Strong Gradients Research Articles

Aerobic and anaerobic mineralisation of sediment organic matter in the tidal River Elbe

PurposeThe share of microbially degradable sediment organic matter (SOM) and the degradation rate depend, among others, on the intrinsic properties of SOM as well as on the type and concentration of terminal electron acceptors (TEA). Next to its role as TEA, molecular oxygen enhances SOM decay by oxygenase-mediated breakdown of complex organic molecules. This research investigated long-term SOM decay (> 250 days) under aerobic and anaerobic conditions to (1) provide a basis for sediment carbon flux estimates from the River Elbe estuary and (2) assess the potential for carbon burial in relation to redox conditions and dredging interventions.MethodsLong-term aerobic and anaerobic SOM decay in fluid mud, pre-consolidated and consolidated sediment layers was investigated over three years along a transect of ca. 20 km through the Port of Hamburg, starting at the first hydrodynamically determined hotspot of sedimentation after the weir in Geesthacht. Absolute differences between aerobic and anaerobic cumulative carbon mineralization were calculated, as well as their ratio. Findings were correlated to a suite of solids and pore water properties.ResultsSOM decay followed first order multi-phase exponential decay kinetics. The ratio between C release under aerobic and anaerobic conditions ranged around 4 in the short-term, converging to a value of 2 in the long term. Strong gradients in absolute C release along the upstream–downstream transect did not reflect in a corresponding gradient of the aerobic-anaerobic ratio. C release was most strongly correlated to the water-soluble organic matter, in particular humic acids. Contact of anaerobically stabilized sediment with the oxygenated water phase induced significant release of carbon.ConclusionSOM degradability in the study area exhibited strong spatial gradients in relation to the organic matter source gradient but was mainly limited by the high extent of organic matter stabilization. Under these conditions, molecular oxygen as TEA provides little thermodynamic advantage. Carbon-sensitive sediment management, considering SOM reactivity patterns in stratified depositional areas, is a powerful strategy to reduce environmental impacts of dredging measures.

On the characterization of Cloud occurrence and its impact on solar radiation in Mbour, Senegal

The objective of this study is to evaluate the clouds seasonal occurrence characteristics, and to estimate their impact on solar radiation in Mbour, Senegal, West Africa. Here, we use datasets from various sources including: i) observations from the Clouds and Earth's Radiant Energy System satellite sensors, ii) in situ shortwave radiation measurement obtained from the Mbour station, and iii) the outgoing longwave radiation (OLR) obtained from the National Centers for Environmental Prediction reanalysis data. Results show a marked seasonality, associated with high spatial variation in terms of cloud occurrence over Senegal. The maximum cloud occurrences are observed during the wet summer season (June–October), whilst the minimum cloud occurrences are recorded during the long-dry season from November to May. During the monsoon season the cloud activity becomes more intense with a total cloud cover of about 80%, a cloud optical depth of around 7, and a high convective activity illustrated by a low OLR (below 240 W/m2). Likewise, across Senegal a strong north-south gradient of the cloud characteristics is observed. Based on quantitative comparison between cloud occurrence and radiation measurement, results show an important seasonal impact on available solar potential in Mbour. Conversely to the cloud occurrence, the maximum of both direct normal and global solar potentials is recorded during the dry season, coinciding with the period with clean sky. An investigation of the cloud influence on solar radiation on selected study cases indicates a decrease of 60% (80%) for the total (direct normal) radiation during the peak of the summer monsoon season.

