Biosphere‐climate interactions in a changing climate over North America

Abstract

This study focuses on projected changes to vegetation characteristics and their interactions with the atmosphere under future climatic conditions over North America, using four transient climate change simulations of the Canadian Regional Climate Model (CRCM5). Here CRCM5 performs dynamical downscaling of the Canadian Earth System Model (CanESM2) simulated data, for Representative Concentration Pathways (RCPs) 4.5 and 8.5. For each RCP, two CRCM5 simulations are performed-one with static vegetation phenology and the other with dynamic vegetation phenology-for the 1950-2100 period over North America. The dynamic vegetation model used here is the Canadian Terrestrial Ecosystem Model. Results show that the extension of the growing season under future climatic conditions in the dynamic phenology simulations leads to higher annual vegetation productivity and biomass. In comparison with projected changes based on CRCM5 with static phenology, CRCM5 with phenology dynamics leads to an albedo-mediated warming enhancement across most of North America in spring. In summer, results suggest a warming enhancement in the northern latitudes and an attenuation of warming for more southern regions due to hydrological feedbacks. Furthermore, results suggest that vegetation enhances its water-use efficiency with rising atmospheric CO 2 concentrations. Over southeastern United States, in the dynamic phenology simulation corresponding to the RCP8.5 scenario, the adverse effects of the projected increase in temperatures and decrease in precipitation on vegetation dominate the CO 2 fertilization effect, leading to decreasing trends in productivity during the 2071-2100 period. This study thus clearly demonstrates that phenology dynamics modulate greenhouse gas-mediated warming through various biophysical feedbacks.

Influences of agricultural phenology dynamic on land surface biophysical process and climate feedback

“…Coupling static and dynamic phenology in the CanESM2 model shows that a longer growing season causes higher plant productivity and biomass. The dynamic phenology resulted in a warmer spring controlled by the decreased surface albedo in North America and offset the fertilization effect of carbon dioxide via a temperature increase and a rainfall reduction under the RCP8.5 scenario (radiant energy increased by 8.5 W m −2 by 2100) in southeastern America (Garnaud and Sushama, 2015). These study results highlight the importance of dynamic phenology in climate feedbacks via biophysical processes.…”

Land–climate interactions

“…In boreal regions, the combined northward migration of the treeline and increased growing season length in response to increased temperatures in those regions (Section 2.2) will have positive feedbacks both on global and regional annual warming (high confidence) (Garnaud and Sushama 2015;Jeong et al 2014a;O'ishi and Abe-Ouchi 2009;Port et al 2012;Strengers et al 2010).…”