Mass Balance Data Research Articles

Snow cover evolution at Qasigiannguit Glacier, southwest Greenland: A comparison of time-lapse imagery and mass balance data

In a warming climate, understanding seasonal fluctuations in snowline position is key to accurately predicting the melt contribution of glaciers to sea-level rise. Snow and ice conditions have a large impact on freshwater availability and supply on seasonal and multi-annual timescales. Factors such as snow extent and physical characteristics affect predictions in snowmelt- and glacier-fed catchments, influencing the potential of hydropower and drinking water supply in these areas, as well as ecosystems and fjord waters. Summer snow monitoring on glaciers and ice caps peripheral to the Greenland Ice Sheet are limited, and are typically excluded from ice-sheet wide assessments. Here, we analyse snow extent evolution on Qasigiannguit Glacier (QAS), a small coastal mountain glacier in Kobbefjord, southwest Greenland, with the aim of obtaining a baseline dataset of snow and ice conditions. Maximum snowline altitude and bare ice extent are extracted using terrestrial time-lapse photogrammetry, and compared to mass balance and automated weather station observations since 2014. The number of days of visible bare ice, cumulative Positive Degree Days (PDD) and mass balance are closely linked, with 2016 and 2019 experiencing the most negative mass balance, earliest onset of PDDs and greatest cumulative PDDs. 2021 had a relatively small negative mass balance (−0.072 m w.e.) despite having the longest bare ice exposure (112 days). This is attributed to the timing of bare ice exposure relative to the mean 90% cumulative PDD (28th August). Longer periods of bare ice exposure precede the mean 90% cumulative PDD in both 2016 and 2019, which reflects differences in the amount of melt energy available at different times in the melt season. This has far reaching implications for mass balance modelling efforts as this study demonstrates that spatial and temporal variability in snow/bare ice cover are linked to differences in melt factors and energy required to melt snow and ice. Snowline position provides a coarse indication of surface conditions, but future modelling efforts need to incorporate the complex spatial evolution of snow-to-bare ice ratios in order to improve estimates of mass loss from glaciarised mountain catchments.

Daptomycin Physiology-Based Pharmacokinetic Modeling to Predict Drug Exposure and Pharmacodynamics in Skin and Bone Tissues.

Daptomycin has been recommended in the treatment of bone and joint infection. Previous work showed that the approved dosage of daptomycin may be insufficient to achieve optimal exposure in patients with bone and joint infection. However, those studies assumed that bone exposure was similar to steady-state daptomycin-free plasma concentrations. We sought to establish a physiologically based pharmacokinetic (PBPK) model of daptomycin to describe the dynamics of daptomycin disposition in bone and skin tissue. A PBPK model of daptomycin was built using PK-Sim®. Daptomycin concentrations in plasma and bone were obtained from three previously published studies. Physicochemical drug characteristics, mass balance, anthropometrics, and experimental data were used to build and refine the PBPK model. Internal validation of the PBPK model was performed using the usual diagnostic plots. The final PBPK model was then used to run simulations with doses of 6, 8, 10, and 12 mg/kg/24 h. Pharmacokinetic profiles were simulated in 1000 subjects and the probabilities of target attainment for the area under the concentration-time curve over the bacterial minimum inhibitory concentration were computed in blood, skin, and bone compartments. The final model showed a good fit of all datasets with an absolute average fold error between 0.5 and 2 for all pharmacokinetic quantities in blood, skin and bone tissues. Results of dosing simulations showed that doses ≥10 mg/kg should be used in the case of bacteremia caused by Staphylococcus aureus with a minimum inhibitory concentration >0.5 mg/L or Enterococcus faecalis with a minimum inhibitory concentration >1 mg/L, while doses ≥12 mg/kg should be used in the case of bone and joint infection or complicated skin infection. When considering a lower minimum inhibitory concentration, doses of 6-8 mg/kg would likely achieve a sufficient success rate. However, in the case of infections caused by E. faecalis with a minimum inhibitory concentration >2 mg/L, a higher dosage and combination therapy would be necessary to maximize efficacy. We developed the first daptomycin PBPK/pharmacodynamic model for bone and joint infection, which confirmed that a higher daptomycin dosage is needed to optimize exposure in bone tissue. However, such higher dosages raise safety concerns. In this setting, therapeutic drug monitoring and model-informed precision dosing appear necessary to ensure the right exposure on an individual basis.

