The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms

In eastern Africa, there are few long, high-quality records of environmental change at high altitudes, inhibiting a broader understanding of regional climate change. We investigated a Holocene lacustrine sediment archive from Lake Garba Guracha, Bale Mountains, Ethiopia, (3,950 m a.s.l.), and reconstructed high-altitude lake evaporation history using δ18O records derived from the analysis of compound-specific sugar biomarkers and diatoms. The δ18Odiatom and δ18Ofuc records are clearly correlated and reveal similar ranges (7.9‰ and 7.1‰, respectively). The lowest δ18O values occurred between 10 and 7 cal ka BP and were followed by a continuous shift towards more positive δ18O values. Due to the aquatic origin of the sugar biomarker and the similar trends of δ18Odiatom, we suggest that our lacustrine δ18Ofuc record reflects δ18Olake water. Therefore, without completely excluding the influence of the ‘amount-effect’ and the ‘source-effect‘, we interpret our record to reflect primarily the precipitation-to-evaporation ratio (P/E). We conclude that precipitation increased at the beginning of the Holocene, leading to an overflowing lake between ~10 and ~8 cal ka BP, indicated by low δ18Olake water values interpreted as reduced evaporative enrichment. This is followed by a continuous trend towards drier conditions, indicating at least a seasonally closed lake system

Electrical Conductivity, DOC, CDOM, stable water isotopes and major ions of the ice core LD18-BH-8 samples near the Samoylov Island Research Station

Current warming, shifting hydrological regimes and accelerated permafrost thaw in the catchment of the Arctic rivers will affect their water biogeochemistry and the ice that covers the river for more than half of the year. The Lena River is the second largest Arctic river and 71 % of its catchment is characterized by continuous permafrost. Large amounts of ice melt water is exported in spring to the Laptev Sea shelf water where it modifies the biogeochemistry of the shelf water. This dataset presents electrical Conductivity, DOC, CDOM, stable water isotopes and major ions in the ice core LD18-BH-8 samples near the Samoylov Island Research Station

Oceanic surface water isotopic compositions calibrated data from POLARSTERN cruise PS93.1 (ARK-XXIX/2.1)

Isotopic measurements of seawater sampled on-board Polarstern research vesse

Stable water isotopes from repeated snow profile sampling during the summer season 2019 at the EastGRIP deep drilling site

A dataset containing surface snow profiles of stable water isotopic composition (d18O, dD, d-excess). Snow profiles had a depth of 30 cm and were sampled with a 2 cm vertical resolution. Profiles were taken at 20 positions with 2 m spacing between each on six dates during the spring and summer of 2019 in northeast Greenland. In the same area, a photogrammetry structure-from-motion approach was performed to generate digital elevation models for each day (cross-ref to other PANGAEA submission). All measurements were taken at the East Greenland Ice Core Project site (EastGRIP) situated in the accumulation zone of the Greenland Ice Sheet. The snow profiles were cut in the field and stored in WhirlPaks. The samples were kept frozen and were shipped to the ISOLAB Facility at the Alfred-Wegener-Institute in Potsdam, Germany. The samples were measured with an L2140-i CRDS device from Picarro Inc. with a high-throughput vaporizer. All data were corrected for memory and instrumental drift as suggested in van Geldern and Barth (2012) using the calibration algorithm described in Münch et al. (2016). The mean measurement uncertainty for δ18O and δD derived from an independent quality control standard was 0.13 and 1.4 ‰ for samples, respectively, and 0.09 and 0.7 ‰ for all used reference waters. The ISOLAB Facility metadata is part of the sensor web: Sensor (2022): Metadata for laboratory ISOLAB Facility - Stable Isotope Laboratory Potsdam at Current Version. hdl:10013/sensor.ddc92f54-4c63-492d-81c7-696260694001 Sensor (2022): Metadata for Isotopic Water Liquid Analyzer for the online determination of the hydrogen and oxygen isotopic composition in water samples using Cavity Ring-Down Spectroscopy (CRDS) L2140-i: https://sensor.awi.de?urn=laboratory:isolab_facility_potsdam:picarro_crds_l2140i_

Stable water isotopologues of arrays of high resolution 1 m snow cores from across Dronning Maud Land, East Antarctic Plateau

A set of 1 m firn profiles was sampled in December 2018 across a traverse of ~ 100 km near Kohnen Station to quantify stratigraphic noise in high resolution isotope records. At each of six different locations (D2, C4, C5, D7, D24, D38), 5 profiles were extracted on one line, perpendicularly to the overall large scale wind direction and with an interprofile spacing of 10 m. Each firn profile was vertically extracted from the snow surface by inserting a 1 m pipe of carbon fiber at the sidewall of a snow-pit. Vertical target resolution was 1.1 cm in the upper 16.5 cm and 3.3 cm in the lower part. Due compression and expanding while handling, transportation and cutting at site, we assume a maximum depth uncertainty from these steps of 2 cm. All samples (N = 1249) were packed in plastic bags and transported to Germany in a constantly frozen state. Measurements of the stable water isotopic composition (δ¹⁸O, δD) of the firn samples were done using a Cavity Ring-Down Spectroscopy instrument (CRDS) of PICARRO Inc (model L2140-i) in the Stable Isotope Facility at the Alfred Wegener Institute in Potsdam, Germany. Post-run correction was done as described in Münch et al., (2016 - doi:10.5194/cp-12-1565-2016). Scaling to the VSMOW/SLAP (Vienna Standard Mean Ocean Water/StandardLight Antarctic Precipitation) scale results in the δ-notation, describing the ratio of heavy to light isotopes in ‰. In-house standards were used for quality control. The mean combined measurement uncertainty is 0.07‰ for δ¹⁸O and 0.5‰ for δD (root mean square deviation, RMSD)

