Natural and anthropogenic radionuclides in bottom sediments of flooded delta lakes of the pechora river (Arctic ocean Basin)

Abstract Barrow Canyon is a major conduit through which Pacific‐origin water enters the Arctic Basin. Mooring data acquired across the mouth of Barrow Canyon from 2000 to 2022 have enabled direct computation of seawater transports. No significant decadal trend in volume transport of Barrow Canyon throughflow was observed, although an upward trend of Bering Strait throughflow has been reported. Annual heat transport through the canyon varied widely, ranging from 0.93 to 7.05 TW, and larger values of heat transport occurred more often in the 2010s compared to the 2000s. The interannual variability of heat transport was not correlated with the Bering Strait heat transport, even though most of the Pacific water inflow through the Bering Strait flows along an eastern path toward Barrow Canyon during summer. Instead, year‐to‐year variation in Barrow Canyon heat transport was driven by variation in summertime sea ice coverage of the northeastern Chukchi Sea, because early ice clearance reduces sensible heat loss to thawing ice and increases direct warming of the surface water via insolation. Using sea surface temperature and wind data from the Chukchi Sea, we derived a proxy for estimating volume and heat transport through Barrow Canyon over the last 40 years. Estimated heat transport in the canyon doubled between 1980s and 2010s likely because of decreasing sea ice presence in summer. This change in heat transport has been sufficient to explain the increase in the heat content of Pacific summer water in the Canada Basin over the same interval.

Regional assessments of lake shrinkage in response to permafrost thaw and climate change across arctic north American basins: regulating effects of lake geometry

The paper presents the results of processing special shipboard observations of the ice cover in the Arctic basin, carried out along the route from the Franz Josef Land archipelago to the North Pole in the summer of 2024. The latitudinal distribution of ice concentration along the route of the nuclear icebreaker “50 Let Pobedy” to the North Pole is presented. The results of assessing the thickness and age composition of level ice (beyond hummocky formations) are obtained based on visual observations and using a ship TV complex.

Abstract A Drift-Towing Ocean Profiling (DTOP) system has been designed for polar regions to study upper-ocean processes across seasons with the capability for continuous long-term operation. It is comprised of a surface package on an ice floe, a cable for data/power transmission, and a subsurface CTD profiler measuring hydrographic properties to a maximum depth of 125 m. The surface package includes meteorological sensors, an ice temperature chain, and GPS/Iridium antennae. The profiler floats up and down driven by oil bladder expansion and contraction, ensuring safe ice bottom contact for data collection at the ice–water interface. Data collected by the profiler are sent to a shore-based server via an Iridium transmitter. Deployed since 2018 in the Canadian and Eurasian Basins during the Chinese National Arctic Research Expedition (CHINARE) and the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition, DTOPs have gathered 2700 profiles and 48 000 meteorological records by September 2022. Observations reveal seasonal fluctuations in meteorological conditions near the ice surface, sea ice growth/ablation, and water mass characteristics. CTD profiles document polar surface water, near-surface temperature maximum, and Pacific-origin waters, aiding in studying spatiotemporal variations in the mixed layer depth and supercooled water. Future plans involve expanding DTOP deployment with biogeochemical sensors in Arctic basins as part of Arctic Observing Networks. Significance Statement Processes at the ice–water interface in the Arctic are crucial both physically and biologically. Regrettably, conventional underice profilers often start sampling below 10 m to protect their sensors, leaving a significant observational gap just beneath the ice. This study introduces the Drift-Towing Ocean Profiler (DTOP), a new ice-borne drifting air–ice–ocean observing system designed to bridge this gap. This innovative ice-tethered system captures hydrographic and biogeochemical properties throughout the water column from just below the ice, down to a maximum depth of 125 m. By enabling enhanced real-time monitoring, DTOP offers vital insights into the rapidly changing Arctic environment, improving our understanding of ice–ocean interactions and climate dynamics.

