Mass Balance Research Articles

The Impact of Storm Sewer Network Simplification and Rainfall Runoff Methods on Urban Flood Analysis

Due to the impact of climate change, the importance of urban flood analysis is increasing. One of the biggest challenges in urban flood simulations is the complexity of storm sewer networks, which significantly affects both computational time and accuracy. This study aimed to analyze and evaluate the impact of sewer network simplification on the accuracy and computational performance of urban flood prediction by comparing different rainfall runoff methods. Using the hyper-connected solution for urban flood (HC-SURF) model, two rainfall runoff methods, the SWMM Runoff method and the Surface Runoff method, were compared. The sewer network simplification was applied based on manhole catchment areas ranging from 10 m2 to 10,000 m2. The analysis showed that the computation time could be reduced by up to 54.5% through simplification, though some accuracy loss may occur depending on the chosen runoff method. Overall, both methods produced excellent results in terms of mass balance, but the SWMM Runoff method minimized the reduction in analytical performance due to simplification. This study provides important insights into balancing computational efficiency and model accuracy in urban flood analysis.

Origin of Intercrystalline Brine Formation in the Balun Mahai Basin, Qaidam: Constraints from Geochemistry and H-O-Sr Isotopes

The Balun Mahai Basin (BLMH), located in the northern Qaidam Basin (QB), is endowed with substantial brine resources; however, the genetic mechanisms and potential of these brine resources remain inadequately understood. This study investigated the intercrystalline brine (inter-brine) in BLMH, performing a comprehensive geochemical analysis of elemental compositions and H-O-Sr isotopes. It evaluated the water source, solute origin, evolutionary process, and genetic model associated with this brine. Moreover, a mass balance equation based on the 87Sr/86Sr isotopic ratio was developed to quantitatively evaluate the contributions of Ca-Cl water and river water to the inter-brine in the study area. The results suggest that the hydrochemical type of inter-brine in the north part of BLMH is Cl-SO4-type and in the south part is Ca-Cl-type. The solutes in brine are mainly derived from the dissolution of minerals such as halite, sylvite, and gypsum. The hydrochemical process of brine is controlled by evaporation concentration, water–rock interaction, and ion exchange interaction. Hydrogen and oxygen isotopes suggest that the inter-brine originates from atmospheric precipitation or ice melt water and has experienced intense evaporation concentration and water–rock interaction. The strontium isotopes suggest that the inter-brine was affected by the recharge and mixing of Ca-Cl water and river water, which controlled the spatial distribution and formation of brine hydrochemical types. The analysis of ionic ratios suggest that the inter-brine is derived from salt dissolution and filtration, characterized by poor sealing and short sealing time in the salt-bearing formation. The differences in hydrochemical types and spatial distribution between the north and the south are fundamentally related to the replenishment and mixing of these two sources, which can be summarized as mixed origin model of “dissolution and filtration replenishment + deep replenishment” in BLMH.

Contrasting Precipitation Variations over the Himalayas–Southeastern Tibetan Plateau in Winter: Insights from the Perspectives of Anthropogenic Warming and Arctic Sea Ice Variations

Abstract Climate warming has caused widespread glacier retreat across the Tibetan Plateau (TP), with notable impacts observed in both the western Himalayas and southeastern TP. Remarkably, over the past two decades, the rate of glacier mass loss has remained stable or even declined in the western Himalayas, whereas a contrasting trend of acceleration has been evident in the southeastern TP. Among various factors considered, the contrasting winter precipitation pattern across the Himalayas–southeastern TP stands out as an important contributor to the observed differences in glacier mass balances. However, the underlying mechanisms behind this phenomenon remain unclear. Here, we provide evidence of a noticeable shift in the climate regime due to anthropogenic warming, altering atmospheric circulation patterns. This, in turn, has led to a significant change in the dominant winter precipitation pattern, favoring the observed contrasting glacier mass balances trend in winter. Additionally, the Barents–Kara Sea ice has emerged as a plausible driver of the interannual variability of the contrasting precipitation pattern, acting by exerting force on the atmosphere and stimulating the Rossby wave propagation. Consequently, it led to the opposite vertical motion and alterations in the moisture budget between the western Himalayas and southeastern TP. Thus, it is crucial to consider the unprecedented anthropogenic warming and Arctic Sea ice variations as potential drivers shaping both past and future glacier behaviors within this domain.

