Land Carbon Sink Distribution in Northern Eurasia Is Driven by Climate Change

Boreal forests are a major contributor to the global land carbon sink under rising CO2 concentrations and a changing climate. Carbon sink estimates for Northern Eurasia from forest inventories, flux mapping, and remote sensing have moved toward convergence over the past decade, although substantial differences remain. Several bottom-up and top-down estimates exceed Russia's national greenhouse gas inventory values. Here, we combine data from four independent sources—machine-learning-based FLUXCOM, atmospheric inversion models, the TRENDY ensemble of dynamic global vegetation models, and CMIP6 Earth System Models—to assess the spatial and temporal characteristics of the Northern Eurasian net carbon sink and discuss the differences. Our multi-approach assessment yields a regional estimate of 0.47 ± 0.20 GtC year−1 for the 2001–2015 period, which accounts for one-third of the global land carbon sink. CMIP6 model estimates are broadly consistent with those from other approaches, lending confidence to their future projections, although regional differences persist across individual models. We find a pronounced spatial flux gradient from south to north and west to east along a mean temperature gradient, with stronger carbon sinks in the warmer southern regions and weaker sinks in the cooler northeastern regions. Despite rapid warming in the northern parts of Northern Eurasia, CO2- and warming-induced carbon sink enhancement contributes little to the overall regional sink due to its initially low net productivity. These results underscore the importance of forest productivity in shaping the terrestrial carbon sink and provide a multi-perspective view of its evolution under continued anthropogenic forcing.