Carbon isotope fractionation and its tracer significance to carbon source during precipitation of calcium carbonate in the presence of Bacillus cereus LV-1

Microbial-induced carbonate precipitation (MICP) has the potential to immobilize carbon durably. The carbon source of carbonate minerals is the crucial issue for understanding the fixation mechanism of CO2 by MICP. However, the carbon source and its temporal changes in microbial-induced carbonate minerals remain little explored. In this study, calcium carbonate (CaCO3) biomineralization experiments have been carried out using Bacillus cereus in the medium without additional dissolved inorganic carbon (DIC). X-ray diffraction (XRD), attenuated total reflection-infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM) indicated that the precipitate produced mainly consisted of rhombohedral and irregular calcite. The δ13C values of DIC, dissolved organic carbon (DOC), and calcite were the main parameters studied. Carbon isotope fractionation was characterized by carbon isotope offset (Δ13Ccalcite-DIC or Δ13Ccalcite-fluid). The Δ13Ccalcite-DIC values ranged from +8.2‰ to +21.5‰, indicating that strain LV-1 induced the accumulation of 13C in calcite. The Δ13Ccalcite-fluid values indicated that the calcite was up to +15.0‰ (on average) 13C-enriched relative to the fluid. Calculated chemical mass balance data showed that the proportion of CO2(g) derived from DOC on days 16 and 20 was negative, but it became positive after day 20. Meanwhile, the δ13CCO2(g) value calculated by isotope mass balance was −8.5‰, near to δ13C for air (−8.0‰) on day 16, and then shifted to −16.4‰, similar to δ13C for tryptone (−17.2‰) after day 20. These results suggested that the amount of CO2 arising from organic matter through bacterial respiration and the action of enzymes might determine whether the carbon in calcite was derived from organic carbon or atmospheric CO2. Our findings corroborate the potential utility of MICP for immobilization of CO2 to reduce net soil CO2 emissions and to mitigate the greenhouse effect. Microbial-driven carbon isotope fractionation can also cause great carbon isotope shifts in calcite. Thus, carbon isotope value might be used as a marker to identify whether carbonate minerals/rocks are of microbial origin.

Rescue and homogenization of 140 years of glacier mass balance data in Switzerland

Abstract. Glacier monitoring in Switzerland has resulted in some of the longest and most complete data series globally. Mass balance observations at individual locations, starting in the 19th century, are the backbone of the monitoring as they represent the raw and original glaciological data demonstrating the response of snow accumulation and snow/ice melt to changes in climate forcing. So far, however, the variety of sources of historic measurements has not been systematically processed and documented. Here, we present a new complete and extensive point glacier mass balance dataset for the Swiss Alps that provides attributes for data quality and corresponding uncertainties. Original sources were digitized or re-assessed to validate or to correct existing entries and to identify metadata. The sources of data are highly diverse and stem from almost 140 years of records, originating from handwritten field notes, unpublished project documents, various digital sources, published reports, and meta-knowledge of the observers. The project resulted in data series with metadata for 63 individual Swiss glaciers, including more than 60 000 point observations of mass balance. Data were systematically analysed and homogenized, e.g. by supplementing partly missing information based on correlations inferred from direct measurements. A system to estimate uncertainty in all individual observations was developed indicating that annual point balance is measured with a typical error of 0.07 m water equivalent (w.e.), while the average error in winter snow measurements is 0.20 m w.e. Our dataset permits further investigating the climate change impacts on Swiss glaciers. Results show an absence of long-term trends in snow accumulation over glaciers while melt rates have substantially increased over the last 3 decades. The complete dataset is available at DOI https://doi.org/10.18750/massbalance.point.2021.r2021 (GLAMOS, 2021).

