On the causes of trends in the seasonal amplitude of atmospheric CO 2

• Published in: Global Change Biology
• Main Authors: Piao, Shilong, Liu, Zhuo, Wang, Yilong, Ciais, Philippe, Yao, Yitong, Peng, Shushi, Chevallier, Frédéric, Friedlingstein, Pierre, Janssens, Ivan A., Peñuelas, Josep, Sitch, Stephen, Wang, Tao
• Other Authors: National Natural Science Foundation of China, Federaal Wetenschapsbeleid, H2020 European Research Council
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Arctic; Climate change
• Online Access: http://dx.doi.org/10.1111/gcb.13909; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgcb.13909; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.13909; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/gcb.13909

Abstract No consensus has yet been reached on the major factors driving the observed increase in the seasonal amplitude of atmospheric CO 2 in the northern latitudes. In this study, we used atmospheric CO 2 records from 26 northern hemisphere stations with a temporal coverage longer than 15 years, and an atmospheric transport model prescribed with net biome productivity ( NBP ) from an ensemble of nine terrestrial ecosystem models, to attribute change in the seasonal amplitude of atmospheric CO 2 . We found significant ( p < .05) increases in seasonal peak‐to‐trough CO 2 amplitude ( AMP P ‐T ) at nine stations, and in trough‐to‐peak amplitude ( AMP T ‐P ) at eight stations over the last three decades. Most of the stations that recorded increasing amplitudes are in Arctic and boreal regions (>50°N), consistent with previous observations that the amplitude increased faster at Barrow (Arctic) than at Mauna Loa (subtropics). The multi‐model ensemble mean ( MMEM ) shows that the response of ecosystem carbon cycling to rising CO 2 concentration ( eCO 2 ) and climate change are dominant drivers of the increase in AMP P ‐T and AMP T ‐P in the high latitudes. At the Barrow station, the observed increase of AMP P ‐T and AMP T ‐P over the last 33 years is explained by eCO 2 (39% and 42%) almost equally than by climate change (32% and 35%). The increased carbon losses during the months with a net carbon release in response to eCO 2 are associated with higher ecosystem respiration due to the increase in carbon storage caused by eCO 2 during carbon uptake period. Air‐sea CO 2 fluxes (10% for AMP P ‐T and 11% for AMP T ‐P ) and the impacts of land‐use change (marginally significant 3% for AMP P ‐T and 4% for AMP T ‐P ) also contributed to the CO 2 measured at Barrow, highlighting the role of these factors in regulating seasonal changes in the global carbon cycle.