Contribution Of Glacier Meltwater Research Articles

Incorporating glacier processes into hydrological simulations in the headwaters of the Yangtze and yellow Rivers

Contemporary hydrological models often oversimplify or neglect the effects of glacier ablation on watershed hydrological processes, leading to inaccurate simulations. To address this issue, we introduce a glacier ablation module that incorporates glacier ablation, sublimation, meltwater refreezing, and snow accumulation, integrated with the fully distributed hydrological model ESSI-3, forming the Glacier-ESSI-3 model. Application of the Glacier-ESSI-3 model in the headwaters of the Yangtze River (HYaR) and Yellow River (HYeR) demonstrates superior accuracy compared to the ESSI-3 model, effectively capturing the impact of glacier ablation on hydrological dynamics. Validation with remotely sensed data of snow cover and glacier dynamics confirms the model's efficacy in reproducing actual conditions in both watersheds. The results indicate that snow meltwater contributes more significantly to runoff than glacier meltwater, and the HYaR exhibiting a larger glacier meltwater contribution than the HYeR. Over time, the contribution rate of snow+glacier meltwater to runoff in the HYaR shows a fluctuating upward trend (10.04 % ± 1.13 % to 25.02 % ± 2.80 %), while it remains relatively stable in the HYeR (6.83 % ± 1.13 % to 10.19 % ± 0.89 %). This study highlights the critical role of glacier ablation in hydrological processes within glacierized watersheds. The Glacier-ESSI-3 model proves to be a robust tool for enhancing hydrological simulations in cold plateau regions, providing valuable insights into the intricate interactions between glaciers and hydrological dynamics.

Runoff Response to Climate in Two River Basins Supplied by Small Glacier Meltwater in Southern and Northern Tibetan Plateau

The Tibetan Plateau (TP) has experienced amplified warming in recent decades, causing glaciers to melt and affecting river runoff. It is well established that the southern and northern areas of the TP have responded to climate changes differently, with the north dominated by a westerly climate and the south by the Indian monsoon. While there are more glaciers in the TP than in any other region outside the polar areas, most of these glaciers are tiny, and only a limited number of them have been monitored to study mass balance and downward runoff. This study used the mass balance measured at two glaciers along with in situ and satellite data to drive a hydrological model called the Alpine Runoff Predictor that includes glacier melt to simulate glacial melting and the accompanying hydrological processes of the two glacierized basins, analyze their contributions to the river runoffs, and investigate their responses to local climate changes. The results show that the glacier meltwater in both river basins showed an increasing trend, with values of 0.001 × 108 m3 a−1 in the Kyanjing River basin and 0.0095 × 108 m3 a−1 in the Tuole River basin. However, their multi-year average contributions to the runoff were 12.5% and 5.6%, respectively. In contrast to the Tuole River basin, where runoff is increasing (0.0617 × 108 m3 a−1), the Kyanjing River basin has decreasing runoff (−0.0216 × 108 m3 a−1) as a result of decreasing precipitation. This result highlights the dominant role played by precipitation changes in the two basins under study, which are characterized by small glacier meltwater contributions.

What Controls Lake Contraction and Then Expansion in Tibetan Plateau’s Endorheic Basin Over the Past Half Century?

AbstractThe evolutions of climate‐sensitive lakes on the Tibetan Plateau’s endorheic basin exhibited lake shrinkage before the mid‐1990s, but widespread and rapid lake expansions ever since. However, the quantitative contribution of glacier meltwater to lake changes, and the exact mechanisms behind its dominant drivers remain elusive. Here, a comprehensive examination of glacier mass balance since ∼1975 reveals that excess glacier meltwater compensated for net lake volume loss by 21% ± 5% during its contraction period 1975–1995, whereas promoted net volume gain by 9% ± 1% during expansion period 1995–2020 and by 17% ± 2% over the entire period 1975–2020. Further analyses reveal that the interdecadal variations of sea surface temperatures in the Atlantic, Pacific, and Indian Oceans favor a net moisture inflow to the Tibetan Plateau, leading to increased precipitation since 1995 relative to 1970s–1995, which effectively elucidates the climatic process causing rapid lake volume expansion in the endorheic basin.

