In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 10 ( 2022-05-31), p. 6953-6970
Abstract:
Abstract. We analyzed air samples collected on board a C-130 cargo
aircraft over the western North Pacific from May 2012 to March 2020
for atmospheric δ(O2 / N2) and CO2 amount fraction.
Observations were corrected for significant artificial fractionation of
O2 and N2 caused by thermal diffusion during the air sample
collection using the simultaneously measured δ(Ar / N2). The
observed seasonal cycles of the δ(O2 / N2) and atmospheric
potential oxygen (δ(APO)) varied nearly in opposite phase to the cycle of
the CO2 amount fraction at all latitudes and altitudes. Seasonal
amplitudes of δ(APO) decreased with latitude from 34 to
25∘ N, as well as with increasing altitude from the surface to 6 km by 50 %–70 %, while those of the CO2 amount fraction decreased by less
than 20 %. By comparing the observed values with the simulated δ(APO) and CO2 amount fraction values generated by an atmospheric
transport model, we found that the seasonal δ(APO) cycle in the
middle troposphere was modified significantly by a combination of the
northern and southern hemispheric seasonal cycles due to the
interhemispheric mixing of air. The simulated δ(APO) underestimated
the observed interannual variation in δ(APO) significantly, probably
due to the interannual variation in the annual mean air–sea O2 flux.
Interannual variation in δ(APO) driven by the net marine biological
activities, obtained by subtracting the assumed solubility-driven component
of δ(APO) from the total variation, indicated a clear influence on
annual net sea–air marine biological O2 flux during El Niño and
net air–sea flux during La Niña. By analyzing the observed secular
trends of δ(O2 / N2) and the CO2 amount fraction, global
average terrestrial biospheric and oceanic CO2 uptakes for the period
2012–2019 were estimated to be (1.8±0.9) and (2.8±0.6) Pg a−1 (C equivalents), respectively.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-22-6953-2022
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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