DOI: 10.5285/1ad461f3-ac80-447f-9e68-d755bd3e7fb6
title: Multiproxy sediment analysis from marine sediment core PS100-198 collected during the cruise of RV Polarstern, PS100, to northeast Greenland, 2016

description: A 9.5 m long gravity core (PS100-198GC) and 44 cm box core (PS100-198BC) were collected from the same location from a water depth of 398 m from the Norske Trough on the inner continental shelf of NE Greenland. The material was collected during cruise PS100 of the RV Polarstern to NE Greenland in 2016 to investigate the interaction between the Northeast Greenland Ice Stream (NEGIS) and ocean circulation through the Holocene. The following parameters were measured: GEOTEK Multi-Sensor Core Logger (MSCL, gravity core only, Durham University, DU); foraminiferal faunal analysis (DU) and stable isotopes (oxygen and carbon, measured at the NERC National Environmental Isotope Facility); carbon analysis (box core only, DU); dinoflagellate cysts and other palynomorphs (box core only, Geological Survey of Denmark and Greenland, GEUS); sea ice biomarkers (IP25 and HBI III, box core only, University of Helsinki). 

Alfred Wegener Institute (AWI) grant for ship time: AWI_PS100_01; NERC standard grant: NE/N011228/1; NERC National Environmental Isotope Facility grant: IP-1816-0618; NERC Radiocarbon Facility grant: NRCF010001, allocation no. 2113.0418; Independent Research Council Denmark grant to Sofia Ribeiro: 9064-00039B.
description: A box core (PS100-198BC) and Gravity core (PS100-198GC) were collected from the location of PS100-198 during cruise PS100 of the RV Polarstern in 2016 to the Northeast Greenland continental shelf. The cores were split lengthwise, photographed and described on board before being wrapped and stored at 4°C. Box and gravity core were x-rayed using a GEOTEK XCT scanner at Durham University. The gravity core was passed through a GEOTEX Multi-Sensor Core Logger at Durham University. Detailed methodology for the range of analyses undertaken is provided below:

Foraminiferal analysis: a sample volume of between 0.5 and 4 ml of sediment was soaked in deionised water for several hours then washed through 500 µm and 63 µm mesh sieves. The material retained on the 63 µm sieve was retained for foraminiferal analysis. Foraminifera were picked and counted from the wet residue under a binocular microscope immediately to reduce damage to agglutinated specimens and smaller, more fragile calcareous specimens.

Dinoflagellate cyst analysis: Samples for marine palynological analyses were taken from the box-core only, at a resolution of 2 cm for the upper 22 cm, and 2-4 cm for the lowermost part of the core (total of 18 samples). For each sample, 2-4 g of freeze-dried sediment were prepared at the Geological Survey of Denmark and Greenland, following a standard protocol and using the Lycopodium marker-grain method (Mertens et al. 2009). One Lycopodium-spore tablet was added to each sample prior to acid treatment. Acid treatment included removal of carbonates with room temperature 2 M hydrochloric acid (HCl) (for 24 hours) and removal of silicates with room temperature hydrofluoric acid (40 % HF) for up to 48 hours, followed by an additional HCl treatment (24 hours). The samples were then gently ultra-sonicated (30-45 sec), sieved and rinsed through an 11 µm-mesh nylon filter and pH neutralized. The organic residue was collected and mounted on a microscope slide with glycerol gelatin using a heating plate. Slides were analyzed with an upright light microscope (Olympus BX51/BX60) using Differential Interference Contrast (DIC) optics at 400x or 1000x magnification. Data presented here include relative abundances of the dinocyst taxa, concentrations of Halodinium spp. and total dinocyst concentrations as calculated by the marker-grain method.

