Summary:
A new study has revealed the complex and shifting paths by which Siberian river water and matter travel across the Arctic Ocean, raising new concerns about the distribution of pollutants and the vulnerability of polar ecosystems.
The research, published in Nature Communications, provides the most detailed year-round picture to date of the Transpolar Drift (TPD) — a surface current that moves sea ice, fresh water, and various substances from the Siberian Shelf toward the North Atlantic. Led by scientists from the University of Bristol and based on geochemical tracer data collected during the year-long MOSAiC expedition, the study highlights how dynamic seasonal conditions — shifting ocean currents, sea ice drift, and river discharge — reshape this vast Arctic transport system.
By analyzing seawater, sea ice, and snow samples for isotopic and elemental signatures, researchers found that the TPD is far more variable than previously assumed, challenging its long-standing reputation as a stable Arctic conveyor. The study also identifies the increasing role of sea ice not just as a passive carrier, but as an active agent shaping dispersal patterns of river-sourced matter. With sea ice retreating and ocean circulation changing under climate pressure, scientists warn these shifting pathways could have major consequences for Arctic ecosystems and global ocean dynamics.
Pioneering research reveals Arctic matter pathways poised for major shifts amidst climate change
The international research, led by the University of Bristol, in the UK, provides the clearest ever picture of how the underlying transport system, known as TPD, operates. It also uncovers the various factors controlling this major Arctic surface current, including warmer temperatures which could increase the spread of human-made pollutants.
The Transpolar Drift carries sea ice, fresh water, and suspended matter from the Siberian shelves across the central Arctic towards the Fram Strait channel, which connects to the Nordic Seas.
This cross-Arctic flow influences the delivery of both natural substances, such as nutrients, gases, organic compounds, and human-made pollutants – including microplastics and heavy metals – from Siberian river systems into the central Arctic and the North Atlantic. This material affects Arctic biogeochemistry and ecosystems, while the fresh water itself alters ocean circulation.
As the Arctic Ocean is a highly changeable environment, rather than following a steady course, river-sourced matter takes diverse, seasonally shifting routes shaped by changing shelf conditions and ocean currents, along with the formation, drift, and melting of sea ice. This results in rapid and widespread redistribution of both natural and pollutant matter.
Lead author Dr Georgi Laukert, Marie Curie Postdoctoral Fellow in Chemical Oceanography at the University of Bristol, UK and Woods Hole Oceanographic Institution in Massachusetts, US, said: “We found pronounced changes in the composition of Siberian river water along the Transpolar Drift, demonstrating this highly dynamic interplay. Seasonal shifts in river discharge and dynamic circulation on the Siberian shelf drive ocean surface variability, while interactions between sea ice and the ocean further increase the redistribution of river-borne matter.
“Another key discovery is the increasingly central role of sea ice formed along the Transpolar Drift – not only as a passive transport medium, but as an active agent in shaping dispersal patterns. This sea ice captures material from multiple river sources during growth, unlike most coastal sea ice, creating complex mixtures that are transported across vast distances.”
To decode these complex pathways, the international research team analysed seawater, sea ice, and snow samples using oxygen and neodymium isotopes, along with measurements of rare earth elements to produce geochemical tracer data. This geochemical fingerprinting allowed the researchers to track the origins of river-sourced matter and follow how it evolved along its route through the central Arctic over a year-long period.
The study draws on samples from MOSAiC, the largest-ever Arctic expedition and among the most ambitious polar research efforts, involving seven ice breakers and more than 600 global scientists.
Co-author Dr Dorothea Bauch, Researcher at Kiel University in Germany, said: “The findings represent unprecedented year-round observations. Previously, we only had summer data because it was too slow and hard to break through the ice in the winter. This sustained, interdisciplinary Arctic evidence offers important and comprehensive insights, which help us better understand highly complex ocean systems and the possible future implications.”
As summer sea ice continues to retreat due to warmer temperatures, circulation and drift patterns are changing.
Co-author Professor Benjamin Rabe, Research Scientist from the Alfred Wegener Institute and Honorary Professor at the University of Applied Science, in Bremerhaven, Germany said: “These shifts could significantly alter how fresh water and river-derived matter spread through the Arctic, with far-reaching implications for ecosystems, biogeochemical cycles, and ocean dynamics.”
The research also challenges a long-standing perception of the Transpolar Drift as a stable conveyor of river water. First observed during Norwegian explorer Fridtjof Nansen’s historic Fram expedition in the 1890s, these latest findings discovered more than 130 years later indicate the Transpolar Drift is highly variable in both space and time.
Dr Laukert added: “While the study does not focus on individual compounds, it illuminates the underlying transport mechanisms — a critical step for predicting how Arctic matter transport will evolve in a warming climate. If even this iconic current is so dynamic, then the entire Arctic Ocean may be more variable and vulnerable than we thought.”
Journal Reference:
Laukert, G., Bauch, D., Rabe, B. et al., ‘Dynamic ice–ocean pathways along the Transpolar Drift amplify the dispersal of Siberian matter’, Nature Communications 16, 3172 (2025). DOI: 10.1038/s41467-025-57881-9
Article Source:
Press Release/Material by University of Bristol
Featured image: The German research icebreaker Polarstern moored to an ice floe during the polar night (MOSAiC Leg 1). Credit: Esther Horvath | Alfred-Wegener-Institut | CC-BY 4.0
