Norwegian Geological Survey

Abstract Continental margins, situated at the nexus of land and ocean, act as major burial hotspots for terrestrial and marine organic matter, creating a critical interface between the short-term carbon cycle and long-term geological storage. Although this burial largely regulates atmospheric CO₂, O₂ and thus climate, its magnitude and spatial distribution remain poorly constrained due to sparse observations and an extraordinary environmental variability. Here we present the first global, observation-constrained assessment of organic-carbon transfer and burial along the global continental margin, integrating observational data with spatial machine learning and three-dimensional reaction–transport modelling. We estimate a global organic-carbon transfer flux of 367 Tg C yr⁻¹ on centennial timescales, decreasing to 293 and 246 Tg C yr⁻¹ on millennial and multi-millennial scales. These results show that continental-margin sediments form one of Earth’s largest and most persistent long-term carbon sinks, exceeding lakes, reservoirs and all major vegetated coastal ecosystems combined. Burial is strongly heterogeneous, with ~70% occurring in the Northern Hemisphere and ~50% in equatorial regions, and with pronounced hotspots in tropical margins and marginal seas. These findings reduce a central uncertainty in the coastal carbon budget and thus refine global carbon cycle assessments, constrain ocean–atmosphere CO₂ exchange, and provide the first spatial framework to guide marine conservation, management, and climate policy.

This study compares methodologies and provides insights on best approaches for quantifying EU-listed critical raw materials. Europe's strategy towards greater resilience involves valorization of secondary resources such as mine tailings or by-products of metallurgical production that are typically discarded as waste, despite containing valuable resources. Thus, identifying the best methods to determine elemental concentrations in various resources is crucial for evaluating their recovery, both environmentally and economically. Elemental content is usually determined using techniques such as inductively coupled plasma mass spectrometry (ICP-MS) by digesting solid samples into liquid solutions, although challenging for some refractory materials. Direct analysis of solids by laser ablation (LA)-ICP-MS is another alternative and can be used for both bulk analysis and spatially resolved mapping of critical elements throughout the supply value chain, from raw materials to refined products. Here, we compare ICP-MS/MS analysis on dissolved samples, obtained after microwave-assisted acid dissolution, with LA-ICP-MS analysis on solid samples for determining rare earth element (REE) compositions of manganese ores and slags. For LA-ICP-MS, we present two approaches, particularly useful in cases where dissolution proves challenging: (i) analysis of glass beads obtained through borate flux fusion of raw powders, and (ii) direct analysis on pelletized powders using a novel non-matrix matched calibration strategy. Each method's feasibility and strengths are considered for the specific chemical composition of the samples of interests. The study shows that different methods have advantages and disadvantages related to particle size distributions and preparation costs that need to be considered during characterization of secondary resources.

Arctic fjord sediments store significant amounts of organic matter (OM), contributing to the global carbon cycle, but are increasingly influenced by climate change. This study investigates OM distribution and sources in sediments from 24 stations across three West Spitsbergen fjords (Hornsund, Isfjord, and Kongsfjord-Krossfjord), focusing on relationships with porewater chloride concentrations and stable water isotopes. Freshening of porewater indicated by low chlorinity was detected in Isfjord and Hornsund. In Hornsund and Tempelfjord (Isfjord), water isotope signatures point to a meteoric origin, likely via submarine groundwater discharge (SGD). In contrast, Ekmanfjord (Isfjord) shows isotopic evidence of gas hydrate dissociation as the freshening source. Both Isfjord sites contain OM with low δ 13 Corg (< −26.8 ‰) and δ 15 Ntot (< 3.1 ‰) values, which are inconsistent with known OM sources in Svalbard fjords. We propose that carbon released from SGD and gas hydrate dissociation, along with methane oxidation and nitrogen assimilation by methanotrophic microbes, contribute to OM formation. These findings suggest that Arctic fjord sediments may help mitigate climate change by supporting microbial processes that consume methane, a potent greenhouse gas. • Gas hydrates found in Svalbard fjord sediments. • Porewater freshening linked to gas hydrates or meteoric water input. • Unusual carbon and nitrogen isotopes suggest microbial methane use. • Fjord sediments may act as natural filters for methane release. • Findings offer new insights into Arctic carbon cycling and feedbacks.