Indus River Basin Glacier Melt at the Subbasin Scale

Pakistan is the most glaciated country on the planet but faces increasing water scarcity due to the vulnerability of its primary water source, the Indus River, to changes in climate and demand. Glacier melt constitutes over one-third of the Indus River’s discharge, but the impacts of glacier shrinkage from anthropogenic climate change are not equal across all eleven subbasins of the Upper Indus. We present an exploration of glacier melt contribution to Indus River flow at the subbasin scale using a distributed surface energy and mass balance model run 2001–2013 and calibrated with geodetic mass balance data. We find that the northern subbasins, the three in the Karakoram Range, contribute more glacier meltwater than the other basins combined. While glacier melt discharge tends to be large where there are more glaciers, our modeling study reveals that glacier melt does not scale directly with glaciated area. The largest volume of glacier melt comes from the Gilgit/Hunza subbasin, whose glaciers are at lower elevations than the other Karakoram subbasins. Regional application of the model allows an assessment of the dominant drivers of melt and their spatial distributions. Melt energy in the Nubra/Shyok and neighboring Zaskar subbasins is dominated by radiative fluxes, while turbulent fluxes dominate the melt signal in the west and south. This study provides a theoretical exploration of the spatial patterns to glacier melt in the Upper Indus Basin, a critical foundation for understanding when glaciers melt, information that can inform projections of water supply and scarcity in Pakistan.

Recent evolution of glaciers in the Cocuy‐Güican Mountains (Colombian Andes) and the hydrological implications

AbstractThis study extends knowledge of the evolution of glacier shrinkage in the Cocuy‐Güican Mountains since the maximum glacier extent of the Little Ice Age (LIA). Mass balance data for the Ritacuba Glacier since 2009 were acquired and compared with available data for the Conejeras Glacier (Los Nevados National Park). This study also investigated the hydrological significance of Colombian glaciers, which is still largely unknown because the available information is very limited. Glaciers in the Cocuy‐Güican Mountains covered 13.2 km2 in 2019 compared with 127.8 km2 during the maximum LIA, representing a shrinkage of 89.7%. Analysis of glacier cover observations made in 1955, 1994, 2010, and 2019 revealed that the rate of ice loss was greatest from 1994 to 2010 (0.59 km2 yr−1), and was then almost halved from 2010 to 2019 (0.34 km2 yr−1). This slowing of glacier retreat is consistent with the moderate negative mass balance measured for 2009–2019, and an accumulated loss of 1766 mm w.e. (mm water equivalent). The progressive confinement of glaciers to higher elevations, ice accumulation in topographic locations providing shelter from solar radiation, and an absence of recent marked climatic anomalies could explain why the Cocuy‐Güican glaciers have temporally reached a near equilibrium state conditions. This contrasts with the Conejeras Glacier, where 47,000 mm w.e. has been lost in the same period. The available data on runoff and isotope tracers of streamflow and precipitation suggest that precipitation rather than glacier melt water exerts primary control over the hydrological variability at high elevation sites.

Mass Balance and Compositional Analysis of Biomass Outputs from Cacao Fruits.

The global chocolate value chain is based exclusively on cacao beans (CBs). With few exceptions, most CBs traded worldwide are produced under a linear economy model, where only 8 to 10% of the biomass ends up in chocolate-related products. This contribution reports the mass balance and composition dynamics of cacao fruit biomass outputs throughout one full year of the crop cycle. This information is relevant because future biorefinery developments and the efficient use of cacao fruits will depend on reliable, robust, and time-dependent compositional and mass balance data. Cacao husk (CH), beans (CBs), and placenta (CP) constitute, as dry weight, 8.92 ± 0.90 wt %, 8.87 ± 0.52 wt %, and 0.57 ± 0.05 wt % of the cacao fruit, respectively, while moisture makes up most of the biomass weight (71.6 ± 2.29 wt %). CH and CP are solid lignocellulosic outputs. Interestingly, the highest cellulose and lignin contents in CH coincide with cacao’s primary harvest season (October to January). CB contains carbohydrates, fats, protein, ash, and phenolic compounds. The total polyphenol content in CBs is time-dependent, reaching maxima values during the harvest seasons. In addition, the fruit contains 4.13 ± 0.80 wt % of CME, a sugar- and nutrient-rich liquid output, with an average of 20 wt % of simple sugars (glucose, fructose, and sucrose), in addition to minerals (mainly K and Ca) and proteins. The total carbohydrate content in CME changes dramatically throughout the year, with a minimum of 10 wt % from August to January and a maximum of 29 wt % in March.

