Synthesis of observed air–sea CO<sub>2</sub> exchange fluxes in the river-dominated East China Sea and improved estimates of annual and seasonal net mean fluxes
Limited observations exist for a reliable assessment of annual CO<sub>2</sub> uptake that takes into consideration the strong seasonal variation in the river-dominated East China Sea (ECS). Here we explore seasonally representative CO<sub>2</sub> uptakes by the whole East Chi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-07-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/11/3855/2014/bg-11-3855-2014.pdf |
| Summary: | Limited observations exist for a reliable assessment of annual CO<sub>2</sub> uptake
that takes into consideration the strong seasonal variation in the
river-dominated East China Sea (ECS). Here we explore seasonally
representative CO<sub>2</sub> uptakes by the whole East China Sea derived from
observations over a 14-year period. We firstly identified the biological
sequestration of CO<sub>2</sub> taking place in the highly productive,
nutrient-enriched Changjiang River plume, dictated by the Changjiang River
discharge in warm seasons. We have therefore established an
empirical algorithm as a function of sea surface temperature (SST) and
Changjiang River discharge (CRD) for predicting sea surface <i>p</i>CO<sub>2</sub>.
Syntheses based on both observations and models show that the annually
averaged CO<sub>2</sub> uptake from atmosphere during the period 1998–2011 was
constrained to about 1.8 ± 0.5 mol C m<sup>−2</sup> yr<sup>−1</sup>. This assessment
of annual CO<sub>2</sub> uptake is more reliable and representative, compared to
previous estimates, in terms of temporal and spatial coverage. Additionally,
the CO<sub>2</sub> time series, exhibiting distinct seasonal pattern, gives mean
fluxes of −3.7 ± 0.5, −1.1 ± 1.3, −0.3 ± 0.8 and
−2.5 ± 0.7 mol C m<sup>−2</sup> yr<sup>−1</sup> in spring,
summer, fall and winter, respectively, and also reveals apparent
interannual variations. The flux seasonality shows a strong sink in spring
and a weak source in late summer–mid-fall. The weak sink status during
warm periods in summer–fall is fairly sensitive to changes of <i>p</i>CO<sub>2</sub> and
may easily shift from a sink to a source altered by environmental changes
under climate change and anthropogenic forcing. |
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| ISSN: | 1726-4170 1726-4189 |