Characterization of heated volume generation by nanosecond pulsed plasma actuator with various pressure environments

Nanosecond dielectric barrier discharge (NS-DBD) has emerged as a promising technique for controlling high-speed flows, generating a heated volume that generates strong density and viscosity gradients, thereby perturbing flow dynamics. Since its potential application in low-pressure, high-speed flows, understanding how the size and growth of the heated volume correlate with surrounding pressure is crucial. In this study, we employed typical schlieren and background-oriented schlieren (BOS) techniques to investigate the heated volume’s sensitivity to surrounding pressure in quiescent air. The observed heated volume’s size variations with surrounding pressure likely stemmed from the increase in thermal diffusivity at lower pressures. BOS findings unveiled a nearly linear decrease in heated volume’s core density with energy input. Meanwhile, the heated volume’s size augmented with energy input but exhibited gradual saturation, attributable possibly to shear stresses impeding volume expansion as temperature and viscosity rose, or to consumption of energy in vibration excitation and other reactions. In the cases of 100 and 50 kPa, the sensitivity of the heated volume’s size to the reduced electric field appeared to be similar. However, at 10 kPa, where the reduced electric field is higher compared to that of the 100 and 50 kPa cases due to the lower air density, the size sensitivity drastically decreased. This suggested a transition in discharge mode from filamentary to diffusive behavior at lower pressures.

Methane plume detection after the 2022 Nord Stream pipeline explosion in the Baltic Sea

On September 26th, 2022, the detonations at the gas pipelines Nord Stream 1 and 2 resulted in some of the largest non-natural releases of methane known. The distribution of methane in the surrounding seawater and the possible effects were not apparent. To trace the pathways of methane we recorded CH4 concentrations and the isotopic signal (δ13C-CH4) in seawater, and air. A week post-explosion, we detected methane concentrations up to 4 orders of magnitude above the natural Baltic Sea background. The released fossil methane created a distinct plume with δ13C-CH4 ratios differing from natural background values. The strong water stratification preserved the distribution pattern initiated by the explosion, shown by the laterally strong concentration gradient within the plume. Our analysis encompasses three stages of the explosion's impact; the initial sea-air methane release, measurements taken during our research expedition one week later, and a third stage triggered by the shift from summer to winter conditions as an outlook on how winter mixing and microbial activity will influence the plume.

Distribution of nutrients and dissolved organic matter in a eutrophic equatorial estuary: the Johor River and the East Johor Strait

Abstract. Estuaries have strong physicochemical gradients that lead to complex variability and often high rates of biogeochemical processes, and they are also often impacted by humans. Yet, our understanding of estuarine biogeochemistry remains skewed towards temperate latitudes. We examined seasonal and spatial variability in dissolved organic matter (DOM) and nutrients along a partly eutrophic, agricultural–urban estuary system in Southeast Asia: the Johor River and the East Johor Strait. Dissolved organic carbon (DOC) and coloured DOM (CDOM) showed non-conservative mixing, indicating significant DOM inputs along the estuary. The CDOM spectral slopes and CDOM : DOC ratios suggest that terrigenous, soil-derived DOM dominates along the Johor River, while phytoplankton production and microbial recycling are important DOM sources in the Johor Strait. CDOM properties were not unambiguous source indicators in the eutrophic Johor Strait, which is likely due to heterotrophic CDOM production. Nitrate concentrations showed conservative mixing, while nitrite concentrations peaked at intermediate salinities of 10–25. Ammonium concentrations decreased with salinity in the Johor River but increased up to 50 µmol L−1 in the Johor Strait, often dominating the dissolved inorganic nitrogen (DIN) pool. Phosphate concentrations were low (<0.5 µmol L−1) throughout the Johor River but increased in the Johor Strait, where DIN : phosphate ratios were typically ≥ 16 : 1. This suggests that the Johor Strait may experience phosphorus limitation and that internal recycling is likely important for maintaining high nutrient concentrations in the Johor Strait. Overall, our results indicate that the Johor River and Johor Strait are clearly not part of the same estuarine mixing continuum and that nutrient recycling processes must be quantified to understand nutrient dynamics in the Johor Strait. Moreover, our results highlight the need for better techniques for DOM source tracing in eutrophic estuaries.