Revisiting glacier mass-balance sensitivity to surface air temperature using a data-driven regionalization

AbstractThis study involves examination of glaciological mass-balance time series, glacier and climatic descriptors, the application of machine learning methods for glaciological clustering, and computation of mass-balance time series based upon the clustering and statistical analyses relative to gridded air temperature datasets. Our analysis revealed an increasingly coherent mass-balance trend but a latitudinal bias of monitoring programs. The glacier classification scheme delivered three clusters, suggesting these correspond to climate-based first-order regimes, as glacier morphometric characteristics weighed little in our multivariate analysis. We combined all available surface mass-balance data from in situ monitoring programs to study temperature sensitivity for each cluster. These aggregated mass-balance time series delivered spatially different statistical relationships to temperature. Results also showed that surface mass balance tends to have a temporal self-correlation of ~20 years. Using this temporal window to analyze sensitivity since ~ 1950, we found that in all cases temperature sensitivity, while generally negative, tended to fluctuate through time, with the largest absolute magnitudes occurring in the 1980s and becoming less negative in recent years, revealing that glacier sensitivity is non-stationary. These findings point to a scenario of a coherent signal of change no matter the glacier regime. This work provides new insights into glacier–climate relationships that can guide observational and analytical strategies.

Legume nutrition is improved by neighbouring grasses

BackgroundCombinations of grasses and nitrogen-fixing legumes are ubiquitous in most natural and derived pastoral grasslands. This was not formerly the case in New Zealand’s unique indigenous grasslands that are now frequently impacted by exotic pasture grasses and legumes. Understanding the co-existence of native and exotic plants is the broad focus of this research.AimsSpillover of nitrogen (N) from clovers to grasses in diverse pasture is well known. We question whether grasses provide reciprocal nutritional benefits to legumes. Does the mutual exploitation of soil biogeochemistry by legumes and grasses help to explain their coexistence and, if so, does this have implications for biodiversity in NZ’s novel native grassland communities?MethodsCombinations of grasses and legumes, including a native tussock grass, were grown in a nutrient-poor (low P, S, Ca, Mg, Mn, and B) high country soil in a pot experiment, quantifying the foliar acquisition of nutrients from soil. Field data were obtained by sampling foliage of clover in single- and mixed-species patches in a more fertile lowland pasture.ResultsBenefits of legume and grass growing together were reflected in enhanced productivity and higher uptake of a range of key nutrients. This was most evident but not restricted to a combination of two exotic species: cocksfoot and white clover. In the nutrient-poor soil, legumes grew better in combination with different species of introduced grasses. Uptake of key elements from soil to plants significantly differed with combinations of legumes and grasses compared to individual species. Elevated concentrations of P, K and S were recorded in clover when growing with grasses, although Ca uptake was lower. Expected reciprocal reduction of clover N or enhanced grass N were not recorded. Mass balance data (total extraction of key nutrients from the soil pool) showed that combination of grasses and legumes exploit soil nutrients (particularly P, Zn, Mn and Mo) more effectively than single species alone. In grasses, only tissue concentrations of K, S and Zn significantly increased when growing with legumes, but native tussock grass procured less nutrients when growing with the exotic legumes. Field sampling of clover from the more fertile lowland soil showed significantly higher foliar concentrations of K, Mn, Cu and B, but less Ca.ConclusionsThe findings are indicative of a mutualistic relationship: legumes derive nutritional benefits from growing with grasses. Native tussock grass contained less N when growing with the exotic legumes, suggesting less compatibility and a lack of adaptation to coexistence.

Meighen Ice Cap: changes in geometry, mass, and climatic response since 1959

Remote sensing (satellite and airborne) and in situ monitoring measurements indicate that the Meighen Ice Cap has thinned by 10 ± 3 m between 1960 and 2016, resulting in areal shrinkage by 32 km2 (38%) and total mass loss of 0.71 ± 0.2 gigatonnes. Retreat of the ice margin along the North basin by up to 2.5 km accounted for 50% of the total area loss over the 56-year period of this study. A strong inverse relationship between atmospheric summer temperature anomalies, and in situ mass balance measurements (r = −0.74) indicates that accelerated rates of mass loss from the Meighen Ice Cap are largely driven by regional scale summer warming. Increases in summer temperature anomalies by 1.9 °C from 1960–2004 to 2005–2016 coincided with a five-fold increase in surface melt across the Meighen Ice Cap. Since the 1990s, the Equilibrium Line Altitude has been positioned above the summit of the Meighen Ice Cap, resulting in loss of the accumulation zone that persisted for the first three decades of this study. Since the early 2000s, the ice cap summit has thinned by more than 4 m, which is unprecedented in the period of record. Response time calculations based on 2006–2016 average mass balance data indicate that the Meighen Ice Cap, which has been in existence for ∼3500 years, will completely disappear in ∼175 years.

