Sensitivity of land carbon sinks to the three major oscillations in the Northern Hemisphere.

The Arctic Oscillation (AO), North Atlantic Oscillation (NAO), and Pacific-North American Pattern (PNA) cause climate variability in the Northern Hemisphere (NH), which affects the carbon cycle of terrestrial ecosystems. Based on a dynamic global vegetation model, we analysed the impacts of the AO, NAO and PNA on changes in terrestrial climate and carbon cycle dynamics from 1980 to 2017. The positive AO (pAO), positive NAO (pNAO), and positive PNA (pPNA) mainly led to warmer and more humid conditions in the North Asia (NA) and Europe (EUR), whereas the negative AO (nAO), negative NAO (nNAO), and negative PNA (nPNA) resulted in colder and drier conditions. Furthermore, the nAO, nNAO, and nPNA increased the carbon sinks of terrestrial ecosystems, whereas the pAO, pNAO, and pPNA reduced the carbon sinks, especially in EUR. We also quantified the direct impacts of the oscillations in the concurrent season and their legacy impacts from the preceding season separately. Increased AO and NAO indices increased the carbon sinks in the East Asia (EA) and EUR, whereas an increased PNA index reduced the carbon sinks in most parts of the NH. With respect to legacy impacts, increased AO and PNA indices enhanced the carbon sinks in the Central-Western Asia and North Africa (CWN), Temperate North America (TNA) and Boreal North America (BNA), whereas an increased NAO index strengthened the carbon source capacity in the CWN, EUR, TNA, BNA. These results provide a framework for conducting further research on the mechanisms of interannual variability of the terrestrial carbon cycle.