Palynology of strata associated with the Hercynian Unconformity across the Arabian Plate, from the Levant to southern Arabia

Abstract A survey of the palynostratigraphy of the strata above and below the Hercynian Unconformity indicates that the range of its associated hiatus, due to either non-deposition or erosion (or both), varies considerably across the Arabian Plate depending on the position of the succession in relation to the three main highs or arches, the Levant, Al Batin and Oman-Hadhramaut arches, and any Hercynian faulting or other uplift in basinal regions, for example in the Ghawar region. As expected, the succession spanning the Hercynian Unconformity is most complete in basinal areas, for example in the Faydah-Jafurah and Nafud-Ma'aniya basins. The well with the shortest hiatus, corresponding approximately to a maximum duration of part of the Serpukhovian and Bashkirian, appears to be KH-5/1, close to the axis of the Nafud-Ma'aniya Basin. Palynological assemblages in rocks above the Hercynian Unconformity indicate the diachronous onset of the basal Khuff clastics NW through the Arabian Plate over a period of c. 15 Myr. The oldest strata above the Hercynian Unconformity across the Arabian Plate also indicate systematic variation, probably due to palaeoclimate, with assemblages of similar age in Iraq and northern Saudi Arabia showing some similarities to those of Oman, but differences probably due to a strong climatic gradient at the time.

High-Z impurity neoclassical transport in the tokamak plasmas due to the single-null divertor configuration

A new mechanism for the high-Z impurity neoclassical particle transport in the tokamak plasmas due to the single-null divertor configuration is discovered for the first time. It will play an important role in the tokamak plasma pedestal region with the coexisting of the strong bulk ion radial gradients and the up/down asymmetry of the poloidal magnetic field. The outward (inward) high-Z impurity neoclassical particle transport will be driven with the B×∇B drift towards (away from) the X-point. The new finding indicates that the International Thermonuclear Experimental Reactor lower single-null divertor configuration will be beneficial for screening and flushing out the high-Z impurity in the pedestal region with the toroidal magnetic field in the normal direction ( B×∇B drift towards the X-point).

Predictability of European winter 2021/2022: Influence of La Niña and stratospheric polar vortex

AbstractThe Northern Hemisphere winter of 2021/2022 exhibited a positive North Atlantic Oscillation (NAO) which led to largely mild and wet conditions for Northern Europe. A moderate La Niña in the tropical Pacific and a stronger than average stratospheric polar vortex together explained the observed anomalies over the winter. Winter 2021/2022 was well predicted in general by seasonal forecast systems. The ensemble mean indicated a positive winter NAO and the forecast spread of forecasts from the Met Office GloSea6 seasonal prediction system spanned the observed mean sea level pressure anomaly for the whole winter and the individual months. However, December showed the largest departure from the mean of the forecast which is consistent with evidence from previous work that early winter ENSO teleconnections are too weak in model predictions. Nevertheless, around one in four members captured the negative NAO pattern in December. The strong pressure gradient and positive NAO predicted for the latter part of the winter allowed successful warning of the possibility of above average storminess and strong winds which occurred in February 2022. This is potentially useful information for the energy sector who increasingly rely on wind power and the insurance industry for warning of storm damage.

A hyperbolic–elliptic PDE model and conservative numerical method for gravity-dominated variably-saturated groundwater flow

Richards equation is often used to represent two-phase fluid flow in an unsaturated porous medium when one phase is much heavier and more viscous than the other. However, it cannot describe the fully saturated flow for some capillary functions without specialized treatment due to degeneracy in the capillary pressure term. Mathematically, gravity-dominated variably saturated flows are interesting because their governing partial differential equation switches from hyperbolic in the unsaturated region to elliptic in the saturated region. Moreover, the presence of wetting fronts introduces strong spatial gradients often leading to numerical instability. In this work, we develop a robust, multidimensional mathematical model and implement a well-known efficient and conservative numerical method for such variably saturated flow in the limit of negligible capillary forces. The elliptic problem in saturated regions is integrated efficiently into our framework by solving a reduced system corresponding only to the saturated cells using fixed head boundary conditions in the unsaturated cells. In summary, this coupled hyperbolic–elliptic PDE framework provides an efficient, physics-based extension of the hyperbolic Richards equation to simulate fully saturated regions. Finally, we provide a suite of easy-to-implement yet challenging benchmark test problems involving saturated flows in one and two dimensions. These simple problems, accompanied by their corresponding analytical solutions, can prove to be pivotal for the code verification, model validation (V&V) and performance comparison of simulators for variably saturated flow. Our numerical solutions show an excellent comparison with the analytical results for the proposed problems. The last test problem on two-dimensional infiltration in a stratified, heterogeneous soil shows the formation and evolution of multiple disconnected saturated regions.