Hydrological process controls on streamflow variability in a glacierized headwater basin

AbstractMountain glacierized headwaters are currently witnessing a transient shift in their hydrological and glaciological systems in response to rapid climate change. To characterize these changes, a robust understanding of the hydrological processes operating in the basin and their interactions is needed. Such an investigation was undertaken in the Peyto Glacier Research Basin, Canadian Rockies over 32 years (1988–2020). A distributed, physically based, uncalibrated glacier hydrology model was developed using the modular, object‐oriented Cold Region Hydrological Modelling Platform to simulate both on and off‐glacier high mountain processes and streamflow generation. The hydrological processes that generate streamflow from this alpine basin are characterized by substantial inter‐annual variability over the 32 years. Snowmelt runoff always provided the largest fraction of annual streamflow (44% to 89%), with smaller fractional contributions occurring in higher streamflow years. Ice melt runoff provided 10% to 45% of annual streamflow volume, with higher fractions associated with higher flow years. Both rainfall and firn melt runoff contributed less than 13% of annual streamflow. Years with high streamflow were on average 1.43°C warmer than low streamflow years, and higher streamflow years had lower seasonal snow accumulation, earlier snowmelt and higher summer rainfall than years with lower streamflow. Greater ice exposure in warmer, low snowfall (high rainfall) years led to greater streamflow generation. The understanding gained here provides insight into how future climate and increased meteorological variability may impact glacier meltwater contributions to streamflow and downstream water availability as alpine glaciers continue to retreat.

Effects of the glacial meltwater supply on carbonate chemistry in Bowdoin Fjord, Northwestern Greenland

To understand the effects of the glacial meltwater supply on carbonate chemistry and the air–sea CO2 flux within the fjord, water samples were collected in Bowdoin Fjord in northwestern Greenland for dissolved inorganic carbon (DIC) concentration, total alkalinity (TA), oxygen isotopic ratio (δ18O), and chlorophyll a concentration analyses in the summers of 2016 and 2017. The partial pressure of CO2 (pCO2) in surface water, calculated from DIC and TA, was less than 200 µatm, and was significantly lower than that in the atmosphere (399 ± 3 µatm). Therefore, surface water of the fjord acts as sink for CO2 in the atmosphere (–4.9 ± 0.7 mmol m–2 d–1). To evaluate the effects of freshwater and land-derived substances by glacial meltwater on pCO2 in the fjord, we calculated the changes of pCO2 in salinity and carbonate chemistry that would result from the inflow of glacial meltwater into the fjord. The calculated pCO2 was high near the calving front, where the contribution of glacier meltwater was significant. Examination of the relationship between salinity-normalized DIC and TA, which was considered DIC and TA input from the land, suggested that the land-derived high pCO2 freshwater affected mainly by the remineralization of the organic matter by bacterial activity was supplied to the Bowdoin Fjord.

Changes in atmospheric circulation and glacier melting since the last deglaciation revealed by a lacustrine δD record at Ngamring Co, the upper-middle Yarlung Tsangpo watershed

