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An alternative representation of Synthetic Aperture Radar images as an aid to the interpretation of englacial observations
Get PDFGround-penetrating radar reveals subsurface geometry and ice stratigraphy that contains information about past and present dynamics of the cryosphere. Synthetic Aperture Radar (SAR) is a processing technique based on averaging the radar echoes received at multiple locations as the radar moves relative to the target. Due to this averaging, the directional properties of the back-scattering from the target received at these multiple locations are lost. We introduce an alternative representation of SAR images that preserves directional information encoded in its Doppler spectrum: the Doppler frequency accounts for the time-delay variation from the radar to the target. With this technique, called Red–Green–Blue Doppler Decomposition (RGB-DD), the Doppler spectrum of a SAR image is split into three equalised bands, each band representing a primary direction of arrival of the radar echoes. A primary colour is assigned to each band to allow joint representation in a single RGB image. We apply our representation framework to several datasets acquired with the British Antarctic Survey (BAS) airborne ice-sounding radar over three Antarctic ice streams. Compared to the standard SAR method that is based solely on the averaged intensity level, this method facilitates the enhanced interpretation of englacial features such as ice stratigraphy, crevasses, tephra layers, and along-flow transitions in strain rate. The technique may be extended to other sensors and applications
High temporal variability not trend dominates Mediterranean precipitation
Get PDFState-of-the-art climate models project a substantial decline in precipitation for the Mediterranean region in the future. Supporting this notion, several studies based on observed precipitation data spanning recent decades have suggested a decrease in Mediterranean precipitation with some attributing a large fraction of this change to anthropogenic influences. Conversely, certain researchers have underlined that Mediterranean precipitation exhibits considerable spatiotemporal variability driven by atmospheric circulation patterns maintaining stationarity over the long term. These conflicting perspectives underscore the need for a comprehensive assessment of precipitation changes in this region, given the profound social, economic and environmental implications. Here we show that Mediterranean precipitation has largely remained stationary from 1871 to 2020, albeit with significant multi-decadal and interannual variability. This conclusion is based on the most comprehensive dataset available for the region, encompassing over 23,000 stations across 27 countries. While trends can be identified for some periods and subregions, our findings attribute these trends primarily to atmospheric dynamics, which would be mostly linked to internal variability. Furthermore, our assessment reconciles the observed precipitation trends with Coupled Model Intercomparison Project Phase 6 model simulations, neither of which indicate a prevailing past precipitation trend in the region. The implications of our results extend to environmental, agricultural and water resources planning in one of the world’s prominent climate change hotspots.
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Ocean Acidification around the UK and Ireland
Get PDFAtmospheric CO2 exceeded 420 ppm in 2024 and has continued to increase by approximately 2.5 ppm per year over the last decade. The global ocean absorbs approximately a quarter of anthropogenic carbon dioxide (CO2) emissions annually.
The North Atlantic Ocean contains more anthropogenic CO2 than any other ocean basin, and surface waters are experiencing an ongoing decline in pH (increasing acidity). Rates of acidification in bottom waters are occurring faster at some locations than in surface waters. Some species are already showing effects from ocean acidification when exposed to short-term fluctuations and could be used as
indicator species for long-term impacts on marine ecosystems
Could underground disposal of carbon dioxide help to reduce India’s emissions?
Get PDFBGS geologists have partnered with research institutes in India to explore the potential for carbon capture and storage, with an emphasis on storage
Recent benthic foraminifera communities offshore of Thwaites Glacier in the Amundsen Sea, Antarctica: implications for interpretations of fossil assemblages
Get PDFBenthic foraminiferal assemblages are useful tools for paleoenvironmental studies but rely on the calibration of live populations to modern environmental conditions to allow interpretation of this proxy downcore. In regions such as the region offshore of Thwaites Glacier, where relatively warm Circumpolar Deep Water is driving melt at the glacier margin, it is especially important to have calibrated tracers of different environmental settings. However, Thwaites Glacier is difficult to access, and therefore there is a paucity of data on foraminiferal populations. In sediment samples with in situ bottom-water data collected during the austral summer of 2019, we find two live foraminiferal populations, which we refer to as the Epistominella cf. exigua population and the Miliammina arenacea population, which appear to be controlled by oceanographic and sea ice conditions. Furthermore, we examined the total foraminiferal assemblage (i.e., living plus dead) and found that the presence of Circumpolar Deep Water apparently influences the calcite compensation depth. We also find signals of retreat of the Thwaites Glacier Tongue from the low proportion of live foraminifera in the total assemblages closest to the ice margin. The combined live and dead foraminiferal assemblages, along with their environmental conditions and calcite preservation potential, provide a critical tool for reconstructing paleoenvironmental changes in ice-proximal settings
A network of precipitation observations to improve Antarctic climate and ice sheet projections [News & Views]
No full textStatistical Analysis of Comet Disconnection Events Using STEREO HI and a Data-assimilative Solar Wind Model
