Abstract The global thermohaline circulation, driven by density contrasts in seawater, plays a fundamental role in global climate regulation. Within this system, the Atlantic meridional overturning circulation (AMOC) governs large-scale heat redistribution between hemispheres. However, anthropogenic forcing in the Anthropocene threatens to weaken the AMOC, with profound consequences for regional climates and ecosystems. In this study, we applied a global atmospheric circulation model coupled with a dynamic global vegetation model to evaluate two sea surface temperature scenarios: a control case and an anomaly experiment based on Manabe and Stouffer. The simulations revealed pronounced precipitation anomalies, including substantial reductions in rainfall during several months that typically belong to the wet season and enhanced rainfall during months historically associated with the dry season in parts of the Amazon, linked to a displacement of the intertropical convergence zone (ITCZ). Additional impacts included surface cooling in the Amazon, warming in central Brazil, and weakening of the South Atlantic subtropical high, which enhanced frontal system penetration in southeastern Brazil. Vegetation dynamics indicated an expansion of tropical forests into Caatinga regions, where Caatinga is a semiarid dense shrubland ecosystem in Northeast Brazil, reflecting strong biosphere–climate feedbacks. Moreover, the reorganization of Hadley cell circulation confirmed large-scale atmospheric adjustments. Altogether, these results suggest that AMOC weakening may substantially reshape rainfall regimes, temperature patterns, pressure systems, and vegetation cover across Brazil. Significance Statement The Atlantic meridional overturning circulation (AMOC) is a critical component of Earth’s climate system, redistributing heat and regulating precipitation patterns across continents. Our modeling experiments reveal that AMOC weakening could profoundly alter Brazil’s climate, producing large shifts in seasonal rainfall regimes, marked changes in hydroclimatic variability, and substantial shifts in vegetation cover. These findings highlight the interconnectedness of oceanic and terrestrial systems, showing that large-scale circulation changes in the Atlantic can cascade into regional hydroclimatic and ecological transformations. Understanding these mechanisms is crucial for anticipating future climate resilience and for guiding adaptation strategies in tropical regions under anthropogenic pressure.
Over the past century, groundwater overexploitation has triggered severe land subsidence in coastal megacities like Tianjin, China. However, with policy changes such as enforced extraction restrictions and large-scale water diversion, the downward trend has now been reversed, unexpectedly leading to strange phenomena. Long-term monitoring in Tianjin (2013-23) reveals a complex spatiotemporal pattern where areas of persistent land subsidence coexist with zones of recent uplift, following shifts in groundwater policy. The mechanisms governing this transition, particularly the lagged, nonelastic nature of the uplift, remain poorly quantified. The decade-long leveling data and field experiments were integrated to elucidate the differential hydromechanical response of layered soils. Especially, the field experiments reveal distinct deformation mechanisms: Sand layers exhibit primarily elastoplastic behavior, whereas clay layers are dominated by viscoplastic deformation. These contrasting responses, combined with variations in layer thickness, lead to spatially heterogeneous ground movement. These insights inform the development of a 3D visco-elasto-plastic hydromechanical coupling model, explicitly incorporating state-dependent parameters to capture hysteresis and inelasticity. The validated model not only reproduces the observed decadal deformation field but also enables a quantitative, scenario-based risk assessment for critical infrastructure, projecting differential displacement under various groundwater management futures. SIGNIFICANCE STATEMENT: This study reveals how policies restricting groundwater extraction in coastal cities can unexpectedly cause ground uplift alongside subsidence, creating new risks for infrastructure like railways and tunnels. By analyzing a decade of data from Tianjin, China, we show that rising groundwater levels lead to uneven ground movement some areas lift while others sink due to differing soil properties. Our predictive model helps cities anticipate these shifts, enabling proactive protection of critical infrastructure. This work is vital for urban planners and policymakers seeking to balance water resource management with public safety, especially as global coastal cities face similar challenges from climate adaptation strategies.
