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Journal articleZhou Z, Whittaker A, Bell R, et al., 2024,
Unravelling tectonic and lithological effects on transient landscapes in the Gulf of Corinth, Greece
, Basin Research, Vol: 36, ISSN: 0950-091XLandscapes are the integrated product of external forcings (e.g. tectonics and climate) and intrinsic characteristics (e.g. bedrock erodibility). In principle, hardbedrock with low erodibility can steepen rivers in a similar way to tectonic uplift. A key challenge in geomorphic analysis is thus separating the tectonic and lithologicaleffects on landscapes. To address this, we focus on multiple rivers that are transiently incising through contrasting lithologies in the Gulf of Corinth, Greece,where tectonic history is broadly well constrained. We first exploit topographic metrics and river long profiles to demonstrate that landscapes are responding to both tectonics and lithology. In particular, the long profiles are divided into knickpoint-bounded segments, and at this scale, channel steepness is shown to be more sensitive to lithology than the entire catchment, possibly due to relatively uniform erosion rate at the segment scale. We then use segment-scale steepness variations between different lithologies to constrain their relative erodibilities(Klime:Kcong.:Ksand-silt: Kp-con sed. = 1:2:3:4), which are further converted into actual lithology-dependent erodibilities by modelling a well-constrained, ca. 700 kaknickpoint in the Vouraikos catchment. The effectiveness of lithology-dependent erodibilities is supported by the observation that if lithology-dependent erodibilitiesare used to calibrate studied river long profiles in χ distance, we obtain long profile concavities that fall within the theoretical range. Finally, we use lithology-calibrated metrics to provide new geomorphic constraints on the timing and magnitude of tectonic perturbations in these catchments. These geomorphic results are interpreted in conjunction with previous onshore and offshore studies to shed new light on fault growth and linkage history in the Gulf of Corinth. Our study therefore provides a topographic analysis-based approach to quantify lithological effects on transient catchments
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ReportClarke B, Zachariah M, Barnes C, et al., 2024,
Climate change increased Typhoon Gaemi's wind speeds and rainfall, with devastating impacts across the western Pacific region
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Journal articleKelly H, Archer M, Ma X, et al., 2024,
Identification of Kelvin-Helmholtz generated vortices in magnetised fluids
, Frontiers in Astronomy and Space Sciences, Vol: 11, ISSN: 2296-987XThe Kelvin-Helmholtz Instability (KHI), arising from velocity shear across the magnetopause, plays a significant role in the viscous-like transfer of mass, momentum, and energy from the shocked solar wind into the magnetosphere. While the KHI leads to growth of surface waves and vortices, suitable detection methods for these applicable to magnetohydrodynamics (MHD) are currently lacking. A novel method is derived based on the well-established λ-family of hydrodynamic vortex identification techniques, which define a vortex as a local minimum in an adapted pressure field. The J × B Lorentz force is incorporated into this method by using an effective total pressure in MHD, including both magnetic pressure and a pressure-like part of the magnetic tension derived from a Helmholtz decomposition. The λMHD method is shown to comprise of four physical effects: vortical momentum, density gradients, fluid compressibility, and the rotational part of the magnetic tension. A local three-dimensional MHD simulation representative of near-flank magnetopause conditions (plasma β’s 0.5–5 and convective Mach numbers Mf ∼ 0.4) under northward interplanetary magnetic field (IMF) is used to validate λMHD. Analysis shows it correlates well with hydrodynamic vortex definitions, though the level of correlation decreases with vortex evolution. Overall, vortical momentum dominates λMHD at all times. During the linear growth phase, density gradients act to oppose vortex formation. By the highly nonlinear stage, the formation of small-scale structures leads to a rising importance of the magnetic tension. Compressibility was found to be insignificant throughout. Finally, a demonstration of this method adapted to tetrahedral spacecraft observations is performed.
