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| Titel |
Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates |
| VerfasserIn |
M. Sarnthein  , G. Bartoli, M. Prange, A. Schmittner, B. Schneider, M. Weinelt, N. Andersen, D. Garbe-Schönberg |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 5, no. 2 ; Nr. 5, no. 2 (2009-06-30), S.269-283 |
| Datensatznummer |
250002402
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| Publikation (Nr.) |
 copernicus.org/cp-5-269-2009.pdf |
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| Zusammenfassung |
| A major tipping point of Earth's history occurred during the
mid-Pliocene: the onset of major Northern-Hemisphere Glaciation
(NHG) and of pronounced, Quaternary-style cycles of
glacial-to-interglacial climates, that contrast with more uniform
climates over most of the preceding Cenozoic and continue until
today (Zachos et al., 2001). The severe deterioration of climate
occurred in three steps between 3.2 Ma (warm MIS K3) and 2.7 Ma
(glacial MIS G6/4) (Lisiecki and Raymo, 2005). Various models (sensu
Driscoll and Haug, 1998) and paleoceanographic records
(intercalibrated using orbital age control) suggest clear linkages
between the onset of NHG and the three steps in the final closure of
the Central American Seaways (CAS), deduced from rising salinity
differences between Caribbean and the East Pacific. Each closing
event led to an enhanced North Atlantic meridional overturning
circulation and this strengthened the poleward transport of salt and
heat (warmings of +2–3°C) (Bartoli et al., 2005). Also, the
closing resulted in a slight rise in the poleward atmospheric
moisture transport to northwestern Eurasia (Lunt et al., 2007),
which probably led to an enhanced precipitation and fluvial run-off,
lower sea surface salinity (SSS), and an increased sea-ice cover in
the Arctic Ocean, hence promoting albedo and the build-up of
continental ice sheets. Most important, new evidence shows that the
closing of the CAS led to greater steric height of the North Pacific
and thus doubled the low-saline Arctic Throughflow from the Bering
Strait to the East Greenland Current (EGC). Accordingly, Labrador
Sea IODP Site 1307 displays an abrupt but irreversible EGC cooling
of 6°C and freshening by ~2 psu from
3.25/3.16–3.00 Ma, right after the first but still reversible
attempt of closing the CAS. |
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