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| Titel |
Stratigraphic significance and global distribution of the δ13C Suess effect during the Anthropocene |
| VerfasserIn |
Andre Paul, Stefan Mulitza |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250109871
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| Publikation (Nr.) |
 EGU/EGU2015-9819.pdf |
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| Zusammenfassung |
| The Anthropocene is the proposed term for the present geological epoch (from the time of the
Industrial Revolution onwards), during which human influence significantly impacts the
environment. We argue that the burning of isotopically light fossil fuel that causes the
so-called “δ13C Suess effect” leaves such a strong imprint on marine sediments that it may
serve to define the onset of this geological epoch, at least since the so-called “Great
Acceleration”, i.e., the second half of the 20th century.
Sediment data with high temporal resolution from the recent past indeed reveal a trend
that corresponds to a negative carbon isotope excursion of the order of one permil,
comparable to carbon isotope excursions in the deep past that define stratigraphic boundaries
such as the Paleocene–Eocene Thermal Maximum (PETM). A global carbon cycle model
based on the MIT general circulation model (MITgcm), fitted with carbon isotopes 13C and
14C and forced with observed changes in the atmospheric carbon dioxide partial pressure and
carbon isotopic ratio 13C/12C, allows to investigate the temporal evolution and
three-dimensional structure of the anomaly.
We show the carbon isotopic ratios of fossil shells of benthic foraminifera (δ13Cc) from
two ocean sediment cores GeoB6008 (31° N) und GeoB9501 (17° N) over the
Anthropocene (mainly the 20th century). The decrease in δ13Cc at 31° N is about 0.8
permil; off Mauretania (at 17° N in the shadow zone of the subtropical gyre) it
still amounts to about 0.4 permil. While the magnitude of the change in the global
carbon cycle model is similar, the difference is smaller: The decrease in the model is
around 0.9 permil near the location of the northern core and around 0.8 permil
near the location of the southern core. The smaller difference of only about 0.1
permil points to a bias in the simulated as opposed to the observed ventilation of the
thermocline.
We further use a carbon cycle multi-box model to extrapolate this change in δ13Cc to the
future. Our data and models highlight the role of the North Atlantic Ocean for the uptake and
storage of anthropogenic carbon and offer a link between proxy and instrumental records
from the recent past. |
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