick-slip fault, the kind that can generate massive destruction.

Publication date: Available online 19 June 2024

Source: Advances in Space Research

Author(s): F. Rahmanifard, M. MacLeod, W.C. de Wet, A.P. Jordan, J.K. Wilson, H.E. Spence, N.A. Schwadron

Publication date: 15 July 2024

Source: Advances in Space Research, Volume 74, Issue 2

Author(s): Eloy Peña-Asensio, Juan Miguel Sánchez-Lozano

Publication date: 15 July 2024

Source: Advances in Space Research, Volume 74, Issue 2

Author(s): Shota Kikuchi, Kei Shirai, Ko Ishibashi, Koji Wada, Yasuhiro Yokota, Rie Honda, Toshihiko Kadono, Yuri Shimaki, Naoya Sakatani, Kazunori Ogawa, Hirotaka Sawada, Takanao Saiki, Yuya Mimasu, Yuto Takei, Seiji Sugita, Toru Kouyama, Naru Hirata, Satoru Nakazawa, Makoto Yoshikawa, Satoshi Tanaka

Publication date: 15 July 2024

Source: Advances in Space Research, Volume 74, Issue 2

Author(s): Aminu Yaradua Sabiru, Akinsanmi Akinbolati, Florence N. Ikechiamaka, Bolanle T. Abe

Publication date: 15 July 2024

Source: Advances in Space Research, Volume 74, Issue 2

Author(s): Zhihao Wang, Hongzhou Chai, Peng Chen, Naiquan Zheng, Qiankun Zhang