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Journal articleLi J, Prentice IC, 2024,
Global patterns of plant functional traits and their relationships to climate
, Communications Biology, ISSN: 2399-3642 -
Journal articleHaas O, Keeping T, Gomez-Dans J, et al., 2024,
The global drivers of wildfire
, Frontiers in Environmental Science, ISSN: 2296-665XChanges in wildfire regimes are of growing concern and raise issues about how well we can model risks in a changing climate. Process-based coupled fire-vegetation models, used to project future wildfire regimes, capture many aspects of wildfire regimes poorly. However, there is now a wealth of information from empirical studies on the climate, vegetation, topography and human activity controls on wildfire regimes. The measures used to quantify these controls vary among studies, but certain variables consistently emerge as the most important: gross primary production as a measure of fuel availability, vegetation cover as a measure of fuel continuity, and atmospheric humidity as a measure of fuel drying. Contrary to popular perception, ignitions are generally not a limiting factor for wildfires. In this review, we describe how empirical fire models implement wildfire processes, synthesise current understanding of the controls on wildfire extent and severity, and suggest ways in which fire modelling could be improved.• Empirical analyses of the controls on wildfires consistently identify vegetation properties associated with fuel availability and continuity and climate factors associated with fuel drying as the most important influences on wildfire extent and severity. • Ignitions, whether anthropogenic or natural, are generally not limiting.• Fire size, burnt area and fire intensity are influenced by different factors; current relationships between these aspects of wildfire could become decoupled in an altered climate. • Some hypotheses embedded in 'process-based' fire-vegetation models are inconsistent with empirical evidence, implying a need for a re-design.
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Journal articleKhurana M, Curran-Sebastian J, Scheidwasser N, et al., 2024,
High-resolution epidemiological landscape from ~290,000 SARS-CoV-2 genomes from Denmark
, Nature Communications, Vol: 15, ISSN: 2041-1723Vast amounts of pathogen genomic, demographic and spatial data are transforming our understanding of SARS-CoV-2 emergence and spread. We examined the drivers of molecular evolution and spread of 291,791 SARS-CoV-2 genomes from Denmark in 2021. With a sequencing rate consistently exceeding 60%, and up to 80% of PCR-positive samples between March and November, the viral genome set is broadly whole-epidemic representative. We identify a consistent rise in viral diversity over time, with notable spikes upon the importation of novel variants (e.g., Delta and Omicron). By linking genomic data with rich individual-level demographic data from national registers, we find that individuals aged < 15 and > 75 years had a lower contribution to molecular change (i.e., branch lengths) compared to other age groups, but similar molecular evolutionary rates, suggesting a lower likelihood of introducing novel variants. Similarly, we find greater molecular change among vaccinated individuals, suggestive of immune evasion. We also observe evidence of transmission in rural areas to follow predictable diffusion processes. Conversely, urban areas are expectedly more complex due to their high mobility, emphasising the role of population structure in driving virus spread. Our analyses highlight the added value of integrating genomic data with detailed demographic and spatial information, particularly in the absence of structured infection surveys.
