Communications Earth & Environment最新文献

Basal melting of Antarctic ice shelves is primarily driven by heat delivery from warm Circumpolar Deep Water. Here we classify near-shelf water masses in an eddy-resolving numerical model of the Southern Ocean to develop a unified view of warm water intrusion onto the Antarctic continental shelf. We identify four regimes on seasonal timescales. In regime 1 (East Antarctica), heat intrusions are driven by easterly winds via Ekman dynamics. In regime 2 (West Antarctica), intrusion is primarily determined by the strength of a shelf-break undercurrent. In regime 3, the warm water cycle on the shelf is in antiphase with dense shelf water production (Adélie Coast). Finally, in regime 4 (Weddell and Ross seas), shelf-ward warm water inflow occurs along the western edge of canyons during periods of dense shelf water outflow. Our results advocate for a reformulation of the traditional annual-mean regime classification of the Antarctic continental shelf.

Human well-being relies on the presence and role of pollinators, as they contribute to the vitality of ecosystems, support the reproduction of wild plants, increase crop yields, and strengthen overall food security. While wild bee populations are dwindling due to climate and environmental change, there has been a notable 45% rise globally in the number of managed honey bee (Apis mellifera) colonies over the past five decades. Given their economic significance and their relative ease of tracking, honey bees have the potential to serve as bioindicators of global pollinator health. Consequently, honey bees have emerged as a keystone species requiring protection and conservation efforts. Here, we investigate the intricate relationship between air quality, environmental factors, and honey bee mortality across Canada and the United States. Using statistical and machine learning modeling, our findings underscore the honey bee's role as a bioindicator. We found that air quality is an important predictor of honey bee mortality. The risk of honey bee mortality increased with poor air quality (ozone and Air Quality Health Index) but was substantially reduced in regions with greater vegetation availability (Normalized Difference Vegetation Index). Therefore, our study offers a beacon of hope: improving management practices by increasing greenery can significantly mitigate the impact of deteriorating air quality on honey bees, providing a vital solution to safeguard our essential pollinators.

The presence and stability of brines on Mars's surface remain a significant mystery in planetary exploration. Previous mechanisms proposed for brine formation include melting of ice-salt mixtures and salt deliquescence. However, melting lacks a recharge mechanism, and deliquescence is impeded by Mars's extreme surface aridity. This study explores an underexplored process: the role of seasonal frost in brine formation. Utilizing meteorological data from the Viking 2 lander-the only mission, with Phoenix, to observe in situ water frost formation-I demonstrate that brines can form over approximately 30 sols at the end of winter as frost sublimates. The stable brines exhibit a water activity upper limit of 0.52, corresponding to the eutectic point of calcium perchlorate, a salt detected in various Martian regions, likely including the Viking 2 landing site. Consequently, I conclude that calcium perchlorate can generate small amounts of liquid brine in contact with frost for brief periods. The seasonal nature of frost suggests these brines recur and may leave long-term imprints. Therefore, frost-covered regions are prime candidates for future habitability and astrobiological exploration.

Despite their relative rarity, atmospheric rivers are key contributors to the surface mass balance of Antarctica. However, the future role of atmospheric rivers in modulating Antarctic sea-level contributions is a major area of uncertainty. Here, we leverage high-resolution climate simulations to show that Antarctic atmospheric rivers are highly sensitive to future increases in atmospheric moisture, leading to a doubling of atmospheric river frequencies and 2.5 × increase in precipitation from 2066-2100 under present-day thresholds for atmospheric river detection. However, future precipitation impacts are critically dependent on the detection threshold: accounting for moisture increases in the threshold produces smaller, regional changes in atmospheric river frequency, primarily resulting from an eastward shift in the polar jet maximum wind speeds. Our results underscore the importance of using large ensembles to quantify Antarctic atmospheric river responses to variability in projected moisture, which may not be captured when using only a few ensemble members.

The weathering and erosion of emerged land profoundly influences the Earth system, including the composition of the atmosphere and the type of nutrients delivered to the oceans. The emergence of land allowed for the formation of lakes and continental shelves, important habitats for the origin and evolution of life. Recent studies indicate a difference in silicon isotopes between Archean granitoids and their modern counterparts, which is explained by the incorporation of seawater-derived silica in the melting sources of the former. We show that this signature changed rapidly around 3.6 billion years ago, and that this shift is likely linked to an increase in the dissolved silicon flux from terrestrial weathering. Modeling suggests that the amount of oceanic silicon derived from terrigenous sources increased from near zero to around 32 ± 15% between 3.8 and 3.6 billion years ago. This indicates that, from this point onward, continental weathering feedbacks were established, and mass flux from land became an important source in the chemical budget of seawater, changes that likely exerted positive effects on the evolution of life.

