Arctic coastlines experience unprecedented retreat through coastal erosion and thaw of permafrost. This causes the release of large amounts of organic carbon into the ocean. The degree of decomposition of this organic carbon in marine systems will determine its eventual role in global climate feedback mechanisms. Where a high degree of decomposition will generate greenhouse gases, a low degree of decomposition will lead to long-term burial of organic carbon in marine sediments. The pathways and fate of this organic carbon (decomposition vs. burial) remains unclear.
Canada
In the study, which was published in Nature Communications Earth & Environment, earth scientists Fleur van Crimpen and Jorien Vonk, together with international colleagues, looked at forms and amounts of organic carbon in the Beaufort Sea coastal region in NW Canada. They sampled material on land (eroding coastal cliffs) and in the shallow and deeper marine system.
Revision of current views
The study revealed two surprising findings that may require revision of our current views on land-ocean carbon cycling. First of all, the dominant form in which organic carbon is ‘enroute’ to the ocean, is different than what we used to think. Most of the carbon travels in a free form, as loose debris, instead of sorbed to (clay) minerals. Furthermore, our study shows that hardly any free organic carbon is found in deeper marine waters, suggesting that the shallow nearshore zone (less than 5m water depth) seems to selectively trap this free organic carbon and functions as an incubator. As the nearshore zones is notoriously undersampled - less than 6% of all arctic marine sediment data - this could mean we are missing a key component in the quickly changing arctic carbon cycle.
Vonk: “It seems we may need to redefine our view on arctic land-ocean carbon dynamics, yet it is important to first see if these striking patterns we find in the Beaufort Sea are representative for other areas where permafrost coasts are retreating”.
Shallow arctic coastal zones as incubators of thawing carbon
19 November 2025
New research by earth scientists Fleur van Crimpen and Jorien Vonk, among others, shows that current insights in the arctic land-ocean carbon cycle may need to be revised.
