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The lifetime and thickness of Arctic sea ice have markedly decreased in the recent past. This affects Arctic marine ecosystems and the biological pump, given that sea ice acts as platform and transport medium of marine and atmospheric nutrients. At the same time sea ice reduces light penetration to the Arctic Ocean and restricts ocean/atmosphere exchange. In order to understand the ongoing changes and their implications, reconstructions of source regions and drift trajectories of Arctic sea ice are imperative. Automated ice tracking approaches based on satellite-derived sea-ice motion products (e.g. ICETrack) currently perform well in dense ice fields, but provide limited information at the ice edge or in poorly ice-covered areas. Radiogenic neodymium (Nd) isotopes (εNd) have the potential to serve as a chemical tracer of sea-ice provenance and thus may provide information beyond what can be expected from satellite-based assessments. This potential results from pronounced εNd differences between the distinct marine and riverine sources, which feed the surface waters of the different sea-ice formation regions. We present the first dissolved (< 0.45 µm) Nd isotope and concentration data obtained from optically clean Arctic first- and multi-year sea ice (ice cores) collected from different ice floes across the Fram Strait during the RV POLARSTERN cruise PS85 in 2014. Our data confirm the preservation of the seawater εNdsignatures in sea ice despite low Nd concentrations (on average ~ 6 pmol/kg) resulting from efficient brine rejection. The large range in εNd signatures (~ -10 to -30) mirrors that of surface waters in various parts of the Arctic Ocean, indicating that differences between ice floes but also between various sections in an individual ice core reflect the origin and evolution of the sea ice over time. Most ice cores have εNd signatures of around -10, suggesting that the sea ice was formed in well-mixed waters in the central Arctic Ocean and transported directly to the Fram Strait via the Transpolar Drift. Some ice cores, however, also revealed highly unradiogenic signatures (εNd < ~ -15) in their youngest (bottom) sections, which we attribute to incorporation of meltwater from Greenland into newly grown sea ice layers. Our new approach facilitates the reconstruction of the origin and spatiotemporal evolution of isolated sea-ice floes in the future Arctic.

The Polar Prediction Project (PPP, www.polarprediction.net) is a 10-year (2013–2022) endeavour initiated by the World Meteorological Organization’s (WMO) World Weather Research Programme (WWRP). Aim of this wide international endeavour is to promote cooperative weather and sea-ice research enabling development of improved environmental prediction services for the polar regions, on time scales from hours to seasonal.The PPP flagship activity, the Year of Polar Prediction (YOPP), has been launched in mid-2017 as a coordinated two-year period of intensive observing, modelling, verification, user-engagement and education activities. Since then, scientists and operational forecasting centers worldwide have closely worked together to observe, model, and improve forecasts of the Arctic and Antarctic weather and climate systems. During three Special Observing Periods in the Arctic and Antarctic, routine observations such as radiosonde launches and buoy deployments were enhanced (in the Arctic: 1 February ­– 31 March 2018 and 1 July – 30 September 2018, in the Antarctic: 16 November 2018 – 15 February 2019), aiming to close gaps in atmospheric and sea-ice observations and to enable significant progress in environmental prediction capabilities for the polar regions and beyond.in mid-2019, PPP has moved into its Consolidation Phase which will be key for the success of the initiative. Central activities and projects such as the YOPPSiteMIP initiative or the EU-project APPLICATE will significantly contribute to improving forecasts of weather and sea-ice conditions in polar regions and to make them available to its user community. Data collected during YOPP are available for everyone through the YOPP Data Portal (https://yopp.met.no/) to feed into improved environmental forecasting systems.In this presentation, an overview of the main achievements accomplished during the three YOPP Special Observing Periods, current activities including two more Special Targeted Observing Periods (TOPs) as well as prospects for future evaluations of PPP are provided.