Empirical glacier mass-balance models for South America

AbstractWe investigate relationships between synoptic-scale atmospheric variability and the mass-balance of 13 Andean glaciers (located 16–55° S) using Pearson correlation coefficients (PCCs) and multiple regressions. We then train empirical glacier mass-balance models (EGMs) in a cross-validated multiple regression procedure for each glacier. We find four distinct glaciological zones with regard to their climatic controls: (1) The mass-balance of the Outer Tropics glaciers is linked to temperature and the El Niño-Southern Oscillation (PCC ⩽ 0.6), (2) glaciers of the Desert Andes are mainly controlled by zonal wind intensity (PCC ⩽ 0.9) and the Antarctic Oscillation (PCC ⩽0.6), (3) the mass-balance of the Central Andes glaciers is primarily correlated with precipitation anomalies (PCC ⩽ 0.8), and (4) the glacier of the Fuegian Andes is controlled by winter precipitation (PCC ≈ 0.7) and summer temperature (PCC ≈ −0.9). Mass-balance data in the Lakes District and Patagonian Andes zones, where most glaciers are located, are too sparse for a robust detection of synoptic-scale climatic controls. The EGMs yieldR2values of ~ 0.45 on average and ⩽ 0.74 for the glaciers of the Desert Andes. The EGMs presented here do not consider glacier dynamics or geometry and are therefore only suitable for short-term predictions.

Hydrogeochemical and isotopic evaluation of VOC commingled plumes in a weathered fractured bedrock aquifer treated with thermal and bioremediation

Chlorinated ethanes and ethenes isotopic analyses in groundwater and hydrogeochemical results from a former industrial area in Sao Paulo (Brazil) were used to confirm the existence and allow further characterization of source areas and their commingled plumes, both before and after thermal and bioremediation treatments. Prior to full scale remediation, a recently identified off-site source area with unknown history and limited access for further intrusive works presented lower δ13C values (−6.5‰ to −1.8‰ for 1,2-DCA) than the downgradient on-site source area (+8.6‰ to +20.0‰). Intermediate δ13C values for 1,2-DCA were identified further downgradient from the sources, within commingled plumes patterns. The isotope and concentration results show the typical degradation patterns associated with biotic reductive dechlorination for chlorinated ethenes and dihaloelimination for 1,2-DCA. Results following remediation treatments show further levels of isotopic enrichment, for chlorinated ethenes and chlorinated ethanes in the tropically weathered and deeper fractured bedrock (gneisses) groundwater. Hydrogeochemical results, isotopic mass balance and Carbon-Chlorine isotope slopes data are coherent with remediation treatment and a complex commingled plume setting. The results of this study confirmed the Temporal Conceptual Model proposed by Hart et al. (2021) and identified the need for further studies to evaluate isotopic dynamics under thermal remediation, including thermal-induced hydrolysis processes.

Physiologically-based pharmacokinetic modeling to predict CYP3A4-mediated drug-drug interactions of finerenone.