Both the Indian Summer Monsoon (ISM) and glacier meltwater are suggested to significantly influence the modern discharge of the Yarlung Tsangpo River, which is the longest river of Tibet and is an important freshwater source for the local population as well as for the large populations in India and Bangladesh in the lower reaches. Understanding past hydroclimatic variations of the region is therefore important for predicting future changes under global warming scenarios. Here we present a continuous compound-specific hydrogen isotope record of sedimentary leaf waxes covering the past 18 ka (ka = 1000 yr) from Ngamring Co, located in the upper-middle Yarlung Tsangpo range, a typical monsoonal region, with the aim of documenting hydroclimatic changes since the last deglaciation. Compared with measurements of continuous scanning XRF and magnetic susceptibility, the δD at Ngamring Co is believed to reflect atmospheric circulation and glacial meltwater input rather than direct local humidity. In detail, the record indicates relatively enriched δD values during the Late Pleistocene, suggesting the predominance of the Westerlies and limited moisture delivery by the ISM, which was associated with cooling at high northern latitudes. The fast δD depletion indicates that ISM penetrated into TP since ~10.5 ka BP (before present, the present is 1950 CE), then the gradually increased δD values suggested the ISM attenuated in phase with summer insolation during early to middle Holocene. The negative deviation of δD (>80‰, abrupt depleted at 3 ka BP) since ~6 ka BP suggested glacier melting in the catchment and ended at ~0.2 ka BP, which emphasizes the glacial contribution to the hydroclimatic change in Yarlung Tsangpo watershed. Such depletion was also observed at Aweng Co in the western TP, which suggests that a glacier meltwater contribution to lakes and rivers may be a large-scale phenomenon on the TP. Comparison of the δD record from Ngamring Co with independent paleotemperature records indicates the control of summer temperature/insolation on glacier melting may not be the most important factor during the late Holocene, and instead we propose that the mean annual air temperature and glacier volume were more crucial to the melting process. If our inference is correct, the disappearance of a glacier from the Ngamring Co basin at ~0.2 ka BP is likely to be indicative of the fate of other glaciers on the TP under ongoing global warming. However, independent reconstructions of temperature and direct glacier dynamics from the same site are needed to validate our hypothesis.

Contemporary Trends in High and Low River Flows in Upper Indus Basin, Pakistan

The Upper Indus Basin (UIB) features the high mountain ranges of the Hindukush, Karakoram and Himalaya (HKH). The snow and glacier meltwater contribution feeds 10 major river basins downstream including Astore, Gilgit, Hunza, Jhelum, Kabul, Shyok and Shigar. Climate change is likely to fluctuate the runoff generated from such river basins concerning high and low streamflows. Widening the lens of focus, the present study examines the magnitude and timing of high flows variability as well as trends variability in low streamflows using Sen’s slope and the Mann-Kendall test in UIB from 1981 to 2016. The results revealed that the trend in the magnitude of the high flows decreased at most of the sub-basins including the Jhelum, Indus and Kabul River basins. Significantly increased high flows were observed in the glacier regime of UIB at Shigar and Shyok while decreased flows were predominant in Hunza River at Daniyor Bridge. A similar proclivity of predominantly reduced flows was observed in nival and rainfall regimes in terms of significant negative trends in the Jhelum, Kunhar, Neelum and Poonch River basins. The timing of the high flows has not changed radically as magnitude at all gauging stations. For the low flows, decreasing significant trends were detected in the annual flows as well as in other extremes of low flows (1-day, 7-day, 15-day). The more profound and decreasing pattern of low flows was observed in summer at most of the gauging stations; however, such stations exhibited increased low flows in autumn, winter and spring. The decrease in low flows indicates the extension of dry periods particularly in summer. The high-water demand in summer will be compromised due to consistently reducing summer flows; the lower the water availability, the lower will be the crop yield and electricity generation.