Probabilistic projections of the Amery Ice Shelf catchment, Antarctica, under conditions of high ice-shelf basal melt

Abstract. Antarctica's Lambert Glacier drains about one-sixth of the ice from the East Antarctic Ice Sheet and is considered stable due to the strong buttressing provided by the Amery Ice Shelf. While previous projections of the sea-level contribution from this sector of the ice sheet have predicted significant mass loss only with near-complete removal of the ice shelf, the ocean warming necessary for this was deemed unlikely. Recent climate projections through 2300 indicate that sufficient ocean warming is a distinct possibility after 2100. This work explores the impact of parametric uncertainty on projections of the response of the Lambert–Amery system (hereafter “the Amery sector”) to abrupt ocean warming through Bayesian calibration of a perturbed-parameter ice-sheet model ensemble. We address the computational cost of uncertainty quantification for ice-sheet model projections via statistical emulation, which employs surrogate models for fast and inexpensive parameter space exploration while retaining critical features of the high-fidelity simulations. To this end, we build Gaussian process (GP) emulators from simulations of the Amery sector at a medium resolution (4–20 km mesh) using the Model for Prediction Across Scales (MPAS)-Albany Land Ice (MALI) model. We consider six input parameters that control basal friction, ice stiffness, calving, and ice-shelf basal melting. From these, we generate 200 perturbed input parameter initializations using space filling Sobol sampling. For our end-to-end probabilistic modeling workflow, we first train emulators on the simulation ensemble and then calibrate the input parameters using observations of the mass balance, grounding line movement, and calving front movement with priors assigned via expert knowledge. Next, we use MALI to project a subset of simulations to 2300 using ocean and atmosphere forcings from a climate model for both low- and high-greenhouse-gas-emission scenarios. From these simulation outputs, we build multivariate emulators by combining GP regression with principal component dimension reduction to emulate multivariate sea-level contribution time series data from the MALI simulations. We then use these emulators to propagate uncertainty from model input parameters to predictions of glacier mass loss through 2300, demonstrating that the calibrated posterior distributions have both greater mass loss and reduced variance compared to the uncalibrated prior distributions. Parametric uncertainty is large enough through about 2130 that the two projections under different emission scenarios are indistinguishable from one another. However, after rapid ocean warming in the first half of the 22nd century, the projections become statistically distinct within decades. Overall, this study demonstrates an efficient Bayesian calibration and uncertainty propagation workflow for ice-sheet model projections and identifies the potential for large sea-level rise contributions from the Amery sector of the Antarctic Ice Sheet after 2100 under high-greenhouse-gas-emission scenarios.

Advances in 3-D printing: polymers, fabrication mechanisms, mass balance models and applications

AbstractIn Science and Engineering, additive manufacturing, which is synonymously known as 3-D printing is a layer-by-layer computer-aided approach that is used to produce high precision commercial industrial products. So far, 3-D printing techniques, which translate computer-aided virtual 3-D models into physical objects, are gaining traction globally. However, the current evolution from conventional molding and machining to rapid prototyping followed by rapid additive manufacturing prompts new challenges for engineers and scientists alike. This review is particularly prompted by novel innovations in 3-D printing with respect to emerging fabrication designs and mechanisms, printable polymeric materials, and current applications. Central to all spotlights is the discussion on 3-D printing techniques discussed under 3 broad categories; (i) extrusion-based methods, (ii) powder binding technologies and (iii) photopolymerization methods and corresponding polymer design aspects, processing parameters and mass balance models. Aspects of mass-balance models addressed in this review include models of multimaterial 3-D printing of viscoelastic inks, Newtonian fluid in extrusion, the Gaussian Beam model and multiscale computational simulations for prediction of macroscale properties of various polymeric materials. This review also highlights selected applications that demonstrate how polymer-based 3-D printing is being exploited in industry, and future perspectives.

Validated Multimethod Approach for Full Characterization of 2'-Fucosyl-d-lactose as an Industrially Produced Human Milk Oligosaccharide.