Finerenone is a nonsteroidal, selective mineralocorticoid receptor antagonist that recently demonstrated its efficacy to delay chronic kidney disease (CKD) progression and reduce cardiovascular events in patients with CKD and type 2 diabetes. Here, we report the development of a physiologically‐based pharmacokinetic (PBPK) model for finerenone and its application as a victim drug of cytochrome P450 3A4 (CYP3A4)‐mediated drug‐drug interactions (DDIs) using the open‐source PBPK platform PK‐Sim, which has recently been qualified for this application purpose. First, the PBPK model for finerenone was developed using physicochemical, in vitro, and clinical (including mass balance) data. Subsequently, the finerenone model was validated regarding the contribution of CYP3A4 metabolism to total clearance by comparing to observed data from dedicated clinical interaction studies with erythromycin (simulated geometric mean ratios of the area under the plasma concentration‐time curve [AUCR] of 3.46 and geometric mean peak plasma concentration ratios [CmaxRs] of 2.00 vs. observed of 3.48 and 1.88, respectively) and verapamil (simulated AUCR of 2.91 and CmaxR of 1.86 vs. observed of 2.70 and 2.22, respectively). Finally, the finerenone model was applied to predict clinically untested DDI studies with various CYP3A4 modulators. An AUCR of 6.31 and a CmaxR of 2.37 was predicted with itraconazole, of 5.28 and 2.25 with clarithromycin, 1.59 and 1.40 with cimetidine, 1.57 and 1.38 with fluvoxamine, 0.19 and 0.32 with efavirenz, and 0.07 and 0.14 with rifampicin. This PBPK analysis provides a quantitative basis to guide the label and clinical use of finerenone with concomitant CYP3A4 modulators.

A restitution method to reconstruct the 2001–13 surface evolution of Hurd Glacier, Livingston Island, Antarctica, using surface mass balance data

AbstractThe surface restitution method we present reconstructs the evolution of a glacier surface between two time-separated surface topographies using seasonal surface mass balance (SMB) data. A conservative and systematic error analysis is included, based on the availability of surface elevation measurements within the period. The method is applied from 2001 to 2013 at Hurd Glacier (a 4 km2 glacier), where we have sufficient SMB and elevation data. We estimate surface elevation changes in two steps: (1) elevation change due to SMB and (2) elevation change due to glacier dynamics. Four different models of the method are compared depending on whether or not accumulation is memorised at each time step and whether they employ balance profiles or SMB maps. Models are validated by comparing a set of surface measurements retrieved in 2007 with the corresponding restituted elevations. Although surface elevation change between 2001 and 2007 was larger than 10 m, more than 80% of the points restituted by the four models showed errors below ±1 m compared to only 33% when predicted by a linear interpolator. As error estimates between models differ by 0.10 m, we recommend the simplest model, which does not memorise accumulation and interpolates SMB by elevation profiles.

Physiologically based pharmacokinetic modelling to predict the clinical effect of CYP3A inhibitors/inducers on esaxerenone pharmacokinetics in healthy subjects and subjects with hepatic impairment

PurposeEsaxerenone is a novel, oral, nonsteroidal treatment for hypertension. Physiologically based pharmacokinetic (PBPK) modelling was performed to predict the drug–drug interaction (DDI) effect of cytochrome P450 (CYP)3A modulators on esaxerenone pharmacokinetics in healthy subjects and subjects with hepatic impairment.MethodsIn our PBPK model, the fraction of esaxerenone metabolised by CYP3A was estimated from mass-balance data and verified and optimised by clinical DDI study results with strong CYP3A modulators. The model was also verified by the observed pharmacokinetics after multiple oral dosing and by the effect of hepatic impairment on esaxerenone pharmacokinetics. The model was applied to predict the DDI effects on esaxerenone pharmacokinetics with untested CYP3A modulators in healthy subjects and with strong CYP3A modulators in subjects with hepatic impairment.ResultsThe PBPK model well described esaxerenone pharmacokinetics after multiple oral dosing. The predicted fold changes in esaxerenone plasma exposure after coadministration with strong CYP3A modulators were comparable with the observed data (1.53-fold with itraconazole and 0.31-fold with rifampicin). Predicted DDIs with untested moderate CYP3A modulators were less than the observed DDI with strong CYP3A modulators. The PBPK model also described the effect of hepatic impairment on esaxerenone plasma exposure. The predicted DDI results with strong CYP3A modulators in subjects with hepatic impairment indicate that, for concomitant use of CYP3A modulators, caution is advised for subjects with hepatic impairment, as is for healthy subjects.ConclusionThe PBPK model developed predicted esaxerenone pharmacokinetics and DDIs and informed concurrent use of esaxerenone with CYP3A modulators.

