The Arctic is undergoing unprecedented environmental transformation, with temperatures rising nearly four times faster than the global average. These dramatic changes, such as melting ice, extensive wildfires, and shifting ecosystems, demand a coordinated, adaptive, and inclusive approach to environmental monitoring. This requires a shift away from fragmented and siloed efforts and towards a more cohesive network. One that is inclusive of scientific knowledge, Indigenous Knowledge, and local knowledge, while delivering actionable knowledge for decision-makers, businesses, researchers, and local people alike. Arctic PASSION, an EU and Canadian funded initiative, has spent the past four and a half years working together in international collaboration to build this vision by strengthening the components and connection of the many observing systems that make up the Arctic Observing System of Systems (AOSS). By doing so Arctic PASSION has enhanced our capacity to monitor, interpret, and respond to Arctic change in ways that are both scientifically robust and socially relevant. At its core, the AOSS addresses a fundamental challenge: no single organisation or technology can comprehensively monitor the vast, complex Arctic environment. Instead, the system connects diverse observing efforts, from satellite networks to community-based monitoring, into an interconnected framework that produces reliable, accessible information for climate adaptation, sustainable resource management, and emergency response. Arctic PASSION has significantly advanced this system by fostering inclusive governance structures that empower Indigenous Peoples and Arctic residents as equal partners in observation design and implementation.The project's co-creation of the Event Database of Community-Based Monitoring stands as a groundbreaking achievement, preserving and presenting previously unreleased Indigenous Knowledge while providing unprecedented insights into Arctic environmental change. Similarly, the establishment of Shared Arctic Variables Expert Panels has created structured platforms where Indigenous knowledge holders collaborate with scientists to define observing priorities that reflect both cultural values and scientific rigor. The project has also significantly advanced how Arctic data is collected, processed, and utilized for society. Through innovative services such as the Arctic Landscape EXplorer (ALEX) for permafrost monitoring, the Integrated Fire Risk Management (INFRA) service for wildfire information and many more, Arctic PASSION has demonstrated how observations can be transformed into practical tools for community resilience and policy development. These services, partly co-designed with Indigenous communities and local authorities, exemplify the project's commitment to making data not just available, but truly actionable. The enhancement of data interoperability, semantic mapping and catering the SAON Data Portal has further ensured that Arctic information can flow seamlessly between scientific repositories and decision-making processes, adhering to both FAIR, CARE and TRUST principles to maintain ethical standards and cultural relevance.In the field of Arctic observation and monitoring governance Arctic PASSION has played a pivotal role in strengthening international coordination. The project's successful advocacy for 'GEO Convener' status for Arctic GEOSS has elevated the region's profile in global observing systems, while its support for the Arctic Ocean Regional Alliance (ArORA) and the expansion of the Distributed Biological Observatory (DBO) concept has established a stable framework for marine observations, and the support of INTERACT has strengthened the terrestrial network. Intense interaction with local and regional policy and decision-making players offered important insights into their needs and their offerings. These governance advancements have been complemented by efforts to maintain dialogue during geopolitical disruptions, ensuring that Arctic observing remains a collaborative endeavour even in challenging circumstances. Looking ahead, the future of the AOSS must build on such foundations while addressing persistent challenges. Sustainable, long-term funding remains critical to maintain observing networks that can detect and respond to Arctic changes over decades rather than project cycles. The inclusion of Indigenous Peoples and other Arctic residents must continue to evolve from consultation to genuine co-leadership, with simplified and accordingly realigned funding processes. Holistic approaches including different Knowledge Systems are needed and require open minds and capacity building on all sides. Science - policy/decision-making communication channels need strengthening to ensure that research informs action and that societal needs guide observing priorities. Advances in technologies like AI, autonomous systems and community-based monitoring will reshape the AOSS. These and other developments must be carefully balanced with ethical considerations and Indigenous data sovereignty principles.The Arctic PASSION experience has shown that building a truly effective observing system requires more than technical solutions, it demands trust, meaningful engagement, and a commitment to equity at every level. Our project's most relevant legacy lies not just in the tools and services it has developed, but in the collaborative relationships it has fostered between scientists, Indigenous communities, and local decision- and policymakers. As climate change continues to reshape the Arctic at an accelerating pace, this integrated, inclusive approach to observing will be essential for developing the resilience and adaptive capacity needed to navigate the challenges ahead. The time has come to transition from demonstration projects to sustained implementation, ensuring that the AOSS becomes a funded, permanent, yet evolving system that serves both the Arctic and the global community for the future.