Human milk oligosaccharides are of high interest as active ingredients in infant formulas and dietary food supplements. Full characterization of members of this compound class is challenging due to the intrinsic complexity of byproducts during synthesis by fermentation. Moreover, when method validation is targeted for a regulated environment, a robust chromatographic separation of the highly polar oligosaccharides needs to be addressed, including isomers and compounds relevant for potential product adulteration. We present a combined approach of validated chromatography and NMR spectroscopy, which allows for full mass balancing of industrially produced 2'-fucosyl-d-lactose. A combination of NMR spectroscopy, mass spectrometry, and action IR spectroscopy tackles structural elucidation of monoacetylated species as a new class of byproducts.

Comparative study of deterministic and stochastic optimization algorithms applied to the absorption of CO2 by alkanolamine solution

Abstract A model based on simulated annealing approach is used with e-UNIQUAC model as well as two other algorithms to study the absorption of carbon dioxide by monoethanolamine solutions. In this work, we propose to compare the performance (through the knowledge of RMSD values) of two stochastic methods, namely the GA (genetic algorithm) and SA (simulated annealing) methods and a deterministic method that is the simplex method. These methods were applied to the absorption of carbon dioxide by an alkanolamine solution using a chemical equilibrium model and a thermodynamic equilibrium model. The latter is based on the use of the modified-UNIQUAC (UNIQUAC-electrolyte) model instead of e-NRTL model for the liquid phase and a fugacity model for the vapor phase. The chemical equilibrium in this work represents the absorption of CO2 by monoethanolamine solution at different temperatures. Solving the coupled system of material and charge balances gives us the carbon dioxide pressure while taking into account the non-ideality of the system. The three-optimization methods show good agreement with the experimental data with a better performance of the simulated annealing method..

The Role of Benthic TA and DIC Fluxes on Carbon Sequestration in Seagrass Meadows of Dongsha Island

Coastal blue carbon ecosystems sequester carbon, storing it as plant biomass and particulate organic matter in sediments. Recent studies emphasize the importance of incorporating dissolved inorganic and organic forms into carbon assessments. As sediment-stored organic matter decomposes, it releases dissolved inorganic carbon (DIC) and total alkalinity (TA), both of which are critical for regulating the partial pressure of CO2 (pCO2) and thus carbon sequestration. This study investigated the role of benthic DIC and TA fluxes in carbon sequestration within seagrass meadows in Dongsha Island’s inner lagoon (IL) during the winter and summer seasons. Chamber incubation experiments revealed elevated benthic DIC and TA fluxes compared to global averages (107 ± 75.9 to 119 ± 144 vs. 1.3 ± 1.06 mmol m−2 d−1 for DIC, and 69.7 ± 40.7 to 75.8 ± 81.5 vs. 0.52 ± 0.43 mmol m−2 d−1 for TA). Despite DIC fluxes being approximately 1.5 times higher than TA fluxes, water pCO2 levels remained low (149 ± 26 to 156 ± 18 µatm). Mass balance calculations further indicated that benthic DIC was predominantly reabsorbed into plant biomass through photosynthesis (−135 to −128 mmol m−2 d−1). Conversely, TA accumulated in the water and was largely exported (−60.3 to −53.7 mmol m−2 d−1), demonstrating natural ocean alkalinity enhancement (OAE). This study highlights the crucial role of IL seagrass meadows in coastal carbon sequestration through net autotrophy and carbonate dissolution. Future research should explore the global implications of these processes and assess the potential of natural OAE in other coastal blue carbon ecosystems.

Spatiotemporal mass balance variability of Jostedalsbreen ice cap, Norway, revealed by a temperature-index model with data assimilation

Spatiotemporal mass balance variability of Jostedalsbreen ice cap, Norway, revealed by a temperature-index model with data assimilation

Carbon Flow Allocation Patterns of CH4, CO2, and Biomass Production Vary with Sewage and Sediment Microbial and Biochemical Factors in the Anaerobic Sewer Environment.

