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Methane from the destroyed Nord Stream pipelines spread over a large part of the southern Baltic Sea and remained for several months. This is according to a study by researchers from the University of Gothenburg and the Voice of the Ocean research foundation.

From drops to data: Researchers propose algorithm to improve precipitation predictions worldwide

Phys.org: Earth science - Wed, 01/15/2025 - 17:39

With the increase in climate change, global precipitation estimates have become a necessity for predicting water-related disasters like floods and droughts, as well as for managing water resources. The most accurate data that can be used for these predictions are ground rain gauge observations, but it is often challenging due to limited locations and sparse rain gauge data.

Critical ocean current has not declined in the last 60 years, AMOC study finds

Phys.org: Earth science - Wed, 01/15/2025 - 17:00

Earth, being 71% covered in water, is influenced by the ocean and its movements. In the Atlantic Ocean, a system of connected currents, called the Atlantic Meridional Overturning Circulation (AMOC), moves water throughout the world's oceans powered by a combination of winds and ocean density. It not only distributes the ocean's heat, moisture, and nutrients, but regulates the Earth's climate and weather.

Technology for oxidizing atmospheric methane won't help the climate, researchers say

Phys.org: Earth science - Wed, 01/15/2025 - 15:53

As the atmosphere continues to fill with greenhouse gases from human activities, many proposals have surfaced to "geoengineer" climate-saving solutions, that is, alter the atmosphere at a global scale to either reduce the concentrations of carbon or mute its warming effect.

Measurement of femtosecond incoherent XUV pulses using shot-noise-driven fluctuations in plasma betatron sources

Physical Review E (Plasma physics) - Wed, 01/15/2025 - 10:00

Author(s): A. Curcio, M. L. Berlanga, N. Boudjema, E. Chiadroni, A. Cianchi, A. Del Dotto, D. Francescone, M. Galletti, V. Horny, A. Huerta, A. Mostacci, J. A. Pérez-Hernández, M. Petrarca, I. Rodriguez, C. Salgado-López, F. Stocchi, P. Tomassini, I. Vladisavlevici, M. D. Frias, M. Ferrario, and G. Gatti

The duration of incoherent XUV pulses down to the femtoseconds (fs) can be retrieved through a statistical analysis of the modulations on the observed radiation spectrum. Uncorrelated shot-noise fluctuations in the pulse temporal profile result in incoherent radiation showing a multispike spectrum w…

[Phys. Rev. E 111, L013201] Published Wed Jan 15, 2025

Regional triple-frequency integer clock estimation for augmented real-time positioning services

GPS Solutions - Wed, 01/15/2025 - 00:00

Abstract

This study addresses the frequent convergence issues of satellite clocks within regional network, with a particular focus on the multifrequency advantages using data from 25 uniformly distributed reference stations across China. Experimental results demonstrate that incorporating the third frequency significantly enhances the accuracy of BDS-3 clock solutions, reducing the root mean square (RMS) by 44.5%. Additionally, employing a 2-min smoothing interval, multifrequency inclusion increases the wide-lane (WL) fixing rate by 30.4% at low elevation angles, which in turn leads to a marked improvement in narrow-lane (NL) ambiguity resolution. By leveraging phase-wide-lane observations, the stable wide-lane phase bias enables the continuous generation of inter-frequency clock bias (IFCB), ensuring reliable cyclic sequence construction even when satellites exit the observed region. The effectiveness of regional observable specific bias (OSB) on ambiguity resolution at the user level is highlighted, and over 95% of GPS, BDS-3, and Galileo NL fractional biases below 0.15 cycles could be achieved. Furthermore, the single-epoch convergence rates of multi-constellation precise point positioning (PPP) reach horizontal 91.9% and vertical 84.5% for multifrequency, a substantial improvement over the dual-frequency, which does not exceed 25%.