Understanding changing levels of risk exposure for vessels in Arctic waters has become highly relevant due to the increasingly variable ice conditions and increased interest for economic and geopolitical purposes. This paper presents the first systematic evaluation of the changing levels of navigational risk exposure among ships operating in Arctic waters from 2015 to 2021. By combining historic sea ice conditions, ship position data, and ship attribute data such as ice strengthening, and using International Maritime Organization’s Polar Operational Limit Assessment Risk Indexing System risk index outcome function, we are able to better understand the varying levels of risk exposure over time, across geographic regions and among different vessel types. There has been more than a doubling of in Arctic maritime operations in ice covered waters over the six-year study period. Despite increases in activity levels, overall risk exposure is decreasing in part due to changing sea ice conditions. However, risk exposure is higher among certain vessel types and regions including among fishing, cargo, and tourism vessels in the Kara Sea, Norwegian Sea north-west of Svalbard, in Baffin Bay, in the eastern Bering Sea, and to a lesser extent in North Labrador and Hudson Strait in Canada.

The Atlantic Meridional Overturning Circulation (AMOC) plays a central role in the climate system by transporting and redistributing heat to depth, thereby regulating the effective heat capacity of the ocean under global warming. Observations and projections indicate a potential decline of the AMOC in response to climate change, with far-reaching climate consequences. The Nordic Seas are a key region for the overturning circulation, as dense water formation north of the Greenland–Scotland Ridge feeds the lower limb of the AMOC.Within this context, the ARCTIC-FLOW project aims to improve our understanding of water mass transformation and overturning processes in the Nordic Seas. The project focuses on identifying the main regions of surface water transformation, quantifying water mass transformation rates, characterizing the temporal and spatial scales of dense water formation, and assessing the impact of extreme freshening events across different subregions of the Nordic Seas.To support these objectives, we have developed a novel 11-year satellite-based time series of freshwater and density fluxes for the Arctic and sub-Arctic regions. This dataset is derived from the combination of satellite sea surface salinity, sea surface temperature, and surface velocity fields, together with information on mixed layer depth. The satellite products are evaluated and complemented using an extensive set of in situ observations and results from numerical model experiments.In this contribution, we will present preliminary results on the variability of the newly developed satellite-derived density flux product, highlighting its relevance for studying variability of water-mass transformation processes in the Nordic Seas.

Fram Strait is one of the main gateways for fresh water leaving the Arctic Ocean toward the deep-water formation regions of the North Atlantic. Monitoring transport through Fram Strait is important to quantify the impact of Arctic amplification on the hydrography in lower latitudes. We update existing time series from the moorings in the western Fram Strait and investigate the monthly and interannual variability of the liquid freshwater transport (FWT, reference salinity 34.9), volume transport and freshwater content between 2003 and 2020. We examine composites and correlations of sea-level pressure (SLP) reanalysis, and remote-sensing dynamic-ocean topography (DOT) in the Arctic Ocean. We identify two remote forcing mechanisms of FWT: (a) North Pole convergence freshens the region north of Fram Strait 13-24 months before high FWT events. (b) Beaufort Gyre weakening allows spreading of fresh water to the margins of the Arctic Basin zero to 9 months before high FWT events. In addition a third mechanism occurs locally, (b) Fram Strait northerly winds confine freshwater to the Greenland shelf and drive stronger southward FWT. Additionally, we find a decreasing trend in the total volume transport, concurrent with weakening northerly winds and reducing north-south DOT gradient across the strait. We also examined correlations between the Fram Strait time series and the Arctic Oscillation and Arctic Ocean Oscillation. Both are found to correlate positively with the total volume transport, while the Arctic Oscillation correlates negatively with FWT with 1-year lag. The East Greenland Current brings fresh water from the central Arctic Ocean to lower latitudes. The exported fresh water affects stratification, and can contribute to variations of the global meridional overturning circulation. In Fram Strait, between Greenland and Svalbard, the properties of this current have been systematically monitored using moored instruments. We present updated time series of freshwater transport from the moorings in the Fram Strait, and analyze their variability between 2003 and 2020. We identify three mechanisms that contribute to high freshwater transport in the Strait. (a) 13-24 months before, clockwise wind anomalies in the Eurasian Arctic drive converging current anomalies and freshen the area preconditioning fresh outflow events. (b) 0-9 months before, anticlockwise wind anomalies in the Canadian Arctic drive diverging current anomalies directing fresh water to the periphery and Fram Strait. (c) Northerly winds over the strait drive southward transport instantly. We find additionally that total volume transport in the Fram Strait decreases in relation to weakening northerlies that could be a result of a warming Greenland. Fram Strait local northerly winds force instant southward volume and freshwater transport Arctic Ocean large-scale wind variability forces two distinguished lagged responses of freshwater content and transport in Fram Strait Between 2004 and 2019 freshwater transport shows no trend but total volume transport of the East Greenland Current decreases by similar to 0.1 SV/year

