Dominant Flux Research Articles

Insights into freeze–thaw and infiltration in seasonally frozen soils from field observations

AbstractSnowmelt infiltration into frozen soils in seasonally frozen landscapes is a critically important hydrological process, with consequences for agriculture, water resources, and flooding. The partitioning of snowmelt between infiltration and runoff in any given location and in any given year is highly uncertain. While it is intuitive to expect lower infiltration capacities in frozen soils, extensive past field research has shown that infiltration is often the dominant flux over runoff during this process, and this is attributed to infiltration into air‐filled macropores. Despite this understanding, we still lack models that can predict frozen soil infiltration reliably. In this study, we examine detailed field observations from the seasonally frozen Canadian Prairies to determine the controls on soil freeze/thaw, snowmelt partitioning, and groundwater recharge. We show how soil moisture, water table depth, snow water equivalent, and air temperature are all significant and confounding factors that determine soil freezing depth and snowmelt partitioning.

Distributed energy balance, mass balance and climate sensitivity of upper Chandra Basin glaciers, western Himalaya

Abstract Glacier and snow melt are the primary sources of water for streams, and rivers in upper Indus region of the western Himalaya. However, the magnitude of runoff from this glacierized basin is expected to vary with the available energy in the catchment. Here, we used a physically based energy balance model to estimate the surface energy and surface mass balance (SMB) of the upper Chandra Basin glaciers for 7 hydrological years from 2015 to 2022. A strong seasonality is observed, with net radiation being the dominant energy flux in the summer, while latent and sensible heat flux dominated in the winter. The estimated mean annual SMB of the upper Chandra Basin glaciers is −0.51 ± 0.28 m w.e. a−1, with a cumulative SMB of −3.54 m w.e during 7 years from 2015 to 2022. We find that the geographical factors like aspect, slope, size and elevation of the glacier contribute towards the spatial variability of SMB within the study region. The findings reveal that a 42% increase in precipitation is necessary to counteract the additional mass loss resulting from a 1°C increase in air temperature for the upper Chandra Basin glaciers.

An Invasive Predator Substantially Alters Energy Flux Without Changing Food Web Functional State or Stability

ABSTRACTUnderstanding how invasive species affect the stability and function of ecosystems is critical for conservation. Here, we quantified the effect of an actively suppressed invasive species on the Yellowstone Lake ecosystem using a food web energetics approach. We compared energy flux, functional state, and stability of four food web states: a pre‐invasion network and three post‐invasion networks undergoing active invasive species suppression, namely, initial invasion, expansion, and decline. Invasion caused ≥ 25% change (±) in energy flux for most consumers, and total flux increased twofold post‐invasion. Flux to the species of conservation concern, Yellowstone cutthroat trout (Oncorhynchus virginalis bouvieri), was 2.8 times less post‐invasion versus pre‐invasion, whereas invasive lake trout (Salvelinus namaycush) flux was up to 17.3 times higher compared to the initial invasion network. The dominant functional state and food web stability did not change post‐invasion, likely due to introduction of a generalist predator and the stabilizing effect of suppression. Lake trout invasion in Yellowstone Lake caused large changes to energy flux, shifting dominant fluxes away from the species of conservation concern, despite not changing functional state or stability. We demonstrate that changes in energy flux may signal invasions in ecosystems, but functional state or stability may not necessarily reflect the magnitude of invasion influences. For invaded fish communities, a better understanding of how the invasive species control the food web beyond just the direct influence on prey can be achieved by investigating energy flux, functional state, and food web stability. Furthermore, evaluating the effect of suppression beyond the invasive species can demonstrate the far‐reaching value of suppression management actions for conservation.

Can changes in land use in a semi-arid region of Brazil cause seasonal variation in energy partitioning and evapotranspiration?