Structure of the Autotrophic Component of the Biological Carbon Pump in the Western Periphery of the Central Arctic Basin in Summer 2021

Arctic amplification caused by global warming is accelerating an unprecedented loss of Arctic sea ice due to thinning of multi-year sea ice and increased export through Fram Strait, which is the largest Arctic gateway for ice export. The transition to a thinner and younger Arctic ice cover has resulted in a steady surface albedo decline of 1.25–1.51% per decade, weakening the radiative cooling effect of sea ice by 0.04–0.05 W m – ² per decade. The Fram Strait ice export (FSIE) is a major sink in the Arctic ice mass balance, accounting for approximately 14% of the annual sea ice volume loss. As the ice becomes thinner, it drifts faster, leading to enhanced ice export. The annual and summer FSIE have increased by about 6% and 11% per decade, respectively, further accelerating Arctic sea ice decline. Surface Albedo Modification (SAM) has been considered among variety of climate intervention solutions to slow down the transition of the Arctic into a seasonally ice-free ocean by mid-century, in concert with the greenhouse emissions mitigation efforts. Using climate model simulations, we evaluate the impacts of SAM application on the Arctic radiation budget and ice cover in two deployment scenarios: Arctic-wide and regional in Fram Strait. We model such an increase in sea ice albedo as a perturbation to the present-day climate state. Our results show that enhancing the surface albedo by up to 20% Arctic-wide during summer reduces the absorbed radiation at the surface by 11.16 W/m² and increases outgoing radiation at the top of the atmosphere by 10.70 W/m². This results in surface cooling of –1.33°C and recovers approximately 10% of the present-day Arctic sea ice radiative cooling power. These findings suggest that large-scale surface albedo modification could offset Arctic warming and contribute measurably to global cooling. The regional targeted deployment in Fram Strait yields more spatially limited but dynamically significant responses. SAM in Fram Strait enhances surface albedo both locally and in adjacent regions (Barents, Kara Sea) through advection of thicker, more reflective ice. The resulting radiative cooling alters atmospheric circulation, strengthening the low-pressure system over the Barents–Kara sector and triggering a negative Arctic Dipole pattern. This reduces sea-ice export by 2.4% through Fram Strait via weakening the Transpolar Drift in addition to the local thickening and slowing of the ice in the FS region, supporting ice retention within the Arctic basin. Furthermore, the modified atmospheric circulation induces dynamically driven nonlocal ice growth in areas of Central Arctic which persist year-round. These results highlight the potential of Fram Strait albedo enhancement to support multi-year ice recovery and reduce its loss via the Fram Strait. While basin-wide SAM offers the greatest potential benefits, it remains logistically challenging and carries higher risks of unintended consequences. Targeted regional interventions—such as in the Fram Strait and marginal seas (Barents, Kara, and Beaufort)—present a more feasible and cost-effective alternative, with lower risks and the potential to induce basin-wide responses through coupled atmosphere–ice–ocean interactions. These regions are dynamically linked to major circulation centers, including the Barents–Kara Low and Beaufort High, making them promising leverage points for intervention. A strategy for Arctic climate intervention, where a coordinated, regionally targeted, and seasonally adaptive deployment—combining summer albedo enhancement with winter ice thickening—may offer the greatest potential to stabilize Arctic sea ice while minimizing risks.

Abstract As the number of in situ measurements of ocean currents in the central Arctic Ocean remains very limited, much of our understanding of the Arctic Ocean circulation is based on idealized wind‐driven models. In this paper, we make use of the latest available hydrography and Mean Dynamic Topography to study the Arctic Ocean time‐mean circulation. Key concepts such as to what degree the flow is steered by bathymetry, equivalent barotropic, and consistent in direction along isobaths are evaluated. Comparing along‐ and cross‐isobath velocities, we find that while the former generally has a larger magnitude, they are locally comparable in many regions. In these regions, the estimated cross‐isobath velocities imply vertical velocities that can be orders of magnitude larger than typical surface Ekman pumping velocities. Even so, we find that the surface and bottom flow is generally well‐aligned along closed ambient potential vorticity contours spanning local basins as well as the entire Arctic Ocean. In some regions of the central Arctic Ocean, where the hydrographic coverage is relatively sparse, bathymetric alignment is stronger in the surface. Despite this, our results suggest that the circulation is essentially equivalent barotropic and even barotropic in some regions. At some locations where water enters or exits the deep Arctic Basin, along‐isobath flow reversals are observed at the surface as well as the bottom. Finally, the direction and magnitude of the bottom flow in regions of anti‐cyclonic surface circulation are found to be sensitive to the choice of data set.

