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| Titel |
A 150,000 year marine δ¹³C synthesis and its use in Earth System modelling |
| VerfasserIn |
Kevin Oliver, Babette Hoogakker, Simon Crowhurst, Gideon Henderson, Ros Rickaby, Neil Edwards, Harry Elderfield |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032898
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| Zusammenfassung |
| The isotopic composition of carbon, δ13C, in seawater is used in reconstructions of ocean
circulation, marine productivity, air-sea gas exchange, and biosphere carbon storage. We
present a synthesis of δ13CÂ measurements taken from foraminifera in marine sediment cores
over the last 150,000 years, comprising previously published and unpublished data from
benthic and planktonic records throughout the global ocean. Data are placed on a common
δ18OÂ age scale and filtered to remove timescales shorter than 6 kyr. Error estimates
account for the resolution and scatter of the original data, and uncertainty in the
relationship between δ13CÂ of calcite and of dissolved inorganic carbon (DIC) in
seawater.
The presentation focuses on the use of the data synthesis as a modelling target, and for
assimilation into Earth system models (ESMs), with two scientific questions used as
examples: (1) changes in biosphere carbon storage; (2) changes in atmospheric pCO2 on
glacial timescales. We discuss problems of uneven sampling, and dealing with records which
often contain greater errors in absolute δ13CÂ than in δ13C changes. We also consider the use
of ESM outputs such as temperature, DIC concentration, and alkalinity to inform the
assimilation process.
Whereas planktonic data place a weak constraint on ESM simulations, due to large error
estimates, benthic data provide a strong constraint, which coherent changes throughout much
of the ocean on orbital timescales. Global deep ocean δ13CÂ is high during Marine Isotope
Stages (MIS) 1, 3, 5a, 5c and 5e, and low during MIS 2, 4 and 6, which are temperature
minima, with larger amplitude variability in the Atlantic Ocean than the Pacific Ocean. The
ESM GENIE is able to adequately reproduce most aspects of the the last glacial maximum
(during MIS 2) distribution under a variety of forcing conditions, indicating that
further proxies are required to constrain the glacial carbon cycle problem. However,
GENIE systematically overestimates the Atlantic-Pacific δ13CÂ difference; methods
to account for systematic structural errors in models, such as this, are discussed. |
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