As Arctic sea ice deteriorates, more light enters the ocean, causing largely unknown effects on the ecosystem. Using an autonomous biophysical observatory, we recorded zooplankton vertical distribution under Arctic sea ice from dusk to dawn of the polar night. Here we show that zooplankton ascend into the under-ice habitat during autumn twilight, following an isolume of 2.4 × 10 −4 W m −2 . We applied this trigger isolume to CMIP6 model outputs accounting for incoming radiation after sunset and before sunrise of the polar night. The models project that, in about three decades, the total time spent by zooplankton in the under-ice habitat could be reduced by up to one month, depending on geographic region. This will impact zooplankton winter survival, the Arctic foodweb, and carbon and nutrient fluxes. These findings highlight the importance of biological processes during the twilight periods for predicting change in high-latitude ecosystems.

Abstract As Arctic sea ice deteriorates, more light enters the Arctic Ocean, causing largely unknown effects on the ecosystem. A novel autonomous bio-physical observatory provided the first record of zooplankton vertical distribution under sea ice drifting across the Arctic Ocean from dusk to dawn of the polar night. Its measurements revealed that zooplankton ascend into the under-ice layer during autumn twilight, following an isolume of 5.5 10-4 W m-2. We applied this trigger isolume to IPCC models enabled to incorporate incoming radiation after sunset and before sunrise of the polar night. The models project that, in about three decades, the total time spent by zooplankton in the under-ice layer will be reduced by up to one month, depending on geographic region. This will impact zooplankton winter survival, the Arctic foodweb, carbon- and nutrient fluxes. These findings highlight the importance of processes in the twilight periods for predicting change in high-latitude ecosystems.

The spatial distributions of anthropogenic 129I and natural 127I in iodide (I−) and iodate (IO3−) of anthropogenic 129I and natural 127I were investigated in the upper central Arctic Ocean. The results show that the molecular ratios of reductive iodide (I−) to oxidative iodate (IO3−) ranged from 0.228 to 0.560 for 127I and 0.383 to 0.827 for 129I in the Polar Mixed Layer (PML). Greater 127I− concentrations and markedly higher I−/IO3− ratios for both 129I and 127I were found in the PML over the Lomonosov and Alpha Ridges. This suggests that the in-situ formation of I− occurs as a result of enhanced reductive environments at these locations due to bacterial-mediated decomposition of dissolved organic matter (DOM) that likely originates from the inflow of river water into the central Arctic Ocean. Ratios of 129I−/129IO3− and 127I−/127IO3− decrease gradually along the main transport pathway of the Atlantic water, revealing that I− is gradually oxidized back to IO3− at a slow net rate within the Atlantic Water Layer. Our study provides insights into the marine geochemical cycling of iodine and raises the potential for iodine species, notably of 129I, to be used as indicators of changes in the redox condition of surface water in the Arctic Ocean, which may occur due to the predicted impacts of climate change.

Arctic Ocean gateway fluxes play a crucial role in linking the Arctic with the global ocean and affecting climate and marine ecosystems. We reviewed past studies on Arctic–Subarctic ocean linkages and examined their changes and driving mechanisms. Our review highlights that radical changes occurred in the inflows and outflows of the Arctic Ocean during the 2010s. Specifically, the Pacific inflow temperature in the Bering Strait and Atlantic inflow temperature in the Fram Strait hit record highs, while the Pacific inflow salinity in the Bering Strait and Arctic outflow salinity in the Davis and Fram straits hit record lows. Both the ocean heat convergence from lower latitudes to the Arctic and the hydrological cycle connecting the Arctic with Subarctic seas were stronger in 2000–2020 than in 1980–2000. CMIP6 models project a continuing increase in poleward ocean heat convergence in the 21st century, mainly due to warming of inflow waters. They also predict an increase in freshwater input to the Arctic Ocean, with the largest increase in freshwater export expected to occur in the Fram Strait due to both increased ocean volume export and decreased salinity. Fram Strait sea ice volume export hit a record low in the 2010s and is projected to continue to decrease along with Arctic sea ice decline. We quantitatively attribute the variability of the volume, heat, and freshwater transports in the Arctic gateways to forcing within and outside the Arctic based on dedicated numerical simulations and emphasize the importance of both origins in driving the variability.

