(Table S1) General information of solid phase extracted dissolved organic matter from porewater and overlying bottom water collected during Maria S. Merian cruise MSM29 and Polarstern cruise PS85 to the Fram Strait

Molecular analysis of dissolved organic matter in overlying bottom water and porewater was performed on a Solarix FT-ICR-MS equipped with a 15 Tesla superconducting magnet (Bruker Daltonic) using an electrospray ionization source (Bruker Apollo II) in negative ion mode. Molecular formula calculation for all samples was performed using a Matlab (2010) routine that searches, with an error of < 0.5 ppm, for all potential combinations of elements including the elements C∞, O∞, H∞, N ≤ 4; S ≤ 2 and P ≤ 1. Combination of elements NSP, N2S, N3S, N4S, N2P, N3P, N4P, NS2, N2S2, N3S2, N4S2, S2P was not allowed. Mass peak intensities are normalized relative to the total molecular formulas in each sample according to previously published rules (Rossel et al., 2015; doi:10.1016/j.marchem.2015.07.002). Additionally, the contribution of molecular formulas with different elemental composition (carbon = C; hydrogen = H; oxygen = O; nitrogen = N; sulfur = S; phosphorus = P) is expressed as a percentage of the total intensity in each sample. Furthermore, in this table,Molecular weight~wa~ was calculated considering the intensity of the mass peak in each sample (i.e. wa stands for intensity weighted-average).