This dataset includes concentrations of Particulate Organic Carbon (POC) from the sea water and melt pond water. Samples were collected in August 2018 as part of cruise 2018707, JC1_2, in the northern Barents Sea as part of the Nansen Legacy project. Sea water was sampled at seven different stations using Niskin bottles attached to a rosette onboard R/V Kronprins Haakon. Under-ice water (0.5m) was collected at two stations (gear: Go-Flo Water Sampler) from a hole in the ice. Samples from melt ponds were collected at four stations (five sites) using a bottle. All samples were collected on pre-combusted Whatman GF/F filters. For sea water we prepared duplicate subsamples (250-700 mL). For melt pond water the volume of water was limited and/or the particle load high, the sample volume was reduced (150-500 mL) or occasionally limited to one sample. Filters were air dried and stored at room temperature until analysis on a Flash 2000 Organic Elemental Analyzer (Thermo Scientific). Presented are averaged POC values (in mg m-3). (PON data omitted due to inconsistent results). Standard errors were estimated according to Hozo et al 2005.