Impact of High-Resolution Land Cover on Simulation of a Warm-Sector Torrential Rainfall Event in Guangzhou

This study on the warm-sector heavy rainfall event in Guangzhou on 7 May 2017, examined the effects and mechanisms of incorporating 30 m high-resolution land surface data into its numerical simulation. The updated 1km numerical model, integrating 30 m high-resolution land surface data, successfully captured the initiation, back-building, and organized development of warm-sector convections in Huadu and Zengcheng District. The analysis revealed that the high spatial resolution of the surface data led to a reduced urban area footprint (urban −6.31%), increased vegetation cover (forest 11.63%, croplands 1%), and enhanced surface runoff (water 2.77%) compared with a model’s default land cover (900 m). These changes mitigated the urban heat island (UHI) effect within the metropolitan area and decreased the surface sensible heat flux. This reduction contributed to a pronounced temperature gradient between Huadu Mountain and the urban area. Additionally, a stronger high-pressure recirculation and sea–land breezes facilitated the transport of warm and moist air from the sea inland, creating a humid corridor along the sea–land interface. The consistent influx of warm and moist air near the mountain front, where strong temperature gradients were present, forcibly triggered warm-sector convection, intensifying its organization. This study highlighted the critical role of high-resolution land surface data in the accurate numerical simulation of warm-sector heavy rainfall.

Challenges and perspective on the modelling of high-Re, incompressible, non-equilibrium, rough-wall boundary layers

The present paper gives an overview of the recent modelling activities under NATO-STO AVT-349, focussed on the understanding and modelling of boundary layers for incompressible, high-Reynolds-number flows subject to non-equilibrium conditions such as strong pressure gradients, three-dimensionality, and surface roughness and heterogeneity. For this, we consider simpler cases where the above flow conditions are present separately or in a reduced number of combinations. First, we focus on the effect of roughness on the outer flow and the problems associated to its characterisation and prediction, with a particular emphasis on the conditions necessary for outer-layer similarity to hold. We then focus on how the presence of adverse and favourable pressure gradients affects the effect of roughness, and to what extent the figures used to quantify it are still useful under such conditions. We also consider the effect of surface heterogeneity, the shortcomings when modelling it and how these can be addressed. We then focus on the effect on the outer layer of pressure gradients and non-equilibrium conditions, to what extent similarity holds in those conditions, and how RANS models perform for such flows, identifying routes for their improvement to handle pressure gradients and non-equilibrium. We also discuss the use of data-driven and machine-aided methods in closure models.

Transport Barriers in magnetized plasmas- general theory with dynamical constraints

A fundamental dynamical constraint—that fluctuation induced charge-weighted particle flux must vanish- can prevent instabilities from accessing the free energy in the strong gradients characteristic of Transport Barriers (TBs). Density gradients, when large enough, lead to a violation of the constraint and hence preclude unstable modes and turbulent transport. This mechanism, then, broadens the class of configurations (in magnetized plasmas) where these high confinement states can be formed and sustained. The need for velocity shear, the conventional agent for TB formation, is obviated. The most important ramifications of the constraint is to permit a charting out of the domains conducive to TB formation and hence to optimally confined fusion worthy states; the detailed investigation is conducted through new analytic methods and extensive gyrokinetic simulations.

Enhanced trapping properties of coupled plasmonic tweezers via plasmon-exciton interaction.