Understanding the carbon (C) fate in municipal sewers is imperative for optimizing current sewer-C-degradation control and treatment efficiency, aligning with China's C-neutrality strategy in determining the exact C budget of the wastewater system. This study used laboratory batch tests mimicking the anaerobic sewer environment and sewage-sediment stratification to evaluate C flow allocation (CFA) patterns in response to biotic and abiotic variables. We quantified the C equivalent mass (CEM) and used absolute quantitative 16S rRNA gene amplicon sequencing to characterize the microbiome. The substantial methane production (CH4, 17.2%-18.8%) required both activated sediment and exogenous C, while biomass production (BP, 63.1%-74.9%) formed C sink predominated as the main CFA direction under the stratified state. This was supported by the high diversity, interspecific interactions, and metabolic capacity of the sediment microbiome. However, CH4 and BP patterns demonstrated non-synchronicity and opposite dynamic characteristics. Carbon dioxide (CO2, 64.0%-81.3%) production dominated the sewage CFA. The absolute abundance of the sediment microbiome, which was 5.6 times higher than that of the sewage, exhibited a strong increase in magnitude across the phases. It was primarily associated with biomass growth and N metabolism, whereas sewage showed differentiated and competing communities and appeared to act mainly as the exogenous C sources. We constructed a binary quadratic linear model revealing the non-linear relationship between ACK activity, DOC degradation rate, and CEMCH4 rate; the former maintained low CH4 production when the available substrate was insufficient. The influence of N and S factors on the CFA is complex and multi-faceted. These findings highlight the importance of further investigations into the process-based framework of the sewer C budget, focusing on the C source-emission-sink functions and mass balance.

Projected changes of Greenland’s periphery glaciers and ice caps

Abstract Rapid global warming has caused drastic mass loss in Greenland’s peripheral glaciers and ice caps (GICs), contributing to a rise of global sea levels. To better understand future changes under different emission scenarios, we used the Open Global Glacier Model to simulate glacier dynamics and runoff changes from 2015 to 2100. The results show that their area and volume will decrease by 38.88% (SSP1-2.6) to 60.84% (SSP5-8.5) and 47.56% (SSP1-2.6) to 67.10% (SSP5-8.5) by 2100, with regions that have larger glacierized areas and are farther from the ocean experiencing less volume loss. Meanwhile, the predicted surface mass balance of Greenland’s peripheral GICs in 2100 is −0.58 ± 0.92, −1.18 ± 1.13, −2.04 ± 0.79 and −3.16 ± 0.96 m w.e. a−1 under four emission scenarios. The runoff under higher emission scenarios is larger than that under lower emission scenarios, with peak water occurring later in regions that have larger glacierized areas and are farther from the ocean.

Effect of gypsum on transport of IMX-104 constituents in overland flow under simulated rainfall.

Residue of energetic formulations, which is deposited on military training grounds following incomplete detonation, poses biotic hazards. This residue can be transported off-site, adsorb to soil clays and organic matter, transform or degrade, or taken up by plants and animals. Its harmful effects can be mitigated by localizing the energetics at the site of initial deposition using soil amendments and allowing them to bio- and photodegrade in situ. Small plots with coarse loamy soil were used to study the effect of gypsum (CaSO4·2H2O) on transport and redistribution under simulated rainfall of various sizes of insensitive munition explosive (IMX)-104 particles, which consist of 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tertranitro-1,3,5,7-tetrazocine (HMX). The addition of gypsum more than doubled infiltration and decreased sediment loss by 16% compared to the control. The post-rainfall mass balance of IMX-104 in the order from greater to smaller pools was as follows: (1) soil surface retention, (2) off-site loss to overland flow, and (3) sub-surface infiltration. Overall, the application of gypsum significantly decreased concentration and the total mass loss of dissolved DNAN, RDX, and HMX in surface runoff. In addition, gypsum significantly decreased (for NTO, DNAN, and HMX) or delayed (for NTO, DNAN, RDX, and HMX) the peak discharge of <2mm particulate energetics. The infiltration of NTO in the gypsum treatment was fivefold greater than in the control. Moreover, DNAN and RDX were also present in infiltration, while in the gypsum-free control none were found. Gypsum shifted the total mass balance of energetics toward subsurface flow. This study indicates that gypsum may decrease off-site transport of energetic constituents in the soils that are subject to surface sealing.

