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| Titel |
Spatiotemporal variations of fCO2 in the North Sea |
| VerfasserIn |
A. M. Omar, A. Olsen, T. Johannessen, M. Hoppema, H. Thomas, A. V. Borges |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 6, no. 1 ; Nr. 6, no. 1 (2010-01-29), S.77-89 |
| Datensatznummer |
250003347
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| Publikation (Nr.) |
 copernicus.org/os-6-77-2010.pdf |
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| Zusammenfassung |
| Data from two Voluntary Observing Ship (VOS) (2005–2007) augmented
with data subsets from ten cruises (1987–2005) were used to
investigate the spatiotemporal variations of the CO2 fugacity
in seawater (fCO2sw) in the North Sea at seasonal and
inter-annual time scales. The observed seasonal fCO2sw
variations were related to variations in sea surface temperature
(SST), biology plus mixing, and air-sea CO2 exchange. Over the
study period, the seasonal amplitude in fCO2sw induced
by SST changes was 0.4–0.75 times those resulting from variations
in biology plus mixing. Along a meridional transect, fCO2sw
normally decreased northwards (−12 μatm per degree
latitude), but the gradient disappeared/reversed during spring as a
consequence of an enhanced seasonal amplitude of fCO2sw
in southern parts of the North Sea. Along a zonal transect, a weak
gradient (−0.8 μatm per degree longitude) was observed
in the annual mean fCO2sw. Annually and averaged over
the study area, surface waters of the North Sea were CO2
undersaturated and, thus, a sink of atmospheric CO2. However,
during summer, surface waters in the region 55.5–54.5° N
were CO2 supersaturated and, hence, a source for atmospheric
CO2. Comparison of fCO2sw data acquired within two
1°×1° regions in the northern and southern
North Sea during different years (1987, 2001, 2002, and 2005–2007)
revealed large interannual variations, especially during spring and
summer when year-to-year fCO2sw differences
(≈160–200 μatm) approached seasonal changes
(≈200–250 μatm). The springtime variations
resulted from changes in magnitude and timing of the phytoplankton
bloom, whereas changes in SST, wind speed and total alkalinity may
have contributed to the summertime interannual fCO2sw
differences. The lowest interannual variation
(10–50 μatm) was observed during fall and early winter.
Comparison with data reported in October 1967 suggests that the
fCO2sw growth rate in the central North Sea was similar
to that in the atmosphere. |
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