Journal of Geophysical Research: Earth Surface最新文献

Glacial watersheds provide an ideal setting for studying chemical weathering, sediment transport and circulation at high altitudes. This study analyzed cryoconite, river sediments, and water samples from the Muztagh glacial watershed in the Pamir Plateau. The results showed that the cryoconite dust in the glacier originated mainly from the Asia arid regions. The (²³⁴U/²³⁸U) activity ratio of river sediments ranges from 0.998 to 0.976, in which the uranium comminution age indicates that the fine-particles age from bedrock is approximately 3.3–43.6 ka. Correlation analysis with topographic, climatic, and hydrological parameters reveals that glacial (physical) erosion is the primary factor driving the variability of sediment surface processes between the tributary and mainstream in the glacier watershed. Glacier erosion contributes a mean of 67 ± 25% of the sediment input of the glacier-fed tributaries of the Muztagh watershed, while down to the main stream in the Gaizi River, the contribution drops to 60 ± 26%. The concentrations of [U] and [Li] in river water increased along the glacier to downstream area, while U-Li isotope ratios showed high (²³⁴U/²³⁸U) and δ⁷Li values at the glacier terminus, showing a gradual decrease mode subsequently. These findings suggest that glacial action in the Muztagh Glacier region causes extensive physical comminution of mineral particles, leading to strong α recoil, in which ²³⁴U is preferentially ejected from damaged crystal lattice sites, while limited chemical weathering. In contrast, non-glacial regions experience reduced recoil effects and enhanced chemical weathering. This study provides new insights into the sediment production and transported process in glacial watersheds.

Tectonic fracturing in uplifting mountains facilitates fluid-rock interactions, causing downward propagation of chemical weathering fronts. In contrast, erosion in uplifting mountains removes fractured and chemically altered bedrock, thinning the weathering zone. The interplay of these processes sets weathering zone thickness, but despite the disproportionate influence of chemical weathering in mountains on global biogeochemical cycles, it is unclear where within the weathering zone those chemical reactions predominantly occur. Here we present geochemical data from a 300 m-deep drill core and results from reactive transport modeling to assess weathering zone characteristics in the Southern Alps/Kā Tiritiri o te Moana of New Zealand/Aotearoa. Our findings indicate that soil is thin and chemical weathering fronts are shallow, with only apatite (and likely calcite) weathering extending below the soil-bedrock boundary. Simulations indicate that soil thickness is primarily controlled by porosity-generating plagioclase weathering and that simulated soil thicknesses are consistent with local precipitation and denudation rates. However, simulations also show that if all 6 m of annual precipitation infiltrated bedrock, chemical weathering fronts would extend substantially deeper than observed. We infer that the porosity contrast between soil and rock limits bedrock fluid flow, slowing the propagation of chemical weathering. Erosion and limited fluid-mineral interaction in deep fractures result in a thin weathering zone, suggesting that silicate weathering in uplifting mountains occurs primarily within soil, rather than bedrock. Our measurements suggest that oxidative weathering of petrogenic carbon has been overestimated previously, but, consistent with prior work, surface processes in the study area result in net consumption of atmospheric CO₂.

Instream large wood (LW) plays a vital role in river morphology and ecology, but its transport can pose risks to infrastructure during floods. Monitoring LW transport during flood events remains limited due to technical and logistical limitations. This study employs drone-based video monitoring and machine learning to analyze LW dynamics during an experimental flood in the Spöl River, Swiss Alps. Using three drones covering a 200-m stretch, we created a high-resolution data set of over 560 pieces and 36,000 wood detections (including individual pieces captured in multiple frames). Convolutional neural networks (CNNs) detected and tracked LW, enabling detailed analysis of trajectories, rotation, and velocity, complemented with flow field characteristics (i.e., surface velocity) derived from Large-Scale Particle Image Velocimetry (LSPIV). Results showed that LW transport was concentrated in high-velocity flow paths and influenced by wood piece dimensions. Longer, thinner pieces moved faster, while thicker pieces faced greater resistance. Flow convergence aligned wood pieces with flow direction, reducing rotation, especially for larger pieces. Although wood piece rotation increased with flow velocity, it plateaued at the highest velocities. Large pieces, while fewer, represented 65% of the total transported volume, emphasizing their role in LW dynamics. By leveraging unmanned aerial vehicles (UAVs) and convolutional neural networks (CNNs), this study offers new insights into interactions between flow conditions, wood size, and transport behavior. Our findings contribute to the understanding of LW dynamics in flood conditions and provide valuable information that can enhance flood risk assessment, support early warning systems, and inform sustainable river management strategies.