The Arctic marine ecosystem is shaped by the seasonality of the solar cycle, spanning from 24-h light at the sea surface in summer to 24-h darkness in winter. The amount of light available for under-ice ecosystems is the result of different physical and biological processes that affect its path through atmosphere, snow, sea ice and water. In this article, we review the present state of knowledge of the abiotic (clouds, sea ice, snow, suspended matter) and biotic (sea ice algae and phytoplankton) controls on the underwater light field. We focus on how the available light affects the seasonal cycle of primary production (sympagic and pelagic) and discuss the sensitivity of ecosystems to changes in the light field based on model simulations. Lastly, we discuss predicted future changes in under-ice light as a consequence of climate change and their potential ecological implications, with the aim of providing a guide for future research.

Arctic sea ice is shifting from a year-round to a seasonal sea ice cover. This substantial transformation, via a reduction in Arctic sea ice extent and a thinning of its thickness, influences the amount of light entering the upper ocean. This in turn impacts under-ice algal growth and associated ecosystem dynamics. Field campaigns have provided valuable insights as to how snow and ice properties impact light penetration at fixed locations in the Arctic, but to understand the spatial variability in the under-ice light field there is a need to scale up to the pan-Arctic level. Combining information from satellites with state-of-the-art parameterizations is one means to achieve this. This study combines satellite and modeled data products to map under-ice light on a monthly time-scale from 2011 through 2018. Key limitations pertain to the availability of satellite-derived sea ice thickness, which for radar altimetry, is only available during the sea ice growth season. We clearly show that year-to-year variability in snow depth, along with the fraction of thin ice, plays a key role in how much light enters the Arctic Ocean. This is particularly significant in April, which in some regions, coincides with the beginning of the under-ice algal bloom, whereas we find that ice thickness is the main driver of under-ice light availability at the end of the melt season in October. The extension to the melt season due to a warmer Arctic means that snow accumulation has reduced, which is leading to positive trends in light transmission through snow. This, combined with a thinner ice cover, should lead to increased under-ice PAR also in the summer months.

Arctic observing and data systems have been widely recognized as critical infrastructures to support decision making and understanding across sectors in the Arctic and globally. Yet due to broad and persistent issues related to coordination, deployment infrastructure and technology gaps, the Arctic remains among the most poorly observed regions on the planet from the standpoint of conventional observing systems. Sustaining Arctic Observing Networks (SAON) was initiated in 2011 to address the persistent shortcomings in the coordination of Arctic observations that are maintained by its many national and organizational partners. SAON set forth a bold vision in its 2018 – 28 strategic plan to develop a roadmap for Arctic observing and data systems (ROADS) to specifically address a key gap in coordination efforts—the current lack of a systematic planning mechanism to develop and link observing and data system requirements and implementation strategies in the Arctic region. This coordination gap has hampered partnership development and investments toward improved observing and data systems. ROADS seeks to address this shortcoming through generating a systems-level view of observing requirements and implementation strategies across SAON’s many partners through its roadmap. A critical success factor for ROADS is equitable participation of Arctic Indigenous Peoples in the design and development process, starting at the process design stage to build needed equity. ROADS is both a comprehensive concept, building from a societal benefit assessment approach, and one that can proceed step-wise so that the most imperative Arctic observations—here described as shared Arctic variables (SAVs)—can be rapidly improved. SAVs will be identified through rigorous assessment at the beginning of the ROADS process, with an emphasis in that assessment on increasing shared benefit of proposed system improvements across a range of partnerships from local to global scales. The success of the ROADS process will ultimately be measured by the realization of concrete investments in and well-structured partnerships for the improved sustainment of Arctic observing and data systems in support of societal benefit.

