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  • 2020-2024  (177)
  • 2020-2023  (15)
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  • 1
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    Kali Gandaki High Mountain Observatory, Stable Water Isotope database (2021)
    GFZ Data Services
    Details
    Publication Date: 2022-11-24
    Description: Abstract
    Description: This dataset was collected during field-based monitoring in the Kali Gandaki River catchment be-tween the years 2013 and 2017. The monitoring aims to understand the hydrological fluxes and feedback with weathering and erosion processes across the mountain range. The Kali Gandaki River sources its water in the North and traverses through the Himalayan Mountain Range, along a north-south transect. The field-based monitoring comprises targeted field campaigns to revisit locations at different years and seasons in order to constrain the annual and intra-annual variability. This is complemented by permanent installations and routine river and rain sampling at two loca-tions, Lete and Purtighat. Lete is situated at the orographic barrier, at ~2500 m asl. and the up-stream catchment integrates the northern part of the Himalayan Range as well as some of the southern edge of the Tibetan Plateau. Purtighat is located further south and integrates the north-ern part as well as south-facing flanks of the Higher and Lower Himalayas. At both locations, auto-mated river monitoring is installed as well as a trained station ward for daily routine sampling. At Lete, rainfall samples are obtained on a daily resolution during the monsoon. This sampling was not feasible at Purtighat for logistic reasons. Instead, rain was sampled daily in Kathmandu. This dataset contains five tables of stable water isotope analysis. One containing grab samples from the Kali Gandaki river in its vicinities and 4 tables with time series sampling from the Kali Gandaki River and from rainfall.
    Description: Methods
    Description: Grab sampling: Grab samples were obtained from all hydrological compartments (spring, river, tributary, snow, ice, and rain) in the Kali Gandaki catchment and its surroundings. The samples were taken during repeated field campaigns covering all seasons during the years 2013 to 2016. Samples were filtered in the field and stored 30ml Nalgene bottles. Snow and ice samples were melted at ambient temperatures before filtering and storing. Stable water isotope time series of rainfall: Samples were collected by a local, trained station ward, during rainfall periods 2016 and 2017. Samples were recuperated always between 8 and 9 o’clock local time (GMT+5:45) if sufficient rainwater was accumulated. At both locations Lete and Kathmandu we used Palmex Rain Sampler RS1 (Gröning et al., 2012). The following isotope ratios, expressed as δ values with VSMOW as a standard, were measured: δ18O and δ2H. Stable water isotope time series of river water: Samples were collected by a local, trained station ward, between the 10th of June 2015 and October 2018 daily during the monsoon (June to Septem-ber) and bi-weekly (October to May) during the dry season. Sampling time was always between 8 and 9 o’clock local time (GMT+5:45). Samples were typically analyzed for stable water isotopic com-position with weekly resolution. The following isotope ratios, expressed as δ values with VSMOW as a standard, were measured: δ18O and δ2H. River time series samples in Purtighat were first obtained at Mirmi Hydropower Intake, upstream of the confluence with Andhi Khola from a suspension bridge in the middle of the river. The sampling location was later moved upstream to Purthighat village, roughly 10km upstream with no major tributary in between.