The study focuses on the scale dependence of surface energy fluxes in topographically diverse landscapes, where variations in soil moisture and vegetation types significantly influence evapotranspiration processes. Land-atmosphere interaction plays a major role in atmospheric processes in the Qinghai-Tibet Plateau (QTP) region, and the inability of current land-atmosphere models to capture the landscape-scale heterogeneity in the latent heat flux introduces uncertainties in these models. To address this issue, the remote sensing-based fine-scale energy balance modeling [Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC)] was combined here with topographical analysis [2D FFT spectral analysis and Landscape Unit Mapping Program (LUMP) hillslope discretization] to identify a representative elementary area (REA) for latent heat flux. A scale dependence analysis within a 1-10-km range is performed, and two flux aggregation methods are proposed: the mechanistic approach to define REA, which identifies optimal aggregation areas for latent heat through window size variations, and the landscape-explicit approach, which upscales latent heat based on hillslope elements of dominant quasi-periodic topographic features. It was established that the representative elementary area for latent heat at QTP is in the 2-4-km range. Moreover, REA is formed by characteristic topographical patterns that can be defined through regularity and repetition, which can be seen in representative hillslopes. Benchmark simulations conducted with the METRIC model indicate that ignoring topographical influences results in the absence of REA. The landscape-explicit approach may offer greater interpretability and predictive capability for future land-atmosphere model development as it considers topographic effects on lateral water redistribution and surface energy transfer.
The northeastern Sylhet region of Bangladesh has faced severe flooding, leading to tragic consequences such as loss of life, displacement, and economic challenges. This study evaluates the impact of flooding on various land uses in the region from 2018 to 2022. Flood-affected areas were identified using Sentinel-1 SAR images in Google Earth Engine (GEE), and land use was analyzed with the Dynamic World dataset of Sentinel-2 images. The study found that cropland has been significantly impacted, with two-thirds affected by floods from 2018 to 2022, and 84% in 2023, causing economic hardship. In 2018, 27% of vegetation coverage was affected, decreasing in subsequent years but rising to 30% during the 2022 flood. In 2018, about 47.83 km2 of built-up area was impacted, increasing to 128.135 km2 in 2022. The total affected population (TAP) in Sylhet district increased from 27% in 2021 to 43% in 2022, while Sunamganj exhibited the highest vulnerability, with TAP rising from 65% in 2021 to 74% in 2022. These findings highlight the increasing severity of flood events, likely driven by climate change and inadequate infrastructure, and emphasize the urgent need for integrated flood management strategies to protect the population and environment in Sylhet.
At 2020 UTC 16 March 2024, the Sundhnuksg & imath;gar crater row located north of the town of Grindav & imath;k on the Reykjanes Peninsula, Iceland, erupted. Forty minutes after the start of the eruption, a significant rain shower started 20 km downwind of the eruption site to the west of the Keflav & imath;k International Airport. Since there was no precipitation over the peninsula prior to the eruption and the precipitation event started shortly after the eruption and downwind from the volcano, we were led to believe that it was linked to the eruption. In the style of a mystery novel, we sought to elucidate the mechanism linking the eruption and the rain shower. Two different mechanisms were initially investigated: 1) the volcano heat and moisture led to convection and 2) the volcanic ash created condensation nuclei. Using radar data, ground-based measurements, and model soundings, it was found that the eruption could not be directly responsible for the precipitation event through either of these mechanisms. As such, another process had to be involved, namely, that the eruption acted as an obstacle to the atmospheric flow causing precipitation. SIGNIFICANCE STATEMENT: Shortly after a volcano in southwest Iceland erupted, an unforecasted heavy rain shower started west of the Keflav & imath;k International Airport, the main airport deserving Reykjavik, Iceland. Such a heavy shower could have disrupted the airport activities and might have been a hazard to landing and departing aircraft should it have occurred over the airport. We investigated how the volcano caused the rainstorm as the rain started shortly after and downwind of the eruption. The uncovered process proved to be unexpected, justifying this publication: It appears that the eruption acted as an obstacle that wind had to leap over, and this sudden ascending motion quickly produced significant precipitation downwind.
