This dataset contains the floe size distribution (FSD) data derived from high-resolution satellite imagery data acquired at two fixed locations in the Arctic Ocean. Satellite imagery data include MEDEA images and WorldView images. These satellite images have a spatial resolution of 1 m or higher, thus providing the FSD information, especially for small floes. The derived data contain floe size (calliper diameter), shape factor, minor/major axis, perimeter and area of the floes. This dataset has been used to evaluate the sea ice models with the FSD parameterisations. The retrieval of the FSD data was done by the University of Huddersfield team. This work was funded by NERC standard grant NE/R000654/1 and NERC MOSAiC program NE/S002545/1.

Collection and preservation of open ocean water samples from stations along a transect up the east coastline of Greenland and then across the Fram Strait to Svalbard during May 2018. The cruise was to observe spring bloom conditions, on board the RRS James Clark Ross. A standard CTD cast was deployed to collect the samples, depths were surface, the chlorophyll maximum and a deep sample, selected to support zooplankton net sampling and other on-board experiments. Research assistants from SAMS (Scottish Association for Marine Science) were responsible for the sample collection on JR17005, Elaine Mitchell of SAMS was responsible for the sample analysis and data processing. Funding was provided from the DIAPOD - NERC thematic grant - Changing Arctic Ocean programme - NE/P006280/1.

The dataset (FSD-GFL-res2m-Preponding) contains sea-ice floe ice distribution (FSD) data derived from the Global Fiducials Library (GFL) imagery during the pre-ponding period at the three fiducial sites, using the algorithms described in Hwang et al. (2017). The GFL imagery is 1-m resolution declassified National Technical Means satellite imagery, also known as the Literal Image Derived Products (LIDPs) (Kwok, 2014). The FSD data derived from the GFL imagery cover the period of 2000 to 2014 at the three fiducial sites at Chukchi Sea (70 deg N and 170 deg W), East Siberian Sea (82 deg N and 150 deg E), and Fram Strait (84.9 deg N and 0.5 deg E). For the production of this dataset, the spatial resolution of the GFL imagery degraded to 2 meters ("res2m") for fast processing. The FSD data are produced for robust model calibration and validation for FSD parameterisations within sea-ice models, and also to improve our understanding of spatial and temporal variations of FSD across the Arctic Ocean. The FSD data have been generated by B. Hwang. This FSD dataset is produced as part of NERC MIZ NE/R000654/1 (Towards a marginal Arctic sea ice cover).

At the basis of the marine Arctic food web, there are several carbon sources including ice-associated (sympagic) algae that live primarily in sea ice, melt ponds or underneath sea ice; pelagic algae that live primarily in open waters; terrestrial detritus that got incorporated into sea ice forming on the Siberian Shelf and being transported with the transpolar drift across the Central Arctic Ocean (CAO); and detritus that derives with currents from the Atlantic ocean. Copepods and amphipods are diverse and often biomass-dominant zooplankton groups in the CAO that include taxa specialised in feeding on algae and small heterotrophs, on sinking detritus or other zooplankton. Gelatinous (cnidaria, appendicularia) and semi-gelatinous (chaetognaths) taxa, ostracods, pteropods, euphausiids and pelagic decapods are other important zooplankton groups in the CAO that likewise feed on a range of food sources. With the loss of Arctic sea ice, the relative importance of ice-associated carbon in the Arctic food web became a central research topic, and multiple trophic marker approaches have been developed to distinguish between pelagic and sympagic carbon transfer to higher trophic levels. During the MOSAiC expedition in the CAO (2019-2020), zooplankton was sampled weekly to fortnightly. A range of nets were used to sample either horizontally underneath the sea ice or vertically from a maximum depth of 2000 m to the surface. Onboard, abundant zooplankton taxa were sorted from each catch, photographed, rinsed with freshwater to remove salt and frozen at -80 degrees Celsius for subsequent analysis of their total dry mass (DM), lipid content, lipid classes and a suite of trophic markers, including bulk stable isotopes (BSI), phytosterols (PS), total fatty acids (TFA), total fatty alcohols (TFAlc), highly-branched isoprenoids (HBI) and the carbon isotopic composition of key FA and FAlc (CSIA-FA; CSIA-FAlc). We had ~10 target species that were sampled in all seasons (the copepods C. hyperboreus, C. glacialis, Metridia longa, the ice amphipods Apherusa glacialis and Eusirus spp., the pelagic amphipods Themisto abyssorum and T. libellula, the euphausiid Thysanoessa spp., chaetognaths and the shrimp H. glacialis). Further zooplankton taxa were collected when available in the net catches and time permitted. Additionally, Polar cod was collected in early and late summer. The initial separation of the various trophic markers was carried out at the University of Plymouth. After estimating the total DM, subsamples for BSI were sent to the Littoral, Environment and Societies Joint Research Unit stable isotope facility (CNRS - University of La Rochelle, France) for analysis. Three internal standards were added to the samples used for lipid analysis to quantify the TFA, TFAlc, PS and HBI content. As a first step, the total lipid content of the animals was extracted in dichloromethane : methanol. The lipid samples were split into two equal subsamples, one was sent to the Alfred-Wegener-Institute (AWI) in Bremerhaven/Germany for FA and FAlc analyses and the second was used for PS and HBI analyses in Plymouth. This dataset is linked to a manuscript that assesses trophic relationships in the CAO to understand the carbon fluxes in the current Arctic food web and to predict potential changes in a future ice-free Arctic. Contributions by KS were funded by the UK's Natural Environment Research Council MOSAiC Thematic project SYM-PEL: "Quantifying the contribution of sympagic versus pelagic diatoms to Arctic food webs and biogeochemical fluxes: application of source-specific highly branched isoprenoid biomarkers"/ (NE/S002502/1). CJA, RGC, CEG, KMS and RJ were funded by the US National Science Foundation Office of Polar Programs (OPP-1824447 and OPP-1824414).