Organic carbon and mercury exports from pan-Arctic rivers in a thawing permafrost context – A review

• Published in: The Science of the total environment 2024-12, Vol.954, p.176713, Article 176713
• Main Authors: Fabre, Clément, Sonke, Jeroen E., Tananaev, Nikita, Teisserenc, Roman
• Format: Article
• Language: English
• Subjects: Mercury; Organic carbon; Pan-Arctic Rivers
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.176713

Climate change affects more than elsewhere the northern circumpolar permafrost region. This zone comprises large rivers flowing mainly to the Arctic Ocean, delivering about 10 % of the global riverine water flux. These pan-Arctic Rivers drive the dynamics of northern organic carbon (OC) and mercury (Hg) cycling. Permafrost degradation may release substantial amounts of OC and Hg, with potential regional and global impacts. In this review, we summarise the main findings in the last three decades about the role of the pan-Arctic Rivers in OC and Hg cycling and the effect of climate change on these dynamics. Total DOC and POC fluxes delivered by the pan-Arctic rivers presently reach 34.4 ± 1.2 TgC·yr−1 and 7.9 ± 0.5 TgC·yr−1, while the export of Hg reaches 38.9 ± 1.7 Mg·yr−1. This review highlights future challenges for the scientific community in evaluating spatial and temporal dynamics of the processes involved in OC and Hg cycling in permafrost-affected areas. Permafrost thawing could lead to greater fluxes of OC and Hg with ill-known resulting risks for food chains. Within this context, efforts should be made to study OC effects on Hg methylation. Moreover, assessing the spatial variability of OC and Hg mobilisation and transport within the pan-Arctic watersheds may help understand the future OC and Hg cycling dynamics in the northern circumpolar permafrost region. [Display omitted] •OC and Hg fluxes to the Arctic Ocean reach 43.9 TgC·y−1 and 38.9 Mg·y−1.•OC and Hg fluxes from Arctic permafrost require improved Arctic rivers monitoring.•Remote sensing tools should improve understanding of total OC and Hg budgets.•Sampling and models help to predict warming effects on fluxes at various scales.