With rapid sea-ice decline, ocean warming and increasing Atlantic inflow, the ecosystem of the Central Arctic Ocean (CAO) is experiencing an unprecedented, potentially disruptive transformation. While this transformation is affecting the biodiversity of marine communities and the ecosystem functions they fulfil, major knowledge gaps about the distribution of pelagic macrofauna (zooplankton and fish) complicate the assessment of the impact of this transformation on biodiversity and marine resources. The largest blind spot remains in the central Arctic Basin, which has been difficult to sample with large sampling gear such as fishing nets due to a year-round ice coverage. However, in the face of increasing human activities and international efforts to implement marine management in the CAO, it becomes important to monitor pelagic fauna in this remote area. One possibility to enable a better sampling of pelagic macrofauna is to use sea-ice thethered autonomous observatories. Within the British/German project EcoLight, we developed a new autonomous sea-ice observatory comprising an ASL Acoustic Zooplankton and Fish Profiler (AZFP). The device has 4 frequencies targeting different size classes of animals. It samples automatically at predefined intervals and transmits the data to a server in Europe via Iridium. It is possible to change the sampling parameters via a remote connection at any time. The AZFP buoy was deployed in the CAO in September 2020, shortly before the end of the MOSAiC expedition. Since then, the buoy has been recording the vertical zooplankton distribution in the water column under the ice. First data show a light-induced change of the vertical distribution of scatterers, transitioning from deep distribution during the polar day, through a short period of diel vertical migration during the twilight period, to a constant presence of scatterers in the surface layer in the polar night. Furthermore, AZFP data suggest an enhancement of zooplankton between the upper pycnocline and ~50 m depth during in an eddie transition. The data collected by the EcoLight AZFP buoy constitute the first hydroacoustic record of zooplankton distribution near the North Pole sampled with a fully autonomous system in the absence of disturbing light sources. They demonstrate the feasibility of year-round automated monitoring of macrofauna in the CAO in relation to environmental properties. Similar autonomous devices may serve as key elements in the future monitoring of biological resources in the CAO and other inaccessible areas.

Anthropogenic chemical tracers are powerful tools to study pathways, water mass provenance and mixing processes in the ocean. Releases of the long-lived anthropogenic radionuclides 129I and 236U from European nuclear reprocessing plants label Atlantic Water entering the Arctic Ocean with a distinct signal that can be used to track pathways and timescales of Atlantic Water circulation in the Arctic Ocean and Fram Strait. Apart from their application as transient tracers, the difference in anthropogenic radionuclide concentrations between Atlantic- and Pacific-origin water provides an instrument to distinguish the interface between both water masses. In contrast to classically used water mass tracers such as nitrate-phosphate (N:P) ratios, the two radionuclides are considered to behave conservatively in seawater and are not affected by biogeochemical processes occurring in particular in the broad shelf regions of the Arctic Ocean. Here we present a time-series of 129I and 236U data across the Fram Strait, collected in 2016 (as part of the GEOTRACES program) and in 2018 and 2019 (by the Norwegian Polar Institute). While the overall spatial distribution of both radionuclides was similar among the three sampling years, significant differences were observed in the upper water column of the EGC, especially between 2016 and 2018. This study is the first attempt to investigate the potential of 129I and 236U as water mass composition tracers in the East Greenland Current (EGC). We discuss how the 129I - 236U tracer pair can be applied to estimate fractions of Atlantic and Pacific Water, especially considering their time-dependent input into the Arctic Ocean.

129I measurements on samples collected during GEOTRACES oceanographic missions in the Arctic Ocean in 2015 have provided the first detailed, synoptic 129I sections across the Eurasian, Canada and Makarov Basins. 129I is discharged from European nuclear fuel reprocessing plants since several decades and is carried north into the Arctic Ocean with waters of Atlantic origin. Here the measurements of its passage can be used to identify the ocean circulation at different depth horizons. Elevated 129I levels measured over the Lomonosov and Alpha-Mendeleyev Ridges in 2015 were associated with tracer labeled, Atlantic-origin water bathymetrically steered by the ridge systems through the central Arctic while lower 129I levels were evident in the more poorly ventilated basin interiors. 129I levels of 200-400 x 107 at/l measured in intermediate waters had increased by a factor of 10 compared to results from the same locations in 1994-1996 owing to the arrival of a strong increase in the discharges from La Hague, that occurred during the 1990s. Comparisons of the patterns of 129I between the mid-1990s and 2015 delineate large scale circulation changes that occurred during the shift from a positive Arctic Oscillation and a cyclonic circulation regime in the mid-1990s to anticyclonic circulation in 2015. These are characterized by a broadened Beaufort Gyre in the upper ocean, a weakened boundary current and partial AW flow reversal in the southern Canada Basin at mid-depth. Tracer 129I simulations using the coupled ocean-sea ice model NAOSIM agree with both, the historical 129I results and recent GEOTRACES data sets, thereby lending context and credibility to the interpretation of large-scale changes in Arctic circulation and their relationship to shifts in climate indices revealed by the tracer 129I distributions. We will present measurements and simulation results of 129I for the 1990s and 2015 and put them into the context of ocean circulation responses to changing atmospheric forcing regimes.