Pockmarks are widespread along continental margins and are commonly aligned in chains that may interact with turbidity currents. Although their potential role in initiating submarine channels has been proposed, the governing processes remain unclear. We use numerical simulations to examine how an initially gentle, subcritical turbidity currents interact with pockmarks and promote channel inception. As currents enter a pockmark, erosion localizes on the upper steep reaches of the upstream sidewall, driving sidewall retreat. Along the downstream wall, the gradually steep downstream sidewall make the flow generate reverse currents that propagate upstream and interact with the incoming current, producing deceleration, separation, and recirculating eddies. These reverse flows enhance sediment trapping on the pockmark floor. The coupled effects of upstream erosion and central infilling progressively reshape individual depressions and encourage partial coalescence of adjacent pockmarks, which organizes the emergence of incipient channels. With sustained input, erosion and deposition rates decline as the evolving morphology approaches a quasi-steady state characterized by multiple recirculating eddies that separate intermittent near-bed reverse flow from the steadier downstream current above. Our results show that relative moderate turbidity currents can opportunistically exploit pre-existing pockmarks to nucleate channels, refining the mechanics of channel initiation and offering new insights into sediment routing and organic-carbon burial in pockmark-dominated deep-water environments.

Wildfires can play an important role in shaping bedrock-dominated landscapes. Fire can break down rock by spalling exposed surfaces. In massive rock, spalled flakes tend to be of the order of 1 cm thick and several to tens of centimeters in diameter. In central Australia, erosion rates from fire-induced rock spalling have been proposed by Buckman et al. (2021, https://doi.org/10.1038/s41467-021-22451-2) to result in unique overhangs called flared slopes that ornament the base of bedrock outcroppings (inselbergs) that dot the otherwise flat landscape. The long-term evolution of rock surfaces exposed to repeated fires inspires our numerical modeling of the fire spall process. We honor the radiative balance on the rock wall and address two fire geometries. We incorporate a thermally modulated damage criterion to mimic the cracking of the rock. The penetration depth of the thermal perturbation is scaled by the square root of the duration of the fire, reaching many cm for a tree fire, and several mm for a brush fire. Modeled erosion of rock walls due to repeated fires is rapid at first but slows as the distance to the fires increases. The emergent steady shape is scaled by the height of the vegetation. The pattern of radiation from a tree fire, and the predicted damage caused by it, mimic the geometry of flared slopes that ring Australian inselbergs, supporting the hypothesis of long-term wildfire driven lateral erosion of these features. The timescale predicted is an order of magnitude larger than the erosion rates measured across the inselberg tops in previous work.

Tête Rousse glacier is a small polythermal glacier in the Mont-Blanc massif (French Alps) that released a large outburst flood in 1892 when a water-filled intraglacial cavity suddenly drained. A new water-filled cavity was detected again in the central part of the glacier by a geophysical campaign in 2007. It has been pumped three times since to avoid another catastrophic flood. The volume of water in this central reservoir has decreased recently but recent geophysical surveys suggested that significant volumes of water could be stored in the upper part of the glacier. Here, we describe a seismic tremor signal detected in May 2022 probably generated by a water-filled reservoir within the glacier. The tremor started on 15 May a few days after temperature first increased above 0°C. Tremor amplitude was stronger in the evening and is correlated with water level measured in a crevasse about 230 m downglacier. The time delay between temperature and tremor or water level is consistent with the time needed for water to infiltrate within the snow and into the glacier. We used different methods to locate this signal both from amplitude decay and from P and S waves arrival times. Both methods provide a similar location near the northern boundary of the glacier. Ground penetrating radar surveys performed in May 2024 have since detected a water-filled reservoir near this location. These results validate our interpretation of this seismic tremor being produced by changes in water-level in this reservoir.

Permafrost coastal systems are critical to Arctic environmental processes, and understanding their erosion dynamics is essential for addressing climate change impacts. These coastlines undergo unique thermomechanical erosion, where wave action, rising sea levels, and thermal degradation jointly drive a rapid coastline recession. This study demonstrates advancements in physically modeling coastal permafrost erosion using a laboratory setup that replicates natural Arctic coastal conditions. A wave flume with a representative nearshore slope and reproducible permafrost specimen preparation methodology allowed isolation of the hydrodynamic and thermodynamic effects. Distinct erosion patterns and rates were quantified under varying wave heights, periods, and thermal conditions. Results indicate that wave height is a dominant mechanical driver, with mean erosion rates increasing by over 100% from low to high wave conditions. Even low-energy waves (H = 0.02 m) enhanced erosion by more than 50% compared to still-water conditions. Additionally, a higher ice content reduced niche deepening rates by 38%, which is attributed to latent heat delaying thawing. A new scalable thermomechanical model for erosional niche incision on an Arctic bluff is proposed based on a power-law relationship that integrates the Froude, Iribarren, and Stefan numbers. This dimensionless approach captures the coupled influence of wave-induced forces and permafrost thermal properties, exhibiting a strong predictive capability (R² = 0.90) and outperforming existing analytical models. The experimental framework and new model offer new insights into Arctic coastal retreat mechanisms and provide a promising foundation for regional-scale applications in coastal management under changing climatic conditions.

