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| Titel |
Late Eocene sea surface cooling of the western North Atlantic (ODP Site 647A) |
| VerfasserIn |
Kasia K. Sliwinska, Helen K. Coxall, Stefan Schouten |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132927
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| Publikation (Nr.) |
 EGU/EGU2016-13480.pdf |
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| Zusammenfassung |
| The initial shift out of the early Cenozoic greenhouse and into a glacial icehouse climate
occurred during the middle to late Eocene and culminated in the abrupt growth of a
continental-scale ice cap on Antarctica, during an episode known as the Oligocene Isotope
Event 1 (Oi-1) ∼33.7 Ma. Documenting the patterns of global and regional cooling prior to
Oi-1 is crucial for understanding the driving force and feedback behind the switch in climate
mode. Well-dated high-resolution temperature records, however, remain sparse and the
climatic response in some of the most climatically sensitive regions of the Earth, including
the high latitude North Atlantic (NA), where today large amounts of ocean heat are
exchanged, are poorly known.
Here we present a sea surface palaeotemperature record from the late Eocene to the early
Oligocene (32.5 Ma to 35 Ma) of ODP Hole 647A based on archaeal tetraether lipids
(TEX86H). The site is located in the western North Atlantic (Southern Labrador Sea) and is
the most northerly located (53˚ N) open ocean site with a complete Eocene-Oligocene
sequence which yields both calcareous and organic microfossils suitable for detailed proxy
reconstructions. Our record agrees with the magnitude of temperature decrease (∼3 ˚ C sea
surface cooling) recorded by alkenones and pollen data from the Greenland Sea, but our
higher resolution study reveals that the high latitude NA cooling step occurred about
500 kyrs prior to the Oi-1 Antarctic glaciation, at around ∼34.4 Ma. This cooling
can be explained by regional effects related to local NA tectonics including ocean
gateways, known to have changed at the time, with potential to effect NA overturning
circulation due to adjustments in the thermohaline density balance. Alternatively, the
cooling itself may be due to changes in NA circulation, suggesting that global ocean
circulation played a role in pre-conditioning the Earth for Antarctic glaciation. |
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