Worldwide impacts of atmospheric vapor pressure deficit on the interannual variability of terrestrial carbon sinks

Atmospheric vapor pressure deficit has worldwide impacts on the interannual variability of terrestrial carbon sinks and atmospheric carbon dioxide concentrations. Interannual variability of the terrestrial ecosystem carbon sink is substantially regulated by various environmental variables and highly dominates the interannual variation of atmospheric carbon dioxide (CO2) concentrations. Thus, it is necessary to determine dominating factors affecting the interannual variability of the carbon sink to improve our capability of predicting future terrestrial carbon sinks. Using global datasets derived from machine-learning methods and process-based ecosystem models, this study reveals that the interannual variability of the atmospheric vapor pressure deficit (VPD) was significantly negatively correlated with net ecosystem production (NEP) and substantially impacted the interannual variability of the atmospheric CO2 growth rate (CGR). Further analyses found widespread constraints of VPD interannual variability on terrestrial gross primary production (GPP), causing VPD to impact NEP and CGR. Partial correlation analysis confirms the persistent and widespread impacts of VPD on terrestrial carbon sinks compared to other environmental variables. Current Earth system models underestimate the interannual variability in VPD and its impacts on GPP and NEP. Our results highlight the importance of VPD for terrestrial carbon sinks in assessing ecosystems' responses to future climate conditions.

Automated summary

The interannual variability of atmospheric vapor pressure deficit has global impacts on terrestrial carbon sinks and atmospheric carbon dioxide concentrations. It is necessary to determine the dominating factors affecting the carbon sink's interannual variability in order to improve predictions of future carbon sinks. This study shows that vapor pressure deficit significantly impacts net ecosystem production and the interannual variability of atmospheric CO2 growth rate, highlighting its importance in assessing ecosystems' responses to future climate conditions.