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Nigeria vegetation trend during recent West African monsoon season and the near future implications in CORDEX-Africa
No full textHighlights:
• Mean NDVI indicate increase in trend of vegetation pattern.
• WAM seasonal rainfall exerted characteristic impact on the vegetation trend.
• Bias-corrected CORDEX-Africa enhances reasonable simulation of the WAM.
• Projected implication of vegetation trend by the mid-21st century.
Abstract:
This study investigated the impact of recent West African monsoon seasonal rainfall on the vegetation trend in Nigeria. Using Mann-Kendall test, the satellite estimates revealed increasing trends in the mean Normalized Difference Vegetation Index (NDVI) at 95 % in area of the location between 1981 and 2020 with statistical significance (at
levels of significance) in the south-western States. The 6-month Standardized Precipitation Index (SPI) from the Climate Research Unit (CRU) observational rainfall within the same period indicated increasing trends at 73 % of the area with statistical significance (at levels of significance) in the northern States above the 9° N latitude. From the temporal correlations between the seasonal rainfall and vegetation trends, there was significant (at 95 % confidence level from the t-test) positive characteristic impact on 89 % of the area. The CORDEX-Africa historical experiment outputs (1981–2005) of the selected models and the ensemble mean revealed strong correlation values with high normalized RMSE when representing the seasonal rainfall simulation. The bias-corrected output (2006–2020) in the RCP 8.5 experiment showed notably enhanced representation quality of the models and the ensemble mean, with 87 % of the area demonstrating “reasonable performance” efficiency. The 6-month SPI projection from 2021 to 2050 indicated positive trends in 84 % of the area. Indeed, the relative percentage difference between projected and baseline trends compellingly suggests a decrease in seasonal rains by 2050, intensifying the demand on vegetation and introducing additional climate challenges
Eurasian ice sheet formation promoted by weak AMOC following MIS 3
No full textThe Eurasian ice sheet complex (EIS) was the third largest ice sheet complex at the Last Glacial Maximum (LGM). Although temporal and spatial evolution of the EIS during the last glacial cycle has not been well-established, strong evidence indicates the existence of nearly ice-free conditions during Marine Isotope Stage 3 (MIS 3). Between MIS 3 and the LGM, the EIS likely experienced substantial expansions. These expansions were accompanied by decreasing boreal summer insolation, a slight reduction in greenhouse gases, and millennial-scale abrupt shifts between stadial and interstadial conditions. Using the state-of-the-art Earth system model AWI-ESM with asynchronously coupled dynamic ice sheets, we performed transient simulations focusing on this period. Our study shows that the formation of the EIS resembles a bifurcation transition. Only in case of a relatively weak background Atlantic Meridional Overturning Circulation (AMOC), a sufficiently large thin ice/snow cover develops to accommodate a subsequent ice volume growth as Northern Hemisphere summer insolation further decreases. Furthermore, sensitivity experiments show a large non-linearity in surface mass balance changes in response to varying temperature and precipitation, indicating a high sensitivity of the EIS buildup. Our study highlights the large complexity and strong non-linearity of the Earth system induced by internal climate feedbacks, particularly the interactions between ice sheets and other climate components
What Controls the Evolution of Pacific Coastal Niño Events in the CESM Large Ensemble?
No full textAbstract:
Coastal Niños, warm events in the far eastern tropical Pacific without corresponding strong anomalies in the central equatorial Pacific, strongly influence local rainfall and fisheries. However, individual events strongly differ from each other. They can develop into a basin-wide El Niño (as in 2023) or stay confined to the South American coast (as in 2017). The large event-to-event variability in combination with the rarity of events in the observational record limits our understanding of Coastal Niños. The Community Earth System Model Large Ensemble Project (CESM-LE) simulates Coastal Niños realistically, including their phase-locking to boreal spring and variable evolution. Conditions in the subtropical Pacific, equatorial wave dynamics and western tropical Pacific wind anomalies are identified as factors important for the evolution of Coastal Niños in the CESM-LE. Coastal Niños in turn increase the probability of a basin-wide El Niño in the following months.