Recent Glacier Shrinkage on Kilimanjaro and the Possibility of the Contribution of Glacier Meltwater to Hillside River Water

キリマンジャロ (5,895 m) の氷河は近年の気候変動により急速に縮小している。また，キリマンジャロは“Water Tower”とも称されるように地域の給水塔として重要な役割を果たしている。本研究では近年の氷河の縮小面積の分析を踏まえた上で，その縮小する氷河の融氷水が山腹河川水に寄与している可能性について，衛星画像解析と同位体比分析から考察した。先行研究の結果と今回の衛星画像解析から，キリマンジャロの氷河は1912～2019年の間，速いスピードで縮小していることがわかった。氷河の年平均縮小面積は 0.066 km2 (1989～2000年)，0.067 km2 (2000～2010年)，0.088 km2 (2010～2019年) と増加傾向にあり，このペースが続けば2030年頃にはキリマンジャロから氷河が姿を消すことが予想される。

Glaciers Control the Hydrogeochemistry of Proglacial Streams During Late Summer in the Wind River Range, Wyoming, United States

Glaciers alter the geochemistry of sensitive alpine streams by exposing freshly weathered bedrock and releasing atmospherically deposited trace metals from melting ice. Changes in the timing and quantity of glacial melt also affect discharge and temperature of alpine streams. To investigate the effects of glacier meltwater on the geochemistry and hydrology of proglacial streams in the western US, we sampled supraglacial meltwaters and proglacial streams in the Dinwoody Creek watershed in the Wind River Range, Wyoming during a one-week period in 2015. The upper watershed contains Gannett Glacier ( ∼ 5 km2) and Dinwoody Glacier ( ∼ 4 km2) at elevations between 3,300–4,000 m asl. Samples were collected during late summer (27 August–4 September) when the contributions of glacier meltwater were highest. Supraglacial meltwater was enriched in a suite of trace metals (Cd, Co, Cu, Hg, Mn, Pb, Zn) relative to proglacial streams, suggesting an atmospheric source of metals to the glaciers. Concentrations of major ions and the remaining 30+ analyzed trace elements were enriched in proglacial streams relative to supraglacial meltwater, reflecting weathering of granite and gneiss bedrock. To evaluate the diurnal effects of glacier meltwater inputs, we deployed loggers to monitor water levels, temperature, and specific conductance at 15 min intervals over a one-week period and collected hourly water samples from Dinwoody Creek for a 24 h period. The influx of glacial meltwater during the daytime diluted major ion and rare earth element concentrations and caused increased concentrations for a subset of trace metals. Stable water isotopes (δD and δ18O) in Dinwoody Creek were more depleted during peak flow relative to baseflow due to contributions from isotopically depleted meltwater. The combination of multiple hydrologic tracers (solute concentrations, high frequency logger data, water isotopes) shows strong potential to improve estimates of glacier meltwater contributions to proglacial streams. Changes in water chemistry and discharge need to be monitored as glaciers recede across the Wind River Range and other midlatitude mountain ranges for mitigating negative impacts on alpine ecosystems and downstream water resources.

Assessment of water stress level about global glacier-covered arid areas: A case study in the Shule River Basin, northwestern China

Study regionThe Shule River Basin (SRB) in northwestern China is a representative area of global glacier-covered arid areas. Study focusWater resources have greatly influenced sustainable development in global arid regions where glacier runoff is an important component of water resource supply. This study focused on the assessment of the water resources–carrying capacity in the SRB based on the United Nations Sustainable Development Goals (SDGs) indicator 6.4.2, level of water stress (LWS). New hydrological insights for the regionDuring the period between 2000 and 2030, the runoff of the SRB was predicted to follow an overall increasing trend. From 2000 to 2020, the annual average runoff in the upper reaches of the SRB was 10.9 × 108 m3, and then from 2021 to 2030, it increased by 22.8 %. According this trend, the average contribution of glacier meltwater to the total basin runoff is expected to decrease from the current 23 % to 15 % by 2030 (Representative Concentration Pathway 2.6, RCP 2.6). The supply of fresh-water resources has been close to the level of demand since 2015 and the LWS may increase between 2021 and 2030. The existence of glacial meltwater is expected to result in the continued reduction of basin water stress in the SRB by an average of 0.71 during the period between 2000 and 2030. Therefore, it is necessary to control water consumption of the socioeconomic system and adjust the industrial structure to face or adapt to the crisis of water shortage in global glacier-covered arid areas.

