Communications Earth & Environment最新文献

The Gulf Stream is important for the climate system through its transport and air-sea exchange of heat. What is less well accepted is the role of the Gulf Stream in the carbon cycle. Here we examine how the Gulf Stream provides a "biogeochemical stream", a sub-surface horizontal flux carrying waters with high concentrations of nutrients and low concentrations of anthropogenic carbon. Model experiments reveal particles released in dense layers at the start of the Gulf Stream follow trajectories extending into the subpolar gyre, while particles released at the surface are confined to the subtropics. Following a pathway to the subpolar gyre, the biogeochemical stream carries older, nutrient-rich and anthropogenically carbon-depleted waters along density layers and, when those dense layers outcrop into the mixed layer, enhances the subpolar drawdown of atmospheric carbon. This connectivity is supported by model sensitivity experiments revealing the subpolar upper ocean carbon content and upstream dense waters in the Gulf Stream connecting on timescales of 4 to 8 years. The likely effect of climate change on the biogeochemical stream is a decrease in the delivery of these older waters, both high in concentrations of nutrients and depleted in anthropogenic carbon, to the subpolar mixed layer, so weakening future North Atlantic carbon uptake from the atmosphere.

One of the most intriguing attributes of Earth's magnetic field is that it reverses polarity. Previous palaeomagnetic records mainly from the last ~17 million years indicate that the reversal process typically occurs over ten thousand or fewer years. Here we present an exceptionally resolved deep sea sedimentary palaeomagnetic record that captures two polarity transitions that occurred ~40 million years ago. These transitions occur over 18 and 70 thousand years and are much longer than the typical 10 kyr duration for younger reversals. Longer-duration transitions like these are calculated in numerical geodynamo models, suggesting that variable reversal durations are an intrinsic property of the geodynamo. This variability predicts that polarity transition durations can be much longer than 10 kyr. Occasional prolonged intervals of transitional, and weaker, geomagnetic fields would have exposed Earth's Eocene environments to greater high-energy radiation from the sun for longer intervals of time, with potential impacts on biota.

The surface and interior ocean are connected through physical processes that act in three dimensions and on subseasonal timescales. Numerical models and observations both highlight the importance of these eddying dynamics on shaping the biogeochemical and biological variability in the upper mesopelagic ocean. The resulting subsurface tracer variance outside of the photic zone has implications for ocean ventilation timescales as well as biogeochemical function and microbial community composition. Subsurface patchiness is best described using water mass frameworks that account for the dynamic processes that drive the transport of biogeochemical tracers between the photic zone and the mesopelagic. Investments in co-located and coincident measurements of physical and biological properties in the subsurface ocean will contribute to the growing understanding of mesopelagic biogeochemistry in the next decade.

As climate change intensifies, internal migration due to extreme climate events is becoming increasingly common in the Global South. Yet, little is known about how rural host communities respond to incoming environmental migrants. Here, we study attitudes toward environmentally displaced people in northern Bangladesh, focusing on perceived deservingness, empathy through shared experience, and exploratory proxy indicators of prior migrant exposure/contact. Using a pre-registered face-to-face survey of 265 rural residents, including a forced-choice conjoint experiment, we assess how migrant characteristics (reason for migration, occupation, religion, distance to origin) affect host community attitudes. We find that migrants displaced by riverbank erosion are more likely to be accepted than economic migrants (by 21%-points, p < 0.01) and face less discrimination based on other characteristics, indicating that deservingness strongly shapes attitudes. Regarding shared experience of erosion, which we propose as a proxy for empathy, models estimated a positive coefficient (13%-points, p = 0.122), hence not supporting, but indicative of a positive association between experiential proximity and greater acceptance of environmental migrants. We find no credible evidence for heterogeneity in migrant acceptance using coarse proxy measures of prior migrant exposure/contact. These results suggest that, even in resource-constrained regions, moral judgments play a central role, and that experiential proximity may be associated with more inclusive attitudes, informing policies for societal resilience under environmental stress.

The 2017 Pohang M _w 5.5 earthquake is currently the largest seismic event induced by Enhanced Geothermal Systems. The high uncertainty on geological and mechanical conditions of the rupture fault of this earthquake has originated a debate on its triggering mechanisms. Here, we propose a stochastic poromechanical analysis approach that combines Monte Carlo sampling and poromechanical models to address the uncertainty problem. By conducting a large number of coupled poromechanical simulations varying the uncertain geomechanical parameters, we yield an exceedance probability of 7%-15% for the Pohang mainshock. Remarkably, this physics-based stochastic prior forecast is quite comparable to the posterior likelihood inferred from the magnitude-frequency relationship of recorded seismicity. Our results reveal a scaling relationship between the earthquake magnitude and the initial fault stability, which indicates a threshold of the initial Coulomb Failure Stress to differentiate if faults are initially, critically stressed, and thus, the earthquake magnitude. This Pohang threshold is -0.2 to -0.1 MPa, about one order of magnitude larger than that proposed for natural earthquakes. This study highlights that the reactivation of critically stressed faults may trigger damaging earthquakes even for small poromechanical perturbations and opens a promising avenue for assessing the likelihood of induced earthquakes based on physical understanding.