    Keywords: rainfall isotopes ; Precipitation ; Nepal ; Himalayas ; perturbations ; Kali Gandaki River ; time series ; groundwater ; monsoon ; pre-monsoon ; river isotopes ; climate 〉 climate type 〉 continental climate 〉 mountain climate ; EARTH SCIENCE 〉 ATMOSPHERE 〉 PRECIPITATION 〉 RAIN ; EARTH SCIENCE 〉 CLIMATE INDICATORS 〉 PALEOCLIMATE INDICATORS 〉 OXYGEN ISOTOPE ANALYSIS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEOCHEMISTRY 〉 GEOCHEMICAL PROPERTIES 〉 ISOTOPES ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEOMORPHIC LANDFORMS/PROCESSES 〉 FLUVIAL LANDFORMS 〉 STREAM ; EARTH SCIENCE 〉 TERRESTRIAL HYDROSPHERE 〉 WATER QUALITY/WATER CHEMISTRY 〉 STABLE ISOTOPES ; hydrosphere 〉 hydrologic cycle 〉 hydrologic balance 〉 runoff 〉 drainage 〉 drainage system 〉 natural drainage system ; hydrosphere 〉 water body 〉 aquifer ; land 〉 natural area 〉 terrestrial area 〉 mountainous area 〉 mountain 〉 high mountain ; land 〉 world 〉 Asia 〉 Southern Asia ; science 〉 natural science 〉 water science 〉 hydrology
    Type: Dataset , Dataset
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    DATA GFZ
  • 2
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    Meltwater layer dynamics in a central Arctic lead: Effects of lead width, re-freezing, and mixing during late summer (2023)
    University of California Press
    Details
    Publication Date: 2024-02-07
    Description: Leads play an important role in the exchange of heat, gases, vapour, and particles between seawater and the atmosphere in ice-covered polar oceans. In summer, these processes can be modified significantly by the formation of a meltwater layer at the surface, yet we know little about the dynamics of meltwater layer formation and persistence. During the drift campaign of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), we examined how variation in lead width, re-freezing, and mixing events affected the vertical structure of lead waters during late summer in the central Arctic. At the beginning of the 4-week survey period, a meltwater layer occupied the surface 0.8 m of the lead, and temperature and salinity showed strong vertical gradients. Stable oxygen isotopes indicate that the meltwater consisted mainly of sea ice meltwater rather than snow meltwater. During the first half of the survey period (before freezing), the meltwater layer thickness decreased rapidly as lead width increased and stretched the layer horizontally. During the latter half of the survey period (after freezing of the lead surface), stratification weakened and the meltwater layer became thinner before disappearing completely due to surface ice formation and mixing processes. Removal of meltwater during surface ice formation explained about 43% of the reduction in thickness of the meltwater layer. The remaining approximate 57% could be explained by mixing within the water column initiated by disturbance of the lower boundary of the meltwater layer through wind-induced ice floe drift. These results indicate that rapid, dynamic changes to lead water structure can have potentially significant effects on the exchange of physical and biogeochemical components throughout the atmosphere–lead–underlying seawater system.
    Type: Article , PeerReviewed
    Format: text
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    PAPER (OCEANREP)
  • 3
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    Impacts of glacier and sea ice melt on methane pathways on the Northeast Greenland shelf (2022)
    Elsevier
    Details
    Publication Date: 2024-02-07
    Description: Highlights • CH4 excess is detected in water masses interacting with sea ice. • CH4 excess in surface waters is sea ice-sourced. • The meltwater layer restricts the sea-to-air flux via increased stratification. • CH4 excess is redistributed in the marine environment. • In water masses transported to the shelf, CH4 oxidation acts as biological CH4 sink. Global warming has led to a sharp decrease in Arctic summer sea ice extent and a dramatic ice mass loss of the Greenland Ice Sheet over the past three decades. The Northeast Greenland continental shelf is a site of intense water mass transformation involving both sea ice processes and glacier dynamics. The Arctic shelf waters are considered to be a net source of atmospheric methane (CH4); however, the effect of glacier and sea ice melt on oceanic CH4 concentrations still needs to be investigated. To better understand the effect of meltwater on the CH4 budget of the ocean, our study constrains the CH4 pathways by following changes in water mass properties and infers potential CH4 sources and sinks. Based on measurements of concentration and carbon isotope delta (δ13C) of CH4, the water mass tracer δ18O(H2O) and physical properties of the water masses, we detected CH4 excess in surface waters, which we attribute to brine release during sea ice formation. We show that this CH4 excess is sustained throughout the melt season, due to a freshwater lid formed at the ocean surface. The meltwater hardly alters the CH4 excess, but enhances water stratification, which, in turn, restricts the sea-to-air flux. The CH4 excess is subject to mixing with surrounding shelf waters influenced by basal glacial meltwater discharge. We suggest that the CH4 excess of Northeast Greenland continental shelf waters is redistributed in the marine environment, while CH4 emission to the atmosphere is limited to regions not covered by sea ice.