Surface sediment samples from the Kara Sea and adjacent areas were analyzed to investigate diatom distribution patterns in high latitude regions based on species and their relationship with temperature. Samples from the deep Arctic Basin and Kara Sea primarily comprised pennatic diatoms and centric diatoms, respectively. Rare Sea ice diatoms, including Fragilariopsis oceanica and Fragilariopsis cylindrus, were found in the northern regions of the Kara Sea, close to the Center Arctic Ocean. This region usually has sea ice and ice packs, which account for a relatively low surface temperature. Diatoms near Arctic regions, which are located south of the Kara Sea, included Bacterosira bathyomphala, Thalassiosira antarctica borealis, T. antarctica, Dentonula confervaceae, and Porosira glacialis resting spores. Melting of the Arctic sea with a rise in seasonal temperature has been observed in this region. Coastal Benthic diatoms, such as Paralia sulcata and Delphineis, were found near the surface runoff of the Yenisey, Ob, Pyasina, and Kara. Based on the findings, the distribution and growth of diatoms in surface sediments are strongly influenced by perennial sea ice in the Arctic Ocean regions.

Abstract The bottom waters of the Arctic Ocean's Canada Basin are vertically homogeneous and have C isolation age of 450 years. Understanding the evolution of this geothermally heated isolated bottom water and the overlying water layer can provide insights into Arctic circulation patterns, including interactions between shallow and deep waters, as well as past climate conditions that may have resulted in their isolation. Observations of deep and bottom‐water potential temperature , salinity , and dissolved oxygen from the Beaufort Gyre Observing System/Joint Ocean Ice Study (BGOS/JOIS) program are analyzed in context with property conservation equations, geothermal heating, vertical diffusion, and biological consumption. We find an approximately linear warming trend of the bottom waters over 2003–2024, updating a previous study ending in 2010. We additionally find trends of decreasing salinity and dissolved oxygen over the record. The structure of the bottom water varies spatially, with thinner, warmer, and fresher bottom waters with lower observed near the boundaries. Bottom‐water properties are fluxed vertically into an overlying potential temperature minimum layer, with enhanced vertical fluxes of heat, salt, and dissolved oxygen in turbulent regions near the basin boundaries, and lower, likely molecular vertical fluxes in the basin interior. Heat is fluxed laterally in the layer from the boundaries to the interior, resulting in approximately spatially uniform rates of warming of the layer. Over 2005–2024, decreasing bottom‐water suggests an important influence of organic matter remineralization. The findings in this study are consistent with continued isolation of bottom waters.

Abstract. Ocean bottom pressure (pb) variations from high-resolution climate model simulations under the CMIP6 (Coupled Model Intercomparison Project Phase 6) HighResMIP protocol are potentially useful for oceanographic and space-geodetic research, but the overall signal content and accuracy of these pb estimates have hitherto not been assessed. Here, we compute monthly pb fields from five CMIP6 HighResMIP models at 1/4° grid spacing over both historical and future time spans and compare these data, in terms of temporal variance, against observation-based pb estimates from a 1/4° downscaled GRACE (Gravity Recovery and Climate Experiment) product and 23 bottom pressure recorders, mostly in the Pacific. The model results are qualitatively and quantitatively similar to the GRACE-based pb variances, featuring – aside from eddy imprints – elevated amplitudes on continental shelves and in major abyssal plains of the Southern Ocean. Modeled pb variance in these regions is ∼ 10 %–80 % higher and thus overestimated compared to GRACE, whereas underestimation relative to GRACE and the bottom pressure recorders prevails in more quiescent deep-ocean regions. We also form variance ratios of detrended pb signals over 2030–2049 under a high-emission scenario relative to 1980–1999 for three selected models and find statistically significant increases in future pb variance by ∼ 30 %–50 % across deep Arctic basins and the southern South Atlantic. The strengthening appears to be linked to projected changes in high-latitude surface winds and, in the case of the South Atlantic, intensified eddy kinetic energy. The study thus points to possibly new pathways for relating observed pb variability from (future) satellite gravimetry missions to anthropogenic climate change.

This volume, Sedimentary Successions of the Arctic Region and their Hydrocarbon Prospectivity , developed around maps of the sedimentary successions of the Arctic Region, and contains a brief, but comprehensive compilation of geological and geophysical data characterizing all significant sedimentary successions in the Arctic, which cover 57% of the polar area north of 64° N. Its two main goals are to provide, based on present-day knowledge and data, a characterization of all Arctic sedimentary successions (or sedimentary accumulations) and to supply a snapshot of hydrocarbon-related exploration in the Arctic at the end of the first quarter of this century. To achieve these goals, we represent sedimentary successions as consisting of one or several ‘tectono-sedimentary elements’ (TSEs) based on the main tectonic regimes that formed accommodation space for accumulation of sediments. A TSE characterization template has been developed as an efficient method of organizing and presenting the most important information about the stratigraphy, structure and petroleum geology of a TSE, including the most significant exploration facts. This organizational architecture is the backbone of the volume and is a key feature that distinguishes it from other studies of Arctic sedimentary basins. The online volume includes six large-size foldout maps portraying the mapped TSEs in the Circum-Arctic context, including tectonic grain of the consolidated basement, anomalous gravity and magnetic fields, location of the Arctic sampling sites and seismic profiles.