Past ‘peak water’ in the North Caucasus: deglaciation drives a reduction in glacial runoff impacting summer river runoff and peak discharges

At the end of the 20th—early twenty-first century, mountain glaciers exhibited the most negative mass balances since the beginning of observations. The hydrological consequence of deglaciation is a rise in glacial runoff until a maximum (‘peak water’) is reached, beyond which runoff decreases as glacier extents are reduced. It is likely that the peak water of glacial runoff has already been passed in the central North Caucasus. River basins with more than 1% glacier cover show consistent decreases in mean monthly discharge in July and August (up to 4–6% per decade during 1945–2018), when glacier meltwater contribution to river runoff is high. Meanwhile, in neighbouring non-glacierised basins, runoff in July and August mostly rose. The runoff in June, when glaciers are typically mostly covered by seasonal snowpack, has increased by 2–9% at most gauges. Hydrological data from the Djankuat alpine research catchment in the central North Caucasus indicate a reduction of glacial runoff contribution in recent decades, as the area reduction of Djankuat glacier and increase in debris cover compensate for the increase in glacier melt. The Djankuat river runoff decreased by 29% in July, 42% in August, and 26% in September in 2007–2020 compared with 1968–1978. The mean annual peak discharge has dropped by 1–5% per decade in the central North Caucasus, and it occurs 1–2 weeks earlier. Possible mechanisms of observed changes are discussed. This study provides the data on climate-related changes in the glacial runoff for a previously not investigated region.

Stable water isotope modeling reveals spatio-temporal variability of glacier meltwater contributions to Ganges River headwaters

Himalayan headwater rivers are sourced from glacier meltwater and from Indian summer monsoon (ISM) precipitation, both of which are strongly influenced by ongoing and future climate change. Hydrologic modeling studies indicate that the glacier meltwater contribution is highest during the hot, summer pre-ISM months, but this hypothesis cannot be rigorously tested due to lack of observational data. To provide new spatial and temporal constraints on water source contributions in Himalayan streams, we measured stable water isotopes (18O/16O and 2H/1H, expressed as δ18O and δD) and temperature compensated electrical conductivity in nested catchments throughout the Upper Ganges Basin across three seasons: pre-ISM (April-June), ISM (July-September), post-ISM (October-December) over three years (2014–2016). For all time points we observed a sharp decrease in δ18O and δD values moving toward higher elevations. To interpret these results, we tested two environmental tracer approaches for water source apportionment. Using a new isotope mixing approach, our analyses reveal large seasonal variability in water source contributions from glacier meltwater, precipitation, and groundwater to streamflow throughout the basin. Electrical conductivity, δ18O, and deuterium excess were also analyzed through optimum multiparameter analysis (OMPA). Results from our isotope mixing model and OMPA are in close agreement. Glacier meltwater contributions were highest during the ISM and post-ISM seasons, contrary to previous model predictions. In addition to protracted release of glacier meltwater, this result is consistent with “rain-induced” glacier melting during the ISM, which we show can produce 3–11% of total discharge at the glacier snout. Glacier meltwater contributions to Himalayan streams exhibit complex seasonal dynamics; such contributions should be considered when predicting hydrologic responses to climate change in this region.

Projected glacier meltwater and river run‐off changes in the Upper Reach of the Shule River Basin, north‐eastern edge of the Tibetan Plateau

