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Complex past ice flow from Norway to the North Sea Plateau during the Quaternary: evidence from Marstein Trough and earlier reconstructions using 3D seismic data sets
Get PDFBased on a regional 3D seismic data set and a small high‐resolution 3D seismic data set (~40 km 2 ) we have mapped a buried glacially eroded trough on the North Sea Plateau, west of the Norwegian Channel (latitude 59°N, longitude 3°E). The trough, which we informally name Marstein Trough, is 60 km long, 30 km wide, 120 m deep, and trends NE–SW. Marstein Trough contains an extensive pattern of glacial lineations at its base, which follow the trough axis, and is infilled by two seismic units interpreted as tills. From its stratigraphical position, we infer that the trough was eroded by an ice stream that flowed from western Norway and crossed the Norwegian Channel in a southwesterly direction, probably during the penultimate, Saalian glaciation. Marstein Trough, and its diagnostic landforms, provide detailed evidence of complex, switching ice flow across the North Sea during the Quaternary. Westward ice flow from Norway took place during early Scandinavian Ice‐Sheet build‐up prior to the activation of the Norwegian Channel Ice Stream. In contrast, ice‐flow patterns during full‐glacial conditions caused ice flow to reorientate to a S–N direction when the Norwegian Channel Ice Stream with a huge catchment that included the Baltic was established. Our results highlight the complex patterns of ice flow experienced over this region of the North Sea, with implications for reconstructions of Quaternary history, modern renewable energy infrastructure installation, and glacial processes during the build‐up phase of ice sheets
Presence of two eddies in close proximity drives large spatial and temporal heterogeneity in the euphotic zone
Get PDFOceanic mesoscale structures, such as eddies, play a fundamental role in ocean circulation, ocean biogeochemical cycles and plankton ecology. They cause lateral and vertical advection, as well as interact with vertical mixing, which is predicted to promote episodic fluxes of macronutrients to the surface ocean. However, the interactions between mesoscale eddies can generate submesoscale fronts and filaments occurring over short temporal and spatial scales and thus their impact on ocean biogeochemistry has been difficult to characterize. During an expedition to the Porcupine Abyssal Plain (PAP) site in the Northeast Atlantic in June 2013, we studied the interface between a cyclonic and an anticyclonic eddy, measuring nutrient and chlorophyll-a concentrations, zooplankton abundance and community structure, and marine snow aggregate abundance and sinking velocities. We observed that eddy rotation and a storm event induced, respectively, lateral stirring and vertical mixing of the two distinct water masses, driving spatial and temporal biogeochemical heterogeneity at the PAP site. Furthermore, we observe that diel and vertical variations in aggregate type and abundance were closely linked to the vertical distribution and abundance of zooplankton, suggesting that zooplankton were the main gatekeepers of carbon flux. Our findings suggest that the interactions between mesoscale structures could significantly modify organic carbon export, as well as provide sustenance for higher trophic levels, processes that have implications for fisheries and global climate
Species responses to weather anomalies depend on local adaptation and range position
Get PDFSpecies show intra-specific variation in responses to climate change linked to adaptation to the local climatic conditions. Likewise, species are expected to be more resilient to climate change at the centre of their bioclimatic niche, but this pattern is not general. We show that species sensitivity to climatic anomalies varies with local adaptation and the position in the bioclimatic niche, using long-term butterfly monitoring data for 34 species. Climatic anomalies negatively affected all populations of locally adapted species. Globally adapted species were positively or negatively affected by climatic anomalies, depending on population location and direction of anomalies. These responses impacted population trends as globally adapted species showed steeper declines at the trailing margin. Surprisingly, locally adapted species showed stable abundances at the trailing margin, but declines at the leading; which could be explained by the with the 'warmer is better' hypothesis where thermodynamics limit insect performance at cooler conditions
Experiments on buoyancy-driven instability ahead of a dissolution front in a porous rock
Get PDFFluid-rock reactions are of great interest in many engineered geological storage and disposal systems where the long term integrity of the system is key, and where fluid seepage through a permeable rock may lead to reaction and convective transport of material through the formation. If an unsaturated fluid displaces formation fluid in equilibrium with a reactive porous medium, a reaction front develops, across which the invading fluid becomes saturated with the soluble matrix material. Depending on the composition of the invading fluid, it may initially be less dense than the formation fluid, but following reaction it may become denser than the formation fluid. If the invading fluid displaces the formation fluid downwards through the porous layer, the reaction front may then be stabilized by buoyancy, but a Rayleigh-Taylor type instability can develop at the interface between the reacted fluid and the original formation fluid ahead of the reaction front. We present a series of new analog experiments of this process by injecting aqueous sugar solutions into a porous layer containing saturated salt solution, salt powder, and glass ballotini. As an analog of a reaction front, a dissolution front develops as the aqueous sugar solution dissolves the salt powder and becomes denser than the saturated salt solution. The buoyancy instability then leads to a growing finger interface. If the buoyancy speed of the fluid, u B , is smaller than u F − u R , where the speed of the advancing fluid-fluid front is u F and the speed of the dissolution front is u R then the instability grows as if the system were unconfined. However, if u B > u F − u R , then the supply of fluid at the dissolution front limits the growth of the instability. We present an idealised model for the speed of the non-linear buoyancy-driven fingers, and we consider the implications of our results for the long term integrity of a number of geological storage systems.
