Low frequency changes in CO 2 concentration in East Asia related to Pacific decadal oscillation and Atlantic multi-decadal oscillation for mid-summer and early fall.

The climatological seasonal maximum and minimum CO ₂ concentrations in East Asia for 1987-2020 have been recorded at April and August, respectively. We found that the CO ₂ concentration in East Asia during July, August, and September (JAS) is lower than normal before the late 1990s and after the early 2010s (Low_CO ₂ period), and higher than normal from the late 1990s to the early 2010s (High_CO ₂ period). The low-frequency variability of CO ₂ concentration in East Asia during JAS correlates with both Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO)-related sea surface temperatures (SSTs). We analyzed atmospheric and oceanic conditions during JAS between the two periods, finding that precipitation in East Asia decreased during JAS in High_CO ₂ period than that in Low_CO ₂ period, possibly due to PDO and AMO-related SST forcing, which decreases vegetation's photosynthetic activity. This may lead to a higher CO ₂ concentration than normal in East Asia in High_CO ₂ period through reduced uptake of CO ₂ from the atmosphere. This implies that terrestrial vegetation activity influenced by remote SST forcings should be monitored to better understand regional carbon cycles in East Asia.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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