Changes to forests due to deforestation, or their replacement by agricultural areas, alter evapotranspiration and the partitioning of available energy. This study investigated seasonal variations in the energy balance and evapotranspiration in landscapes under different levels of anthropogenic intervention in the semi-arid region of Brazil. Micrometeorological data was obtained from September 2020 to October 2022 for three areas of the semi-arid region: preserved Caatinga (CAA, native vegetation), Caatinga under regeneration (REGE) and a deforested area (DEFA). Here, we use the Bowen ratio energy balance method. Measurements were taken of global solar radiation, air temperature, relative humidity, vapour pressure deficit, rainfall, net radiation, latent heat flux, sensible heat flux, soil heat flux, evapotranspiration, volumetric soil water content and Normalised Difference Vegetation Index. Sensible heat flux was the dominant flux in both areas with 66% for preserved Caatinga vegetation, 63% for Caatinga under regeneration and 62% deforested area. The latent heat flux was equivalent to 28% of the net radiation for preserved Caatinga vegetation, Caatinga under regeneration and deforested area. The evapotranspiration in turn responded as a function of water availability, being higher during the rainy seasons, with average values of 1.82mm day-1 for preserved Caatinga vegetation, 2.26mm day-1 for Caatinga under regeneration and 1.25mm day-1 for deforested area. The Bowen ratio presented values>1 in deforested area, preserved Caatinga vegetation and Caatinga under regeneration. Thus, it can be concluded that the change in land use alters the energy balance components, promoting reductions in available energy and latent and sensible heat fluxes during the rainy-dry transition in the deforested area. In addition, the seasonality of energy fluxes depends on water availability in the environment.

High-Resolution Precipitation Mapping for Morocco: Integrating Orographic and Geographic Influences

Morocco's mountainous regions play a crucial role in shaping its precipitation patterns, influencing everything from water resources to agricultural potential. However, accurately mapping precipitation in such complex terrain is challenging for traditional methods. This study proposes a model that incorporates both topographic and geographic features and prevailing weather patterns to create more accurate maps of average annual precipitation across Morocco. What sets this model apart is its ability to determine the direction of prevailing weather circulation and incorporate geographic and topographic parameters that influence precipitation patterns. Using data from 1965 to 2010, the model estimates an average annual rainfall of 206.4 mm, equivalent to 146.6 billion cubic meters per year, with a terrain aspect deviation to the dominant moisture flux direction set at 280 degrees. This approach is particularly valuable in regions with limited climate data networks, as it leverages existing information to fill in the gaps. By providing more accurate precipitation maps, this model can be a valuable tool for environmental modeling, water resource management, and agricultural planning in Morocco.

On the impact of true polar wander on heat flux patterns at the core–mantle boundary

Abstract. The heat flux across the core–mantle boundary (CMB) is a fundamental variable for Earth evolution and internal dynamics. Seismic tomography provides access to seismic heterogeneities in the lower mantle, which can be related to present-day thermal heterogeneities. Alternatively, mantle convection models can be used to either infer past CMB heat flux or to produce statistically realistic CMB heat flux patterns in self-consistent models. Mantle dynamics modifies the inertia tensor of the Earth, which implies a rotation of the Earth with respect to its spin axis, a phenomenon called true polar wander (TPW). This rotation must be taken into account to link the dynamics of the mantle to the dynamics of the core. In this study, we explore the impact of TPW on the CMB heat flux over long timescales (∼1 Gyr) using two recently published mantle convection models: one model driven by a plate reconstruction and a second that self-consistently produces a plate-like behaviour. We compute the geoid in both models to correct for TPW. In the plate-driven model, we compute a total geoid and a geoid in which lateral variations of viscosity and density are suppressed above 350 km depth. An alternative to TPW correction is used for the plate-driven model by simply repositioning the model in the original paleomagnetic reference frame of the plate reconstruction. The average TPW rates range between 0.4 and 1.8° Myr−1, but peaks up to 10° Myr−1 are observed. We find that in the plate-driven mantle convection model used in this study, the maximum inertia axis produced by the model does not show a long-term consistency with the position of the magnetic dipole inferred from paleomagnetism. TPW plays an important role in redistributing the CMB heat flux, notably at short timescales (≤10 Myr). Those rapid variations modify the latitudinal distribution of the CMB heat flux, which is known to affect the stability of the magnetic dipole in geodynamo simulations. A principal component analysis (PCA) is computed to obtain the dominant CMB heat flux pattern in the different cases. These heat flux patterns are representative of the mantle convection cases studied here and can be used as boundary conditions for geodynamo models.

Latitudinal Profiles of Auroral Forms/Motions and Plasma Properties Based on Simultaneous Image‐Particle Measurements by Reimei in the Midnight Auroral Oval

