AGU Advances最新文献

Anthropogenic climate change affects regional hydrological cycles and poses significant challenges to the sustainable supply of freshwater. The Central China water tower (CCWT) is the key source region feeding the Yangtze and Yellow Rivers, and its runoff is indispensable for the surrounding mega-city clusters. Here we present a reconstruction of CCWT runoff depth (RD) back to 1595 CE, based on a new dendrochronological network including 100 tree-ring sampling sites and an ensemble averaging approach that combines multiple regression models. Comparison of this reconstruction with similar records from six water tower regions along the Pacific Rim (Mongolian Plateau, Tibetan Plateau TP, Great Dividing Range, Southern and Northern Rocky Mountains, Andes Mountains) revealed that the CCWT provide the most stable water supply, while the TP to be most susceptible to extreme runoff events. Twenty-first century projections indicate generally increasing runoff across most Pacific Rim water towers, whereas the Northern Rocky Mountains are projected to decline substantially. We attribute the differences in runoff variability and projected trends across Pacific Rim water towers to their distinct geographies and synoptic climatic conditions. The long-term runoff reconstructions and projected changes highlighted in this study provide insights for adaptive management strategies in China and all other regions relying on supply from mountain water towers.

Earth observation (EO) technologies are increasingly driving parametric insurance and risk financing for climate disasters, yet few operational programs demonstrate effective integration within national government systems. Uganda's Disaster Risk Financing Program (2016–2020) provides a rare example of satellite-triggered financing operating at scale. Using MODIS vegetation indices to trigger drought response, the $14 million program supported over 452,000 people. It generated $11.1 million in immediate emergency aid savings, achieving a total return on investment of approximately 2.9 and an Internal Economic Rate of Return of 28.2%. This commentary synthesizes lessons from program implementation, highlighting that institutional and financial barriers, rather than technical limitations, now constrain the scaling of this EO-driven climate resilience mechanism. While the program successfully integrated satellite data with transparent triggers and financial instruments, its sustainability depended on financial commitment extending beyond experimental phases. As climate risks intensify globally, Uganda's experience demonstrates that data-triggered financing can operate within government institutions, but successful replication requires prioritizing institutional architecture and sustained financing over technical perfection.

Cratonic lithospheres carry a long history of tectonic modifications that result in heterogeneous structures, as revealed by an increasing number of geophysical observations. The existence of cratonic basins indicates protracted periods of tectonic modification, causing subsidence within global continental interiors. An enigmatic aspect of this process is the cessation of subsidence in cratonic basins with unclear mechanisms. Here, using full-wave ambient noise tomography, we reveal distinct seismic low-velocity anomalies below 60 km beneath the Illinois and Michigan Basins, where subsidence terminated in the late Paleozoic to the early Mesozoic. These low-velocity volumes, surrounded by distinctly higher velocities, are attributed to asthenospheric materials upwelling to shallow mantle depths during lithospheric foundering or delamination. This lithospheric modification may be associated with a major regional tectonic exhumation in the early Mesozoic that could have terminated basin subsidence and unroofed upper portions of basin stratigraphy. This timing coincides with the passage of this region over mantle plumes, which likely triggered lithospheric delamination and asthenospheric upwelling. Geodynamic modeling shows that the emplacement of these buoyant asthenospheric materials would lead to an uplift of about 3.5 km, sufficient to terminate the subsidence in the cratonic basins within this region. These findings document evidence of lithospheric delamination in the North American midcontinent and present important links between geodynamic drivers and geological records of the evolution of the cratonic lithosphere in North America and beyond. They also offer broader implications for understanding how deep Earth processes shape surface environments, influencing resource distribution and long-term landscape evolution.

Geomorphic and stratigraphic studies of Mars prove that extensive liquid water flowed and pooled on the surface early in Mars' history. Martian paleoclimate models, however, have difficulty simulating climate conditions warm enough to maintain liquid water on early Mars. Reconciling the geologic record and paleoclimatic simulations of Mars is critical to understanding Mars' early history, atmospheric conditions, and paleoclimate. This study uses an adapted lake energy balance model to investigate the connections between Martian geology and climate. The Lake Modeling on Mars for Atmospheric Reconstructions and Simulations (LakeM²ARS) model is modified from an Earth-based lake model to function in Martian conditions. We use LakeM²ARS to investigate the conditions necessary to simulate a lake in Gale crater. Working at a localized scale, we combine climate input from the Mars Weather Research & Forecasting general circulation model with geologic constraints from Curiosity rover observations to identify potential climatic conditions required to maintain a seasonally ice-free lake. Our results show that an initially small lake system (10 m deep) with ∼50 mm monthly water input and seasonal ice cover would retain seasonal liquid water for over 100 years, demonstrating conditions close to long-term lake survivability. These results are an important step in resolving the historic disconnect between climate and geology on Mars. Continued use and iteration of LakeM²ARS will strengthen connections between Mars' paleoclimate and geology to inform climate models and enhance our understanding of conditions on early Mars.