In September 2019, the research icebreaker Polarstern started the largest multidisciplinary Arctic expedition to date, the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift experiment. Being moored to an ice floe for a whole year, thus including the winter season, the declared goal of the expedition is to better understand and quantify relevant processes within the atmosphere–ice–ocean system that impact the sea ice mass and energy budget, ultimately leading to much improved climate models. Satellite observations, atmospheric reanalysis data, and readings from a nearby meteorological station indicate that the interplay of high ice export in late winter and exceptionally high air temperatures resulted in the longest ice-free summer period since reliable instrumental records began. We show, using a Lagrangian tracking tool and a thermodynamic sea ice model, that the MOSAiC floe carrying the Central Observatory (CO) formed in a polynya event north of the New Siberian Islands at the beginning of December 2018. The results further indicate that sea ice in the vicinity of the CO (<40 km distance) was younger and 36 % thinner than the surrounding ice with potential consequences for ice dynamics and momentum and heat transfer between ocean and atmosphere. Sea ice surveys carried out on various reference floes in autumn 2019 verify this gradient in ice thickness, and sediments discovered in ice cores (so-called dirty sea ice) around the CO confirm contact with shallow waters in an early phase of growth, consistent with the tracking analysis. Since less and less ice from the Siberian shelves survives its first summer (Krumpen et al., 2019), the MOSAiC experiment provides the unique opportunity to study the role of sea ice as a transport medium for gases, macronutrients, iron, organic matter, sediments and pollutants from shelf areas to the central Arctic Ocean and beyond. Compared to data for the past 26 years, the sea ice encountered at the end of September 2019 can already be classified as exceptionally thin, and further predicted changes towards a seasonally ice-free ocean will likely cut off the long-range transport of ice-rafted materials by the Transpolar Drift in the future. A reduced long-range transport of sea ice would have strong implications for the redistribution of biogeochemical matter in the central Arctic Ocean, with consequences for the balance of climate-relevant trace gases, primary production and biodiversity in the Arctic Ocean.

The volume, characteristics and sources of freshwater circulating in the Arctic Ocean vary in time and are expected to change under a declining sea ice cover, influencing the physical environment and Arctic ecosystem. Relatively fresh (S = 32) Pacific Water, which enters the Arctic Ocean via the Bering Strait makes up a significant part of the liquid freshwater exiting the Arctic Ocean through Fram Strait. If transported to the Nordic Seas and North Atlantic via the East- and West Greenland Currents freshwater from the Pacific could have an effect on convection and dense water formation in those regions.More than 30 repeated sections of nutrient measurements have been collected across Fram Strait between 1980 and 2019. The fraction of Pacific Water along these repeated sections can be estimated from the ratio of nitrate to phosphate. The time-series of repeated Fram Strait sections indicates that the fraction of Pacific Water passing out of the Arctic Ocean has changed significantly over the last 30 years. Pacific water fractions remained high from 1980 to 1998, but in 1999 Pacific water almost disappeared from Fram Strait, reappearing from 2011 to 2012, when there was a peak in freshwater export though Fram Strait.Several hypotheses suggest how variations in the large-scale atmospheric circulation over the Arctic Ocean may influence the transport and pathways of Pacific Water. We show how anomalies in reanalysis wind fields are associated with the reappearance of Pacific Water in Fram Strait in recent years. Repeated sections across Fram Strait are compared with sea ice back-trajectories in the Polar Pathfinder 4 product and a simulated Pacific Water tracer in the NAOSIM numerical model to investigate likely Pacific water pathways through the Arctic Ocean and upstream drivers of changes observed in Fram Strait.