Excited plasmonic nanoantennas enable the manipulation of photons coupled with quantum emitters or the trapping of particles as plasmonic tweezers, leveraging the strong evanescent gradient fields at the nanoscale. However, the ohmic loss of metals presents a significant challenge for the stable and high-precision manipulation of nanoparticles without causing damage. In this study, we investigated the enhanced trapping properties induced by plasmon-exciton interaction for coupled plasmonic tweezers. Through the coupling between plasmons and excitons, dynamic particle trapping is achievable under low excitation power conditions of 0.45 mW, with the trapping stiffness increasing by nearly 20 times. Furthermore, the trapping stiffness can be fine-tuned by modulating the quantity of excitons to regulate the coupling strength. Coupled plasmonic tweezers offer an effective strategy to mitigate the influence of ohmic loss on trapping performance, by manipulating particles with minimal laser power. These findings provide insights into enhancing trapping performance through plasmon-exciton coupling, with potential applications in biomedicine and quantum information science.

Unravelling the impact of soil data quality on species distribution models of temperate forest woody plants

Soil properties influence plant physiology and growth, playing a fundamental role in shaping species niches in temperate forest ecosystems. Here, we investigated the impact of soil data quality on the performance of species distribution models (SDMs) of 41 woody plant species in Swiss forests. We compared models based on measured soil properties with those based on digitally mapped soil properties on regional (Swiss Forest Soil Maps) and global scales (SoilGrids). We first calibrated topo-climatic SDMs with measured soil data and plant species presences and absences from mature temperate forest stand plots. We developed further models using the same soil predictors, but with values extracted from digital soil maps at the nearest neighbouring plots of the Swiss National Forestry Inventory. The predictive power of SDMs without soil information compared to those with soil information, as well as measured soil information vs digitally mapped, was evaluated with metrics of model performance and variable contribution. On average, models with measured and digitally mapped soil properties performed significantly better than those without soil information. SDMs based on measured and Swiss Forest Soil Maps showed higher performance, especially for species with an ‘extreme’ niche position (e.g., preference for high or low pH), compared to those using SoilGrids. Nevertheless, if no regional soil maps are available, SoilGrids should be tested for their potential to improve SDMs. Moreover, among the tested soil predictors, pH, and clay content of the topsoil layers most improved the predictive power of SDMs for forest woody plants. In conclusion, we demonstrate the value of regional soil maps for predicting the distribution of woody species across strong environmental gradients in temperate forests. The improved accuracy of SDMs and insights into drivers of distribution may support forest managers in strategies supporting e.g. biodiversity conservation, or climate adaptation planning.

Water use and water use efficiency of three Brassicaceae oilseeds under high‐ and low‐yielding environments

AbstractBrassicaceae oilseed crops have proven potential as vegetable oil feedstock for biofuels and food uses. However, meeting a growing demand for vegetable oils for food and industrial uses will require identifying oilseed species that are best suited for various growing environments within a particular region. The objective of this study was to compare growth dynamics, seasonal water use (WU), seed yields, and water use efficiency (WUE) of canola (Brassica napus L.), camelina (Camelina sativa L.), and white mustard (Sinapis alba L.) to determine their suitability under three different environments within the northern Great Plains. Comparisons were made among these species over three growing seasons between 2013 and 2016 at Morris, MN; Mandan, ND; and Sidney, MT, situated along a strong precipitation gradient from east to west. Generally, growing season precipitation was similar at Morris and Mandan, but both were considerably greater than at Sidney. Seasonal WU was similar among these oilseed species at Morris and Mandan but was greatest for camelina at the drier Sidney environment. Canola seed yield was the greatest at Morris and had higher WUE than camelina and white mustard. At Mandan and Sidney, canola and camelina had similar seed yields and WUE, which were generally greater than white mustard. Under abundant moisture and low stress (e.g., Morris), seed yield per millimeter of water used could be maximized by growing canola, while in a drier more stressful environment like Sidney, seed yield per millimeter of water used could be maximized by growing camelina.

