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| Titel |
Peak glacial 14C ventilation ages suggest major draw-down of carbon into the abyssal ocean |
| VerfasserIn |
M. Sarnthein  , B. Schneider, P. M. Grootes |
| 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 ; 9, no. 6 ; Nr. 9, no. 6 (2013-11-15), S.2595-2614 |
| Datensatznummer |
250085262
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| Publikation (Nr.) |
 copernicus.org/cp-9-2595-2013.pdf |
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| Zusammenfassung |
| Ice core records demonstrate a glacial–interglacial atmospheric CO2
increase of ~ 100 ppm, while 14C calibration efforts document a
strong decrease in atmospheric 14C concentration during this period. A
calculated transfer of ~ 530 Gt of 14C-depleted carbon is
required to produce the deglacial coeval rise of carbon in the atmosphere and
terrestrial biosphere. This amount is usually ascribed to oceanic carbon
release, although the actual mechanisms remained elusive, since an adequately
old and carbon-enriched deep-ocean reservoir seemed unlikely. Here we present
a new, though still fragmentary, ocean-wide Δ14C data set showing
that during the Last Glacial Maximum (LGM) and Heinrich Stadial 1 (HS-1) the
maximum 14C age difference between ocean deep waters and the atmosphere
exceeded the modern values by up to 1500 14C yr, in the extreme
reaching 5100 14C yr. Below 2000 m depth the 14C ventilation age
of modern ocean waters is directly linked to the concentration of dissolved
inorganic carbon (DIC). We propose as a working hypothesis that the modern
regression of DIC vs. Δ14C also applies for LGM times, which
implies that a mean LGM aging of ~ 600 14C yr corresponded to a
global rise of ~ 85–115 μmol DIC kg−1 in the deep
ocean. Thus, the prolonged residence time of ocean deep waters may indeed
have made it possible to absorb an additional ~ 730–980 Gt DIC, one
third of which possibly originated from intermediate waters. We also infer
that LGM deep-water O2 dropped to suboxic values of <
10 μmol kg−1 in the Atlantic sector of the Southern Ocean,
possibly also in the subpolar North Pacific. The deglacial transfer
of the extra-aged, deep-ocean carbon to the atmosphere via the dynamic
ocean–atmosphere carbon exchange would be sufficient to account for two
trends observed, (1) for the increase in atmospheric CO2 and (2) for the
190‰ drop in atmospheric Δ14C during the so-called HS-1
"Mystery Interval", when atmospheric 14C production rates were largely
constant. |
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