Ibuprofen encapsulation inside non-conventional O/W Pickering emulsions stabilized with partially hydrophobized silica

The encapsulation of active ingredients is an important process in various industrial sectors including pharmaceutics, foods and cosmetics. For the first time, the capacity of non-conventional anti-Bancroft oil-in-water Pickering emulsions stabilized by partially hydrophobized silica to encapsulate an apolar active is addressed. A dispersed phase volume of paraffin oil of 50% coupled to 0.5 wt.% of silica has been employed to avoid excess of silica in the continuous phase and encapsulate higher amount of ibuprofen (the model drug). Three ibuprofen contents ranging from 100 mg (1.6 mg/mL of paraffin) to 420 mg (6 mg/mL of paraffin) have been tested. The encapsulation efficiency as well as the emulsions properties are investigated by the means of light diffusion, microscopy, rheology, and HPLC coupled to mass balance. The Pickering emulsion is very efficient for the encapsulation of ibuprofen with encapsulation rates of 99% obtained inside droplets of 30 µm for all the 3 ibuprofen concentrations. This encapsulation ability is perfectly maintained, whether during ageing (during 90 days), or when the emulsion is diluted by a factor 100 inside physiological media at basic and acidic pH.

Effects of vertical forest stratification on precipitation material redistribution and ecosystem health of Pinus massoniana in the Three Gorges Reservoir area of China.

Vertical stratification of forest plays important roles in the local material balance and in maintaining forest health by distributing and redistributing precipitation materials through adsorption, fixation, and release. Differences in runoff nutrient concentrations among vertical layers are closely related to vertical stratification (factors such as the trunk, canopy, forest litter, and soil physical and chemical properties). Long-term forest observations revealed significant spatial differences in Pinus massoniana (Pinus massoniana Lamb.) forests in the Three Gorges Reservoir area. Pinus massoniana forests on downslopes were characterized by a dense canopy, green needles, and rich forest vegetation, while those on upslopes were characterized by low vegetation cover, dead trees, and decreases in the tree height, diameter at breast height, and volume per plant with increasing slope. By analyzing the soil at different sites, we found that the pH of the forest land soil differed significantly among different slope positions. Soil on upper slopes was significantly more acidic than soil on lower slopes, indicating that acidic substances were intercepted by filtration through the broad litter layer and the soil surface layer. This filtration process resulted in a normal rhizosphere environment suitable for the absorption of nutrients by vegetation on the lower slopes. In this way, downhill sites provided a good microenvironment for the growth of Pinus massoniana and other vegetation. Our results show that direct contact between needles and acid rain was not the main cause of root death. Instead, the redistribution of rainfall substances by forest spatial stratification caused changes in the soil microenvironment, which inhibited the absorption of nutrients by the roots of Pinus massoniana and the growth of understory plants in Pinus massoniana forests on upper slopes. These findings emphasize that increasing land cover with forests with vertical structural stratification plays an important role in woodland material redistribution and forest conservation.

Distribution of Pb, Zn, Fe, As, Sn, Sb, Bi, and Ni Between Oxide Liquid and Metal in the ‘CuO0.5’-CaO-AlO1.5 System in Equilibrium with Cu Metal at 1400 °C

AbstractThe increasing complexity of ore resources and recycled materials in the feed of pyrometallurgical processes present a technical challenge to the metallurgical engineers working on maximizing the recovery of the valuable elements and minimizing the environmental impact of the processes. To address this challenge, the availability of computational tools that can predict the mass and energy balance in complex systems is required. Then, the accurate description of phase equilibria in the complex multicomponent systems describing the chemistry of the pyrometallurgical processes becomes critical for the correct implementation of the indicated tools and facing the outlined industrial challenges. In the present study, the distribution of selected elements (Pb, Zn, Fe, As, Sn, Sb, Bi, and Ni) between oxide liquid and metal in the ‘CuO0.5’–CaO–AlO1.5 system in equilibrium with Cu metal at 1400 °C (liquidus of CaAl2O4) was experimentally studied using the equilibration and quenching technique followed by the electron probe X-ray microanalysis of the resulted samples. The study covered a wide range of effective p(O2) over the system from 10−11 to 10−3.5 (corresponding to formation of immiscible CuO0.5-rich slag). To avoid loss of volatile elements (Pb, Zn, As, Sn, Sb, and Bi), a correlation between ‘CuO0.5’ in oxide liquid and p(O2) in open system was obtained first, followed by studying the volatile elements distribution in closed conditions (Al2O3 crucible sealed in SiO2 ampoule), where ‘CuO0.5’ concentration was used as a marker to evaluate the effective p(O2) over the system. The experimental results were then used for the optimization of the thermodynamic model parameters of the system as part of the integrated experimental and self-consisting thermodynamic modeling research program of phase equilibria in the Cu–Pb–Zn–Fe–Ca–Si–Al–Mg–O–S–(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co, and Na) gas/oxide liquid/matte/speiss/metal/solids system. Graphical Abstract