Ecosystem functional types of the circumpolar Arctic tundra based on the seasonal dynamics of vegetation productivity

Biodiversity, when viewed through the combined lenses of compositional, structural, and functional attributes, provides for a holistic understanding of the complexities found within community assemblages and ecosystems. However, advancement in our understanding of how ecosystem functional diversity interacts with structural and compositional diversity metrics is lacking, in part because universally applied methodologies to derive ecosystem functional classifications are still under development and vary widely across scales, extents and biomes. This study presents a methodology to construct ecosystem functional types (EFTs), or areas of the land surface that function similarly, using the MODIS NDVI record, for the terrestrial circumpolar Arctic. EFTs were derived from the seasonal dynamics of NDVI, over the Arctic tundra at 250 m resolution and compared to bioclimate subzones and to structurally and compositionally defined vegetation units of the Circumpolar Arctic Vegetation Map (CAVM). Correspondence analyses of CAVM EFTs to previously delineated CAVM bioclimatic subzones, physiognomic (vegetation) units and floristic provinces revealed a general congruence, indicating convergence across composition, structure, and function; yet also demonstrated substantial functional variability even within bioclimate subzones and vegetation units. Strong latitudinal gradients in ecosystem function are present, with EFT richness ranging from low (34) in northernmost regions to high (45) in southernmost regions. Locally, the mountainous regions of northern Alaska, and eastern and western Siberia had high spatial variability in ecosystem functioning. Aside from these generalities, we found that EFTs varied widely within individual mapped vegetation units, successfully capturing the functional dimension of biodiversity across the circumpolar Arctic tundra.

Limited intraspecific variation in drought resistance along a pronounced tropical rainfall gradient

Assessing within-species variation in response to drought is crucial for predicting species' responses to climate change and informing restoration and conservation efforts, yet experimental data are lacking for the vast majority of tropical tree species. We assessed intraspecific variation in response to water availability across a strong rainfall gradient for 16 tropical tree species using reciprocal transplant and common garden field experiments, along with measurements of gene flow and key functional traits linked to drought resistance. Although drought resistance varies widely among species in these forests, we found little evidence for within-species variation in drought resistance. For the majority of functional traits measured, we detected no significant intraspecific variation. The few traits that did vary significantly between drier and wetter origins of the same species all showed relationships opposite to expectations based on drought stress. Furthermore, seedlings of the same species originating from drier and wetter sites performed equally well under drought conditions in the common garden experiment and at the driest transplant site. However, contrary to expectation, wetter-origin seedlings survived better than drier-origin seedlings under wetter conditions in both the reciprocal transplant and common garden experiment, potentially due to lower insect herbivory. Our study provides the most comprehensive picture to date of intraspecific variation in tropical tree species' responses to water availability. Our findings suggest that while drought plays an important role in shaping species composition across moist tropical forests, its influence on within-species variation is limited.

Self-rated health, epigenetic ageing, and long-term mortality in older Australians.

Self-rated health (SRH) is a subjective indicator of overall health based on a single questionnaire item. Previous evidence found that it is a strong predictor of mortality, although the underlying mechanism is poorly understood. Epigenetic age is an objective, emerging biomarker of health, estimated using DNA methylation data at hundreds of sites across the genome. This study aimed to assess the overlap and interaction between SRH and epigenetic ageing in predicting mortality risk. We used DNA methylation data from 1059 participants in the Melbourne Collaborative Cohort Study (mean age: 69years) to calculate three age-adjusted measures of epigenetic ageing: GrimAge, PhenoAge, and DunedinPACE. SRH was assessed using a five-category questionnaire item ("excellent, very good, good, fair, poor"). Cox models were used to assess the associations of SRH, epigenetic ageing, and their interaction, with all-cause mortality over up to 17years of follow-up (Ndeaths = 345). The association of SRH with mortality per category increase was HR = 1.29; 95%CI: 1.14-1.46. The association was slightly attenuated after adjusting for all three epigenetic ageing measures (HR = 1.25, 95%CI: 1.10-1.41). A strong gradient was observed in the association of GrimAge (Pinteraction = 0.006) and DunedinPACE (Pinteraction = 0.002) with mortality across worsening SRH strata. For example, the association between DunedinPACE and mortality in participants with "excellent" SRH was HR = 1.02, 95%CI: 0.73-1.43 and for "fair/poor" HR = 1.72, 95%CI: 1.35-2.20. SRH and epigenetic ageing were synergistic risk factors of mortality in our study. These findings suggest that consideration of subjective and objective factors may improve general health assessment, which has implications for the ongoing development of molecular markers of ageing.

