Sediment cores (Rumohr cores) DA17-NG-ST-08-90R, DA17-NG-ST10-109R and DA17-NG-12-134R were collected as part of the NorthGreen expedition to Northeast Greenland in September 2017 onboard the Danish research vessel Dana. The aim of the analysis in this research is to determine the reliability of biomarkers for reconstructing sea-ice conditions in Northeast Greenland. The cores were sampled at 0.5cm resolution for analysis of sea-ice biomarkers (IP25, brassicasterol, dinosterol, campesterol, sitosterol), total organic carbon (TOC). Sea-ice biomarkers were extracted using dichlormethane/methanol (DCM/MeOH, 2:1), followed by ultrasonication. Hexane was then added to the extract and column chromatography undertaken. After purification, samples were analysed using a gas chromatograph Agilent Technologies 7890B GC system (30m DB-1MS column, 0.25 mm i.d., 0.25 μm film thickness) coupled to a mass spectrometer Agilent 5977A MSD (70 eV constant ionization potential, Scan 50–550 m/z, 1 scan/s, ion source temperature 230 °C, Performance Turbo Pump) with the temperature program: 60 °C (3 min), 150 °C (heating rate: 15 °C/min), 320 °C (heating rate: 10 °C/min) and 320 °C (15 min, isothermal). Sterols were measured with a GC Agilent 6850 GC (30m DB-1MS column, 0.25 mm i.d., 0.25 μm film thickness) coupled to an Agilent 5975C VL MSD. For chronological constraint, analyses of natural lead 210Pb and artificial 137Caesium (137Cs) / 205 241Americeum (241Am) radionuclides were carried out by gamma spectrometry with a Ge-detector (BE3830-7500SL-RDC-6-ULB) at IOW and processed with GENIE 2000 software (Canberra Industries Inc., USA). Analysis of mercury (Hg) was undertaken using a DMA-80 Analyzer from MLS Company. This was calibrated against CRM (BCR) 142R certified reference material. Sample weights were 100 mg.