The 21st-century fate of the Mocho-Choshuenco ice cap in southern Chile

Abstract. Glaciers and ice caps are thinning and retreating along the entire Andes ridge, and drivers of this mass loss vary between the different climate zones. The southern part of the Andes (Wet Andes) has the highest abundance of glaciers in number and size, and a proper understanding of ice dynamics is important to assess their evolution. In this contribution, we apply the ice-sheet model SICOPOLIS (SImulation COde for POLythermal Ice Sheets) to the Mocho-Choshuenco ice cap in the Chilean Lake District (40∘ S, 72∘ W; Wet Andes) to reproduce its current state and to project its evolution until the end of the 21st century under different global warming scenarios. First, we create a model spin-up using observed surface mass balance data on the south-eastern catchment, extrapolating them to the whole ice cap using an aspect-dependent parameterization. This spin-up is able to reproduce the most important present-day glacier features. Based on the spin-up, we then run the model 80 years into the future, forced by projected surface temperature anomalies from different global climate models under different radiative pathway scenarios to obtain estimates of the ice cap's state by the end of the 21st century. The mean projected ice volume losses are 56±16 % (RCP2.6), 81±6 % (RCP4.5), and 97±2 % (RCP8.5) with respect to the ice volume estimated by radio-echo sounding data from 2013. We estimate the uncertainty of our projections based on the spread of the results when forcing with different global climate models and on the uncertainty associated with the variation of the equilibrium line altitude with temperature change. Considering our results, we project a considerable deglaciation of the Chilean Lake District by the end of the 21st century.

Regional mass variations and its sensitivity to climate drivers over glaciers of Karakoram and Himalayas

ABSTRACT The regional scale mass change provides a substantial understanding to the influence of climate change on the glacier surface. However, the scarce ground observations and large spatial extent limit the use of field-based mass balance estimation. In this study, the Gravity Recovery and Climate Experiment (GRACE) satellite data were used to estimate the regional glacier mass variation over the Karakoram and Himalayas (KH) region during 2002–2019 hydrological years. Our study showed that the total mass change rate over the KH region was – 55.0 ± 8.7 Gt yr–1 for the study period. We have identified four positive/negative clusters of mass change over the KH region, with the eastern part of the Karakoram (KK) and part of the Central Himalaya (CH) regions have experienced a positive mass change. In contrast, the junction area between the Western Himalaya (WH) and CH region observed an extreme negative mass change. The results demonstrated that the annual mass change for WH become negative or nearly zero from 2007/08 onwards, while for CH and Eastern Himalaya (EH) regions, it became negative since 2005/06. The GRACE-derived mass change was validated with the published in-situ mass balance data, which reveals a high correlation (r = 0.77) over the region. The performance of obtained results were also compared with Ice, Cloud, and Land Elevation Satellite-1 (ICESat-1) data for the period 2003–2009, indicating a correlation of 0.87 and 0.91 for monthly and annual scale, respectively. Moreover, the interannual mass change in the glaciated region was analyzed using hydro-climatic data and energy fluxes, suggesting a higher correlation of mass change with total precipitation and snowfall over the spatiotemporal scale. However, this correlation fails at locations where evaporation, runoff, and radiation have prominently influenced the mass loss. The uncertainty and sensitivity test for mass change demonstrated that snowfall and temperature have a strong influence on the response of mass change. Overall, this study provided regional mass change and their relationship with hydro-climatic variables, which will provide a better understanding related to the water availability in the downstream areas.

Ice thickness distribution of all Swiss glaciers based on extended ground-penetrating radar data and glaciological modeling

AbstractAccurate knowledge of the ice thickness distribution and glacier bed topography is essential for predicting dynamic glacier changes and the future developments of downstream hydrology, which are impacting the energy sector, tourism industry and natural hazard management. Using AIR-ETH, a new helicopter-borne ground-penetrating radar (GPR) platform, we measured the ice thickness of all large and most medium-sized glaciers in the Swiss Alps during the years 2016–20. Most of these had either never or only partially been surveyed before. With this new dataset, 251 glaciers – making up 81% of the glacierized area – are now covered by GPR surveys. For obtaining a comprehensive estimate of the overall glacier ice volume, ice thickness distribution and glacier bed topography, we combined this large amount of data with two independent modeling algorithms. This resulted in new maps of the glacier bed topography with unprecedented accuracy. The total glacier volume in the Swiss Alps was determined to be 58.7 ± 2.5 km3 in the year 2016. By projecting these results based on mass-balance data, we estimated a total ice volume of 52.9 ± 2.7 km3 for the year 2020. Data and modeling results are accessible in the form of the SwissGlacierThickness-R2020 data package.

