As the Arctic continues to experience unprecedented warming, the melting of once-permanently frozen ground, known as permafrost, unfolds a less visible but profoundly impactful consequence: the release of vast quantities of organic carbon into the central Arctic Ocean. Recent investigations led by researchers at the Alfred Wegener Institute have delved into this phenomenon with rigorous scientific inquiry, illuminating the scale and persistence of terrestrial organic carbon contributions in this vulnerable marine environment. Published in the esteemed journal Nature Geoscience, their findings significantly expand our understanding of the Arctic’s carbon cycle, with far-reaching implications for global climate models and marine ecosystem dynamics.
When permafrost thaws, it liberates ancient organic material, entrapped in frozen soils for centuries or longer, encompassing fragments of plants, microorganisms, and animal matter. This organic material, rich in carbon, is transported via Arctic rivers into the ocean, dissolving into the marine environment as dissolved organic matter (DOM). Scientists now recognize that this reservoir of organic carbon rivals the atmospheric CO2 in scale, highlighting the vastness of organic compounds entering Arctic waters from terrestrial sources. This influx, far exceeding that of most global oceans, is driven by the complex interplay of permafrost thaw, riverine discharge, and coastal erosion processes unique to the Arctic’s fragile landscape.
Employing advanced chemical fingerprinting techniques, the international team of scientists set out to quantify just how much terrestrial organic carbon accumulates in the central Arctic Ocean and assess its fate once marine-bound. Dr. Xianyu Kong of the Alfred Wegener Institute, a leading author of the study, reveals that approximately 16% of the dissolved organic carbon budget in this region originates from land-based sources. Remarkably, much of this terrestrial carbon was detected not only at the surface but also persisting in deep ocean waters. This endurance challenges prior assumptions about the rapid degradation of such organic matter and suggests chemical stability that enables its transport over long distances.
This persistence indicates the capacity for land-derived organic matter to traverse the Arctic Ocean and enter the North Atlantic Deep Water, a key component of the Earth’s global ocean conveyor belt. Consequently, processes occurring in the Arctic have broader implications for the global carbon cycle, potentially influencing the sequestration and release of carbon far from the region of origin. Such connectivity underscores the importance of integrating Arctic soil and ocean dynamics into climate models that have historically underestimated or excluded these terrestrial inputs.
One major pathway for the movement of terrestrial dissolved organic carbon (DOC) within the Arctic Ocean is the Transpolar Drift, a powerful current transporting freshwater, sea ice, and nutrients from Siberian rivers across the Arctic toward the North Atlantic. Analysis revealed that areas influenced by this current contain roughly twice the concentration of terrestrial organic carbon compared to adjacent regions, suggesting a significant export flux. Based on these observations, the researchers estimate that around 39 million tons of terrestrial carbon transit from the Arctic to the Atlantic annually, underscoring the region’s role as a major carbon source beyond its geographical boundaries.
This influx of terrestrial DOM is not merely a passive flux but actively shapes biogeochemical processes in the Arctic Ocean. By altering the optical properties of seawater, terrestrial DOM influences light penetration, affecting photosynthesis-driven ecosystems. Additionally, it modulates nutrient availability and microbial community composition, thereby impacting marine food webs and carbon cycling. Profoundly, these changes are intertwined with ongoing climatic shifts, where increased permafrost meltwater inputs contribute to rising DOM concentrations in Arctic freshwater and marine systems, a trend yet to be fully elucidated in this ocean basin due to prior methodological limitations.
Addressing the analytical challenges in quantifying and characterizing these complex organic compounds, the interdisciplinary team collaborated closely with the Helmholtz Centre for Environmental Research. They developed a novel ultra-high-resolution chemical analysis approach using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), an advanced technique enabling the identification and quantification of thousands of individual organic molecular formulas within seawater samples. This methodological breakthrough allowed for the differentiation between organic matter originating from sea ice and the ocean, versus terrestrial inputs, enabling unprecedented insight into the chemical nature and degradation status of Arctic organic carbon pools.
Samples for this pioneering analysis were collected during the landmark Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition conducted between 2019 and 2020. These carefully gathered water fractions from various depths were subjected to ultrahigh-resolution mass spectrometry profiling, providing a depth-resolved characterization of terrestrial dissolved organic carbon. Such spatially explicit data are crucial for pinpointing hotspots of terrestrial carbon accumulation and understanding their vertical and horizontal transport mechanisms throughout the Arctic Ocean’s water column.
This collective body of work represents a vital leap forward in quantifying the terrestrial carbon inventory within the Arctic Ocean, bridging gaps left by previous studies largely limited to surface observations or regional snapshots. The demonstration that terrestrial carbon can remain chemically stable enough to persist in deep ocean layers shifts paradigms about carbon cycling in high-latitude marine environments, with ramifications for predicting carbon fluxes and feedbacks under continued Arctic warming scenarios. Increasing terrestrial runoff, fueled by thawing permafrost and intensified coastal erosion, is expected to amplify these processes, potentially transforming carbon budgets, nutrient dynamics, and ecosystem functioning on a regional and global scale.
Moreover, current climate and carbon cycle models do not yet incorporate these newly quantified terrestrial inputs and their fate with sufficient resolution, potentially underestimating the Arctic Ocean’s role as both a conduit and sink for organic carbon. The findings emphasize an urgent need to integrate these processes to refine predictions of carbon storage and release in the Arctic, particularly under accelerating climate change scenarios. Accurate modeling is essential not only for climate policy but also for managing biological resources and assessing the resilience of Arctic marine ecosystems in a rapidly evolving environment.
The implications expand beyond the Arctic, as the export of terrestrial organic carbon to the North Atlantic intersects with global ocean circulation patterns affecting carbon sequestration and climate regulation worldwide. The linkage between Arctic terrestrial and marine carbon pools offers a vivid demonstration of the interconnectedness of Earth systems and the cascading effects of regional changes on global environmental processes. Understanding these dynamics is fundamental to anticipating future climate trajectories and developing mitigation and adaptation strategies on an international scale.
In summary, the groundbreaking research led by the Alfred Wegener Institute offers compelling evidence that terrestrial carbon contributions to the Arctic Ocean’s dissolved organic carbon reservoir are substantial, chemically stable, and have far-reaching ecological and climatic consequences. As human activities and global warming continue to reshape the Arctic environment, these findings serve as a clarion call for enhanced monitoring, more sophisticated modeling, and holistic approaches to managing the intertwined fate of terrestrial and marine carbon cycles in Earth’s fragile polar frontier.
Subject of Research: Major terrestrial contribution to the dissolved organic carbon budget in the Arctic Ocean
Article Title: Major terrestrial contribution to the dissolved organic carbon budget in the Arctic Ocean
News Publication Date: 7-Nov-2025
Web References: 10.1038/s41561-025-01847-5
References:
Kong, X., Lechtenfeld, O.J., Kaesler, J.M., et al. (2025). Major terrestrial contribution to the dissolved organic carbon budget in the Arctic Ocean. Nature Geoscience. https://doi.org/10.1038/s41561-025-01847-5
Image Credits: Alfred-Wegener-Institut / Jaroslav Obu
Keywords: Arctic ecosystems, Organic carbon, Carbon sinks, Permafrost, Coastal processes, Ocean chemistry