Get PDFComets tails can reveal information about the local solar wind conditions. They can exhibit various signatures of interactions with the solar wind including bending, developing kinks, and sometimes undergoing tail disconnections. In this study, we investigate comet tail disconnection events observed in the STEREO HI data during the period of 2007–2023. Using the Heliospheric Upwind eXtrapolation model with a time-dependency (HUXt) solar wind model alongside novel solar wind data assimilation (DA) techniques, each disconnection event was investigated to determine its cause. The resulting statistical analysis led to three main conclusions: (1) for every heliospheric current sheet (HCS) crossing predicted by HUXt that occurs when the comet is within the region of influence of DA, a tail disconnection follows; (2) for HCS crossings that occur outside the region where DA can be applied, 54.5% are followed by a tail disconnection; and (3) there is an approximately linear relationship between the speed of the solar wind at the HCS crossing and the time delay to the onset of a disconnection given by the equation V rel (km s −1 ) = (2.23 ± 0.35)Δ t (hr) + (400 ± 10)(km s −1 )
Dietary adaptations along the northern limit of distribution: what does the smooth snake Coronella austriaca eat in Norway? Metabarcoding of stomach content and visual analysis of faeces
Get PDFUnderstanding how species survive at their poleward limits of distribution is of interest in species conservation, particularly in light of global warming and predictions of shifting distributions of both predators and prey species. How species adapt to high latitudes and to future climate changes will be impacted both by direct interactions with the environment, such as changing heat tolerances, but also indirectly through biotic interactions with prey and predators. The smooth snake Coronella austriaca in Norway provides an interesting case study of biotic interactions at range limits. The number of potential prey species of C. austriaca is lower in Norway than in southern latitudes. To investigate trophic adaptations at its poleward range limit we used metabarcoding sequencing to identify prey species in stomach samples of a museum collection of 17 preserved C. austriaca from Agder in southern Norway. Eight prey species were detected, four reptiles and four mammals. Field vole Microtus agrestis and common shrew Sorex araneus were the most common prey species, while bank vole Myodes glareolus and wood mice Apodemus sylvaticus were eaten by only a few smooth snakes. Slow worm Anguis fragilis was found in five samples and common lizard Zootoca vivipara in only three samples. DNA was also recovered from grass snake Natrix natrix in all but one sample, and DNA from European adder Vipera berus in one sample, indicating the role of ophiophagy. Visual analysis of 75 faeces from the Oslo region showed that A. fragilis was the most common prey species, followed by shrews. The main conclusion is that C. austriaca in Norway have a higher proportion of mammalian prey and snakes in their diet compared to populations in more southern latitudes
Precipitation and temperature drive woody vegetation dynamics in the grasslands of sub-Saharan Africa
Get PDFIdentifying the drivers of ecosystem dynamics, and how responses vary spatially and temporally, is a critical challenge in the face of global change. Grasslands in sub‐Saharan Africa are vital ecosystems supporting biodiversity, carbon storage, and livelihoods through grazing. However, despite their importance, the processes driving change in these systems remain poorly understood, as cross‐scale interactions among drivers produce complex, context‐dependent dynamics that vary across space and time. This is particularly relevant for woody vegetation dynamics, which are often linked to degradation processes (e.g., woody encroachment), with consequences for biodiversity, forage availability, and fire regimes. Here, we used satellite data and structural equation models to investigate the effects of rainfall, temperature, fire, and population density on woody vegetation dynamics in four African grassland regions (the Sahel grasslands, Greater Karoo and Kalahari drylands, Southeast African subtropical grasslands, and Madagascar) during 1997–2016. Across all regions, rainfall was consistently positively correlated with increased woody vegetation, while higher temperatures were associated with decreased woody vegetation, suggesting that water availability promotes woody plant growth, whereas rising aridity limits it. Unexpectedly, fire had a negative effect on woody cover only in the Greater Karoo and Kalahari drylands, while in Madagascar, higher temperatures and greater population density reduced fire; yet these relationships did not translate into significant indirect effects on woody vegetation. These findings illustrate the complex ways by which environmental and anthropogenic drivers shape woody vegetation dynamics in grasslands across sub‐Saharan Africa. Compared to savannas, fire plays a weaker and more region‐specific role in grasslands, where its feedback with woody cover is less consistent. The opposing effects of rainfall and temperature may currently constrain woody expansion, but climate change could disrupt this balance and further weaken fire's limited regulatory role. These differences highlight the need for management strategies tailored to the distinct climate–vegetation dynamics of grassland systems
Barremian tricolpate pollen from Portugal—New evidence for the age of eudicot-related angiosperms
No full textNew evidence on the timing of early angiosperm evolution is presented through the discovery of four well-dated tricolpate pollen grains from the Early Cretaceous midlatitudes. Recovered from nearshore marine sediments in the Lusitanian Basin of Portugal, these fossils significantly expand the pre-Aptian tricolpate pollen record and document a greater number of pre-Aptian tricolpate grains in the midlatitudes than previously recognized. The fossil evidence was obtained through the innovative application of advanced microscopy techniques and was precisely dated through biostratigraphy and strontium isotope stratigraphy on material from the same section. These findings extend the first occurrence of tricolpate pollen to the early late Barremian (~123.0 Ma) in Portugal and possibly worldwide. Our findings provide fossil evidence with minimal dating uncertainty, as both the fossils and their age determination come from the same well-constrained sections, eliminating the need for cross-correlation. This establishes the most reliable age for the first occurrence of tricolpate pollen, unequivocally linked to the eudicot clade—an early derived lineage within angiosperms. These fossils serve as a robust calibration point for phylogenetic studies. Additionally, our study emphasizes the importance of methodological advancements in refining the fossil plant record. The newly applied fluorescence screening method when adapted also in future research could further enhance the detection of rare fossils, offering insights into the diversification of angiosperms
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