A multi-perspective approach for selecting CMIP6 scenarios to project climate change impacts on glacio-hydrology with a case study in Upper Indus river basin

The selection of future climate change scenarios may have issues in representing the full spectrum of climate projections in glacierized mountain regions, where glaciers play an important role in hydrology. Thus, the effect of glacier storage change must be considered in the selection approaches. Here, a multi-perspective approach was proposed to select climate models from CMIP6 database, considering the full spectrum of future climate change and effects of glaciers on hydrology. This approach combines the envelope-based approach (EA), past performance approach (PPA), and additional criteria to incorporate water-energy balance and glacier storage change based on the Turc-Budyko theory. The approach physically diagnoses GCMs by investigating their effects on glacier storage change compared to reference climate and observed mass balance data. A step-wise shortlisting and selection of appropriate climate models for the Upper Indus Basin (UIB) was made under three Shared Socioeconomic Pathways (SSPs): SSP126, SSP245, and SSP585, based on (a) range of projected changes in mean values for four extreme future projections (cold-dry, cold-wet, warm-dry, and warm-wet), (b) range of projected changes in climatic extremes, (c) representation of water-energy balance and storage change, and (d) skill in representing historical climate. The future projections indicate temperature and precipitation increase by 1.7 ± 0.6 °C and 7 ± 5%, 3.3 ± 1.3 °C and 10 ± 6%, and 6.3 ± 2.6 °C and 22 ± 13% under SSP126, SSP245, and SSP585 in 2071–2100 compared to 1985–2014, respectively. The glacier area, volume, and length are projected to decrease by 22–33%, 51–63%, and 13–22% under ensembled scenarios of full spectrum at selected glaciers. The proposed multi-perspective approach is advantageous in shortlisting a limited number of climate models, representing the full range of possible future climatic conditions, to assess the full range of expected impacts of climate changes on indigenous glacio-hydrology. Such selection eventually reduces the glacio-hydrological simulation task.

Little Ice Age glacier extent and temporal changes in annual mass balance (2016–2019) of Pensilungpa Glacier, Zanskar Himalaya

Glaciers and climate are known to exhibit positive feedbacks that are important for comprehending the overall glacier state. This relation is poorly understood in the relatively unexplored terrain like the Zanskar Himalaya. We have studied the impact of climate change regarding the past and present response of the Pensilungpa Glacier (PG), Zanskar Himalaya. Reconstructing the recent changes in the mass balance (2016–2019) along with the Little Ice Age (LIA) extent of the PG shows that the PG was joined by the five tributary glaciers during the LIA having an area of ~ 18 km2 and extended ~ 3 km downstream from its present-day snout located at 4470 ± 1 m.a.s.l. Since the LIA, the PG has retreated ~ 2941 ± 75 m, at an average rate of 5.6 ± 0.15 m a−1. Field observations for the last 4 years (2015–2019) show that the glacier now is retreating by ~ 27 ± 11 m at an average rate of 6.7 ± 3 m a−1, which is similar to the one since the LIA. The glaciers in the study area (Suru River valley) are mostly nourished by the Western Disturbances (during the December, January, and February) with maximum solid precipitation, and melt during the ablation period (May–October). The observed recessional trends of the PG may, therefore, be attributed to an increase in the temperature and decrease in precipitation during accumulation period. The ablation data reveal the significant influence of debris-cover on the mass balance and terminus retreat of the PG. Furthermore, the mass balance data for the last 3 years (2016–2019) show a negative trend with a small accumulation area ratio (AAR) (43%). The average net annual mass balance is estimated to be ~ − 3.67 × 106 m3 w.e. a−1 with the − 0.36 m w.e. a−1 specific balance between 2016 and 2019. During the period 2016–2019, the PG has lost ~ 11.03 × 106 m3 w.e. ice volume. The slower retreat rate and low AAR of the PG, compared to other glaciers in the area, suggest that its terrain characteristics (hypsometry, size, aspect, and slope) control the glacier dynamics and the glacier continues to adjust geometrically in response to the negative mass balance.