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The Fram Strait plays a crucial role in regulating the heat and sea-ice dynamics in the Arctic. In response to the ongoing global warming, the marine biota of this Arctic gateway is experiencing significant changes with increasing advection of Atlantic species. The footprint of this “Atlantification” has been identified in isolated observations across the plankton community, but a systematic, multi-decadal perspective on how regional climate change facilitates the invasion of Atlantic species and affects the ecology of the resident species is lacking. Here we evaluate a series of 51 depth-resolved plankton profiles collected in the Fram Strait during seven surveys between 1985 and 2015, using planktonic foraminifera as a proxy for changes in both the pelagic community composition and species vertical habitat depth. The time series reveals a progressive shift towards more Atlantic species, occurring independently of changes in local environmental conditions. We conclude that this trend is reflecting higher production of the Atlantic species in the “source” region, from where they are advected into the Fram Strait. At the same time, we observe that the ongoing extensive sea-ice export from the Arctic and associated cooling-induced decline in density and habitat shoaling of the subpolarTurborotalita quinqueloba, whereas the residentNeogloboquadrina pachydermapersists. As a result, the planktonic foraminiferal community and vertical structure in the Fram Strait shifts to a new state, driven by both remote forcing of the Atlantic invaders and local climatic changes acting on the resident species. The strong summer export of Arctic sea ice has so far buffered larger plankton transformation. We predict that if the sea-ice export will decrease, the Arctic gateway will experience rapid restructuring of the pelagic community, even in the absence of further warming. Such a large change in the gateway region will likely propagate into the Arctic proper.

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.

To trace spatial variations in Holocene reservoir ages of surface and subsurface waters we studied narrowly spaced 14C records of planktic foraminifera in three high-sedimentation rate cores from the Nordic Seas, the Barents Sea continental margin and eastern Fram Strait. The two northern cores reveal a distinct Early Holocene 14C plateau in dates on the subsurface dweller Neogloboquadrina pachyderma at 9.3–9.1 14C ka. The plateau was tuned to an atmospheric 14C plateau at 9.0–8.7 14C ka that spans 10.2–9.6 calendar ka. These two plateau boundaries provide robust age control points to estimate short-term changes in sedimentation rate and to correlate paleoceanographic signals over 900 km along the West Spitsbergen Current. The difference between planktic and atmospheric 14C plateau ages suggests local 14C reservoir ages of 370–400 yr. Planktic foraminifera species that inhabit different water masses document different reservoir ages. By comparison, the subpolar N. incompta reveals a reservoir age of 150 yr, probably formed in well-mixed Atlantic-sourced waters during winter. The near-surface dweller Turborotalita quinqueloba shows an age of 290 yr in the Fram Strait, but one of 720 yr at the Barents Sea continental margin. The latter age suggests a calcification within old, meltwater-enriched Arctic surface waters admixed by the East Spitsbergen Current. Likewise, we assign an elevated reservoir age of 760 yr on mixed species at a Norwegian Sea site near 71°N to Preboreal meltwaters that spread from northern Norway far west, also documented by the spatial distribution of a coeval δ13C minimum of N. pachyderma.

Highlights • Holocene sea subsurface temperatures after Husum & Hald (2012) estimated from planktic foraminifer fauna in E Fram Strait. • Biomarkers and IP25-derived indices (including DIP25) indicate surface water variability. • Delayed onset of early Holocene conditions in subsurface (∼10.6 ka) compared to surface (∼11.7 ka) water conditions. • Warm Atlantic layer likely occupied uppermost 200 m in eastern Fram Strait between 10 and 9 ka. • Diverging late Holocene trends in surface and subsurface conditions linked to presence of strong pycnocline/stratification. Abstract Two high-resolution sediment cores from eastern Fram Strait have been investigated for sea subsurface and surface temperature variability during the Holocene (the past ca 12,000 years). The transfer function developed by Husum and Hald (2012) has been applied to sediment cores in order to reconstruct fluctuations of sea subsurface temperatures throughout the period. Additional biomarker and foraminiferal proxy data are used to elucidate variability between surface and subsurface water mass conditions, and to conclude on the Holocene climate and oceanographic variability on the West Spitsbergen continental margin. Results consistently reveal warm sea surface to subsurface temperatures of up to 6 °C until ca 5 cal ka BP, with maximum seawater temperatures around 10 cal ka BP, likely related to maximum July insolation occurring at that time. Maximum Atlantic Water (AW) advection occurred at surface and subsurface between 10.6 and 8.5 cal ka BP based on both foraminiferal and dinocyst temperature reconstructions. Probably, a less-stratified, ice-free, nutrient-rich surface ocean with strong AW advection prevailed in the eastern Fram Strait between 10 and 9 cal ka BP. Weakened AW contribution is found after ca 5 cal ka BP when subsurface temperatures strongly decrease with minimum values between ca 4 and 3 cal ka BP. Cold late Holocene conditions are furthermore supported by high planktic foraminifer shell fragmentation and high δ18O values of the subpolar planktic foraminifer species Turborotalita quinqueloba. While IP25-associated indices as well as dinocyst data suggest a sustained cooling due to a decrease in early summer insolation and consequently sea-ice increase since about 7 cal ka BP in surface waters, planktic foraminiferal data including stable isotopes indicate a slight return of stronger subsurface AW influx since ca 3 cal ka BP. The observed decoupling of surface and subsurface waters during the later Holocene is most likely attributed to a strong pycnocline layer separating cold sea-ice fed surface waters from enhanced subsurface AW advection. This may be related to changes in North Atlantic subpolar versus subtropical gyre activity.