Key Points:
Simulated Pacific Coastal Niños mainly occur in May and June, but strongest precipitation is associated with events earlier in the year
In CESM the evolution of Coastal Niños is governed by equatorial waves and background conditions in the equatorial and subtropical Pacific
Occurrence of Coastal Niños increases the chance for the development of basin-wide El Niño events arising from cold or neutral state
Science Evaluation Panel of the International Ocean Drilling Programme (IODP-cubed) / Panel Member
No full textFAIR Data journey towards a living lab
No full textFollowing the FAIR data lifecycle, we give insights on how data management is practically carried out towards the Living Lab in MULTI-MAREX
Systemic failure of European fisheries management: Overcoming shortsighted interests with politically independent ecosystem-basedcatch limits may end overfishing in EU waters
No full textAs parties to United Nations Convention on the Law of the Sea (UNCLOS) (1), the European Union (EU) and its member states have adopted its obligations in the legally binding EU Common Fisheries Policy (CFP) (2). Yet despite legal commitments (see table S2), overfishing and the collapse of stocks continue in EU waters, prompting the question of why the EU is missing its goals. Fisheries data on the western Baltic Sea illustrate that the EU failed to implement key objectives of the CFP (2) in subsequent laws and regulations. The implementation of basic management has failed because of nonsustainable scientific catch advice along with shortsighted national requests leading to ill-advised proposals by the EU Commission (COM) that were subsequently fixed legally by national ministers in the EU Agriculture and Fisheries Council (the Council). To make catch advice truly science-based and independent of shortsighted influence, we suggest creating a politically independent European Fisheries Authority
Role of Lee Wave Turbulence in the Dispersion of Sediment Plumes
No full textSediment plumes threatening benthic ecosystems are one of the environmental hazards associated with seafloor interventions such as bottom trawling, cabling, dredging, and marine mining operations. This study focuses on sediment plume release from hypothetical future deep-sea mining activities, emphasizing its interaction with turbulent ocean currents in regions characterized by complex seafloor topography. In such environments, turbulent lee waves may significantly enhance the scattering of released sediments, pointing to the clear need for appropriate impact assessment frameworks. Global-scale models are limited in their ability to resolve sufficiently high Reynolds numbers to accurately represent turbulence generated by seafloor topography. To overcome these limitations and effectively assess lee wave dynamics, models must incorporate the full physics of turbulence without simplifying the Navier–Stokes equations and must operate with significantly finer spatial discretization while maintaining a domain large enough to capture the full topographic signal. Considering a seamount in the Lofoten Basin of the Norwegian Sea as an example, we present a novel numerical analysis that explores the interplay between lee wave turbulence and sediment plume dispersion using a high-resolution Large Eddy Simulation (LES) framework. We show that the turbulence occurs within semi-horizontal channels that emerge beyond the topographic highs and extend into sheet-like tails close to the seafloor. In scenarios simulating sediment release from various sites on the seamount, our model predicts distinct behavior patterns for different particle sizes. Particles with larger settling velocities tend to deposit onto the seafloor within 50–200 m of release sites. Conversely, particles with lower settling velocities are more susceptible to turbulent transport, potentially traveling greater distances while experiencing faster dilution. Based on our scenarios, we estimate that the plume concentration may dilute below 1 ppm at about 2 km distance from the release site. Although our analysis shows that mixing with ambient seawater results in rapid dilution to low concentrations, it appears crucial to account for the effects of topographic lee wave turbulence in impact assessments related to man-made sediment plumes. Our high-resolution numerical simulations enable the identification of sediment particle size groups that are most likely affected by turbulence, providing valuable insights for developing targeted mitigation strategies
Environmental concentration of the quaternary ammonium disinfectant benzalkonium chloride strongly induces resistance gene profiles in fish
No full textHighlights
• BAC showed an enhanced potential to stimulate multidrug resistance.
• Environmental doses of BAC have a stronger ARGs-inducing effect than SMZ.
• Bacterial escape mechanisms from host defense differ under BAC and SMZ exposure.
• The resistance effects of commonly used disinfectants warrant more attention.
Disinfectants are non-antibiotic biocides that have been used extensively in daily life, particularly since the onset of the COVID-19 pandemic. However, their effect on drug resistance has not received sufficient attention. Here, marine medaka were subjected to an environmental concentration (10 μg/L) of benzalkonium chloride (BAC), sulfamethazine (SMZ), and their combination, aiming to elucidate their contributions to antibiotic resistance. Overall, 10 μg/L BAC exhibited a stronger induction potential for multiple antibiotic resistance genes (ARGs) relative to a similar level of SMZ. Specifically, tetracycline resistance genes were readily induced, regardless of exposure to BAC, SMZ, or their combination. BAC exhibited a more pronounced induction of ARGs than SMZ and showed a stronger potential to stimulate multidrug resistance. SMZ and BAC induced distinct virulence factors. Bacteria increased pathogenicity primarily through biofilm formation and enhanced community sensing under SMZ exposure, whereas iron acquisition and the production of reactive oxygen species appeared to be the main mechanisms by which bacteria evaded host defenses under BAC exposure. A greater number of ARGs demonstrated a significant positive correlation with virulence factors following BAC exposure compared to both the SMZ exposure group and the co-exposure group, which further confirmed the strong ability of BAC to induce multidrug resistance. In summary, owing to the typically unregulated and low-dose use of disinfectants in daily life and their pseudo-persistence in the environment, their potential to induce resistance may exceed that of antibiotics. Therefore, increased attention and preventive measures are required to address their resistance-inducing effects
Complex architecture of mud volcano systems: New insights on flow pathways unravel intricate fluid circulation
No full textMud volcanoes (MVs) are important gateways for fluid migration, particularly in subduction zones. We investigate five MVs in the Gulf of Cadiz and the Mediterranean Ridge, revealing underappreciated fluid pathways responsible for fluid expulsion. By utilizing pore water geochemistry, advection-diffusion modeling, and high-resolution seismic profiles, we trace fluid origins, quantify fluxes, and constrain migration pathways, focusing on the Ginsburg MV. The Cl-depleted summit fluids originate from clay dehydration within the Allochthonous Unit of the Gulf of Cadiz (AUGC) and are channeled by central conduits, reaching high advection velocities (2.8−15 cm/yr). The Cl-enriched moat fluids exhibit slower advection velocities (0.3 cm/yr) and show additional evaporite effects. To constrain moat fluid sources, fluid formation temperatures have been calculated using water isotopes and Mg-Li geothermometer. The resulting low temperatures suggest source depths atop the AUGC (∼0.8 kmbsf), consistent with seismic data across the Ginsburg MV (showing high-amplitude reflections at the same depths) but different from the summit sites, where the source is deeper within the AUGC (∼2.2 kmbsf). We relate moat seepage occurrence to fractures formed due to edifice subsidence, marked by stacked enhanced reflectors. Upon comparison with all analyzed MVs, we suggest that peripheral seepage of MV edifices is a widespread process that appears in a specific evolutionary stage, during which it represents an important component of fluid budget. This phenomenon, which has been observed in terrestrial MVs, is rarely described for their submarine counterparts but has wide biogeochemical implications for fluid budget in subduction zones and the sustenance of seafloor biological communities