How does the extratropical forest land-atmosphere coupling of energy and water change under elevated CO2 and warming?
Land and atmosphere are closely coupled to one another through their exchange of energy and water; this coupling modulates soil conditions, vegetation processes, and the near-surface climate. These couplings are also expected to evolve with time in response to changing atmospheric forcings. In this work, we document the present-day condition and future response of the coupled land-atmosphere feedback network based on observations and factorial model experiments using the Energy Exascale Earth System Model (E3SM). We employed a transfer entropy approach and novel network metrics to reveal the patterns and strength of land-atmosphere coupling. We found that the land-atmosphere feedback network has high connectivity over extratropical forest regions. Further climate warming will enhance the whole network coupling by 28% under the high emission scenario. In contrast, CO2 fertilization on vegetation productivity will partially close stomata and dampen the coupling strength of water/energy between land and atmosphere. This work provides new metrics to analyze and benchmark complex system feedbacks in the coupled Earth system.