Estimation of the landslide source for the 1929 Grand Banks event using a deep-sea landslide tsunami simulation

Geophysical Journal International - Wed, 01/15/2025 - 00:00

SummaryThe 1929 Grand Banks earthquake (Mw 7.1) generated a large landslide that broke submarine cables near the source area. A large tsunami was generated by the large landslide that killed 28 people on the southern coast of the Burin Peninsula, Canada. The tsunami was also observed at a tide gauge in Halifax, Canada. In this study, the initial landslide mass distribution was estimated by fitting the first pulse of the tsunami waveform observed at Halifax and the timings of the submarine cable break with those computed values. A deep-sea landslide tsunami computation method was developed by modifying a previously developed Tsunami Squares method with a different friction term and an effect of deep water. The results showed that the tsunami waveform and timing of the cable break were well explained by the tsunami computed from the initial landslide mass volume of about 450 km3 located along the continental slope near the source area. The method developed to compute deep-sea landslide tsunamis should be useful for studying other types of landslide tsunamis.

Multi-technique estimation of Ice Mass Balance in Greenland: impact of the uncertainties on firn densification and GIA models

Geophysical Journal International - Wed, 01/15/2025 - 00:00

SummaryWe conduct a comprehensive comparison of Ice Mass Balance (IMB) estimates for Greenland derived from satellite observations of ice Surface Elevation Changes (SEC), gravity and GNSS observations. Our analysis integrates data from the ICESat and CryoSat-2 satellite altimetry missions, augmented by optical stereo-imagery for peripheral glaciers, and GRACE satellite gravimetry mission, spanning the 2003-2008 and 2011-2015 periods. We also consider three firn densification models (FDM) and five Glacial Isostatic Adjustment (GIA) models for correcting the datasets for these effects when necessary. Our results reveal significant differences among FDM corrections applied to SEC observations, with particularly large variations in IMB estimates reaching up to 90 Gt/yr. To address this, we develop an innovative method for estimating equivalent firn corrections to the ice elevation observations, based on a least-squares fit of filtered ice SEC observations to GRACE mass-change estimates. This approach is both simple and independent from climate models assumptions and shows minimal sensitivity to GIA model differences. Using this method, we estimate IMBs for Greenland at -217.6 ± 15.7 Gt/yr for 2003-2008 and -253.2 ± 18.8 Gt/yr for 2011-2015. Importantly, these values indicate an acceleration of the thinning rate, not consistently captured by the IMB estimates inferred from the ice SEC observations corrected by FDMs. Finally, we compute elastic ground deformation induced by ice mass change during 2011-2015, using the four proposed mass-variation distributions and compare the predicted vertical velocities with GNSS observations in Greenland, accounting for all GIA models. While all models are consistent with most of the GNSS-derived uplift rates, they cannot fully explain the observed vertical velocities, especially in the South-East Greenland, which confirms the need to refine our understanding of GIA contributions in this region.

Expected electromagnetic response from natural earthquakes in a layered ocean model

Geophysical Journal International - Wed, 01/15/2025 - 00:00

SummaryIn this study, we adopt a horizontally layered model consisting of air, seawater and undersea porous rock and develop an analytically-based method to calculate the seismic and EM fields generated by undersea earthquakes. We conduct numerical simulations to investigate the characteristics of the EM response at the receivers located at the seafloor, in the seawater near the sea surface and in the air, respectively. The results show that two kinds of EM signals can be identified in the EM records at these receivers, namely, the early EM wave (seismic-to-EM conversion at the seafloor interface) arriving before the seismic waves and the coseismic EM fields with apparent speeds of the seismic waves. The EM signals observed at the seafloor are mostly stronger than those observed in the seawater and air near the sea surface. The method is applied to simulating the EM response to the 2022 Mw 7.3 earthquake that took place in the sea near Fukushima, Japan. At a receiver with 76 km epicentral distance at the seafloor, the predicted coseismic electric and magnetic signals reach 2 μV/m and 2 nT, respectively, which are within the detectability of the current EM equipment. This suggest a possibility to monitor the EM disturbances associated with undersea earthquakes and use them to serve the earthquake early warning, helping to mitigate the societal impact of large earthquakes.