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Journal articleWarwick L, Murray JE, Brindley H, 2024,
The Far-INfrarEd Spectrometer for Surface Emissivity (FINESSE) – Part 2: First measurements of the emissivity of water in the far-infrared
, Atmospheric Measurement Techniques, Vol: 17, Pages: 4777-4787<jats:p>Abstract. In this paper, we describe a method for retrieving the surface emissivity of specular surfaces across the wavenumber range of 400–1600 cm−1 using novel radiance measurements of the Far-INfrarEd Spectrometer for Surface Emissivity (FINESSE) instrument. FINESSE is described in detail in Part 1 (Murray et al., 2024) of this paper. We apply the method to two sets of measurements of distilled water. The first set of emissivity retrievals is of distilled water heated above ambient temperature to enhance the signal-to-noise ratio. The second set of emissivity retrievals is of ambient temperate water at a range of viewing angles. In both cases, the observations agree well with calculations based on compiled refractive indices across the mid- and far-infrared. It is found that the reduced contrast between the up- and downwelling radiation in the ambient temperature case degrades the performance of the retrieval. Therefore, a filter is developed to target regions of high contrast, which improves the agreement between the ambient temperature emissivity retrieval and the predicted emissivity. These retrievals are, to the best of our knowledge, the first published simultaneous retrievals of the surface temperature and emissivity of water that extend into the far-infrared and demonstrate a method that can be used and further developed for the in situ retrieval of the emissivity of other surfaces in the field. </jats:p>
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Journal articleBoyle MJW, Sharp AC, Barclay MV, et al., 2024,
Tropical beetles more sensitive to impacts are less likely to be known to science
, Current Biology, Vol: 34, Pages: R770-R771, ISSN: 0960-9822Insects are posited to be declining globally. This is particularly pertinent in tropical forests, which exhibit both the highest levels of biodiversity and the highest rates of biodiversity loss. However, for the hyper-diverse tropical insects there are scant data available to evidence declines. Understanding tropical insect diversity and its response to environmental change has therefore become a challenge, but it is estimated that 80% of tropical insect species remain undescribed1. Insect biodiversity predictions are based mostly on well-studied taxa and extrapolated to other groups, but no one knows whether resilience to environmental change varies between undescribed and described species. Here, we collected staphylinid beetles from unlogged and logged tropical forests in Borneo and investigated their responses to environmental change. Out of 252 morphospecies collected, 76% were undescribed. Undescribed species showed higher community turnover, reduced abundance and decreased probability of occurrence in logged forests. Thus the unknown components of tropical insect biodiversity are likely more impacted by human-induced environmental change. If these patterns are widespread, how accurate will assessments of insect declines in the tropics be?
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Journal articleGettelman A, Christensen MW, Diamond MS, et al., 2024,
Has reducing ship emissions brought forward global warming?
, Geophysical Research Letters, Vol: 51, ISSN: 0094-8276Ships brighten low marine clouds from emissions of sulfur and aerosols, resulting in visible “ship tracks”. In 2020, new shipping regulations mandated an ∼80% reduction in the allowed fuel sulfur content. Recent observations indicate that visible ship tracks have decreased. Model simulations indicate that since 2020 shipping regulations have induced a net radiative forcing of +0.12 Wm−2. Analysis of recent temperature anomalies indicates Northern Hemisphere surface temperature anomalies in 2022–2023 are correlated with observed cloud radiative forcing and the cloud radiative forcing is spatially correlated with the simulated radiative forcing from the 2020 shipping emission changes. Shipping emissions changes could be accelerating global warming. To better constrain these estimates, better access to ship position data and understanding of ship aerosol emissions are needed. Understanding the risks and benefits of emissions reductions and the difficultly in robust attribution highlights the large uncertainty in attributing proposed deliberate climate intervention.
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Journal articleBurtonshaw JEJ, Paluszny A, Mohammadpour A, et al., 2024,
Effects of mechanical properties of the underburden on induced seismicity along a basement fault during hydrogen storage in a depleted reservoir.
, iScience, Vol: 27This study models the geomechanical deformation of a depleted gas field, wherein gaseous hydrogen is stored in a North Sea reservoir, and is cyclically injected and withdrawn. A fault is modeled within the underburden, and its slip is investigated during a three year storage period. Parametric simulations are conducted to study the influence of the underburden mechanical properties, such as Young's modulus, Poisson's ratio, and permeability on induced seismicity. The fault is predominantly in stick during the bulk of the injection, storage, and withdrawal periods, but minor fault slip ( < 4 mm) occurs shortly after a change in operational regime. The Young's modulus of the underburden unit has the strongest control on fault slip. To reduce the seismic hazard, an underburden with low Young's modulus ( < 15 GPa), high Poisson's ratio ( > 0.25), low Biot coefficient, and low permeability ( < 1 × 10 - 19 m2) is found to be most suitable for hydrogen storage.
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