14:45 〜 15:00
[ACG43-16] Enhanced net CO2 uptake induced by autumn cooling in western-central Siberia
キーワード：炭素循環、シベリア、秋季気温
For the past 60 years, climate change has enhanced the productivity of ecosystems in Siberia. The warming climate has elongated the growing period of vegetation and enhanced the peak productivity during summer. Correspondingly, CO2 uptake in Siberia has continuously increased since the 1960s, playing a significant contributor to the increased amplitude of the atmospheric CO2 seasonal cycle in the Northern Hemisphere.
As the temperature increased over decades, however, the impact of a warming climate has shown different aspects among regions of Siberia. Permafrost thaw could facilitate the release of CO2 through microbial decomposition of carbon stored in frozen soils and through root rot that causes forest dieback. This negative impact of a warming climate on vegetation productivity has begun to be seen in Eastern Siberia and may widely spread over ecosystems standing on permafrost in the future. In western-central Siberia, where permafrost is absent, a warming climate is expected to further increase CO2 uptake during spring and summer. However, continued warming in autumn may facilitate CO2 release from ecosystem respiration, weakening net CO2 uptake during that period.
While the negative impact of a warming climate is becoming a reality in Siberia, a recent study reported that an abrupt and persistent autumn cooling influenced by Pacific Decadal Oscillation (PDO) and Siberian high occurred from 2004 to 2018 around western-central Siberia. This result suggests a possibility that for 2004-2018 CO2 release was suppressed by autumn cooling while having increasing CO2 uptake in warming spring and summer, which leads to a hypothesis that net CO2 uptake in western-central Siberia was the largest ever for 2004-2018.
This study investigates the validity of the hypothesis about recent net CO2 uptake in western-central Siberia. Using atmospheric CO2 measurements in western-central Siberia and upscaled eddy flux observations, we demonstrate how seasonal atmospheric CO2 and net CO2 uptake changed before and after 2004, focusing on autumn.
As the temperature increased over decades, however, the impact of a warming climate has shown different aspects among regions of Siberia. Permafrost thaw could facilitate the release of CO2 through microbial decomposition of carbon stored in frozen soils and through root rot that causes forest dieback. This negative impact of a warming climate on vegetation productivity has begun to be seen in Eastern Siberia and may widely spread over ecosystems standing on permafrost in the future. In western-central Siberia, where permafrost is absent, a warming climate is expected to further increase CO2 uptake during spring and summer. However, continued warming in autumn may facilitate CO2 release from ecosystem respiration, weakening net CO2 uptake during that period.
While the negative impact of a warming climate is becoming a reality in Siberia, a recent study reported that an abrupt and persistent autumn cooling influenced by Pacific Decadal Oscillation (PDO) and Siberian high occurred from 2004 to 2018 around western-central Siberia. This result suggests a possibility that for 2004-2018 CO2 release was suppressed by autumn cooling while having increasing CO2 uptake in warming spring and summer, which leads to a hypothesis that net CO2 uptake in western-central Siberia was the largest ever for 2004-2018.
This study investigates the validity of the hypothesis about recent net CO2 uptake in western-central Siberia. Using atmospheric CO2 measurements in western-central Siberia and upscaled eddy flux observations, we demonstrate how seasonal atmospheric CO2 and net CO2 uptake changed before and after 2004, focusing on autumn.