Modelling snowpack on ice surfaces with the ORCHIDEE land surface model: application to the Greenland ice sheet

Abstract. Current climate warming is accelerating mass loss from glaciers and ice sheets. In Greenland, the rates of mass changes are now dominated by changes in surface mass balance (SMB) due to increased surface melting. To improve the future sea-level rise projections, it is therefore critical to have an accurate estimate of the SMB, which depends on the representation of the processes occurring within the snowpack. The Explicit Snow (ES) scheme implemented in the land surface model Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) has not yet been adapted to ice-covered areas. Here, we present the preliminary developments we made to apply the ES model to glaciers and ice sheets. Our analysis mainly concerns the model's ability to represent ablation-related processes. At the regional scale, our results are compared to the MAR regional atmospheric model outputs and to MODIS albedo retrievals. Using different albedo parameterizations, we performed offline ES simulations forced by the MAR model over the 2000–2019 period. Our results reveal a strong sensitivity of the modelled SMB components to the albedo parameterization. Results inferred with albedo parameters obtained using a manual tuning approach present very good agreement with the MAR outputs. Conversely, with the albedo parameterization used in the standard ORCHIDEE version, runoff and sublimation were underestimated. We also tested parameters found in a previous data assimilation experiment, calibrating the ablation processes using MODIS snow albedo. While these parameters greatly improve the modelled albedo over the entire ice sheet, they degrade the other model outputs compared to those obtained with the manually tuned approach. This is likely due to the model overfitting to the calibration albedo dataset without any constraint applied to the other processes controlling the state of the snowpack. This underlines the need to perform a “multi-objective” optimization using auxiliary observations related to internal snowpack processes. Although there is still room for further improvements, the developments reported in the present study constitute an important advance in assessing the Greenland SMB with possible extension to mountain glaciers or the Antarctic ice sheet.

Monitoring Activity of the Subglacial Lake Mercer Based on CryoSat-2 and ICESat-2 Altimetry Data from 2011 to 2023

Abstract. Active subglacial lakes are capable of exchanging and transporting water through water flow paths, thus having an important impact on ice sheet movement and even on the regional mass balance. The use of satellite altimetry can indirectly reveal internal subglacial hydrological activity through direct surface elevation observation, which plays an important role in the study of the evolution of active subglacial lakes. This paper monitors and analyzes the activity of the subglacial lake Mercer (SLM) in the Whillans and Mercer Ice Stream (WIS/MIS), using data from the CryoSat-2 satellite radar altimetry and ICESat-2 satellite laser altimetry. We adopt the differential DEM model and the repeat orbit model based on their respective data characteristics. Finally, we reveal the temporal and spatial evolution patterns of SLM during 2011-2023, and construct the elevation anomaly time series. The results show that the central and western parts of SLM were the areas with more significant elevation anomalies, and there were three significant fill-drain cycles during the time periods studied in this research, with the elevation anomaly range reaching about 8 m and 4 m for the first and second cycles, respectively, and the lake is currently in the third significant draining phase. Furthermore, the elevation anomalies obtained during the mission overlap time of CryoSat-2 and ICESat-2 data are in good agreement, which confirms the accuracy of our method.