    Type: Article , PeerReviewed
    Format: text
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  • 4
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    Isotopic signatures of snow, sea ice, and surface seawater in the central Arctic Ocean during the MOSAiC expedition (2024)
    University of California Press
    Details
    Publication Date: 2024-04-05
    Description: The Arctic Ocean is an exceptional environment where hydrosphere, cryosphere, and atmosphere are closely interconnected. Changes in sea-ice extent and thickness affect ocean currents, as well as moisture and heat exchange with the atmosphere. Energy and water fluxes impact the formation and melting of sea ice and snow cover. Here, we present a comprehensive statistical analysis of the stable water isotopes of various hydrological components in the central Arctic obtained during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019–2020, including the understudied Arctic winter. Our dataset comprises >2200 water, snow, and ice samples. Snow had the most depleted and variable isotopic composition, with δ18O (–16.3‰) increasing consistently from surface (–22.5‰) to bottom (–9.7‰) of the snowpack, suggesting that snow metamorphism and wind-induced transport may overprint the original precipitation isotope values. In the Arctic Ocean, isotopes also help to distinguish between different sea-ice types, and whether there is a meteoric contribution. The isotopic composition and salinity of surface seawater indicated relative contributions from different freshwater sources: lower δ18O (approximately –3.0‰) and salinities were observed near the eastern Siberian shelves and towards the center of the Transpolar Drift due to river discharge. Higher δ18O (approximately –1.5‰) and salinities were associated with an Atlantic source when the RV Polarstern crossed the Gakkel Ridge into the Nansen Basin. These changes were driven mainly by the shifts within the Transpolar Drift that carried the Polarstern across the Arctic Ocean. Our isotopic analysis highlights the importance of investigating isotope fractionation effects, for example, during sea-ice formation and melting. A systematic full-year sampling for water isotopes from different components strengthens our understanding of the Arctic water cycle and provides crucial insights into the interaction between atmosphere, sea ice, and ocean and their spatio-temporal variations during MOSAiC.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 5
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    A global compilation of diatom silica oxygen isotope records from lake sediment – trends and implications for climate reconstruction (2024)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-05-28
    Description: Oxygen isotopes in biogenic silica (δ18OBSi) from lake sediments allow for quantitative reconstruction of past hydroclimate and proxy-model comparison in terrestrial environments. The signals of individual records have been attributed to different factors, such as air temperature (Tair), atmospheric circulation patterns, hydrological changes, and lake evaporation. While every lake has its own local set of drivers of δ18O variability, here we explore the extent to which regional or even global signals emerge from a series of paleoenvironmental records. This study provides a comprehensive compilation and combined statistical evaluation of the existing lake sediment δ18OBSi records, largely missing in other summary publications (i.e. PAGES network). For this purpose, we have identified and compiled 71 down-core records published to date and complemented these datasets with additional lake basin parameters (e.g. lake water residence time and catchment size) to best characterize the signal properties. Records feature widely different temporal coverage and resolution, ranging from decadal-scale records covering the past 150 years to records with multi-millennial-scale resolution spanning glacial–interglacial cycles. The best coverage in number of records (N = 37) and data points (N = 2112) is available for Northern Hemispheric (NH) extratropical regions throughout the Holocene (roughly corresponding to Marine Isotope Stage 1; MIS 1). To address the different variabilities and temporal offsets, records were brought to a common temporal resolution by binning and subsequently filtered for hydrologically open lakes with lake water residence times 〈 100 years. For mid- to high-latitude (〉 45° N) lakes, we find common δ18OBSi patterns among the lake records during both the Holocene and Common Era (CE). These include maxima and minima corresponding to known climate episodes, such as the Holocene Thermal Maximum (HTM), Neoglacial Cooling, Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). These patterns are in line with long-term air temperature changes supported by previously published climate reconstructions from other archives, as well as Holocene summer insolation changes. In conclusion, oxygen isotope records from NH extratropical lake sediments feature a common climate signal at centennial (for CE) and millennial (for Holocene) timescales despite stemming from different lakes in different geographic locations and hence constitute a valuable proxy for past climate reconstructions.
    Type: Article , PeerReviewed
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  • 6
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    Fluvial and permafrost history of the lower Lena River, north‐eastern Siberia, over late Quaternary time (2022)
    Schwamborn, Georg ; Schirrmeister, Lutz ; Mohammadi, Ali ; [et al.]
