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| Titel |
Ocean circulation in the southern Benguela region from the Pliocene to the Pleistocene: tracking Agulhas leakage into the SE Atlantic |
| VerfasserIn |
Benjamin Petrick, Erin McClymont, Sojna Felder, Melanie Leng |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073696
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| Zusammenfassung |
| The transition from the warmth of the middle Pliocene to the large amplitude, 100 kyr
glacial-interglacial cycles of the late Pleistocene provides a way to understand the forcings
and impacts of regional and global climate change. Here, we investigate changes in ocean
circulation over the period from 3.5 Ma to present using a marine sediment core, ODP Site
1087 (31o28’S, 15o19’E, 1374m water depth). ODP 1087 is located in the South-east
Atlantic Ocean, outside the Benguela upwelling region. Its location allows investigation of
the history of the heat and salt transfer to the Atlantic Ocean from the Indian Ocean
(“Agulhas leakage”), which plays an important part in the global thermohaline circulation. It
is not known how this transfer reacted to generally warmer global temperatures
during the mid-Pliocene, nor to the transition to a globally cooler climate in the early
Pleistocene.
Our approach is to apply several organic geochemistry proxies and foraminiferal analyses
to reconstruct the history of ODP 1087. These include the U37K’ index to reconstruct sea
surface temperatures, pigment analysis for understanding productivity changes, and
foraminifera assemblage analysis to detect the presence of different water masses at the site.
We have identified changes in SSTs and biological productivity that we argue to reflect shifts
in the position of the Benguela upwelling cells, and a changing influence of Agulhas leakage.
Our new data reveal a different organization in the Southeast Atlantic. It shows that during
the Pliocene ODP 1087 was dominated by Benguela upwelling which had shifted south. We
find no evidence for Agulhas leakage during the mid Pliocene, which could mean that
Agulhas Leakage was severely reduced during the mid Pliocene. The implications of these
results for understanding Plio-Pleistocene climate changes will be explored here. |
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