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| Titel |
Holocene sea surface temperatures in the East African Coastal Current region and their relationship with North Atlantic climate |
| VerfasserIn |
Henning Kuhnert, Holger Kuhlmann, Mahyar Mohtadi, Jürgen Pätzold |
| 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 |
250075488
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| Zusammenfassung |
| The East African Coastal Current (EACC) is one of the western boundary currents of the
Indian Ocean and represents the only pathway for southern water masses to enter the Arabian
Sea. Today, sea surface temperatures (SST) in the western boundary currents region covary
with those in large parts of the central tropical Indian Ocean. The latter play an
important role in global climate by influencing the mean state of the North Atlantic
Oscillation (NAO) and associated Atlantic SST anomalies (Hoerling et al., 2001). In the
EACC region paleoclimate data are sparse and its Holocene temperature history is
unexplored.
We present data from a 5 m long sediment core retrieved off northern Tanzania
where the EACC flows northward year-round. Proximity to the Pangani River mouth
provides a steady sediment supply. We have reconstructed SST from Mg/Ca and
stable oxygen isotope ratios (-18O) of the surface-dwelling planktonic foraminifera
species Globigerinoides ruber (sensu stricto). Our record spans the time period
from 9700 to 1400 years BP at an average temporal resolution of 40 years. The
Holocene is characterized by a sequence of intervals representing cool, warm, cool,
and intermediate SST, with boundaries at 7.8, 5.6, and 4.4 ka BP. SST anomalies
relative to the series mean range from -0.6 to +0.75 Ë C. This pattern strikingly
resembles a Northwest Atlantic foraminiferal -18O record (Cléroux et al., 2012), with
warm Indian SST corresponding to low Atlantic foraminiferal -18O (indicating
low sea surface density). This matches the modern situation on the interdecadal
time-scale, where a warm Indian Ocean leads to a shift of the NAO towards a positive
mean state, which is accompanied by SST warming over much of the low- and
mid-latitude western Atlantic and a displacement of the Gulf Stream path. We hypothesize
that this mechanism also operates on millennial time-scales to explain the obvious
similarities in the SST patterns observed in the Northwest Atlantic and western Indian
Oceans.
References
Cléroux, C., M. Debret, E. Cortijo, J.-C. Duplessy, F. Dewilde, J. G. Reijmer, and N.
Massei (2012) High-resolution surface reconstructions off Cape Hatteras over the last 10 ka,
Paleoceanography, 27, PA1205, doi: 10.1029/2011PA002184.
Hoerling, M. P., J. W. Hurrell, and T. Xu (2001) Tropical origins for recent North Atlantic
climate change, Science, 292, 90-92. |
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