|ZHU, PENG - Purdue University|
|ZHUANG, QIANLAI - Purdue University|
|WELP, LISA - Purdue University|
|CIAIS, PHILIPPE - Laboratoire Des Sciences Du Climat Et De L'Environnement (LSCE)|
|HEIMANN, MARTIN - Max Planck Institute Of Chemical Ecology|
|PENG, BIN - Tsinghua University|
|LI, WENYU - Tsinghua University|
|ROEDENBECK, CHRISTIAN - Max Planck Institute Of Chemical Ecology|
|KEENAN, TREVOR - University Of Illinois|
Submitted to: Journal of Climate
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2019
Publication Date: 9/15/2019
Citation: Zhu, P., Zhuang, Q., Welp, L., Ciais, P., Heimann, M., Peng, B., Li, W., Bernacchi, C.J., Roedenbeck, C., Keenan, T.F. 2019. Recent warming has resulted in smaller gains in net carbon uptake in northern high latitudes. Journal of Climate. 32(18):5849-5863. https://doi.org/10.1175/JCLI-D-18-0653.1.
Interpretive Summary: Global warming is having a greater impact at the northern high latitudes (NHL) than anywhere else on the planet. It is uncertain whether vegetation at these locations can continue to sustain growth given these rapid changes. This research analyzed the carbon cycle of the NHL from 1974 to 2014 to determine if we can assess the impact of warming over this time on the ability of plants to remove carbon dioxide from the atmosphere through photosynthesis. The results show that the warming conditions are weakening photosynthesis of plants in this region. In particular, the high latitudes in North America shows the greatest loss of productivity. The impact during spring appears to be related with the soil thermal and soil frozen status, while in summer to decreasing temperature sensitivity of photosynthesis. This study suggests that current NHL carbon sink may become unsustainable as temperatures warm further. Because current carbon cycle models do not represent the decrease in temperature sensitivity of net carbon uptake, we argue that current carbon-climate models may over-estimate the impact of rising CO2 on crops and underestimate warming influence on NHL carbon cycles.
Technical Abstract: Carbon balance in the northern high latitudes (NHL) is particularly sensitive to climate change. It remains uncertain whether current regional carbon uptake capacity can sustain under future warmer conditions. Here the CO2 drawdown rate (CDR) between 1974 and 2014, which is related to the strength of the periodical seasonal NHL carbon uptake, is estimated using atmospheric CO2 observations at Barrow, Alaska. A downward inter-annual sensitivity of CDR is found, resulting in weakened contribution of spring warming and an intensified negative contribution of summer warming to the net carbon uptake. These results generally agree with the sensitivity of CO2 fluxes estimated by the Jena global atmospheric CO2inversion that accounts for interannual varying atmospheric transport. In particular, North America shows larger decrease in summer temperature sensitivity. The weakened spring sensitivity of CDR to temperature seems to be related with the soil thermal and soil frozen status, while the summer change in sensitivity of CDR to temperature seems to be caused by the temporally coincident decreasing temperature sensitivity in photosynthesis.This study suggests that current NHL carbon sink may become unsustainable as temperatures warm further. Because current carbon cycle models do not represent the decrease in temperature sensitivity of net carbon uptake, we argue that current carbon-climate models may over-estimate CO2fertilization and underestimate warming influence on NHL carbon balance.