Dataset: Geochemical data of permafrost brines from the Barrow Permafrost Tunnel in Utqiaġvik, Alaska

Methodology:
Water stable isotopes were measured using a continuous-flow isotope ratio mass spectrometry. pH, salinity, and EC were measured by a LAQUAtwin (HORIBA). Ionic compositions of the brines and selected (melted) samples of massive ice and sediment pore water were determined by ion chromatography. Details of the methodology used for this dataset are described in Iwahana et al. (2021).

Sampling and Analytical Procedures:
We conducted two permafrost (including massive ground ice and frozen sediments) and cryopeg brine sampling campaigns in the permafrost tunnel (71.2945 N, 156.7154 W) in May of 2017 and 2018. We used brushes and spatulas to remove sample remains (ice and frozen or unfrozen sediment) from the geological tools prior to next use to avoid introducing sample material from one hole to another. During every drilling, the sampler was prewashed by massive ground ice until it reached permafrost or the brine-bearing layer. The recovered cores were subsampled into portions of 6 to 12 cm for geochemical analyses. When brine was encountered, we collected it until no further liquid could be withdrawn using a sterile pumping system (described by Cooper et al., 2019 as required for their microbial analyses, and in Supporting Information Text S3 of Iwahana et al., 2021). Collected massive ice and frozen sediments were labeled, packed, transferred without thawing, and kept frozen (below -20 ºC) until further subsampling and analyses (within a year) in the laboratory at the University of Alaska Fairbanks (UAF). All water samples were unfiltered.