Current frameworks for evaluating biogeochemical climate change feedbacks in Earth System Models lack an explicit consideration of nitrogen cycling in the land and ocean spheres despite its vital role in limiting primary productivity. As coupled carbon-nitrogen cycling becomes the norm, a better understanding of the role of nitrogen cycling is needed. Here we develop a new framework for quantifying carbon-nitrogen feedbacks in Earth System Models and show that rising nitrogen deposition acts as a negative feedback over both land and ocean, enhancing carbon dioxide (CO₂) fertilisation in a model ensemble. However, increased CO₂ uptake due to rising nitrogen deposition is small relative to the large reduction in CO₂ uptake when coupled carbon-nitrogen cycling is implemented in Earth System Models. Altogether, rising nitrogen deposition leads to only a minor increase in CO₂ uptake but also enhances nitrous oxide (N₂O) emissions over land and ocean, contributing only marginally to mitigating climate change.

The Western Antarctic Peninsula is undergoing rapid environmental change. Regional warming is causing increased glacial meltwater discharge, but the ecological impact of this meltwater over large spatiotemporal scales is not well understood. Here, we leverage 20 years of remote sensing data, reanalysis products, and field observations to assess the effects of sea surface glacial meltwater on phytoplankton biomass and highlight its importance as a key environmental driver for this region's productive ecosystem. We find a strong correlation between meltwater and phytoplankton chlorophyll-a across multiple time scales and datasets. We attribute this relationship to nutrient fertilization by glacial meltwater, with potential additional contribution from surface ocean stabilization associated with sea-ice presence. While high phytoplankton biomass typically follows prolonged winter sea-ice seasons and depends on the interplay between light and nutrient limitation, our results indicate that the positive effects of increased glacial meltwater on phytoplankton communities likely mitigate the negative impact of sea-ice loss in this region in recent years. Our findings underscore the critical need to consider glacial meltwater as a key ecological driver in polar coastal ecosystems.

Clay surfaces have been invoked as crucial components in the origin of life processes due to their ability to concentrate organics and abiotically catalyse (bio)polymer production. Still, the importance of the mutual nature of organo-clay interactions and the effects of off-world organics in this interplay is a largely unexplored realm. We demonstrate a previously unrecognised phenomenon that occurs upon the transient interaction of montmorillonite clay with the meteorite-common, non-proteinogenic γ-aminobutyric acid. Attenuated total reflectance Fourier transform infrared spectroscopy and X-ray diffraction show that an irreversible structural change is induced by the off-world species. A distinct partial clay exfoliation is correlated with the formation of nanoscale cavities in the mid-layers of the original structure, observable using transmission electron microscopy. This work demonstrates that an exogenous amino acid can alter clay and introduce 3D confined nano-environments, which may facilitate compartmentalisation in prebiotic times. Our findings also highlight new sustainable nanocomposite synthesis routes applicable in environmental/materials sciences.

Seasonal vertical migration of large lipid-rich copepods is often described as a mass descent of animals when primary production ceases, with important implications for mesopelagic food webs and global carbon sequestration. This view ignores the existence of surface-resident individuals, but here we show that non-migrants can form a substantial part of the populations of polar migrant species. In the Central Arctic Ocean, the biomass-dominant Calanus hyperboreus was evenly distributed throughout the water column from November 2019 to March 2020, with ~20% of subadults and adult females remaining in the upper 200 m and ~41% migrating to 1000-2000 m. These vertical positions aligned with differences in the copepods' cholesterol content, which can enhance the tissue density at higher temperatures. Gonad development and the vertical distribution of their offspring indicate that both non-migrant and migrant females contribute to the population recruitment. We reinterpret copepod seasonal migration as a bet-hedging strategy that balances nutritional benefits near the surface with survival benefits at depth, and thereby contributes to the species' resilience under climatic change.

Planktonic foraminifera are key contributors to the oceanic carbon cycle. In pelagic environments, carbonate production by planktonic biomineralizers regulates ocean-atmosphere carbon dioxide exchange and exports surface carbon to the deep ocean. Here we compare shell traits of three planktonic foraminifera species from the central Atlantic with a suite of environmental parameters to discern the factors underlying their variations. Our analysis revealed that calcification in foraminifera is associated with seawater density and depends on species habitat depth, whereas foraminifera bulk shell densities may serve as a seawater density proxy, regardless of species. We observe that their shell weights increased with habitat depth, enabling the living cells to adjust their overall density to match that of the surrounding liquid. This suggests that calcification in nonmotile organisms has a buoyancy regulatory function and will respond to the anthropogenically driven reductions in ocean density (oceanic rarefication), with potential consequences for the carbon cycle.