Triggered by global climate change, the rapidly changing polar environments increasingly capture public awareness. In the north, Arctic sea-ice opening comes with many opportunities for economic development, transport and tourism but also bears substantial changes and high risks for humans and nature.

The paleoceanographic development of the eastern Fram Strait during the transition from the cold Late Glacial and into the warm Early Holocene was elucidated via a multiproxy study of a marine sediment record retrieved at the western Svalbard slope. The multiproxy study includes analyses of planktic foraminiferal fauna, bulk sediment grain size and CaCO3 content in addition to Mg/Ca ratios and stable isotopes (delta C-13 and delta O-18) measured on the planktic foraminifer Neogloboquadrina pachyderma. Furthermore paleosubsurface water temperatures were reconstructed via Mg/Ca ratios (sSST(Mg/Ca)) and transfer functions (sSST(Transfer)) enabling comparison between the two proxies within a single record. The age model was constrained by four accelerator mass spectrometry (AMS) C-14 dates. From 14,000 to 10,300 cal yr B.P. N. pachyderma dominated the planktic fauna and cold polar sea surface conditions existed. The period was characterized by extensive sea ice cover, iceberg transport and low subsea surface temperatures (sSST(Transfer) similar to 2.1 degrees C; sSST(Mg/Ca) similar to 3.5 degrees C) resulting in restricted primary production. Atlantic Water inflow was reduced compared to the present-day and likely existed as a subsurface current. At ca. 10,300 cal yr B.P. Atlantic Water inflow increased and the Arctic Front retreated north-westward resulting in increased primary productivity, higher foraminiferal fluxes and a reduction in sea ice cover and iceberg transport. The fauna rapidly became dominated by the subpolar planktic foraminifer Turborotalita quinqueloba and summer sSST(Transfer) increased by similar to 3.5 degrees C. Concurrently, the sSST(Mg/Ca) recorded by N. pachyderma rose only similar to 0.5 degrees C. From ca. 10,300 to 8600 cal yr B.F. the average sSST(Mg/Ca) and sSST(Transfer) were similar to 4.0 degrees C and similar to 55 degrees C, respectively. The relatively modest change in sSST(Mg/Ca) compared to sSST(Transfer) can probably be tied to a change of the main habitat depth and/or shift in the calcification season for N. pachyderma during this period.

A sediment core from the West Spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last ~9 ka in the eastern Fram Strait. Our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern Fram Strait occurred stepwise, in response to the postglacial sea-level rise and the related onset of modern sea-ice production on the shallow Siberian shelves. The late Early and Mid Holocene interval (9 to 5 ka) was generally characterized by relatively unstable conditions. High abundance of the subpolar planktic foraminifer species Turborotalita quinqueloba implies strong intensity of Atlantic Water (AW) inflow with high productivity and/or high AW temperatures, resulting in a strong heat flux to the Arctic. A series of short-lived cooling events (8.2, 6.9. and 6.1 ka) occurred superimposed on the warm late Early and Mid Holocene conditions. Our proxy data imply that simultaneous to the complete postglacial flooding of Arctic shallow shelves and the initiation of modern sea-ice production, strong advance of polar waters initiated modern oceanographic conditions in the eastern Fram Strait at ~5.2 ka. The Late Holocene was marked by the dominance of the polar planktic foraminifer species Neogloboquadrina pachyderma, a significant expansion of sea ice/icebergs, and strong stratification of the water column. Although planktic foraminiferal assemblages as well as sea surface and subsurface temperatures suggest a return of slightly strengthened advection of subsurface Atlantic Water after 3 ka, a relatively stable cold-water layer prevailed at the sea surface and the study site was probably located within the seasonally fluctuating marginal ice zone during the Neoglacial period.