The modern Arctic has been formed through a series of continent–continent collisions, accretion of terranes and phases of crustal extension. The Neoproterozoic Timanian, Paleozoic Caledonian and Uralian, and late Mesozoic Verkhoyansk–Kolyma, Chukotkan and Brookian orogenies formed several large fold-and-thrust belts (FTBs). The FTBs are exposed across vast areas of continents and continue offshore to form a complex tectonic basement for thick sedimentary basins, playing an important role in the history of accumulation and deformation of younger unmetamorphosed sedimentary successions that are the subject of this volume. Recognition of the importance of FTBs in the Arctic geological history and their role as a controlling factor of development of Arctic sedimentary basins resulted in this chapter, in which we review the current state of knowledge about Arctic FTBs and highlight questions that remain to be addressed. Enclosure D , a map showing boundaries of the FTB and their internal first-order structural fabric, is a part of the overview.

The planktonic pteropod Limacina helicina is increasingly studied as a bioindicator of climate-driven changes in polar marine ecosystems. Although broadly distributed across the Arctic Basin and the North Pacific, its population structure and dispersal pathways remain poorly understood, especially in the Siberian Arctic. We analyzed mitochondrial COI sequences from populations sampled in the Barents, Kara, Laptev, East Siberian, and White Seas, as well as adjacent Pacific regions. Three major haplogroups (H1, H2, H3) were identified with distinct spatial patterns. H1 is widespread, occurring across the Pacific and most Arctic seas except the White Sea. H2 is confined to the western Arctic shelves (Barents–Kara–Laptev), and H3 is unique to the White Sea. We found a pronounced genetic discontinuity corresponding to hydrographic barriers, particularly the strong freshwater inflow from the Lena River, which restricts eastward dispersal of H2 from the Laptev to the East Siberian Sea. These patterns suggest postglacial expansions from geographically separated populations that survived the Last Glacial Maximum in isolated marine regions. The White Sea population is highly isolated and genetically distinct. Our results highlight how both glacial history and modern oceanography shape Arctic plankton diversity and define biogeographic boundaries in a rapidly changing climate.

Abstract Terrestrial water storage (TWS) in northern high‐latitude regions is strongly influenced by climate warming and the resulting permafrost thaw. However, it is not yet fully understood how different permafrost types constrain TWS changes during the rapid warming period. In this study, we focused on the six major Arctic river basins (Ob', Yenisei, Lena, Kolyma, Yukon, and Mackenzie), which are characterized by widespread permafrost, and employed three TWS products derived from remote sensing observations, land surface models, and reanalysis data sets to quantify changes in TWS anomalies during the rapid warming period (1981–2020). Statistical analyses revealed differential TWS declines across all permafrost types, with the most significant decline observed in the discontinuous permafrost regions at −3.05 mm/year, compared to in the continuous permafrost regions (−0.78 mm/year) and in the sporadic permafrost regions (−2.45 mm/year). Correlation analyses further indicated a pronounced negative relationship between permafrost active layer thickness (ALT) and TWS, especially in discontinuous permafrost regions, where a 1‐cm increase in ALT corresponded to a TWS decrease of up to 4.4‐mm. These findings highlight the significant impact of permafrost thawing accelerated by climate warming on TWS changes in permafrost‐dominated Arctic regions, with important implications for regional hydrology, carbon feedback, and ecosystem stability in the pan‐Arctic. Our results underscore the necessity of incorporating permafrost‐specific processes into hydrological models and climate assessments, thereby enhancing projections of water resource a4vailability and environmental changes in northern high‐latitude regions.