AbstractGlacier meltwater change in the north‐eastern edge of the Tibetan Plateau is greatly important for the projection of the impact of future climate change on local water resource management. Although the glaciated area is only approximately 4% of the Upper Reach of the Shule River Basin (URSRB), the average glacier meltwater contribution to river run‐off was approximately 23.6% during the periods 1971/1972 to 2012/2013. A new glacier melting module coupled with the macroscale hydrologic Variable Infiltration Capacity model (VIC‐CAS) was adopted to simulate and project changes in the glacier meltwater and river run‐off of the URSRB forced by downscaled output of the BCC‐CSM1.1(m), CANESM2, GFDL‐CM3, and IPSL‐CM5A‐MR models. Comparisons between the observed and simulated river run‐offs and glacier area changes during the periods 2000/2001, 2004/2006, 2008/2009, and 2012/2013 suggest that the simulation is reasonable. Due to increases in precipitation, the annual total run‐off is projected to increase by approximately 2.58–2.73 × 108 m3 in the 2050s and 0.28–1.87 × 108 m3 in the 2100s compared with run‐off in the 2010s based on the RCP2.6 (low greenhouse gas emission) and RCP4.5 (moderate greenhouse gas emission) scenarios, respectively. The contribution of glacier meltwater to river run‐off will more likely decrease to approximately 10% and less than 5% during the 2050s and 2100s, respectively.

Understanding hydrological processes in glacierized catchments: Evidence and implications of highly variable isotopic and electrical conductivity data

AbstractThe spatial and temporal characterization of geochemical tracers over Alpine glacierized catchments is particularly difficult, but fundamental to quantify groundwater, glacier melt, and rain water contribution to stream runoff. In this study, we analysed the spatial and temporal variability of δ2H and electrical conductivity (EC) in various water sources during three ablation seasons in an 8.4‐km2 glacierized catchment in the Italian Alps, in relation to snow cover and hydro‐meteorological conditions. Variations in the daily streamflow range due to melt‐induced runoff events were controlled by maximum daily air temperature and snow covered area in the catchment. Maximum daily streamflow decreased with increasing snow cover, and a threshold relation was found between maximum daily temperature and daily streamflow range. During melt‐induced runoff events, stream water EC decreased due to the contribution of glacier melt water to stream runoff. In this catchment, EC could be used to distinguish the contribution of subglacial flow (identified as an end member, enriched in EC) from glacier melt water to stream runoff, whereas spring water in the study area could not be considered as an end member. The isotopic composition of snow, glacier ice, and melt water was not significantly correlated with the sampling point elevation, and the spatial variability was more likely affected by postdepositional processes. The high spatial and temporal variability in the tracer signature of the end members (subglacial flow, rain water, glacier melt water, and residual winter snow), together with small daily variability in stream water δ2H dynamics, are problematic for the quantification of the contribution of the identified end members to stream runoff, and call for further research, possibly integrated with other natural or artificial tracers.

Quantifying the contribution of glacier meltwater in the expansion of the largest lake in Tibet

AbstractLake Siling Co is currently the largest endorheic lake in Tibet, and the lake surface area has expanded by about 40% since the 1970s, with a remarkable acceleration after 1999. In this study, a hydrologic modeling framework was established by linking the Variable Infiltration Capacity (VIC) land surface hydrologic model with the degree‐day glacier‐melt model over the Lake Siling Co basin, with an aim to quantify the contribution of each runoff component to changes in the lake storage. We found that glacier melt contributed to less than 10% of the total water input to the lake during 1979–2013, while precipitation‐induced runoff in nonglacierized area was responsible for about 67–75%. The mean annual water input to the lake increased by 2.15 × 109 m3 yr−1 in 2000–2013 relative to that in 1979–1999. The amount of precipitation over the lake surface, precipitation‐induced runoff, and glacier‐melt runoff accounted for 13%, 82%, and 5% of this total increase, respectively, suggesting that the substantial expansion of Siling Co in the 2000s was mostly due to the increase in precipitation‐induced runoff. When modeling lake level changes during 1979–2013, we found that the water level rose by 14.1 m when glacier melt was included and by only 10.5 m, a reduction of about one fourth, when glacier melt was removed. It is concluded that glacier melt played an important role in controlling the water level of Siling Co, although it only contributed less than 10% of water input to the lake during 1979–2013.

