Communications Earth & Environment最新文献

The history of resilience of organisms over geologic timescales serves as a reference for predicting their response to future conditions. Here we use fossil Porites coral records of skeletal growth and environmental variability from the subtropical Central Paratethys Sea to assess coral resilience to past ocean warming and acidification. These records offer a unique perspective on the calcification performance and environmental tolerances of a major present-day reef builder during the globally warm mid-Miocene CO₂ maximum and subsequent climate transition (16 to 13 Ma). We found evidence for up-regulation of the pH and saturation state of the corals' calcifying fluid as a mechanism underlying past resilience. However, this physiological control on the internal carbonate chemistry was insufficient to counteract the sub-optimal environment, resulting in an extremely low calcification rate that likely affected reef framework accretion. Our findings emphasize the influence of latitudinal seasonality on the sensitivity of coral calcification to climate change.

Coastal flooding is occurring more frequently due to global sea-level rise, among other factors. However, current understanding of coastal flood frequency and sea-level rise impacts is predominantly based on tide gauges, which do not measure water levels on land. Here, we present data from a novel network of land-based flood sensors in the state of North Carolina, USA. We demonstrate that tide-gauge data are poor indicators of flooding: floods occur 26-128 days annually, an order of magnitude greater than what regional tide gauges suggest in some places. Improving the accuracy of coastal flood measures is critical for identifying the impacts of sea-level rise and developing effective adaptation strategies.

Landforms created by flowing water with sediment have left deposits on the surface of Mars, allowing study of the ancient environment. These features could provide constraints on surface water activity and past habitability. However, only a few lab studies have investigated the appearance and behavior of sediment-rich flows at relevant Mars surface conditions. We conducted experiments in a Mars environment chamber to understand the rheology and deposit morphology of mud under atmospheric pressures from 5 to 1000 mbar and surface temperatures between 248 and 297 K. We found that sediment flows in the Noachian era, when most aqueous activity occurred, could behave similarly to Earth analogs, but only under certain climate conditions. However, in the Hesperian and Amazonian periods, the dominant physical regime changed due to global atmospheric loss. Sediment flows during these eras would not have been similar to Earth analogs, and would have been dominated by freezing, evaporative cooling, and boiling depending on the microclimate (local pressure and temperature). Thus, regional climate and compositional context are important factors for interpreting satellite remote sensing images of these features on Mars. The results suggest we may be able to discover the paleo-atmospheric pressure record on Mars by analyzing sediment flow morphology.

Wildfires are a key component of Earth system dynamics with respect to carbon cycling. Thus, reconstructing past wildfire dynamics is crucial for understanding potential future climate change as related to (paleo)environmental feedbacks. Here, we explore wildfire during the Early Triassic (Smithian and Spathian, ca. 250 million years ago) - a time interval characterized by scarce fire evidence, perturbation of the carbon cycle, climatic oscillations, vegetation succession and biotic radiation-extinction pulses - using polyaromatic hydrocarbons, which are an organic (geo)chemical fire indicator in sediments. Hydrocarbon abundances in shales from Spitsbergen show a prominent increase after the Smithian-Spathian boundary. Diagnostic ratios of hydrocarbons suggest that these compounds were derived from relatively unaltered biomass as opposed to soil erosion and petrogenic carbon inputs or coal combustion vis-à-vis a coincidental Siberian Trap volcanism. Our data indicates that as temperatures decline during the late Smithian, coeval hydrological conditions become less intense and changing vegetation successions become more amenable to wildfire activity. We hypothesize that changing regional wildfire regimes influenced biogeochemical cycles, potentially affecting long-term carbon sequestration. The observed coupled behavior in water-vegetation-wildfire systems amid key perturbations in Earth's history provides new insights into imminent future climate change consequences.

Antarctica, once considered pristine, is increasingly threatened by plastic pollution, with debris found in its waters, sediments, sea ice, and biota. Here, we provide a comprehensive molecular survey of both prokaryotic and eukaryotic diversity on plastics around the Antarctic Peninsula, addressing a gap in existing research. Using eDNA metabarcoding, we identified diverse communities, with Pseudomonadota and Bacteroidota dominating prokaryotic communities, while Gyrista (mostly diatoms), Fungi and Arthropods were prevalent among eukaryotes. Geographic location significantly influenced community composition, with differences between the Bransfield Strait and the Gerlache Strait/Bellingshausen Sea. Polymer type and plastic shape did not impact species richness or community structure. These findings offer new insights into the complexity of the Antarctic plastisphere, highlighting potential impacts on biodiversity, ecosystem functions, and the broader implications of marine plastic pollution.