Time series of water temperature and conductivity obtained over three years of continuous measurements at seven autonomous moored stations north of the Severnaya Zemlya archipelago located in the Arctic Basin of the Arctic Ocean were analyzed in combination with numerical modeling to investigate the spatiotemporal variability of temperature and salinity in the intermediate layer of Atlantic-origin waters. These waters propagate along the Eurasian continental slope within the Arctic Boundary Current (ABC). Within 85 km of the shelf edge, three distinct branches of Atlantic Water (AW) transport were identified, each characterized by a unique origin history of origin that shapes the variability of its thermohaline properties. The most energetic mode of temporal variability at all stations is associated with oscillations with a period of approximately 12 months. The amplitude of these oscillations decreases with increasing distance from the shelf edge, while their phase differs among the AW branches. Numerical modeling indicates that, in the study region, the typical phase–distance relationship observed in the western Nansen Basin is disrupted by the large-scale input of cold, freshened water through the St. Anna Trough.

Properties of inflowing Pacific and Atlantic water govern total and methylated mercury profiles in the Arctic Ocean.

ABSTRACT While previous studies have investigated environmental and biotic variables influencing plankton community composition, comprehensive analyses across multiple trophic levels and broad spatial scales remain limited. Using a Joint Species Distribution Modelling framework, we identified key abiotic and biotic variables, including body size and fish presence that shape variation in plankton food webs across Canadian lakes. We analyzed the joint responses of plankton biomass to lake morphometry, water physico‐chemistry, and fish species presence, using data collected from 301 lakes spanning the four main national continental catchments. We also examined how the body size trait modulated plankton food web associations with these variables. Results showed that lake nutrient and ion status were the most important factors explaining variation in plankton community composition, particularly in the Arctic and Hudson continental basins, which exhibited large environmental gradients. Lake morphometry also played an important role, especially in shaping communities in large, shallow lakes. Plankton body sizes modulated some niche responses, but these effects varied across continental basins and plankton trophic levels. Little residual variation in the models indicated limited roles of plankton species interactions or unmeasured environmental variables. While fish presence only explained small amounts of variation, further studies should instead assess and incorporate fish biomass data. Our findings suggest that future national strategies for the study of Canadian freshwaters should combine a continental‐scale perspective (e.g., gradients across ecozones, climate regions, biogeographic zones) with regionally focused monitoring programs to better capture critical factors influencing different lake ecosystems.

Abstract Kongsfjorden is located in West Spitsbergen, Svalbard archipelago. Its hydrography is influenced by the West Spitsbergen Current (WSC) transporting warm and saline Atlantic Water (AW) toward the Arctic basin. We assessed changes in fjord water properties over two decades (1999–2020) using summer hydrographic surveys performed by the Norwegian Polar Institute in the fjord, the adjacent shelf, and open ocean regions. The heat content (HC) and salinity within the fjord have increased driven by a larger inflow of AW. These trends are consistent with observations in neighboring Isfjorden but not mirrored in the properties of the WSC over the same timeframe. Therefore, hydrographic changes in these two fjords can be attributed to larger AW intrusions rather than variations in the upstream WSC properties. We hypothesize that the increased HC in Kongsfjorden is driven by shifts in the synoptic wind patterns and larger glacier meltwater release enhancing fjord shelf exchanges. Idealized modeling experiments revealed that although these modifications contribute by increasing the fjord's HC, they explain only a small portion of the observed changes, suggesting that the availability of Atlantic Water on the shelf is the dominant factor.

—Zhokhov Island belongs to the De Long Archipelago located in the Eastern sector of the Russian continental shelf within the Arctic Basin. The island is a young volcanic center and is composed of lava flows of alkaline olivine-porphyry basalts and subordinate limburgites. The study was aimed at identifying the possible regional and geodynamic factors influencing the specifics of the partial melting and mineral transformations in mantle xenoliths of Zhokhov Island. Five xenoliths selected from alkali basalt samples on Zhokhov Island were studied using a scanning electron microscope. The data obtained allowed us to conclude that the formation of high-sodium glasses in the mantle xenoliths of Zhokhov Island is associated with the interaction between spinel lherzolites and parental melts of host olivine basalts. At the same time, high-potassium glasses inside mantle xenoliths were formed in situ during the melting of a primary potassium-bearing phase, likely phlogopite. The formation of two distinct compositionally contrasting recrystallization zones in contact between the mantle xenoliths and the host basalt is caused by the evolution of host alkaline silicate melt from sodic to potassic composition. Signs of activation of young intraplate magmatism that brought up the fragments of metasomatized shallow mantle to the surface are established over a large area of the Arctic Basin within the HALIP large igneous province.