AbstractWe present the simultaneous and conjugated auroral emission and particle data obtained by a low‐altitude polar‐orbiting micro‐satellite, Reimei, for elucidating their latitudinal distributions and variations in the nightside auroral oval. Here are reported a few notable examples of the Reimei observations with high time and spatial resolutions, namely ∼120 msec. and ∼1.2 km × 1.2 km for multispectral auroral images and 40 msec. for energy‐pitch angle distributions of electrons and ions with energies of 10 eV–12 keV, respectively. The auroral images show various fine‐scale auroral activities characterized by the following types of auroral forms and variations: faint bands, streaming multiple arcs, shearing arcs, and vortices/curls, which are typical of the latitudinal properties of auroras. The particle analyzer simultaneously observed various properties of electron energy‐pitch angle and latitudinal distributions, and their temporal variations, each of which corresponds to a type of the auroral activities. Their features are summarized below. Reimei repetitively observed inverted‐V signatures of low‐energy (<1 keV) field‐aligned electrons in addition to the higher‐energy (several keV) diffuse electrons in low‐latitude auroral oval. In more active regions at higher latitudes, the dominant energy flux responsible for the multiple‐arc emissions was carried by the well‐known inverted‐V electron precipitation. The rapidly rotating vortices or so‐called curls of fine‐scale discrete auroras near the poleward boundary of the auroral oval were closely associated with the significant energy fluxes of spiky field‐aligned electron bursts with energy‐time dispersions produced by dispersive Alfvén waves.

Floor of Cosmogenic Neutrino Fluxes above 1017 eV

The search for neutrinos with energies greater than 1017 eV is being actively pursued. Although normalization of the dominant neutrino flux is highly uncertain, a floor level is guaranteed by the interactions of extragalactic cosmic rays with milky Way gas. We estimate that this floor level gives an energy flux of E2ϕν≃10−13−0.5+0.5GeVcm−2sr−1s−1 at 1018 eV, where uncertainties arise from the modeling of the gas distribution and the experimental determination of the mass composition of ultra–high-energy cosmic rays on Earth. Based on a minimal model of cosmic-ray production to explain the mass-discriminated energy spectra observed on Earth above 5 × 1018 eV, we also present generic estimates of the neutrino fluxes expected from extragalactic production that generally exceed the aforementioned guaranteed floor. The prospects for detecting neutrinos above 1018 eV remain challenging, however, unless proton acceleration to the highest energies is at play in a subdominant population of cosmic-ray sources or new physical phenomena are at work.

Variation in the surface heat flux on the north and south slopes of Mount Qomolangma

Variation in the surface heat flux on the north and south slopes of Mount Qomolangma

Estimation of ammonia deposition to forest ecosystems in Scotland and Sri Lanka using wind-controlled NH3 enhancement experiments

Estimation of ammonia deposition to forest ecosystems in Scotland and Sri Lanka using wind-controlled NH3 enhancement experiments

Surface energy and mass balance of Mera Glacier (Nepal, Central Himalaya) and their sensitivity to temperature and precipitation

Abstract The sensitivity of glacier mass balance to temperature and precipitation variations is crucial for informing models that simulate glaciers’ response to climate change. In this study, we simulate the glacier-wide mass balance of Mera Glacier with a surface energy-balance model, driven by in situ meteorological data, from 2016 to 2020. The analysis of the share of the energy fluxes of the glacier shows the radiative fluxes account for almost all the energy available during the melt season (May–October). However, turbulent fluxes are significant outside the monsoon (June–September). On an annual scale, melt is the dominant mass flux at all elevations, but 44% of the melt refreezes across the glacier. By reshuffling the available observations, we create 180 synthetic series of hourly meteorological forcings to force the model over a wide range of plausible climate conditions. A +1 (−1)°C change in temperature results in a −0.75 ± 0.17 (+0.93 ± 0.18) m w.e. change in glacier-wide mass balance and a +20 (−20)% change in precipitation results in a +0.52 ± 0.10 (−0.60 ± 0.11) m w.e. change. Our study highlights the need for physical-based approaches to produce consistent forcing datasets, and calls for more meteorological and glaciological measurements in High Mountain Asia.

High methane concentrations in tidal salt marsh soils: Where does the methane go?