Published by the American Physical Society 202
The genome sequence of the engrailed moth, Ectropis crepuscularia (Denis & Schiffermüller), 1775
Get PDFWe present a genome assembly from a male specimen of Ectropis crepuscularia (Engrailed; Arthropoda; Insecta; Lepidoptera; Geometridae). The genome sequence has a total length of 878.53 megabases. Most of the assembly (99.28%) is scaffolded into 32 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genome has also been assembled, with a length of 15.4 kilobases. Gene annotation of this assembly on Ensembl identified 14,903 protein-coding genes
The genome sequence of the uncertain moth, Hoplodrina octogenaria (Goeze, 1781)
Get PDFWe present a genome assembly from a male specimen of Hoplodrina octogenaria (Uncertain moth; Arthropoda; Insecta; Lepidoptera; Noctuidae). The genome sequence has a total length of 476.65 megabases. Most of the assembly (99.98%) is scaffolded into 31 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genome has also been assembled, with a length of 15.93 kilobases
Using Storage Ponds in Natural Flood Management Schemes in Practice: the Need for Fine‐Tuning and Upscaling
Get PDFThere is increasing interest in installing water storage ponds as part of natural flood management (NFM) approaches being implemented globally. Despite decades of experience with constructing flood storage ponds within civil engineering disciplines, there remains little empirical evidence of their effectiveness in NFM. In NFM, ‘natural’ ponds use green infrastructure, are often smaller but more numerous, and are built and maintained by land managers rather than engineers. Here we investigate six flood storage ponds in the 69 km 2 Eddleston NFM pilot catchment in Scotland, UK, analysing impact on peak stream flows at different scales and pond designs. The ponds generally reduce peak stream flows where they have large available capacity, catchments are small ( 20% Annual Exceedance Probability (AEP)). No discernible flow reduction was observed at the largest pond and catchment (64 km 2 ) for the largest (~21% AEP) event. There was significant variability between ponds, and gains can be made in engineering pond inlet/outlet structures, maintenance, and more widespread installation. The findings suggest that natural storage ponds have most potential to contribute to flood control in small catchments ( 25% AEP), when they are carefully designed and maintained, and sufficient in number
Long-range impacts of biomass burning on PM2.5: a case study of the UK with a globally nested model
Get PDFOpen biomass burning impacts air quality through direct emissions of fine particulate matter (PM2.5) and its role in secondary PM2.5 formation. Here the interest is in the long distance and cumulative influences of biomass burning on annual mean concentrations of PM2.5 in a country far removed from major biomass burning regions: the UK. A novel, globally nested setup of the EMEP4UK atmospheric chemistry transport model is used to isolate contributions to UK PM2.5 from global biomass burning activity. Long-range influences are found to be considerable, with 0.99 μg m-3 of UK-averaged PM2.5 in 2019 being conditional on biomass burning emissions. Of this, 97 % and 73 % are associated with biomass burning outside the UK and outside the model's European domain, respectively – notably from Russia, Asia and boreal North America – which highlights the importance of boundary conditions on regional modelling setups. The simulations suggest some influences of biomass burning have lags of several weeks. The long-range component is enhanced by the role of biomass burning in secondary aerosol formation (58 % of PM2.5 conditional on biomass burning), of which 55 % is organic; the inorganic component (mainly NH4NO3) derives from increased oxidation of local emissions, which may be mitigated through local emissions reductions. The PM2.5 conditional on biomass burning is highly policy relevant for the UK, constituting (for 2019) 20 % of the current WHO target and 10 % of the contribution from all sources. This relative contribution is likely to increase as anthropogenic PM2.5 declines and as climate change increases northern-hemispheric extratropical biomass burning
Brief communication: Sharp precipitation gradient on the southern edge of the Tibetan Plateau during cold season
Get PDFThe Tibetan Plateau is a high-altitude arid region, where limited in-situ precipitation measurements are available. In this communication, we document a strong precipitation gradient at the southern edge of the Paiku Co catchment (southern Tibetan Plateau) from in-situ data and atmospheric model outputs. In particular, we use water pressure time series from proglacial lakes, two automatic weather stations, and data from ERA5-Land reanalysis and CORDEX-FPS-CPTP ensemble. We show that precipitation totals can vary by one order of magnitude over a short distance of 10 km in a rather smooth terrain during the cold season. This large precipitation gradient marks the transition between the great Himalayas and the Tibetan Plateau
Connecting mixing to upwelling along the ocean's sloping boundary
No full textDeep-ocean upwelling, driven by small-scale turbulence, plays a key role in climate by regulating the ocean's capacity to sequester heat and carbon. Recent theoretical studies have hypothesized that such upwelling may primarily occur within a bottom boundary layer (BBL) along the sloping seafloor. A dye experiment in a continental-slope canyon during the BLT-Recipes program revealed very rapid BBL-focussed upwelling, endorsing this notion. Here, we elucidate the dynamical connection between the mixing and the upwelling. We show that along-canyon upwelling stems from episodic turbulent mixing cells up to 250 m high, generated by tides sweeping up- and down-canyon. The tidal currents support a vertical shear that periodically advects dense waters over slower-flowing lighter waters, reducing BBL stratification. This triggers instabilities that mix the dense waters with neighboring lighter waters, resulting in net along-boundary upwelling. Our findings substantiate the view that deep-ocean upwelling can predominantly occur along the ocean's sloping boundaries
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