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| Titel |
Impact of brine-induced stratification on the glacial carbon cycle |
| VerfasserIn |
N. Bouttes, D. Paillard, D. M. Roche |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 6, no. 5 ; Nr. 6, no. 5 (2010-09-15), S.575-589 |
| Datensatznummer |
250003756
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| Publikation (Nr.) |
 copernicus.org/cp-6-575-2010.pdf |
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| Zusammenfassung |
| During the cold period of the Last Glacial Maximum (LGM, about 21 000 years
ago) atmospheric CO2 was around 190 ppm, much lower than the
pre-industrial concentration of 280 ppm. The causes of this substantial drop
remain partially unresolved, despite intense research. Understanding the
origin of reduced atmospheric CO2 during glacial times is crucial to
comprehend the evolution of the different carbon reservoirs within the Earth
system (atmosphere, terrestrial biosphere and ocean). In this context, the
ocean is believed to play a major role as it can store large amounts of
carbon, especially in the abyss, which is a carbon reservoir that is thought
to have expanded during glacial times. To create this larger reservoir, one
possible mechanism is to produce very dense glacial waters, thereby
stratifying the deep ocean and reducing the carbon exchange between the deep
and upper ocean. The existence of such very dense waters has been inferred in
the LGM deep Atlantic from sediment pore water salinity and δ18O
inferred temperature. Based on these observations, we study the impact of a
brine mechanism on the glacial carbon cycle. This mechanism relies on the
formation and rapid sinking of brines, very salty water released during sea
ice formation, which brings salty dense water down to the bottom of the
ocean. It provides two major features: a direct link from the surface to the
deep ocean along with an efficient way of setting a strong stratification. We
show with the CLIMBER-2 carbon-climate model that such a brine mechanism can
account for a significant decrease in atmospheric CO2 and contribute to
the glacial-interglacial change. This mechanism can be amplified by low
vertical diffusion resulting from the brine-induced stratification. The
modeled glacial distribution of oceanic δ13C as well as the deep
ocean salinity are substantially improved and better agree with
reconstructions from sediment cores, suggesting that such a mechanism could
have played an important role during glacial times. |
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