Tidal salt marshes produce and emit CH4 . Therefore, it is critical to understand the biogeochemical controls that regulate CH4 spatial and temporal dynamics in wetlands. The prevailing paradigm assumes that acetoclastic methanogenesis is the dominant pathway for CH4 production, and higher salinity concentrations inhibit CH4 production in salt marshes. Recent evidence shows that CH4 is produced within salt marshes via methylotrophic methanogenesis, a process not inhibited by sulfate reduction. To further explore this conundrum, we performed measurements of soil-atmosphere CH4 and CO2 fluxes coupled with depth profiles of soil CH4 and CO2 pore water gas concentrations, stable and radioisotopes, pore water chemistry, and microbial community composition to assess CH4 production and fate within a temperate tidal salt marsh. We found unexpectedly high CH4 concentrations up to 145,000 μmol mol-1 positively correlated with S2- (salinity range: 6.6-14.5 ppt). Despite large CH4 production within the soil, soil-atmosphere CH4 fluxes were low but with higher emissions and extreme variability during plant senescence (84.3 ± 684.4 nmol m-2 s-1 ). CH4 and CO2 within the soil pore water were produced from young carbon, with most Δ14 C-CH4 and Δ14 C-CO2 values at or above modern. We found evidence that CH4 within soils was produced by methylotrophic and hydrogenotrophic methanogenesis. Several pathways exist after CH4 is produced, including diffusion into the atmosphere, CH4 oxidation, and lateral export to adjacent tidal creeks; the latter being the most likely dominant flux. Our findings demonstrate that CH4 production and fluxes are biogeochemically heterogeneous, with multiple processes and pathways that can co-occur and vary in importance over the year. This study highlights the potential for high CH4 production, the need to understand the underlying biogeochemical controls, and the challenges of evaluating CH4 budgets and blue carbon in salt marshes.

Introducing nano-scale MgO particles into RHQT Nb3Al superconducting wires to significantly improve the critical current density

Introducing nano-scale MgO particles into RHQT Nb3Al superconducting wires to significantly improve the critical current density

Land Surface Modeling in the Himalayas: On the Importance of Evaporative Fluxes for the Water Balance of a High‐Elevation Catchment

AbstractHigh Mountain Asia (HMA) is among the most vulnerable water towers globally and yet future projections of water availability in and from its high‐mountain catchments remain uncertain, as their hydrologic response to ongoing environmental changes is complex. Mechanistic modeling approaches incorporating cryospheric, hydrological, and vegetation processes in high spatial, temporal, and physical detail have never been applied for high‐elevation catchments of HMA. We use a land surface model at high spatial and temporal resolution (100 m and hourly) to simulate the coupled dynamics of energy, water, and vegetation for the 350 km2 Langtang catchment (Nepal). We compare our model outputs for one hydrological year against a large set of observations to gain insight into the partitioning of the water balance at the subseasonal scale and across elevation bands. During the simulated hydrological year, we find that evapotranspiration is a key component of the total water balance, as it causes about the equivalent of 20% of all the available precipitation or 154% of the water production from glacier melt in the basin to return directly to the atmosphere. The depletion of the cryospheric water budget is dominated by snow melt, but at high elevations is primarily dictated by snow and ice sublimation. Snow sublimation is the dominant vapor flux (49%) at the catchment scale, accounting for the equivalent of 11% of snowfall, 17% of snowmelt, and 75% of ice melt, respectively. We conclude that simulations should consider sublimation and other evaporative fluxes explicitly, as otherwise water balance estimates can be ill‐quantified.

Effects of heating configuration and operating parameters on heat transfer and interfacial physics of microgravity flow boiling with subcooled inlet conditions – Experiments onboard the International Space Station

Effects of heating configuration and operating parameters on heat transfer and interfacial physics of microgravity flow boiling with subcooled inlet conditions – Experiments onboard the International Space Station

Discerning the Concentration and Bi‐Directional Flux of Ammonia in an Urban Estuary Using the Relaxed Eddy Accumulation Method

AbstractNarragansett Bay, the largest estuary in New England, is a heavily urbanized watershed impacted by deposition and runoff. Nutrient budgets and local policy rely on deposition data from a 1990 study that did not include any direct observations of dry deposition of gaseous ammonia (NH3(g)) and particulate ammonium (p‐NH4+) due to uncertainties in their flux direction and measurement difficulty. Recent work has shown that wet deposition of ammonium (NH4+) to the Bay has increased by a factor of 6 over the past three decades, leading to a 2.5‐fold increase in wet nitrogen (N) deposition. This documented increase in wet deposition of NH4+ is concurrent with managed nutrient reductions in urbanized estuaries but has potentially increased the impacts of atmospheric N deposition, including the dry deposition of NH3(g) and p‐NH4+. However, the lack of NH3(g) and p‐NH4+ measurements hinders our interpretation of this important N source. For the first time over Narragansett Bay, and to our knowledge over open water, dry (particulate and gas phase) total ammonia (NHx = NH3(g) + p‐NH4+) and the bidirectional NH3(g) flux were quantified using a relaxed eddy accumulation sampling technique. We find that dry deposition of NHx comprises 9.6% of total (wet + dry) N deposition. During the fall season, the dominant flux direction for NH3(g) is upward, which also has implications for urban air quality. We estimate that NH3(g) emitted from the Bay to the atmosphere makes up to 10% of the local NH3(g) emission budget for fall.