Volcanic ash aggregation occurs during transport in the atmosphere when individual ash particles collide and stick together. It significantly impacts ash residence time in the atmosphere, with major consequences for hazard assessment and ash dispersal forecasts. Nonetheless, aggregation processes are still not adequately parametrized, mostly due to the low preservation potential of most aggregate types. We present here the first, detailed structural and morphological characterization of the major aggregate types, combining an innovative field collection strategy, which allows for the original aggregate structure to be preserved at deposition, coupled to X-Ray micro-tomography. Resulting observations together with weather information, allowed for the structure of fragile ash clusters and of the elusive cored Ash Pellets (cAP1s) to be fully resolved and their genesis to be better described. The collected dataset represents a fundamental advancement towards a comprehensive characterization of the principal aggregate categories, which is key to accurately interpreting and modelling the process of volcanic ash aggregation and dispersal.

Large Low Shear Velocity Provinces (LLSVPs) near the core-mantle boundary (CMB) are key yet enigmatic structures. Their origin is often linked to the accumulation of subducted mid-ocean ridge basalt (MORB), but computational models question MORB as the sole source due to its predicted high shear wave velocity compared to normal mantle. This uncertainty is compounded by the lack of direct sound velocity measurements at CMB pressures. Here we address this gap through ultrahigh-pressure shear wave velocity measurements on CaCl₂- and α-PbO₂-type SiO₂, major phases in MORB, at pressures exceeding those of the CMB. Our results show shear velocities in dense SiO₂ phases are ~ 7-14% lower than previous predictions under these conditions. Incorporating these values into MORB models suggests that the typical seismic anomaly of -1.5% (δlnV _S ) observed in LLSVPs can be explained by ~ 23-33 vol.% oceanic crust along a cold slab geotherm, without invoking extreme thermal anomalies (+1500 K). Considering a subduction history exceeding 2 billion years, this scenario supports long-term MORB accumulation at the lowermost mantle. These findings provide new constraints on LLSVP composition and offer critical insights into deep mantle dynamics and the evolution of Earth's interior.

Phreatic eruptions are a potentially lethal type of volcanic activity that is notoriously difficult to forecast. Understanding the complex processes that make eruptions more likely is a key step towards detecting precursory signals. Here, we employ 3-dimensional numerical models of heat and fluid flow based on field and laboratory data from Whakaari/White Island Volcano in New Zealand to explore the thermal, hydraulic, and geologic conditions that promote phreatic eruptions. Our results show that hydrothermally mineralised low-permeability seals can trap rising steam and magmatic gases until the pressure exceeds the tensile strength of the rock within days to months. Changes in persistent degassing through secondary vents can provide valuable insights into when the main sealed conduit is building to eruption. This study provides new insights into the timescales and mechanisms promoting phreatic eruptions, and a starting point to quantitatively interpret volcanic signals in terms of subsurface activity and eruptive potential.

Permafrost thaw poses diverse risks to Arctic environments and livelihoods. Understanding the effects of permafrost thaw is vital for informed policymaking and adaptation efforts. Here, we present the consolidated findings of a risk analysis spanning four study regions: Longyearbyen (Svalbard, Norway), the Avannaata municipality (Greenland), the Beaufort Sea region and the Mackenzie River Delta (Canada) and the Bulunskiy District of the Sakha Republic (Russia). Local stakeholders' and scientists' perceptions shaped our understanding of the risks as dynamic, socionatural phenomena involving physical processes, key hazards, and societal consequences. Through an inter- and transdisciplinary risk analysis based on multidirectional knowledge exchanges and thematic network analysis, we identified five key hazards of permafrost thaw. These include infrastructure failure, disruption of mobility and supplies, decreased water quality, challenges for food security, and exposure to diseases and contaminants. The study's novelty resides in the comparative approach spanning different disciplines, environmental and societal contexts, and the transdisciplinary synthesis considering various risk perceptions.

The Last Ice Area-located to the north of Greenland and the northern Canadian Arctic Archipelago-is expected to persist as the central Arctic Ocean becomes seasonally ice-free within a few decades. Projections of the Last Ice Area, however, have come from relatively low resolution Global Climate Models that do not resolve sea ice export through the waterways of the Canadian Arctic Archipelago and Nares Strait. Here we revisit Last Ice Area projections using high-resolution numerical simulations from the Community Earth System Model, which resolves these narrow waterways. Under a high-end forcing scenario, the sea ice of the Last Ice Area thins and becomes more mobile, resulting in a large export southward. Under this potentially worst-case scenario, sea ice of the Last Ice Area could disappear a little more than one decade after the central Arctic Ocean has reached seasonally ice-free conditions. This loss would have profound impacts on ice-obligate species.