 |
| Titel |
Hydrographic changes in the surface ocean of the sub-Antarctic Atlantic linked to atmospheric CO2 variations over the last deglaciation and Marine Isotope Stage 3 |
| VerfasserIn |
Julia Gottschalk, Luke C. Skinner, Claire Waelbroeck |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095293
|
| Publikation (Nr.) |
 EGU/EGU2014-10742.pdf |
|
|
|
|
|
| Zusammenfassung |
| The deglacial rise in atmospheric CO2 (CO2,atm) is thought to be linked with the evasion of
CO2 from a carbon-enriched reservoir of the deep Southern Ocean. The transfer of carbon
from the deep ocean to the atmosphere is associated with hydrographic changes in the surface
ocean. For instance, exchange of carbon between the ocean and atmosphere is promoted by
upwelling of CO2-rich water masses to the surface, predominantly in winter. This process
may be inhibited by a strong density stratification of the upper water column and the
summer-time biological sequestration of carbon in the surface ocean which has been
suggested to be driven by airborne dust supply. To what extent these hydrographic changes in
the surface ocean and thus, biological and physical processes in the Southern Ocean are
linked to millennial-scale variations in CO2,atm is insufficiently understood. Here, we present
stable oxygen and carbon isotope records of the planktonic foraminifera Globigerina
bulloides and Neogloboquadrina pachyderma (s.) and planktonic foraminiferal
assemblages from the sub-Antarctic sediment core MD07-3076CQ (44°4’S, 14Ë
12’W, 3770 m) in order to reconstruct surface ocean processes in the sub-Antarctic
Atlantic and their linkage to millennial-scale variations of CO2,atm over the last
70 ka. Stable oxygen and carbon isotopes of G. bulloides and N. pachyderma (s.)
are assumed to indicate spring and summer surface water conditions, respectively.
Strong negative excursions of δ13C of G. bulloides indicate nutrient-enriched surface
water during intervals of rising CO2,atm which points at enhanced winter-time
upwelling of CO2- rich water masses in the Southern Ocean during these intervals.
Simultaneously, increasing δ13C of N. pachyderma (s.) paralleling the rate of CO2 change
in the atmosphere hints at enhanced carbon air-sea exchange during summer. A
strong gradient in δ18O between both foraminifera species suggests a strong vertical
stratification of the water column during the LGM promoting an isolation of the
deep carbon rich reservoir from the atmosphere. These results point at the link
between oceanic evasion of CO2 from the deep Southern Ocean and millennial-scale
rises of CO2,atm during the last 70 ka and stress the role of vertical mixing in the
Southern Ocean promoting air-sea equilibration of carbon in the surface ocean. |
|
|
|
|
|
|