The authors declare no conflicts of interest. The data are openly available (https://doi.org/10.5281/zenodo.17241250). The code for data analysis is available on GitHub (https://github.com/aleck111/Risso-s-dolphins-Northern-Norway). Additionally, a photo-identification catalog relating to the manuscript was published (https://doi.org/10.5281/zenodo.15384625). Figure S1: Study area. Tracks of the Whale2Sea whale watching RIBs (orange lines) as recorded in the automatic information system (AIS) and downloaded from the Kystdatahuset online tool of the Norwegian coastal authority (Kystverket 2025) for each summer season (June 1st to September 30th) from 2019 to 2024. Darker shades of blue indicate deeper waters and correspond to the Bleik Canyon, for which depth contours are shown in Figure 1. Figure S2: Distinctiveness scoring of photo-identified individuals. Scoring was based on (a) presence, size, and number of nicks in the dorsal fin along with dorsal fin shape/outline, that is, Score 0: no discernable nicks, Score 1: moderate number and size of nicks, Score 2: clear and distinctive features, for example several or big nicks; and (b) Scaring patterns, that is, Score 0: no to little scaring, Score 1: moderate scaring, Score 2: clear and distinctive scaring. Figure S3: Previous Risso's dolphin sightings in the Northeast Atlantic. The map shows locations of all Risso's dolphin sightings compiled from databases held by Artsdatabanken (Artsdatabanken no. 2025), Faroe Island Whale Watch (FIWW), the Ocean Biodiversity Information System databank (obis.org 2025), the Norwegian Institute for Marine Research (IMR), and Chosson et al. (2023). Countries with existing photo-ID catalogs are shaded in a dark gray. Catalogues exist from Ireland (Felce 2012; Seán O'Callaghan pers. commun.), from the United Kingdom around North Scotland and the Shetland Islands by Whale and Dolphin Conservation (WDC) (WDC 2022a, 2022b), and from France off the Brittany coast (Oihana Olhasque, Association AL LARK, pers. commun.). The blue shaded area in the southwestern part of the map shows the distribution range according to the International Union for Conservation of Nature and Natural Resources (IUCN, Kiszka and Braulik 2018). Table S1: Number of trips, number of documented Risso's dolphin sightings, sighting percentage, number of occasions on which photographs were taken, and total number of photographs taken for each season. Table S2: All individuals that were seen on more than one encounter. Longest stay is counted from first to last encounter within a year. Encounter number refers to the Risso's dolphin encounter on the relevant day. Table S3: Age classes and sex of the study individuals. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

<strong class="journal-contentHeaderColor">Abstract.</strong> Organic carbon stored in continental margin sediments might be at risk by widespread mobile bottom fishing, potentially leading to reductions of organic carbon stocks, increased ocean acidification, additional atmospheric carbon dioxide emissions and a reduction of the buffering capacity of the ocean. Spatially explicit studies that have been conducted to inform marine management have so far looked at organic carbon stocks that have already been affected by mobile bottom fishing. Here, we focus instead on areas on the Norwegian continental margin that are currently not fished, based on fishing data covering the years 2009&ndash;2020. We estimate that the surface sediment layer (0&ndash;2 cm) in unfished areas covering 765,600 km² contains 139.2 Tg of organic carbon. Based on data from a meta-analysis of demersal fishing impacts on organic carbon density, we estimate that 16.4 Tg (1.8&ndash;29.6 Tg) of organic carbon might be vulnerable to mobile bottom fishing in a scenario where each grid cell is fished evenly over the entire area and down to the full depth of the surface layer. Approximately one third of the vulnerable organic carbon is currently located in existing area-based protection measures. Additional protection could be guided by hotspots of vulnerable organic carbon, which are exclusively found in the Barents Sea. We argue that the protection of vulnerable organic carbon that is at high risk of being lost e.g. in areas becoming accessible to fishing due to sea ice retreat such as in the northern Barents Sea should be given a high priority.

