Snow stable water isotopes of a 1 cm deep surface transect at the EastGRIP deep drilling site, summer season 2018

Snow samples were taken on a daily basis along a 100 m wind-parallel transect at the EastGRIP ice core deep drilling site. The snow was collected in the morning at 11 positions with 10 m spacing into three cumulative samples – each for one depth interval. The depth intervals are top 0.5 cm, top 1 cm, and top 2 cm. Each day, undisturbed snow was sampled and the exact sample location was marked to avoid sampling disturbed snow during the next sampling event. The samples were shipped frozen to the Alfred-Wegener-Institut and stored at -25 °C. Prior to measurements, the samples were melted in the sample bags at room temperature. For the measurement of the isotopic composition, a Picarro L2130-i with a high-throughput vaporizer (model A0212) was used. The measurement set-up followed the Van-Geldern protocol. Each sample was injected four times and the standard deviation is computed. We calculate the average over all the standard deviations as a measure of uncertainty. We find this average to be 0.04 permil for δ18O (with stdev 0.02) and 0.13 permil for δD (stdev 0.07). The maximum standard deviation within the data set was found to be 0.14 for δ18O and 0.48 for δD. As a measure of accuracy, the offset between the defined and the measured value of the quality check standard for each measurement run is provided. We calculate the average of this offset for the whole data set and obtain a value of 0.07 permil for δ18O (stdev 0.03) and -0.11 permil for δD (stdev 0.08). The maximum offset found within the data set was 0.12 permil for δ18O and -0.25 permil for δD.