Snow samples of the upper 10 cm were taken between 14 May and 3 August 2018 next to the EastGRIP deep drilling site in northeast Greenland situated in the accumulation zone of the Greenland Ice Sheet. All samples were measured for their stable water isotope composition (δ18O, δD, d-excess). Samples were taken at 30 positions along a 39 m long transect. The first 20 samples had a spacing of 1 m and the remaining 10 samples had a spacing of 2 m. Sampling was performed every third day for three depth intervals (0-1 cm, 1-4 cm, 4-10 cm) with two one-week periods with daily sampling. The first period was from 8 to 14 June with a sampling of six depth intervals (0-1 cm, 1-2 cm, 2-4 cm, 4-6 cm, 6-8 cm, 8-10 cm) at ten locations (4 m spacing). The second period was from 24 to 30 July with a sampling of six depth intervals (0-0.5 cm, 0.5-1 cm, 1-2 cm, 2-4 cm, 4-6 cm, 6-10 cm) at 25 positions (position 1 - 10 with 1 m spacing, afterwards 2 m spacing). The depth indication in the data set always refers to the mean of each sampling interval. All samples were airtightly stored in high-purity sampling bags (®Whirl-Paks) and kept frozen until measurement.
In the same area, a photogrammetry structure-from-motion approach was performed to generate digital elevation models for each day (Zuhr et al., 2022: https://doi.org/10.5194/tc-15-4873-2021, https://doi.org/10.1594/PANGAEA.936082, https://doi.org/10.1594/PANGAEA.923418). Thus, every sampling position has a depth indication, relative to the snow height of the entire transect.
About 70 % of the samples were measured in the ISOLAB Facility at the Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research, 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 and calibrated on the VSMOW-SLAP scale following 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 0.09 and 0.8 ‰, respectively. 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_p
About 30 % of the samples were measured in the Stable Isotope Laboratory of the institute for Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark. The vaporisation of the sample is performed using a high throughput, low volume vaporiser (Picarro-A0212 – discontinued model as of 2016). The raw isotope measurements are calibrated on the VSMOW-SLAP scale using a two fixed-point calibration similar to Gkinis et al. (2011) and following the IAEA recommended procedures. The mean measurement uncertainty for δ18O and δD derived from a quality control standard was 0.04 and 0.33 ‰, respectively. The detailed sample and data handling are described in Gkinis et al. (2021).
All measurements from both laboratories are reported on the international VSMOW-SLAP (VSMOW and SLAP refer to the International Atomic Energy reference water materials and stand for Vienna Mean Ocean Water and Standard Light Antarctic Precipitation) isotope scale after careful calibration using local standards calibrated against the provided international reference materials.
