Sea ice brines were collected by the sackhole brine collection method. Briefly, sea ice cores were drilled approximately three quarters of the way through the ice column and removed to allow brine from the surrounding sea ice to percolate for collection over several hours. Brines were collected and pooled into 20 L acid-washed and sample rinsed cubitainers for transport to the Barrow Arctic Research Center.

 

Cryopeg brines were collected from discrete boreholes drilled in the floor of the CRREL Ice Mine (also known as the Barrow Permafrost Tunnel). Briefly, permafrost boreholes were drilled with an ethanol-rinsed SIPRE corer, and brines were collected from the boreholes with a sterile vacuum pump apparatus. Detailed notes about cryopeg brine collection can be found in Cooper et al. 2019.

 

Biological abundance samples were fixed in the field immediately after each sample collection with formaldehyde at a final concentration of 2%. All samples were placed in insulated containers and transported to the Barrow Arctic Research Center within a few hours of collection and stored at 4˚C until aliquots were taken for each measurement. Nutrient and isotope aliquots were frozen and stored at -20˚C for transport back to the University of Washington and the University of Alaska Fairbanks. All analytical methods except for isotope measurements are detailed in Cooper et al. 2019