International audience; Understanding and responding to the rapidly occurring environmental changes in the Arctic over the past few decades require new approaches in science. This includes improved collaborations within the scientific community but also enhanced dialogue between scientists and societal stakeholders, especially with Arctic communities. As a contribution to the Third International Conference on Arctic Research Planning (ICARP III), the Arctic in Rapid Transition (ART) network held an international workshop in France, in October 2014, in order to discuss high-priority requirements for future Arctic marine and coastal research from an early-career scientists (ECS) perspective. The discussion encompassed a variety of research fields, including topics of oceanographic conditions, sea-ice monitoring, marine biodiversity, land-ocean interactions, and geological reconstructions, as well as law and governance issues. Participants of the workshop strongly agreed on the need to enhance interdisciplinarity in order to collect comprehensive knowledge about the modern and past Arctic Ocean’s geo-ecological dynamics. Such knowledge enables improved predictions of Arctic developments and provides the basis for elaborate decision-making on future actions under plausible environmental and climate scenarios in the high northern latitudes. Priority research sheets resulting from the workshop’s discussions were distributed during the ICARPIII meetings in April 2015 in Japan, and are publicly available online.

A reconstruction of Holocene sea ice conditions in the Fram Strait provides insight into the palaeoenvironmental and palaeoceanographic development of this climate sensitive area during the past 8500 years BP. Organic geochemical analyses of sediment cores from eastern and western Fram Strait enable the identification of variations in the ice coverage that can be linked to changes in the oceanic (and atmospheric) circulation system. By means of the sea ice proxy IP25, phytoplankton-derived biomarkers and ice rafted detritus (IRD) increasing sea ice occurrences are traced along the western continental margin of Spitsbergen throughout the Holocene, which supports previous palaeoenvironmental reconstructions that document a general cooling. A further significant ice advance during the Neoglacial is accompanied by distinct sea ice fluctuations, which point to short-term perturbations in either the Atlantic Water advection or Arctic Water outflow at this site. At the continental shelf of East Greenland, the general Holocene cooling, however, seems to be less pronounced and sea ice conditions remained rather stable. Here, a major Neoglacial increase in sea ice coverage did not occur before 1000 years BP. Phytoplankton-IP25 indices (“PIP25-Index”) are used for more explicit sea ice estimates and display a Mid Holocene shift from a minor sea ice coverage to stable ice margin conditions in eastern Fram Strait, while the inner East Greenland shelf experienced less severe to marginal sea ice occurrences throughout the entire Holocene. Highlights ► Biomarker and IRD data give insight into Holocene sea ice conditions in Fram Strait. ► We find increasing sea ice coverage off West Spitsbergen throughout the Holocene. ► Oceanic/atmospheric variability caused Neoglacial sea ice fluctuations. ► Ice conditions along East Greenland shelf remain rather stable until 1000 years BP.

A multiproxy data set of an AMS radiocarbon dated 46 cm long sediment core from the continental margin off western Svalbard reveals multidecadal climatic variability during the past two millennia. Investigation of planktic and benthic stable isotopes, planktic foraminiferal fauna, and lithogenic parameters aims to unveil the Atlantic Water advection to the eastern Fram Strait by intensity, temperatures, and salinities. Atlantic Water has been continuously present at the site over the last 2,000 years. Superimposed on the increase in sea ice/icebergs, a strengthened intensity of Atlantic Water inflow and seasonal ice-free conditions were detected at ~ 1000 to 1200 AD, during the well-known Medieval Climate Anomaly (MCA). However, temperatures of the MCA never exceeded those of the 20th century. Since ~ 1400 AD significantly higher portions of ice rafted debris and high planktic foraminifer fluxes suggest that the site was located in the region of a seasonal highly fluctuating sea ice margin. A sharp reduction in planktic foraminifer fluxes around 800 AD and after 1730 AD indicates cool summer conditions with major influence of sea ice/icebergs. High amounts of the subpolar planktic foraminifer species Turborotalia quinqueloba in size fraction 150–250 μm indicate strengthened Atlantic Water inflow to the eastern Fram Strait already after ~ 1860 AD. Nevertheless surface conditions stayed cold well into the 20th century indicated by low planktic foraminiferal fluxes. Most likely at the beginning of the 20th century, cold conditions of the terminating Little Ice Age period persisted at the surface whereas warm and saline Atlantic Water already strengthened, hereby subsiding below the cold upper mixed layer. Surface sediments with high abundances of subpolar planktic foraminifers indicate a strong inflow of Atlantic Water providing seasonal ice-free conditions in the eastern Fram Strait during the last few decades.