Root distributions are typically based on root mass per soil volume. This plant-focused approach masks the biogeochemical influence of fine roots, which weigh little. We assert that centimeter-scale root presence-absence data from soil profiles provide a more soil-focused approach for probing depth distributions of root-regolith interfaces, where microsite-scale processes drive whole-ecosystem functioning. In 75 soil pits across the continental USA, Puerto Rico, and the Alps, we quantified fine and coarse root presence as deep as 2 m. In 70 of these pits we estimated root mass and created standardized metrics of both data sets to compare their depth distributions. We addressed whether: (a) depth distributions of root presence-absence data differ from root mass data, thus implying different degrees of root-regolith interactions with depth; and (b) if root presence or any depth-dependent differences between these data sets vary predictably with environmental conditions. Presence of fine roots exhibited diverse depth-dependent patterns; root mass generally declined with depth. In B and C horizons, standardized root presence was greater than standardized root mass; random forest analyses suggest these discrepancies are greater in B horizons with increasing mean annual precipitation and in C horizons with increasing mean annual temperature. Our work suggests that deep in the subsurface, biogeochemical and reactive transport processes result from more numerous root-regolith interfaces than mass data suggest. We present a new paradigm for discerning patterns in depth distributions of root-regolith interfaces across multiple biomes and land uses that promotes understanding of the roles of those interfaces in driving key critical zone processes.

A recent report released by the U.S. Department of Energy concludes that U.S. tide-gauge data in aggregate provide no evidence for relative sea-level (RSL) acceleration above the historical mean trend. However, that conclusion rests largely on cursory analysis of a small number of tide-gauge records that are known to be unrepresentative of large-scale RSL behavior. Here I analyze all long active tide-gauge RSL data records on the contiguous U.S. (CONUS) coast to make a comprehensive estimate of spatially averaged RSL changes over the CONUS (CONUS RSL) during the past 125 years. I find that long-term rates of CONUS RSL rise doubled in the past century, from about 1.7 mm $��{\text{yr}}^{�-�1�}�$ in 1900 to roughly 4.3 mm $��{\text{yr}}^{�-�1�}�$ in 2024, and that recent rates are higher than the longterm historical mean rate since 1900, which is approximately 3.0 mm $��{\text{yr}}^{�-�1�}�$. That is, CONUS tide gauges give obvious evidence of RSL acceleration, which is likely related to ongoing climate change.

Our understanding of the formation and evolution of planetary systems has made major advances in the past decade. This progress has been driven in large part by the Atacama Large Millimeter/submillimeter Array (ALMA), which has given us an unprecedented view of solar system bodies themselves, and of the structure and chemistry of forming exoplanetary systems. Within our own solar system, ALMA has enabled the detection of new molecules and isotopologues across moons and comets, as well as placing new constraints on the compositions and histories of small bodies through thermal emission observations. In this article, we highlight some key areas where ALMA has contributed to a deeper understanding of our solar system's formation and evolution, and place these discoveries in the context of our evolving understanding of protoplanetary disks.

Peat decomposition is progressing in Southeast Asia due to lowered groundwater levels (GWL) caused by drainage. Additionally, droughts during El Niño events significantly lower the GWL, the main environmental factor that controls greenhouse gas (GHG; carbon dioxide (CO₂) and methane) emissions in peatlands. Consequently, tropical peatlands have been recognized as a significant source of carbon emissions, and these emissions have been estimated for the region using constant decomposition rates of peat for each land use (Tier 1 emission factors). However, these factors hardly reflect the spatiotemporal variation of the GWL. Furthermore, these estimates do not account for CO₂ uptake through photosynthesis. To reduce uncertainty, we developed a method to estimate spatiotemporal GWL variation from satellite-derived antecedent precipitation. Using the estimated GWL, we calculated the monthly net ecosystem-scale GHG emissions from peat forests and managed peatlands using the observed relationship between eddy covariance GHG fluxes and GWL, though carbon losses from deforestation, fires, and fluvial export were not covered in this study. Spatiotemporal variations in GHG emissions across Sumatra, Borneo, and the Malay Peninsula over a decade revealed the following: (a) Peat forests are a net source of CO₂-equivalent GHGs, even when undrained, (b) Decadal mean annual GHG emission rates increase 2.8-fold when forests are drained and 6.4-fold when undrained forests are converted to managed peatlands, (c) Droughts increase total annual GHG emissions by 16% across the study area. Additionally, climate models projected precipitation increase in the mid-21st century, suggesting an increase in GWL and a consequent reduction in peat decomposition.

Managing carbon stocks in the land, ocean, and atmosphere under changing climate requires a globally-integrated view of carbon cycle processes at local and regional scales. The growing Earth Observation (EO) record is the backbone of this multi-scale system, providing local information with discrete coverage from surface measurements and regional information at global scale from satellites. Carbon flux information, anchored by inverse estimates from spaceborne Greenhouse Gas (GHG) concentrations, provides an important top-down view of carbon emissions and sinks, but currently lacks global continuity at assessment and management scales (<100 km). Partial-column data can help separate signals in the boundary layer from the overlying atmosphere, providing an opportunity to enhance surface sensitivity and bring flux resolution down from that of column-integrated data (100–500 km). Based on a workshop held in September 2024, the carbon cycle community envisions a carbon observation system leveraging GHG partial columns in the lower and upper troposphere to weave together information across scales from surface and satellite EO data, and integration of top-down/bottom-up analyses to link process understanding to global assessment.

Atmospheric rivers (ARs) play a dominant role in water resource availability in many regions, and can cause substantial hazards, including extreme precipitation, flooding, and moist heatwaves. Despite this, there is substantial uncertainty about recent and ongoing changes in AR frequency and impacts. Here, we place recent observed trends in their longer-term context using AR records extending back to 1940. Our results show that AR frequency has increased broadly across the midlatitudes, bridging the apparent discrepancy between the observed satellite-era poleward shift and the general increase simulated in climate change projections. This increase in AR frequency enhances AR-associated precipitation and snowfall across their region of influence in the mid- and high-latitudes. We also find that, despite warmer surface temperatures associated with ARs, there is a decrease in the magnitude of AR-associated temperature anomalies in high-latitude regions due to Arctic amplification. An increase in AR-associated humid heatwaves underscores the societal importance of changing AR activity.