Dataset: Under the ice bacterial cultures and genome sequences from the R/V Kronprins Haakon in the Arctic Ocean from May 18 to 21, 2023

Samples for cultivation were collected at 81.04° N, 10.62° E, from 25 meters (m) below the ice/water interface using a Hydro-Bios 2-liter (L) water sampler. Fifty milliliters (mL) were transferred to a polycarbonate bottle and then 1 mL of seawater was amended to 10% (v/v) glycerol, flash frozen in liquid nitrogen, and stored at -80 degrees Celsius (°C) until used for high-throughput dilution to extinction cultivation. Seawater for culture media (10 L) was collected at 80.96° N, 9.66° E from 1 m below the ice/water interface into acid washed and miliQ rinsed cubitainers. Seawater was then filter-sterilized using a tangential flow filtration (TFF) system equipped with a 30 kDa Pellicon XL Polyethersulfone Biomax filter (MilliporeSigma, Burlington, MA). The resulting media was collected in 1 L acid-washed and autoclaved polycarbonate bottles, incubated for 2 months at 4 °C, and checked for bacterial growth to ensure sterility prior to use.