    Details
    Publication Date: 2023-11-18
    Description: Arctic warming and permafrost thaw visibly expose changes in the landscape of the Lena River delta, the largest Arctic delta. Determining the past and modern river regime of thick deltaic deposits shaping the Lena River mouth in north‐eastern Siberia is critical for understanding the history of delta formation and carbon sequestration. Using a 65 m long sediment core from the delta apex a set of sedimentological techniques is applied to aid in reconstructing the Lena River history. The analysis includes: (i) grain‐size measurements and the determination of the bedload composition; (ii) X‐ray fluorescence, X‐ray diffractometry, and magnetic susceptibility measurements and heavy mineral analysis for tracking mineral change; (iii) pH, electrical conductivity, ionic concentrations, and the δ〈sub〉18〈/sub〉O and δD stable isotope composition from ground ice for reconstructing permafrost formation. In addition; (iv) total and dissolved organic carbon is assessed. Chronology is based on; (vi) radiocarbon dating of organic material (accelerator mass spectrometry and conventional) and is complemented by two infrared – optically stimulated luminescence dates. The record stretches back approximately to Marine Isotope Stage 7. It holds periods from traction, over saltation, to suspension load sedimentation. Minerogenic signals do not indicate provenance change over time. They rather reflect the change from high energy to a lower energy regime after Last Glacial Maximum time parallel to the fining‐up grain‐size trend. A prominent minimum in the ground ice stable isotope record at early Holocene highlights that a river arm migration and an associated refreeze of the underlying river talik has altered the isotopic composition at that time. Fluvial re‐routing might be explained by internal dynamics in the Lena River lowland or due to a tectonic movement, since the study area is placed in a zone of seismic activity. At the southern Laptev Sea margin, onshore continental compressional patterns are bordering offshore extensional normal faults.
    Description: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
    Description: https://doi.org/10.1594/PANGAEA.945355
    Keywords: ddc:551 ; Lena River ; north‐eastern Siberia ; palaeoenvironment ; permafrost ; Quaternary
    Language: English
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    CITATION GEO-LEO
  • 7
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    A Snapshot on the Buildup of the Stable Water Isotopic Signal in the Upper Snowpack at EastGRIP on the Greenland Ice Sheet (2023)
    Zuhr, Alexandra M. ; Wahl, Sonja ; Steen‐Larsen, Hans Christian ; [et al.]
    Details
    Publication Date: 2024-04-19
    Description: The stable water isotopic composition in firn and ice cores provides valuable information on past climatic conditions. Because of uneven accumulation and post‐depositional modifications on local spatial scales up to hundreds of meters, time series derived from adjacent cores differ significantly and do not directly reflect the temporal evolution of the precipitated snow isotopic signal. Hence, a characterization of how the isotopic profile in the snow develops is needed to reliably interpret the isotopic variability in firn and ice cores. By combining digital elevation models of the snow surface and repeated high‐resolution snow sampling for stable water isotope measurements of a transect at the East Greenland Ice‐core Project campsite on the Greenland Ice Sheet, we are able to visualize the buildup and post‐depositional changes of the upper snowpack across one summer season. To this end, 30 cm deep snow profiles were sampled on six dates at 20 adjacent locations along a 40 m transect. Near‐daily photogrammetry provided snow height information for the same transect. Our data shows that erosion and redeposition of the original snowfall lead to a complex stratification in the δ〈sup〉18〈/sup〉O signature. Post‐depositional processes through vapor‐snow exchange affect the near surface snow with d‐excess showing a decrease in surface and near‐surface layers. Our data suggests that the interplay of stratigraphic noise, accumulation intermittency, and local post‐depositional processes form the proxy signal in the upper snowpack.
    Description: Plain Language Summary: We study the process of the formation of the stable water isotope signal in surface snow on the Greenland Ice Sheet to better understand temperature information which is stored as a climate proxy in snow and ice. Our data consist of high‐resolution surface topography information illustrating the timing and location of snowfall, erosion, and redeposition along a transect of 40 m, as well as stable water isotope records of the upper 30 cm of the snowpack sampled biweekly on 20 positions at the same 40 m long transect. The data cover a 2‐month period during the summer of 2019. We find that the isotopic composition shows spatial variability of layers with low and high values, presumably winter and summer layers. We further observe that prevailing surface structures, such as dunes, influence the snow deposition and contribute to the found variable structure of the climatic information. Eventually, snow accumulation alone cannot explain all of the observed patterns in the isotopic data which is likely related to exchange processes between the snow and the atmosphere which modify the signal in the snow column after deposition.