Group hunting is widespread among large vertebrates and is known to confer considerable advantages compared with foraging alone.1,2,3 Yet, the mechanisms underlying group hunting, including how social predators are organized during a hunt, are largely unknown for marine predators.1,2 Using drone videos,4,5 we tracked the predatory behavior of killer whales along the Norwegian coast to test the hypothesis that group hunting is organized in space, both in terms of individual roles and interactions with conspecifics. Taking advantage of shallow water hunts that reduced the interactions to a 2D horizontal plane, we reveal that whales using underwater tail slaps6 (i.e., "strikers") to stun herring are more likely to hunt near a neighbor (i.e., a "helper") rather than alone, and such "joint slaps" show higher feeding success (measured as feeding bout duration) than "alone slaps." At the onset of a joint slap, the position of the whales follows a specific geometrical pattern. Whales preferentially take roles as strikers or helpers, with division of labor determined by size: larger individuals predominantly act as strikers in line with their higher feeding success compared with smaller whales. Both striking and helping behaviors are more likely to be observed in males than in females. Individuals involved in joint slaps have preferred partners, with whom they share multi-decadal social bonds, likely allowing repeated opportunities to practice and learn to bestow enhanced geometric positioning and hunting success. These findings highlight the importance of social organization, long-term bonding, and developmental learning in the cooperative hunting of marine mammals. VIDEO ABSTRACT.

Abstract. Organic carbon stored in continental margin sediments might be at risk by widespread mobile bottom fishing, potentially leading to reductions of organic carbon stocks, increased ocean acidification, additional atmospheric carbon dioxide emissions and a reduction of the buffering capacity of the ocean. Spatially explicit studies that have been conducted to inform marine management have so far looked at organic carbon stocks that have already been affected by mobile bottom fishing. Here, we focus instead on areas on the Norwegian continental margin that are currently not fished, based on fishing data covering the years 2009–2020. We estimate that the surface sediment layer (0–2 cm) in unfished areas covering 765,600 km2 contains 139.2 Tg of organic carbon. Based on data from a meta-analysis of demersal fishing impacts on organic carbon density, we estimate that 16.4 Tg (1.8–29.6 Tg) of organic carbon might be vulnerable to mobile bottom fishing in a scenario where each grid cell is fished evenly over the entire area and down to the full depth of the surface layer. Approximately one third of the vulnerable organic carbon is currently located in existing area-based protection measures. Additional protection could be guided by hotspots of vulnerable organic carbon, which are exclusively found in the Barents Sea. We argue that the protection of vulnerable organic carbon that is at high risk of being lost e.g. in areas becoming accessible to fishing due to sea ice retreat such as in the northern Barents Sea should be given a high priority.

Abstract During closure of an ocean through subduction and continental collision, bathymetric highs such as microcontinents can accrete, collide, or partially or completely subduct. Such interaction of future allochthonous terranes (FATs) with the overriding continent will modify the dynamics of the subduction zone, affecting its length and frictional resistance, and thus the force balance of the subduction system. Accreted microcontinents and microcontinental fragments are preserved in backarcs and collisional orogens, demonstrating that multiple terranes can accrete during a single Wilson‐cycle, in what is termed accretionary orogenesis. In this study, we use thermo‐mechanical numerical experiments of microcontinent‐continent collision events to investigate parameters that influence whether microcontinents accrete, subduct, or collide. Our results indicate that multiple accretionary episodes are possible, but that a weak basal detachment layer within each FAT is paramount for such a scenario to occur. The introduction of a microcontinent, or FAT, in the subduction zone will affect the balance between slab‐pull, far‐field forces, and the subduction interface resistance. The strength (and rheological stratification) of the microcontinent determines the evolution of the subduction interface resistance throughout the collision event, exerting a first order control on the resulting geodynamic scenario. Collision with a strong microcontinent significantly increases the subduction interface resistance promoting terrane subduction and localization of deformation away from the subduction interface. In turn, collision with a weak microcontinent increases subduction interface resistance only mildly, allowing for multiple accretion events.