GNSS reflectometry from low-cost sensors for continuous in situ contemporaneous glacier mass balance and flux divergence

Abstract Recent advances in remote sensing have produced global glacier surface elevation change data. Parsing these elevation change signals into contributions from the climate (i.e. climatic mass balance) and glacier dynamics (i.e. flux divergence) is critical to enhance our process-based understanding of glacier change. In this study, we evaluate three approaches for direct, continuous measurements of the climatic mass balance, flux divergence and elevation change at a site on Gulkana Glacier in Alaska using low-cost global navigation satellite system (GNSS) sensors, GNSS interferometric reflectometry (GNSS-IR), banded ablation stakes with time-lapse cameras and combinations thereof. Cumulative climatic mass balance over the season was 4.85 m and the three approaches were within 0.08 m through early July before the snowpack melted, and within 0.28 m through mid-August. The flux divergence increased from 0.52 ± 0.03 cm d−1 before June 3 to about 0.73 cm d−1 after June 27. We demonstrate a single GNSS system fixed atop an ablation stake can measure contemporaneous climatic mass balance, flux divergence and elevation change based on the antenna's position and GNSS-IR techniques. The ability of these systems to measure glacier mass balance and flux divergence offers unique opportunities for year-round observations on mountain glaciers in the future.

Comparison of Multiple Methods for Supraglacial Melt-Lake Volume Estimation in Western Greenland During the 2021 Summer Melt Season

Supraglacial melt-lakes form and evolve along the western edge of the Greenland Ice Sheet and have proven to play a significant role in ice sheet surface hydrology and mass balance. Prior methods to quantify melt-lake volume have relied upon Landsat-8 optical imagery, available at 30 m spatial resolution but with temporal resolution limited by satellite overpass times and cloud cover. We propose two novel methods to quantify the volume of meltwater stored in these lakes, including a high-resolution surface DEM (ArcticDEM) and an ablation model using daily averaged automated weather station data. We compare our methods to the depth-reflectance method for five supraglacial melt-lakes during the 2021 summer melt season. We find agreement between the depth-reflectance and DEM lake infilling methods, within +/−15% for most cases, but our ablation model underproduces by 0.5–2 orders of magnitude the volumetric melt needed to match our other methods, and with a significant lag in meltwater onset for routing into the lake basin. Further information regarding energy balance parameters, including insolation and liquid precipitation amounts, is needed for adequate ablation modelling. Despite the differences in melt-lake volume estimates, our approach in combining remote sensing and meteorological methods provides a framework for analysis of seasonal melt-lake evolution at significantly higher spatial and temporal scales, to understand the drivers of meltwater production and its influence on the spatial distribution and extent of meltwater volume stored on the ice sheet surface.

Remote Sensing Data Assimilation to Improve the Seasonal Snow Cover Simulations Over the Heihe River Basin, Northwest China

ABSTRACTThe reliability of seasonal snow cover information is constrained by limitation of in situ observations and uncertainties in remote sensing data and model simulations in alpine region, thus posing important challenges to understanding the climate system and water resource management in alpine region. Here, the assimilation of daily cloud‐free Moderate Resolution Imaging Spectroradiometer (MODIS) normalised difference snow index (NDSI) product into an intermediate complexity snow mass and energy balance model—Flexible Snow Model (version FSM2_MO)—was implemented. The aim is to improve the model simulations of seasonal snow cover (snow‐covered extent; SCE, snow depth; SD, snow water equivalent; SWE, and snowmelt runoff; SMR) in the alpine region (a case of the upper‐middle reaches of the Heihe River basin, Northwest China). The results indicate comprehensive improvement in the simulation of SCE, SD, and SMR in the study area through data assimilation, with the ability to significantly reduce prior biases of the FSM2_MO. Based on the independent daily cloud‐free Advanced Very High Resolution Radiometer (AVHRR) SCE product, the updated SCE simulation (i.e., data assimilation) showed a reduction in mean absolute error (MAE) from 10.46% to 7.16%, root mean square error (RMSE) from 16.14% to 12.26%, and an increase in Pearson's correlation coefficient (CC) from 0.18 to 0.67 compared with the open loop simulation (i.e., without assimilation). The evaluation results of SD observation data showed that data assimilation improved SD simulation compared with the open loop run (OL). And utilising the monthly discharge observations at the Yingluoxia hydrological station, data assimilation slightly improved the SMR simulation. The updated SMR simulation achieved a CC of 0.91, Nash‐Sutcliffe efficiency coefficient (NSE) of 0.73, and Kling‐Gupta efficiency coefficient (KGE) of 0.76. Moreover, the Landsat 8‐derived snow cover map and Sentinel‐1‐derived SD also indicated that the updated simulation effectively filled in the missing snow cover and removed the superfluous snow cover predicted by the OL simulation in terms of spatial distribution.