Streamwater hydrograph separation in an alpine glacier area in the Qilian Mountains, northwestern China

ABSTRACTGlacier-melt-induced changes in runoff are of concern in northwestern China where glacier runoff is a major source for irrigation, industries and ecosystems. Samples were collected in different water mediums such as precipitation, glacial ice/snowcover, meltwater, groundwater and streamwater for the analysis of stable isotopes and solute contents during the 2009 runoff season in the Laohugou Glacial Catchment. The multi-compare results of δ18O values showed that significant difference existed in different water mediums. Source waters of streamflow were determined using data of isotopic and geochemical tracers and a three-component hydrograph separation model. The results indicated that meltwater dominated (69.9 ± 2.7%) streamflow at the catchment. Precipitation and groundwater contributed 17.3 ± 2.3% and 12.8 ± 2.4% of the total discharge, respectively. According to the monthly hydrograph, the contribution of snow and glacier meltwater varied from 57.4% (September) to 79.1% (May), and that of precipitation varied from 0% (May) to 34.6% (September). At the same time, the monthly contribution of groundwater kept relatively steady, varying from 9.7% (June) to 20.9% (May) in the runoff season. Uncertainties for this separation were mainly caused by the variation of tracer concentrations. It is suggested that the end-member mixing analysis (EMMA) method can be used in the runoff separation in an alpine glacial catchment.Editor Z.W. Kundzewicz; Associate editor Not assigned

Continental Glacier meltwater contributions to late summer stream flow and water quality in the northern Wind River Range, Wyoming, USA

The Wind River Range in Wyoming contains more than 60 glaciers that are part of the headwaters for the Wind-Missouri, Green-Colorado and Snake-Columbia River systems. Continental Glacier lies on the crest of the northern Wind River Range and covers approximately 2.5 km2 with meltwater flowing into West Torrey Creek and the Wind River. Discharge measurements of upper Continental Glacier meltwater were made in August 2012 and 2014. Water samples were collected in 2014 for the analysis of stable isotopes, field parameters and 23 trace elements. This study demonstrated that Continental Glacier meltwater accounted for a mean of 32.91 ± 8.4 % of Torrey Creek flow, and 4.11 ± 18.38 % of Wind River flow as measured above Red Creek for August 2012 and 2014. Scaling of these results to all perennial snow and ice in the upper Torrey Creek basin yielded an estimate of 82.70 % contribution to Torrey Creek flow, and 10.32 % of Wind River flow above Red Creek, during August. Glacier meltwater contributions versus snow melt to Torrey Creek based on δ18O ratios ranged from 81.05 to 82.70 % of flow, with a mean of 81.88 ± 1.17 % for August 2014. Continental Glacier meltwater accounted for 89.99 % of nitrate-nitrite and 34.83 % of total phosphorus loading to Torrey Creek in August 2014. The pH of the snow and glacier meltwater was less than 6.0, likely the result of nitrate-nitrite and other atmospheric deposition. Finally, analysis of trace elements showed distinct differences between water sources.

Differences in the water-balance components of four lakes in the southern-central Tibetan Plateau