Diatom analysis: Samples for diatom analysis were taken from the box core only, at 2 cm resolution. Diatom slides for identification and enumeration were prepared using standard palaeoecological methods (Battarbee, 1986) at the Marine Biology Laboratory, University of Helsinki. The sediment samples were treated with 30% hydrogen peroxide for 4 hours to remove organic material and with 10% hydrochloric acid to remove carbonates, and subsequently rinsed 4 times with deionized water. After the last rinse, a known concentration of microspheres was added into each sample for calculating diatom concentrations. A few drops of the cleaned sample were left to dry on cover slips and mounted onto permanent glass slides with Naphram(TM). Diatom taxa were identified with a Zeiss Axio Imager.A2 research microscope, Plan-Apochromat oil immersion objective, phase contrast optics and a total magnification of x1000.
Sea ice biomarker analysis: A total of 20 samples were taken from the box core only (every 2 cm) and processed for HBI analysis (IP25 and HBI III) following the protocol described by Belt et al. (2019). An internal standard (9-octylheptadecene) was added to ~0.5 g of the freeze-dried and homogenized sediment samples before analytical treatment. Total lipids were ultrasonically extracted (3 times) using a mixture of dichloromethane (DCM: CH2Cl2) and methanol (MeOH) (2:1, v/v). Extracts were pooled together, and the solvent was removed by evaporation under a slow stream of nitrogen. The total extract was subsequently suspended in hexane and purified through open column chromatography (SiO2). HBIs were eluted using hexane (8 mL). Procedural blanks and standard sediments were analyzed every 15 samples. Hydrocarbon fractions were analyzed using an Agilent 7890 gas chromatograph (GC) fitted with 50m fused silica Agilent J&C GC columns (0.25 mm internal diameter and 0.25 µm phase thickness) and coupled to an Agilent 5975C Series mass selective detector. Oven temperatures were programmed as follows: 40-300°C at 10°C min-1, followed by an isothermal interval at 300°C for 10 min. The data were collected using ChemStation and analyzed using MassHunter quantification software. IP25 was identified on the basis of retention time and comparison of mass spectra with authenticated standards. Abundances were obtained by comparison of individual GC-mass spectrometry responses against those of the internal standard and concentrations are reported in ng g-1. Response factors of the internal standard vs. IP25 were determined prior and after each analytical sequence (every 15 samples). The extraction and analytical error on the measurements, determined from measurements of standard sediments is ± 8%. 
Carbon analysis: The concentration of Total Carbon (TC), Total Organic Carbon (TOC) and Total Inorganic Carbon (TIC) was measured from 41 samples taken at 1 cm intervals from the box core only, using an Analytik Jena Multi Elemental Analyser 4000. For each sample sediment was freeze-dried and ball milled and weighed into ceramic boats (20 - 30 mg for TC, 40 - 50 mg for TIC). Samples for TC were combusted at a high temperature (1000 - 1500 °C) in the presence of oxygen. Samples for TIC were first treated with 40% orthophosphoric acid to remove the organic carbon component before combustion at high temperature (1000 - 1500°C) in the presence of oxygen. In both cases the gas generated from the burning of the sample is detected by a NDIR (Non-Dispersive Infrared) detector. The instrument measures TC and TIC, then calculates TOC of the sample from the difference between TC and TIC values.
Foraminiferal stable isotope analysis: Oxygen (expressed as δ18O) and carbon (as δ13C) isotopic analyses were carried out separately on benthic and planktic foraminifera from both box core and gravity core. Approximately 20 specimens of the benthic species, Cassidulina neoteretis, and the planktic species Neogloboquadrina pachyderma were picked and measured where possible. Analyses were carried out using an IsoPrime mass spectrometer with a Multicarb preparation system at the Stable Isotope Facility in the British Geological Survey. Stable isotope results were calibrated to the VPDB scale of international standards with an analytical precision for both isotopes of &gt; ± 0.05‰.
description: Sediment cores collected using a box corer and gravity corer. Core scanning data were collected using a GEOTEK XCT scanner and GEOTEK Multi-Sensor Core Logger. Total organic and total inorganic carbon was measured using an Analytik Jena Multi Elemental Analyser 4000. Foraminiferal stable isotope analyses were carried out using an Iso-Prime mass spectrometer with a Multicarb preparation system. For organic geochemistry hydrocarbon fractions were analyzed using an Agilent 7890 gas chromatograph (GC) fitted with 50 m fused silica Agilent J&C GC columns (0.25 mm internal diameter and 0.25 mm phase thickness) and coupled to an Agilent 5975C Series mass selective detector. The data were collected using ChemStation and analyzed using MassHunter quantification software.
description: For all microfossil groups (benthic foraminifera and dinocysts) a target count of 300 individuals was set. However, this was not always possible, but the total specimens counted is quoted for all samples. Some samples were also barren. Stable isotope results were calibrated to the VPDB scale of international standards with analytical precision for both isotopes of &gt; ± 0.05‰. For organic geochemical analysis, the sea ice biomarker IP25 was identified on the basis of retention time and comparison of mass spectra with authenticated standards. The extraction and analytical error on the measurements, determined from measurements of standard sediments, is ± 8 %.

Sample resolution through the box core was every 1 cm for foraminiferal faunal and stable isotope analysis and every 2 cm for dinocysts, carbon and organic geochemistry (IP25). Analysis through the gravity core was restricted to foraminiferal faunal and stable isotope analyses. Sample resolution through the gravity core varied from every 4 cm (44 - 98 cm), decreasing to 16 cm from approximately 100 - 200 cm, then every 100 cm from 200 - 900 cm. The temporal resolution of sampling varied due to changing sedimentation rates as identified by the core age model.