Scientists analyzing sediment cores from an Arctic fjord found that warmer Atlantic waters are increasingly influencing fjord chemistry and boosting marine-derived organic carbon burial. The study, published in Biogeosciences, links glacier melt and shifting currents to changes in how sediments sequester carbon. Researchers warn that fjords could shift from being strong carbon sinks to weaker sinks or temporary sources, and they call for expanded monitoring, improved methods and faster emissions reductions.
Warmer Atlantic Waters Invade Arctic Fjords — Sediment Cores Reveal Shifts in Carbon Storage
Scientists analyzing sediment cores from an Arctic fjord found that warmer Atlantic waters are increasingly influencing fjord chemistry and boosting marine-derived organic carbon burial. The study, published in Biogeosciences, links glacier melt and shifting currents to changes in how sediments sequester carbon. Researchers warn that fjords could shift from being strong carbon sinks to weaker sinks or temporary sources, and they call for expanded monitoring, improved methods and faster emissions reductions.
02:50 PM, 11/15/2025Environment
Warmer Atlantic waters are reshaping Arctic fjords and their role in the carbon cycle
Researchers analyzing sediment cores from an Arctic fjord report that rising temperatures and increased Atlantic inflow are changing how coastal Arctic basins store organic carbon. The study, published in Biogeosciences, used isotopic and chemical tracers to distinguish organic matter sourced from marine organisms, soils, vegetation and ancient bedrock.
What the scientists did
The team collected sediment cores at multiple locations within a fjord and applied isotopic and geochemical analyses to identify shifts in the composition and origin of preserved organic material. These methods allowed them to track changes over time and link sediment signatures to oceanographic and glacial processes.
Key findings
The measurements indicate a growing influence of warmer, Atlantic-derived waters entering the fjord, accompanied by an increase in marine-derived organic carbon preserved in the sediments. By connecting these sedimentary changes with accelerating glacier melt and shifting currents, the researchers showed that the rate and character of carbon burial on fjord floors are changing.
"Given their role as critical organic carbon reservoirs, Arctic fjords may function as both sources and sinks of carbon in a warming climate, emphasizing the need for further research to assess the long-term consequences of climate-induced changes on regional carbon cycling," the authors wrote.
Why it matters
Arctic fjords act as important reservoirs of organic carbon and influence regional and global carbon cycling by sequestering material that might otherwise return to the atmosphere. Changes in the efficiency or rate of carbon burial could therefore affect atmospheric carbon concentrations and climate feedbacks. Under some scenarios, fjords that currently store carbon could become weaker sinks — or even temporary sources — as physical and biological conditions shift.
Next steps and implications
The authors call for expanded monitoring across fjords and seasons, improved isotopic tracing techniques and modeling of how future warming scenarios could alter carbon storage in Arctic coastal systems. The results also strengthen the case for rapid reductions in greenhouse-gas emissions to limit warming and reduce the risk that polar systems cross tipping points that would amplify global change.
While further research will refine projections, this study provides concrete evidence that subtle changes in ocean circulation and temperature leave long-lived records in sediments — records that can help scientists reconstruct recent environmental changes and anticipate future impacts.