Influence of Quadrupolar Molecular Transitions within Plasmonic Cavities.

Optical nanocavities have revolutionized the manipulation of radiative properties of molecular and semiconductor emitters. Here, we investigate the amplified photoluminescence arising from exciting a dark transition of β-carotene molecules embedded within plasmonic nanocavities. Integrating a molecular monolayer into nanoparticle-on-mirror nanostructures unveils enhancements surpassing 4 orders of magnitude in the initially light-forbidden excitation. Such pronounced enhancements transcend conventional dipolar mechanisms, underscoring the presence of alternative enhancement pathways. Notably, Fourier-plane scattering spectroscopy shows that the photoluminescence excitation resonance aligns with a higher-order plasmonic cavity mode, which supports strong field gradients. Combining quantum chemistry calculations with electromagnetic simulations reveals an important interplay between the Franck-Condon quadrupole and Herzberg-Teller dipole contributions in governing the absorption characteristics of this dark transition. In contrast to free space, the quadrupole moment plays a significant role in photoluminescence enhancement within nanoparticle-on-mirror cavities. These findings provide an approach to access optically inactive transitions, promising advancements in spectroscopy and sensing applications.

Geomorphic indicators of continental-scale landscape transience in the Hengduan Mountains, SE Tibet, China

Abstract. Landscapes are sculpted by a complex response of surface processes to external forcings, such as climate and tectonics. Several major river captures have been documented in the Hengduan Mountains, leading to the hypothesis that the region experiences exceptionally high rates of drainage reorganization driven by horizontal shortening and propagating uplift. Here we determine the prevalence, intensity, and spatial patterns of ongoing drainage reorganization in the Hengduan Mountains and evaluate the relative timescales of this transience by comparing drainage divide asymmetry for four geomorphic metrics that operate at different spatial and temporal scales. Specifically, we calculate the migration direction and the divide asymmetry index (DAI) for drainage divides using catchment-restricted topographic relief (CRR), hillslope gradient (HSG), normalized channel steepness (ksn), and normalized channel distance (χ). ksn and χ are both precipitation-corrected to account for the strong precipitation gradient across the region. The different spatial scales of these geomorphic metrics allow us to establish the relative timescales of observed landscape transience in the Hengduan Mountains, where local-scale metrics measure short-term change and integral quantities measure long-term disequilibrium. We find a high incidence of strongly asymmetric divides in all metrics across the Hengduan Mountain region. Although the magnitude of asymmetry varies significantly between metrics, possibly due to a combination of metric-specific thresholds and varying proxy relationships with erosion rate, a majority of divides agree on divide migration direction. Agreement in divide migration direction indicates an actively responding landscape when asymmetry is high and a state of quasi-equilibrium when asymmetry is low. Disagreements between the integral quantity, χ, and the other geomorphic metrics can be explained by different timescales of the underlying geomorphic processes, with χ reflecting a long-term response and CRR, HSG, and ksn capturing short-term perturbations to catchment structure. These perturbations include various transient mechanisms, such as differential tectonic uplift or erodibility, glacial alteration, and river captures. Our work confirms the high incidence of drainage reorganization across the Hengduan Mountains and highlights both transient and stable areas in the landscape with high resolution. We also offer valuable insights into the application of geomorphic metrics that can be generalized and applied to the study of landscape transience and drainage divide asymmetry in other settings.