    Description: Key Points: Combining digital elevation models and repeated snow sampling reveals the heterogeneous buildup of δ〈sup〉18〈/sup〉O signal in the snow column. Surface structures (stratigraphic noise) substantially contribute to internal heterogeneity in δ〈sup〉18〈/sup〉O signature in the upper snowpack. Proxy signals are formed in the surface layer by local processes, advected downwards with limited post‐depositional influences below 10 cm.
    Description: Horizon 2020 Framework Programme http://dx.doi.org/10.13039/100010661
    Description: A. P. Møller Foundation, University of Copenhagen
    Description: US National Science Foundation, Office of Polar Programs
    Description: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
    Description: National Institute of Polar Research and Arctic Challenge for Sustainability
    Description: University of Bergen
    Description: Trond Mohn Foundation
    Description: Swiss National Science Foundation
    Description: French Polar Institute Paul‐Emile Victor, Institute for Geosciences and Environmental Research
    Description: University of Manitoba
    Description: Chinese Academy of Sciences
    Description: Beijing Normal University
    Description: https://doi.org/10.1594/PANGAEA.954944
    Description: https://doi.org/10.1594/PANGAEA.954945
    Description: https://doi.org/10.1594/PANGAEA.951583
    Description: https://doi.org/10.1594/PANGAEA.925618
    Description: https://doi.org/10.1594/PANGAEA.928827
    Description: https://www.agisoft.com/downloads/installer/
    Keywords: ddc:551 ; proxy ; Greenland ; isotopes ; structure‐from‐motion ; snow accumulation ; ice core
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 8
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    Oceanic surface water isotopic compositions calibrated data from POLARSTERN cruise PS93.1 (ARK-XXIX/2.1) (2022)
    PANGAEA
    Details
    Publication Date: 2023-03-16
    Description: Isotopic measurements of seawater sampled on-board Polarstern research vessel
    Keywords: Arctic; ARK-XXIX/2.1; AWI_Envi; CT; d18O; DATE/TIME; Deuterium excess; ISOARC; Isotope signature of water vapour over the Arctic Ocean; LATITUDE; LONGITUDE; Polarstern; Polar Terrestrial Environmental Systems @ AWI; PS93.1; PS93.1-track; surface water; Underway cruise track measurements; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 57 data points
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    DATA PANGAEA
  • 9
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    Oceanic surface water isotopic compositions calibrated data from POLARSTERN cruise PS93.2 (ARK-XXIX/2.2) (2022)
    PANGAEA
    Details
    Publication Date: 2023-03-16
    Description: Isotopic measurements of seawater sampled on-board Polarstern research vessel
    Keywords: Arctic; ARK-XXIX/2.2; AWI_Envi; CT; d18O; DATE/TIME; Deuterium excess; ISOARC; Isotope signature of water vapour over the Arctic Ocean; LATITUDE; LONGITUDE; Polarstern; Polar Terrestrial Environmental Systems @ AWI; PS93.2; PS93.2-track; surface water; Underway cruise track measurements; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 63 data points
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    DATA PANGAEA
  • 10
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    Oceanic surface water isotopic compositions calibrated data from POLARSTERN cruise PS95.1 (ANT-XXXI/1.1) (2022)
    PANGAEA
    Details
    Publication Date: 2023-03-17
    Description: Isotopic measurements of seawater sampled on-board Polarstern research vessel
    Keywords: ANT-XXXI/1.1; AWI_Envi; CT; d18O; DATE/TIME; Deuterium excess; ISOARC; Isotope signature of water vapour over the Arctic Ocean; LATITUDE; LONGITUDE; Polarstern; Polar Terrestrial Environmental Systems @ AWI; PS95.1; PS95.1-track; surface water; Underway cruise track measurements; water isotopes; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 24 data points
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    DATA PANGAEA
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