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| Titel |
Intermediate water response to natural climate variability during the Holocene at the eastern boundary of the subtropical gyre (NW Africa) |
| VerfasserIn |
Audrey Bamberg, David Heslop, Yair Rosenthal, Stefan Mulitza, Andre Paul, Carsten Rühlemann, Michael Schulz |
| 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 |
250041731
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| Zusammenfassung |
| Decadal-to-millennial-scale climate variability during the Holocene is well documented in
numerous paleoclimate records collected from both hemispheres. Nevertheless, our
understanding of the forcing and mechanisms causing rapid climate events is still limited and
a direct role of the thermohaline circulation for climate change during interglacials (i.e., the
Holocene) has so far not been demonstrated. Off northwest Africa, sediment core
GeoB6007-2 (30Ë 51’N, 10Ë 16’E at 900 m depth) is strategically located to record small
changes in the production of Eastern North Atlantic Central Waters and main thermocline
depth at the eastern boundary of the subtropical gyre. Thus GeoB6007-2 provides
an ideal opportunity to record paleoceanographic variability of the intermediate
branch of the Atlantic Meridional Overturning Circulation (AMOC) during the
Holocene.
We present benthic foraminiferal oxygen (δ18Oc) and carbon (δ13C) isotopic records
spanning the past 9500 years. Additionally, we present high-resolution intermediate
water temperature and δ18Oseawater (as a salinity proxy) reconstructions for time
intervals during the early (8-9 ka), mid (4.5-5.5 ka) and late (0-1.2 ka) Holocene,
using a newly developed Mg/Ca-temperature calibration for the benthic foraminifer
Hyalinea balthica. Benthic foraminifera abundances are high throughout the core,
yielding a sample resolution of 0.5 cm for stable isotopic reconstructions and 1 cm
resolution for Mg/Ca based temperatures allowing a temporal resolution of 10-20
years over the past 9000 years. The Late Holocene temperature record indicates
a steady cooling trend of over 1 Ë C from the end of the Medieval Warm Period
(MWP) into the Little Ice Age (LIA) from ca. 9.2 Ë C to modern values of 8.2 Ë C.
Superimposed on this trend is multi-decadal variability of ca. 0.3 Ë C co-varying with
centennial-to-millennial variability in the stable isotopes and associated with known
climate events of the late Holocene such as the 8.2 ka event, MWP and LIA. The new
intermediate water records underscore the coupling between the natural variability of the
AMOC on decadal-to-millennial timescales and northern hemisphere climate change. |
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