First-year and second-year sea-ice samples were collected during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate, PS122) expedition in the central Arctic Ocean. Ice cores were retrieved using a Mark II ice coring system (Kovacs Enterprises, Inc., Indianapolis, USA). The cores were segmented at 10-cm intervals, and the sections were pooled by depth layer and melted in filtered seawater. Particulate combined carbohydrate (PCCHO) concentrations were determined from particulate material retained on 0.2 µm polycarbonate membrane filters. After acid hydrolysis, samples were analyzed using high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), following Zeppenfeld et al. (2020). All concentrations were corrected for the dilution factor resulting from melting the ice sections with filtered seawater. PCCHO concentrations were quantified as the sum of their constituent monosaccharides, including arabinose, glucose, galactose, glucosamine, galactosamine, muramic acid, galacturonic acid, and others.We thank all Polarstern scientists and crew involved in seawater sampling during MOSAiC, with special thanks to the scientists of the ECO team.

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