Stable water isotopes and conductivities of a lead case study during leg 5

The dataset comprises stable water isotopes and conductitities of a lead case study during leg 5 of the MOSAiC campaign. Samples have been taken from different water and ice types for this lead case study. Discrete water samples were taken using a peristaltic pump (Masterflex E/S Portable Sampler, Masterflex, USA) through a 2 m long PTFE tube (L/S Pump Tubing, Masterflex, USA). Water samples for measurement of stable water isotopes (δ18O, δD,) were collected in 50-mL glass screw-cap narrow-neck vials (VWR international LLC, Germany). Snow on the sea ice was sampled with a polyethylene shovel (GL Science Inc., Tokyo, Japan) and placed into a polyethylene zip-loc bag. Ice in the lead was collected and a 0.25 m ' 0.25 m ice block was cut with a hand saw and placed into a zip-lock bag. Ice temperature at the surface was measured with a needle-type temperature sensor (Testo 110 NTC, Brandt Instruments, Inc., USA). Two ice cores from the bottom of a melt pond were collected, using an ice corer with an inner diameter of 0.09 m (Mark II coring system, KOVACS Enterprises, Inc., USA). The cores were cut with a stainless steel saw into 0.1 m thick sections and stored in plastic bags for subsequent salinity and δ18O measurements. Snow and ice samples were immediately placed in a cooler box along with refrigerants to keep their temperature low and to minimize brine drainage. Onboard Polarstern, ice samples were transferred into ice melting bags (Smart bags PA, AAK 5L, GL Sciences Inc., Japan) and melted in the dark at +4°C. After the ice melted, the meltwater was placed in a 30-mL glass screw-cap vial for later stable water isotope measurement and into a 100-mL polypropylene bottle (I-Boy, AS ONE Corporation, Japan) for later salinity measurement. These samples were stored at +4°C in the dark until analysis. Under-ice water samples (from about 10 m depth) were collected via R/V Polarstern's underway water sampling system during leg 5. Samples were placed into 250-mL glass vials (Duran Co. Ltd, Germany) for later δ18O and salinity measurements. Salinity of collected samples was determined with a same conductivity sensor used on sea ice (Cond 315i, WTW GmbH, Germany). Oxygen and hydrogen isotope analyses were carried out at the ISOLAB Facility at AWI Potsdam (hdl:10013/sensor.ddc92f54-4c63-492d-81c7-696260694001) with mass spectrometers (DELTA-S Finnigan MAT, USA): hdl:10013/sensor.af148dea-fe65-4c87-9744-50dc4c81f7c9 and hdl:10013/sensor.62e86761-9fae-4f12-9c10-9b245028ea4c employing the equilibration method (details in Meyer et al., 2000). δ18O and δD values were given in per mil (‰) vs. Vienna standard mean ocean water (V-SMOW) as the standard. The second order parameter d excess was computed according to: d excess = δD-8 δ18O (Dansgaard, 1964)

Oceanic surface water isotopic compositions calibrated data from POLARSTERN cruise PS99.1

Isotopic measurements of seawater sampled on-board Polarstern research vesse

Oceanic surface water isotopic compositions calibrated data from POLARSTERN cruise PS105

Isotopic measurements of seawater sampled on-board Polarstern research vesse

Gapless and high-resolution diatom oxygen isotope record of sediment short core EN18232-1 from Lake Khamra, SW Yakutia, Siberia, Russia

The dataset includes diatom oxygen isotope data for 39 samples from short core EN18232-1, Lake Khamra, and corresponding key geochemical characteristics of the purified lake sediment samples based on Energy-Dispersive X-ray Spectroscopy (EDS) measurements. For each sample (Sample ID) the corresponding core depth (Depth sed top/bottom) and the calculated mean age (Age) are given. EDS measurements were carried out by a JEOL M-IT500HR analytical scanning electron microscope (SEM) with an integrated EDS-system supplied with a Peltier element cooled SD detector (SDD) at AWI Potsdam. The standardless procedure was used according to Chapligin et al. (2012), including 6 repetitions, acceleration voltage of 20.0 kV, magnification of 300 and a measuring time of 30 seconds. All detectable elements are normalized to 100% weight. Elements are given as oxides with weight percentages (in %) and summed up to the total sum (total %) of each sample. The diatom oxygen isotope data was generated in the ISOLAB Facility at AWI Potsdam with a semi-automated laserfluorination line (Chapligin et al., 2010) in combination with a SERCON HS2022 mass spectrometer. All δ18Odiatom values are given in per mill (‰) vs. Vienna Standard Mean Ocean Water (VSMOW). The dataset includes the mean of measured δ18Odiatom values (Diatom δ18O mean), the standard deviation (Diatom δ18O std dev) and number of replicates (Repl), as well as the calculated contamination (Contamination in %) and the δ18Odiatom corrected for contamination (Diatom δ18O corrected). Details of the contamination correction and isotope analytics are given in Stieg et al. (2023, in prep)

Oceanic surface water isotopic compositions calibrated data from POLARSTERN cruise PS103

Isotopic measurements of seawater sampled on-board Polarstern research vesse