Abstract. The contrasting patterns of lake-level fluctuations across the Tibetan Plateau (TP) are indicators of differences in the water balance over the TP. However, little is known about the key hydrological factors controlling this variability. The purpose of this study is to contribute to a more quantitative understanding of these factors for four selected lakes in the southern-central part of the TP: Nam Co and Tangra Yumco (increasing water levels), and Mapam Yumco and Paiku Co (stable or slightly decreasing water levels). We present the results of an integrated approach combining hydrological modeling, atmospheric-model output and remote-sensing data. The J2000g hydrological model was adapted and extended according to the specific characteristics of closed-lake basins on the TP and driven with High Asia Refined analysis (HAR) data at 10 km resolution for the period 2001–2010. Differences in the mean annual water balances among the four basins are primarily related to higher precipitation totals and attributed runoff generation in the Nam Co and Tangra Yumco basins. Precipitation and associated runoff are the main driving forces for inter-annual lake variations. The glacier-meltwater contribution to the total basin runoff volume (between 14 and 30 % averaged over the 10-year period) plays a less important role compared to runoff generation from rainfall and snowmelt in non-glacierized land areas. Nevertheless, using a hypothetical ice-free scenario in the hydrological model, we indicate that ice-melt water constitutes an important water-supply component for Mapam Yumco and Paiku Co, in order to maintain a state close to equilibrium, whereas the water balance in the Nam Co and Tangra Yumco basins remains positive under ice-free conditions. These results highlight the benefits of linking hydrological modeling with atmospheric-model output and satellite-derived data, and the presented approach can be readily transferred to other data-scarce closed lake basins, opening new directions of research. Future work should go towards a better assessment of the model-chain uncertainties, especially in this region where observation data are scarce.

Estimates of Glacier Mass Loss and Contribution to Streamflow in the Wind River Range in Wyoming: Case Study

The Wind River Range is a continuous mountain range, approximately 160 km in length, in west-central Wyoming. The presence of glaciers results in meltwater contributions to streamflow during the late summer (July, August, and September: JAS) when snowmelt is decreasing; temperatures are high; precipitation is low; evaporation rates are high; and municipal, industrial, and irrigation water are at peak demands. Thus, the quantification of glacier meltwater (e.g., volume and mass) contributions to late summer/early fall streamflow is important, given that this resource is dwindling owing to glacier recession. The current research expands upon previous research efforts and identifies two glaciated watersheds, one on the east slope (Bull Lake Creek) and one on the west slope (Green River) of the Wind River Range, in which unimpaired streamflow is available from 1966 to 2006. Glaciers were delineated within each watershed and area estimates (with error) were obtained for the years 1966, 1989, and 2006. Glacier volume (mass) loss (with error) was estimated by using empirically based volume–area scaling relationships. For 1966 to 2006, glacier mass contributions to JAS streamflow on the east slope were approximately 8%, whereas those on the west slope were approximately 2%. The volume–area scaling glacier mass estimates compared favorably with measured (stereo pair remote sensed data) estimates of glacier mass change for three glaciers (Teton, Middle Teton, and Teepe) in the nearby Teton Range and one glacier (Dinwoody) in the Wind River Range.

Dynamics of the last four glacial terminations recorded in Lake Van, Turkey

A well-dated suite of Lake Van climate-proxy data covering the last 360 ka documents environmental changes over 4 glacial/interglacial cycles in Eastern Anatolia, Turkey. The picture of cold and dry glacials and warm and wet interglacials emerging from pollen, organic carbon, authigenic carbonate content, elemental profiling by XRF and lithological analyses is inconsistent with classical interpretation of oxygen isotopic composition of carbonates pointing to a more complex pattern in Lake Van region. Detailed analysis of glacial terminations allows for the constraining of a depositional model explaining different patterns observed in all the proxies. We hypothesize that variations in relative contribution of rainfall, snowmelt and glacier meltwater recharging the basin have a very important role for all sedimentary processes in Lake Van. Lake level of glacial Lake Van, predominantly fed by snowmelt, was low, the water column was oxic, and carbonates precipitating in the epilimnion recorded the light isotopic signature of inflow. During terminations, increasing rainfall and significant supply of mountain glaciers' meltwater contributed to lake level rise. Increased rainfall enhanced density gradients in the water column, and hindered mixing leading to development of bottom-water anoxia. Carbonates precipitating during terminations show large fluctuations in their isotopic composition. Full interglacial conditions in Lake Van are characterized by high or slowly falling lake level. Rainfall and snowmelt feed the lake but due to re-established mixing, the isotopic composition of authigenic carbonates is heavier and closer to that of evaporation-influenced lake water than that of runoff representing snowmelt and atmospheric precipitation.