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| Titel |
Results from IODP Leg 306: Long-term cooling trend in North Atlantic sea-surface temperatures during the last 5 Ma |
| VerfasserIn |
David Naafs, Jens Hefter, Ruediger Stein, Gerald Haug  |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250031866
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| Zusammenfassung |
| In the early Pliocene global surface temperatures were several degrees warmer than today and
ice sheets in the Northern Hemisphere had a limited extent [e.g., Haywood et al., 2005;
Zachos et al., 2001]. This changed during the intensification of Northern Hemisphere
glaciation (INHG) between 3.4 and 2.5 Ma (with a major step around 2.7 Ma), when global
climate cooled and ice sheets in the Northern Hemisphere became more extensive [e.g.,
Zachos et al., 2001].
Here we present results from the first orbitally resolved (~ 4 ka resolution) record of
Uk’37 based sea-surface temperature (SST) in the North Atlantic spanning the last 5 Ma. We
used samples from the recently drilled IODP Site U1313, which is located in the North
Atlantic at 41 oN and is a re-drill of DSDP Site 607. Our results show that the long-term
cooling of SST in the North Atlantic began in the Early Pliocene around 4.1 Ma, which is
earlier than previously thought. During the Pleistocene SST continued to cool and at the
beginning of the mid-Pleistocene transition (MIS 40) glacial SST show a sudden drop to
temperatures comparable to the LGM. At the same time the C37:4 alkenone, an indicator for
arctic water masses [e.g., McClymont et al., 2008], became more abundant. We relate
this to the influence of Arctic waters reaching far into the North Atlantic as the
Arctic Front moved south during the peak glacial conditions of the Middle to Late
Pleistocene.
References:
Haywood, A. M., P. Dekens, A. C. Ravelo, and M. Williams (2005), Warmer tropics
during the mid-Pliocene? Evidence from alkenone paleothermometry and a fully coupled
ocean-atmosphere GCM, Geochem. Geophys. Geosyst., 6(3), doi:10.1029/2004GC000799.
McClymont, E. L., A. Rosell-Melé, G. H. Haug, and J. M. Lloyd (2008), Expansion of
subarctic water masses in the North Atlantic and Pacific oceans and implications for
mid-Pleistocene ice sheet growth, Paleoceanography, 23.
Zachos, J., M. Pagani, L. Sloan, E. Thomas, and K. Billups (2001), Trends, Rhythms, and
Aberrations in Global Climate 65 Ma to Present, Science, 292(5517), 686-693. |
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