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| Titel |
Diagnosing CO2 fluxes in the upwelling system off the Oregon–California coast |
| VerfasserIn |
Z. Cao, M. Dai, W. Evans, J. Gan, R. Feely |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 22 ; Nr. 11, no. 22 (2014-11-24), S.6341-6354 |
| Datensatznummer |
250117686
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| Publikation (Nr.) |
 copernicus.org/bg-11-6341-2014.pdf |
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| Zusammenfassung |
| It is generally known that the interplay between the carbon and nutrients
supplied from subsurface waters via biological metabolism determines the
CO2 fluxes in upwelling systems. However, quantificational assessment
of such interplay is difficult because of the dynamic nature of both
upwelling circulation and the associated biogeochemistry. We recently
proposed a new framework, the Ocean-dominated Margin (OceMar), for
semi-quantitatively diagnosing the CO2 source/sink nature of an ocean
margin over a given period of time, highlighting that the relative
consumption between carbon and nutrients determines if carbon is in excess
(i.e., CO2 source) or in deficit (i.e., CO2 sink) in the upper
waters of ocean margins relative to their off-site inputs from the adjacent
open ocean. In the present study, such a diagnostic approach based upon both
couplings of physics–biogeochemistry and carbon–nutrients was applied to
resolve the CO2 fluxes in the well-known upwelling system off Oregon and northern California of the US
west coast, using data collected along
three cross-shelf transects from the inner shelf to the open basin in
spring/early summer 2007. Through examining the biological consumption on
top of the water mass mixing revealed by the total alkalinity–salinity
relationship, we successfully predicted and semi-analytically resolved the
CO2 fluxes showing strong uptake from the atmosphere beyond the
nearshore regions. This CO2 sink nature primarily resulted from the
higher utilization of nutrients relative to dissolved inorganic carbon (DIC)
based on their concurrent inputs from the depth. On the other hand, the
biological responses to intensified upwelling were minor in nearshore waters
off the Oregon–California coast, where significant CO2 outgassing was
observed during the sampling period and resolving CO2 fluxes could be
simplified without considering DIC/nutrient consumption, i.e., decoupling
between upwelling and biological consumption. We reasoned that coupling
physics and biogeochemistry in the OceMar model would assume a steady state
with balanced DIC and nutrients via both physical transport and biological
alterations in comparable timescales. |
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