 |
| Titel |
Early deglacial Atlantic overturning decline and its role in atmospheric CO2 rise inferred from carbon isotopes (δ13C) |
| VerfasserIn |
A. Schmittner, D. C. Lund |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1814-9324
|
| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 2 ; Nr. 11, no. 2 (2015-02-05), S.135-152 |
| Datensatznummer |
250117159
|
| Publikation (Nr.) |
 copernicus.org/cp-11-135-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| The reason for the initial rise in atmospheric
CO2 during the last deglaciation remains unknown. Most
recent hypotheses invoke Southern Hemisphere processes such as
shifts in midlatitude westerly winds. Coeval changes in the Atlantic meridional
overturning circulation (AMOC) are poorly quantified, and their relation
to the CO2 increase is not understood. Here we compare simulations
from a global, coupled climate–biogeochemistry model that includes
a detailed representation of stable carbon isotopes (δ13C) with
a synthesis of high-resolution δ13C reconstructions
from deep-sea sediments and ice core data. In response to a prolonged
AMOC shutdown initialized from a preindustrial state, modeled δ13C of
dissolved inorganic carbon (δ13CDIC)
decreases in most of the surface ocean and the subsurface Atlantic, with
largest amplitudes (more than 1.5‰) in the intermediate-depth North
Atlantic. It increases in the intermediate and abyssal South Atlantic, as well as
in the subsurface Southern, Indian, and Pacific oceans. The modeled pattern is
similar and highly correlated with the available foraminiferal δ13C
reconstructions spanning from the late Last Glacial Maximum (LGM, ~19.5–18.5 ka BP)
to the late Heinrich stadial event 1 (HS1, ~16.5–15.5 ka BP), but the model
overestimates δ13CDIC reductions in the North Atlantic.
Possible reasons for the model–sediment-data differences are discussed.
Changes in remineralized
δ13CDIC dominate the total δ13CDIC variations in the
model but preformed contributions are not negligible.
Simulated changes in atmospheric CO2
and its isotopic composition (δ13CCO2) agree well with ice core data.
Modeled effects of AMOC-induced wind changes on the carbon and isotope cycles are small, suggesting
that Southern Hemisphere westerly wind effects may have been less important for the global
carbon cycle response during HS1 than previously thought.
Our results indicate that during the early deglaciation the AMOC decreased for several thousand years. We
propose that the observed early deglacial rise in atmospheric CO2 and the decrease in
δ13CCO2 may have been dominated by an AMOC-induced decline of the ocean's biologically sequestered carbon
storage. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|