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| Titel |
The global coastal ocean: trends and variability in air-sea CO2 fluxes |
| VerfasserIn |
Timothée Bourgeois, James Orr, Laure Resplandy, Christian Ethe, Marion Gehlen, Laurent Bopp |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089778
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| Publikation (Nr.) |
 EGU/EGU2014-3991.pdf |
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| Zusammenfassung |
| The coarse spatial resolution of typical global ocean models is inadequate to study the coastal
ocean. But state-of-the-art global ocean models have seen tremendous improvements in
resolution in the last 10 years. Those new high-resolution models are now beginning to be
coupled with biogeochemical models to study the carbon cycle, an effort that allows us to
begin to assess the exceptional nature of the coastal ocean, at the global scale. As a first step
to gauge how the ocean biogeochemical and global circulation model NEMO-PISCES
represents air-sea CO2 fluxes in the coastal ocean, we compared observed to simulated fluxes
at 1/2° global resolution. Simulated fluxes in polar regions, upwelling zones, and areas
influenced by estuaries have phasing delays of up to 1-3 months and seasonal amplitudes
that are underestimated by up to a factor of two. The air-sea CO2 flux is driven
by the difference between atmospheric and oceanic pCO2, with variability in the
latter mainly responsible for flux variability. In order to determine the drivers of
oceanic pCO2 variability, the signal has been decomposed into contributions from
changes in dissolved inorganic carbon, total alkalinity, temperature, and salinity. In
the high latitudes, seasonal variability in surface ocean pCO2 is driven mainly by
variability in dissolved inorganic carbon whereas in low latitudes it is driven by
temperature variations. Variability in total alkalinity also plays a role in regions
influenced by estuaries. According to our model, the global coastal ocean (regions where
depth < 500 m) absorbs 0.35 Pg C yr-1 of total carbon (natural + anthropogenic)
during the 1998-2007, similar to previous estimates. Globally our model took up
2.34 Pg C yr -1 of anthropogenic carbon during the 1998-2007, consistent with
previous estimates. Yet only 6% of that (0.14 Pg C yr-1) is absorbed by the global
coastal ocean, i.e., less than its 9% proportion of the global ocean surface area.
The same analysis is being carried out with a 1/4° version of the same model. |
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