 |
| Titel |
Air–sea exchanges of CO2 in the world's coastal seas |
| VerfasserIn |
C.-T. A. Chen, T.-H. Huang, Y.-C. Chen, Y. Bai, X. He, Y. Kang |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 10 ; Nr. 10, no. 10 (2013-10-15), S.6509-6544 |
| Datensatznummer |
250085364
|
| Publikation (Nr.) |
 copernicus.org/bg-10-6509-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
The air–sea exchanges of CO2 in the world's 165 estuaries and 87
continental shelves are evaluated. Generally and in all seasons, upper
estuaries with salinities of less than two are strong sources of CO2
(39 ± 56 mol C m−2 yr−1, positive flux indicates that the
water is losing CO2 to the atmosphere); mid-estuaries with salinities of
between 2 and 25 are moderate sources
(17.5 ± 34 mol C m−2 yr−1) and lower estuaries with
salinities of more than 25 are weak sources
(8.4 ± 14 mol C m−2 yr−1). With respect to latitude,
estuaries between 23.5 and 50° N have the largest flux per unit area
(63 ± 101 mmol C m−2 d−1); these are followed by
lower-latitude estuaries (23.5–0° S:
44 ± 29 mmol C m−2 d−1; 0–23.5° N:
39 ± 55 mmol C m−2 d−1), and then regions north of
50° N (36 ± 91 mmol C m−2 d−1). Estuaries south
of 50° S have the smallest flux per unit area
(9.5 ± 12 mmol C m−2 d−1). Mixing with low-pCO2
shelf waters, water temperature, residence time and the complexity of the
biogeochemistry are major factors that govern the pCO2 in estuaries,
but wind speed, seldom discussed, is critical to controlling the air–water
exchanges of CO2. The total annual release of CO2 from the world's
estuaries is now estimated to be 0.10 Pg C yr−1, which is much lower
than published values mainly because of the contribution of a considerable
amount of heretofore unpublished or new data from Asia and the Arctic. The
Asian data, although indicating high pCO2, are low in sea-to-air
fluxes because of low wind speeds. Previously determined flux values rely
heavily on data from Europe and North America, where pCO2 is lower but
wind speeds are much higher, such that the CO2 fluxes are higher than in
Asia. Newly emerged CO2 flux data in the Arctic reveal that estuaries
there mostly absorb rather than release CO2.
Most continental shelves, and especially those at high latitude, are
undersaturated in terms of CO2 and absorb CO2 from the atmosphere
in all seasons. Shelves between 0 and 23.5° S are on average a weak
source and have a small flux per unit area of CO2 to the atmosphere.
Water temperature, the spreading of river plumes, upwelling, and biological
production seem to be the main factors in determining pCO2 in the
shelves. Wind speed, again, is critical because at high latitudes, the winds
tend to be strong. Since the surface water pCO2 values are low, the
air-to-sea fluxes are high in regions above 50° N and below
50° S. At low latitudes, the winds tend to be weak, so the
sea-to-air CO2 flux is small. Overall, the world's continental shelves
absorb 0.4 Pg C yr−1 from the atmosphere. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|