Evolution of ecosystem-scale surface energy fluxes of a newly constructed boreal upland-fen watershed

Evolution of ecosystem-scale surface energy fluxes of a newly constructed boreal upland-fen watershed

Extreme Summer Precipitation Characteristics and Associated Water Vapor Transport in Southern Xinjiang

In this study, we analyzed the spatial and temporal characteristics of extreme precipitation in summer in southern Xinjiang (SXJ) using CN05.1 daily precipitation data, the National Centers for Environmental Prediction (NCEP) monthly average data, and ERA5 four-times-daily reanalysis data from 1961 to 2020, determined the interdecadal variation in extreme precipitation, and further explored the circulation mechanisms and anomalous water vapor transport characteristics associated with changes in extreme precipitation. The results showed that extreme precipitation, extreme precipitation days, and extreme precipitation contribution in SXJ all increased significantly, with the turnaround occurring in 1986. Enhanced vertical upward motion, greater convergence of water vapor at lower levels, and a more unstable atmospheric convection led to an increase in extreme precipitation along the southern border region. The eastward Pacific Ocean and southward Indian Ocean provided anomalous water vapor transport, and the boundary water vapor flux trend and its correlated distribution with extreme precipitation showed that southern boundary water vapor transport played an important role in the increase in extreme precipitation. At vertical heights, the dominant longitudinal water vapor transport fluxes were concentrated in the middle and upper layers, whereas the latitudinal water vapor transport fluxes were concentrated in the middle and lower layers.

Enhancements of critical current density in Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductors by additions of SnO2 nanoparticles

The impact of adding SnO2 nanoparticles on the enhancements of critical current density (Jc) of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductors was studied. Polycrystalline superconductors with stoichiometry of (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1−x(SnO2)x where was x was ranged from 0.000, 0.002, 0.004, 0.006, 0.008 to 0.010 were made through traditional solid state reaction technique. X-ray diffraction data revealed that all fabricated samples consisted of Bi-2223 and Bi-2212 superconducting phases. The volume fraction of the Bi-2223 phase decreased with SnO2 addition. Analyses of textural structure using scanning electron microscopy data evidenced a clear decrease in grain orientation and porosity with increased doping levels. SnO2 presence in connection to Bi-2223 deceleration reduced the critical temperature. Values of Jc deduced from the magnetization hysteresis loops measured at different temperatures of 35 K, 45 K, 55 K, 65 K were found to enhance for the SnO2 added samples. In the x = 0.002 samples, the field dependent Jc achieved its maximum values. In order to have a deeper understanding in the improvements of flux pinning properties, small and large bundle fields were determined by using the collective pinning theory. The obtained values indicate the expansion of the two corresponding regimes with appropriate. By analyzing the dependence of normalized Jc versus normalized critical temperature, the dominant flux pinning mechanisms in all samples were consistent with δl pinning. Besides, the addition of SnO2 nanoparticles was likely to produce pinning centers in form of core point as evidenced by using the Dew–Hughes model.

Biogeophysical Effects of Land-Use and Land-Cover Changes in South Asia: An Analysis of CMIP6 Models

The identification of the biogeophysical effects due to land-use, land-cover, and land- management changes (LULCC) is yet to be clearly understood. A range of factors, such as the inclusion of an interactive ocean model component, representation of land management, transient LULCC, and accountability for atmospheric feedback, potentially shifts how models may detect the impacts of the land surface on the climate system. Previous studies on the biogeophysical effects of LULCC in South Asia have either neglected one of those factors or are single model results. Therefore, we analyzed the outputs from 11 models, participants of the Coupled Model Intercomparison Project in its Sixth Phase (CMIP6), which derived from experiments with and without LULCC and compared the two simulations with respect to changes in near-surface temperature and total precipitation means. The CMIP6 simulations, to a certain extent, accounted for the elements previously overlooked. We examined the grid cells that robustly indicated a climatic impact from LULCC. Additionally, we investigated the atmospheric feedback and the dominant fluxes with their associated land surface variables involved in the changes in temperature and precipitation. Our results indicated that the biogeophysical effects from LULCC favored surface net cooling and surface net drying over the robust areas at all seasons. The surface net cooling was strongly influenced by the decrease in available energy and the increase in latent heat and total evapotranspiration. Surface net drying was highly promoted by local hydrological processes, especially in areas outside the monsoon core. The study also revealed that non-local sources might influence precipitation in some parts of South Asia, although this was inconclusive. Our research presented similar results to previous studies but with different magnitudes, which highlighted the added value of CMIP6-GCMs simulations but also their pitfalls.