Two-way Interactions between Terrestrial Ecosystem and Climate System
Better understanding of factors that control the global carbon cycle could increase confidence in climate projections. In this study, long-term simulations of the Earth system models (ESMs) in phase 5 of the Coupled Model Intercomparison Project archive were used to examine the interannual carbon flux variability associated with ENSO. In addition to ENSO-related interannual variation in the global carbon cycle, the relationship between ENSO and the carbon cycle can be modulated by climate change due to anthropogenic forcing. It is shown that the sensitivity of the terrestrial carbon flux to ENSO will be enhanced under greenhouse warming by 44% (±15%), indicating a future amplification of carbon–climate interactions. Separating the contributions of the changes in carbon sensitivity reveals that the response of land surface temperature to ENSO and the sensitivity of gross primary production to local temperature are significantly enhanced under greenhouse warming, thereby amplifying the ENSO–carbon cycle coupling. In a warm climate, depletion of soil moisture increases temperature response in a given ENSO event. These findings suggest that the ENSO-related carbon cycle will be enhanced by hydroclimate changes caused by anthropogenic forcing.
In contrast to ENSO, on the other hand, it is found that cold extreme also has a considerable role in interannual variability of terrestrial ecosystem. It is analyzed that multiple observation data sets and numerical model simulations to evaluate links between Arctic temperatures and primary productivity in North America. It is found that positive springtime temperature anomalies in the Arctic have led to negative anomalies in gross primary productivity over most of North America during the last three decades, which amount to a net productivity decline of 0.31 PgC yr−1across the continent. This decline is mainly explained by two factors: severe cold conditions in northern North America and lower precipitation in the South Central United States. In addition, United States crop-yield data reveal that during years experiencing anomalous warming in the Arctic, yields declined by approximately 1 to 4% on average, with individual states experiencing declines of up to 20%. It is concluded that the strengthening of Arctic warming anomalies in the past decades has remotely reduced productivity over North America.
Lastly, Earth System modelling result based on the modification of the stomatal conductance scheme will be delivered in this presentation that providing better representation of pan-Arctic warming and greening related to the land-atmosphere feedback.