Instability at volcanic edifices poses significant hazards, yet the processes driving rock weakening, particularly on steep, eroding flanks, remain poorly understood due to limited accessibility. Hydrothermal alteration is a key factor in weakening volcanic rocks, contributing to edifice destabilization and flank instability. La Fossa cone (Vulcano, Italy) provides an ideal setting for this study, with accessible hydrothermal alteration at the crater rim and similar alteration along inaccessible flanks that have a recent history of mass wasting. Here, we developed an integrated methodology combining drone photogrammetry with in situ Schmidt hammer testing to derive an empirical alteration-to-strength relationship for the crater rim and applied this knowledge to alteration sites on inaccessible flanks. An alteration map was generated using a Principal Component Analysis (PCA) to aid our classifications. This map was used to transpose over 1000 Schmidt hammer measurements (R-values ranging from 10.5 to 82), creating a thematic strength-alteration map. Results indicate a ~50% reduction in relative rock strength correlating with areas of degassing and hydrothermal activity, which coincides with past mass-wasting events. This integrated approach offers a transferable workflow for assessing volcanic slope instability, with direct applications to hazard monitoring and early warning systems.

In 2023, the United Nations High Commissioner for Refugees reported over 110 million displaced individuals globally, many in regions facing extreme weather and violence. Here we examine how these crises interact to shape household mobility in Bangladesh. Using data linking local conflict events, natural hazards, and household characteristics from 2011 to 2018, we apply machine learning models to capture complex, non-linear relationships between these risks. We find that combining conflict and hazard information improves predictions of household mobility. While exposure to violence or disasters increases mobility, households with remittances are more likely to move, whereas those with loans often remain. Interactions, such as between one-sided violence and landslides, further amplify movement, highlighting the importance of understanding how multiple stressors jointly influence household decisions.

Sea surface temperature is a key indicator of climate change on Earth and is central to all related modelling endeavours. However, sea surface temperature is notoriously difficult to reconstruct accurately in the geological record, especially for the low temperatures of the polar regions, which occupy one-third of the world's oceans. Here we show that a sea surface temperature proxy based on two isomeric diatom lipid biomarkers can be applied to marine sediment archives to reconstruct temperatures in the range -1 to 14 °C for the Arctic and Antarctic using a single calibration. For both regions, our datasets span timeframes from recent decades to the Younger Dryas/Holocene, and we also showcase a 750 kyr record from the Fram Strait, the major gateway between the North Atlantic and the Arctic Ocean. We anticipate that this lipid biomarker-based proxy may become a standard component of the palaeoclimate toolkit, especially for the polar regions.

The oxidative enrichment and isotopic fractionation of cerium (Ce) in contact with vernadite (δ-MnO₂) serve as a proxy for past redox conditions in both terrestrial and marine environments. However, the molecular processes that govern the scavenging of Ce from the dissolved 3+ to the insoluble 4+ oxidation states remain obscure. Adsorption experiments on synthetic δ-MnO₂ suggest that aqueous Ce(III) precipitates as ceric hydroxide (Ce(OH)₄), an unknown mineral. Here, the atomic-scale structure of Ce in natural vernadite from ferromanganese crusts collected across the Pacific, Atlantic, and Indian Oceans was examined using advanced high-energy-resolution extended X-ray absorption fine structure spectroscopy. The findings provide direct evidence for the uptake of Ce as mononuclear Ce(IV) complexes at the layer-edge sites (DES complex) and Mn(IV) vacancy sites of vernadite. Density functional theory-based Gibbs free-energy calculations indicate that hydrolysis of the DES complex promotes the oxidation of Ce(III) to Ce(IV). Quantum mechanical calculations predict that the equilibrium ¹³⁶Ce/¹⁴⁰Ce isotope fractionation factor between Ce(III) dissolved in seawater and the Ce(IV) complexes can reach 1.2-1.3 ‰ at 25 °C, indicating that the ¹³⁶Ce/¹⁴⁰Ce ratio has high potential as a new paleoredox proxy.

Priority areas are typically identified based on mean conditions, while ignoring variance around the mean (i.e., "stochasticity'). This is problematic as high environmental stochasticity can increase extinction risk and reduce the effectiveness of protected areas. Here we use daily Normalized Difference Vegetation Index data from 1981 to 2025 to generate spatially-explicit estimates of both the mean and variance in environmental productivity across Canada. From these models, we found that environmental stochasticity shows strong spatial structure and has been steadily increasing over the past four decades. Additionally, stochasticity had a negative effect on species richness. We found no clear relationship between stochasticity and protection status, suggesting that Canada's network of protected areas are not well-buffered against a climate-change induced increase in stochasticity. Promisingly, we identified 2,709,580 km² of currently unprotected land that may minimise the impact(s) of growing stochasticity. This work provides a framework for incorporating environmental stochasticity into conservation planning.