A 415 cm thick permafrost peat section from the Verkhoyansk Mountains was radiocarbon-dated and studied using palaeobotanical and sedimentological approaches. Accumulation of organic-rich sediment commenced in a former oxbow lake, detached from a Dyanushka River meander during the Younger Dryas stadial, at ∼12.5 kyr BP. Pollen data indicate that larch trees, shrub alder and dwarf birch were abundant in the vegetation at that time. Local presence of larch during the Younger Dryas is documented by well-preserved and radiocarbon-dated needles and cones. The early Holocene pollen assemblages reveal high percentages of Artemisia pollen, suggesting the presence of steppe-like communities around the site, possibly in response to a relatively warm and dry climate ∼11.4–11.2 kyr BP. Both pollen and plant macrofossil data demonstrate that larch woods were common in the river valley. Remains of charcoal and pollen of Epilobium indicate fire events and mark a hiatus ∼11.0–8.7 kyr BP. Changes in peat properties, C31/C27 alkane ratios and radiocarbon dates suggest that two other hiatuses occurred ∼8.2–6.9 and ∼6.7–0.6 kyr BP. Prior to 0.6 kyr BP, a major fire destroyed the mire surface. The upper 60 cm of the studied section is composed of aeolian sands modified in the uppermost part by the modern soil formation. For the first time, local growth of larch during the Younger Dryas has been verified in the western foreland of the Verkhoyansk Mountains (∼170 km south of the Arctic Circle), thus increasing our understanding of the quick reforestation of northern Eurasia by the early Holocene.

Environmental changes in the region connecting the Arctic Ocean and the northern North Atlantic were studied for the last 9,000 years (9 ka) by a combination of proxy-based paleoceanographic reconstructions as well as transient and time-slice simulations with climate models. Today, the area is perennially ice-covered in the west and ice-free in the east. Results show that sea-ice conditions were highly variable on short timescales in the last 9 ka. However, sea-ice proxies reveal an overall eastward movement of the sea-ice margin, in line with a decreasing influence of warm Atlantic Water advected to the Arctic Ocean. These cooling trends were rapidly reversed 100 years ago and replaced by the general warming in the Arctic. Model results show a consistently high freshwater input to the Arctic Ocean during the last 7 ka. The signal is robust against the Holocene cooling trend, however sensitive towards the warming trend of the last century. These results may play a role in the observed Arctic changes.

Sediment core MSM5/5-712 from the West Spitsbergen continental margin has been investigated at high resolution for its seawater-derived neodymium (Nd) and lead (Pb) isotope compositions stored in ferromanganese oxyhydroxide coatings of the sediment particles to reconstruct Holocene changes in the sources and mixing of bottom waters passing the site. The radiogenic isotope data are used in combination with a multitude of proxy indicators for the climatic and oceanographic development of the eastern Fram Strait during the past 8500 years. To calibrate the downcore data, seawater and core top samples from the area were analysed for their radiogenic isotope compositions. Core top leachates reveal relatively high (more radiogenic) Nd isotope compositions between eNd −9.7 and −9.1, which are higher than present-day seawater eNd in eastern Fram Strait (−12.6 to −10.5) and indicate that the seawater values have only been established very recently. The core top data agree well with the downcore signatures within the uppermost 40 cm of the sediment core (eNd −9.1 to −8.8) indicating a reduced inflow of waters from the Nordic Seas, concurrent with cool conditions and a south-eastward shift of the marginal ice zone after ca 2.8 cal ka BP (Late Holocene). High sea-ice abundances in eastern Fram Strait are coeval with the well-known Neoglacial trend in the northern North Atlantic region. In contrast, warmer conditions of the late Early to Mid-Holocene were accompanied by lower (less radiogenic) eNd signatures of the bottom waters indicating an increased admixture from the Nordic Seas (−10.6 to −10.1). A shift to significantly more radiogenic eNd signatures of the detrital material also occurred at 3 cal ka BP and was accompanied by a marked increase in supply of fine-grained ice-rafted material (IRF) from the Arctic Ocean to the core site. The most likely source areas for this radiogenic material are the shallow Arctic shelves, in particular the Kara Sea shelf. The evolution of the Pb isotope compositions of past seawater was dominated by local signatures characterized by high 208, 207, 206Pb/204Pb values during the warm Early and Mid-Holocene periods related to enhanced chemical weathering on Svalbard and high glacial and riverine input derived from young granitic (more radiogenic) material to the West Spitsbergen margin. At 3 cal ka BP both detrital and seawater Pb isotope data changed towards more Kara Sea-like signatures.

The Arctic is responding more rapidly to global warming than most other areas on our planet. Northward-flowing Atlantic Water is the major means of heat advection toward the Arctic and strongly affects the sea ice distribution. Records of its natural variability are critical for the understanding of feedback mechanisms and the future of the Arctic climate system, but continuous historical records reach back only ~150 years. Here, we present a multidecadal-scale record of ocean temperature variations during the past 2000 years, derived from marine sediments off Western Svalbard (79°N). We find that early–21st-century temperatures of Atlantic Water entering the Arctic Ocean are unprecedented over the past 2000 years and are presumably linked to the Arctic amplification of global warming.