Silicate weathering is essential for the global carbon cycle and is a driver of climate change through the consumption of atmospheric CO₂. Recent studies have pointed out that silicate weathering in the late Holocene was widely influenced by human activities, but the carbon sink effect of silicate weathering under anthropogenic influence remains unclear. In this study, we present continuous records of clay minerals, major elements, and terrigenous mass accumulation rates of Core 45A in the Western South China Sea to reconstruct the evolutionary history of weathering and erosion in the Red River Basin since 3800 cal yr BP. We investigate the interactions between weathering, climate, and human activities. Our results reveal that the silicate weathering intensity and erosion rate have increased significantly since ∼1500 cal yr BP, which is decoupled from the trend to a cooler and drier climate but coincides well with stronger human activities, suggesting the significance of anthropogenic influence on silicate weathering. We also reconstruct the CO₂ consumption flux induced by silicate weathering to quantitatively evaluate the impact of human activities on the carbon sink capacity of silicate weathering. The calculated CO₂ consumption fluxes contributed by anthropogenic activities on silicate weathering show an approximate 150% increase compared to natural conditions in the Red River. Thus, this study highlights that human-enhanced silicate weathering has reduced atmospheric CO₂ and played an important role in the global carbon cycle during the late Holocene, which has never occurred in the Earth's geological past.

Saltmarsh cross-shore width is a critical determinant of the ecosystem services it can provide, particularly to what extent waves can be attenuated across its surface. Cliff initiation at the seaward saltmarsh edge typically signifies the onset of marsh retreat, causing the cross-shore marsh width and ecosystem service provisioning to be reduced. Although mechanisms for marsh retreat have been studied before, the processes and conditions under which cliffs form remain unknown, making the moment of cliff initiation unpredictable. Here, we took field measurements of sediment properties and sediment stability at comparable neighboring cliffed and non-cliffed saltmarsh edges in a meso/macro-tidal system, and compared them with flume measurements of sediment erodibility. We identified three sediment-driven conditions that, when occurring concurrently at an exposed marsh edge, increase the vulnerability of a cliff forming when exposed to a hydrodynamic trigger (wind waves or tidal currents): (a) a substantial offset (sharp difference) in sediment erodibility at the saltmarsh-mudflat interface, governed by small-scale gradients in sediment characteristics such as grain size distribution, and within this; (b) a marsh edge with near-negligible erodibility under average wave forcing and (c) site-wide sediment characteristics, such as low cohesivity, resulting in an erodible mudflat. While these conditions make marsh edges cliff prone, we discuss that other mechanisms of cliff-initiation in other parts of the world cannot be excluded. Overall, we provide insight into the role of small-scale gradients in sediment stability for driving the long-term dynamics of biogeomorphic saltmarshes, which can be used as early indicators to identify cliff-prone saltmarsh areas.

Greenland and Antarctica's peripheral glaciers are an important but often overlooked element in the global sea-level rise budget. Here, we use satellite laser altimetry from ICESat and ICESat-2 to assess the mass loss from Greenland's and Antarctica's peripheral glaciers for three periods: February 2003 to October 2009, October 2009 to April 2018, and October 2018 to April 2023. Over these periods, Greenland's peripheral glacier mass loss has increased from 27.3 ± 7.9 Gt yr⁻¹ during 2003–2009, to 35.8 ± 5.3 Gt yr⁻¹ during 2018–2023. The ice loss from Antarctica's peripheral glaciers underwent a more complex change during this time, with a mass loss −4.2 ± 1.3 Gt yr⁻¹ during 2003–2009, sharply rising to −16.0 ± 5.9 Gt yr⁻¹ during 2009–2018, and subsequently declining to −9.0 ± 0.7 Gt yr⁻¹ during 2018–2023. This temporal pattern of mass loss is observed across all Antarctic regions. Notably, the Antarctic Peninsula experienced a mass loss of 2.6 ± 3.1 Gt yr⁻¹ during 2003–2009 followed by gains of 2.7 ± 3.8 Gt yr⁻¹ and 11.9 ± 1.7 Gt yr⁻¹ during 2009–2018 and 2018–2023, respectively. This shift toward mass gain during 2018–2023 can be attributed to exceptional levels of precipitation during the winters of 2019 and 2020. We conclude that increased snowfall played a crucial role in mitigating glacier mass loss during this later period. Overall, our findings show accelerating mass loss of Greenland and Antarctica's peripheral glaciers with complex variability, both spatially and temporally, with certain regions experiencing mass gains through increased snowfall.