 |
| Titel |
The eastern Mediterranean response to climate forcing: comparison between the two most recent interglacial maxima |
| VerfasserIn |
G. Marino, E. J. Rohling, F. Sangiorgi, J. S. Sinninghe Damsté, H. Brinkhuis |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026624
|
|
|
|
|
|
| Zusammenfassung |
| The sensitivity of the Mediterranean marine system to climate forcing is still a matter of
debate. Here we investigate the long-term sensitivity of the eastern Mediterranean water mass
circulation to orbital insolation forcing during the last two interglacial maxima. Both
intervals witnessed a considerable increase of monsoon-fuelled river discharge
along the North African margin, with extensive hydrographic changes that led to
the widespread deposition of organic-rich sediments (sapropels). To quantify the
environmental changes in response to different levels of insolation forcing, we present a set
of highly-resolved paleoceanographic proxy records, which are analyzed within
one and the same sediment archive (south-eastern Aegean core LC21) through
sapropels S5 and S1 from the last and current (Holocene) interglacial maxima,
respectively. Oxygen (δ18O) and carbon (δ13C) isotope ratios for surface water
(Globigerinoides ruber) and sub-thermocline dwelling (Neogloboquadrina pachyderma)
planktonic foraminifera, and total organic carbon data (Corg wt%), are used to
reconstruct water-mass dynamics and the magnitude of Corg burial. We find overall more
pronounced environmental changes in the last interglacial records than in those for the
Holocene. Specifically, Corg mass accumulation rates (MAR) reached ~3 g C m-2 yr-1
during deposition of S5, which is an order of magnitude higher than the highest
Corg MAR for S1 at the same site. In addition, there is a negative δ18O shift in the
record of the summer mixed-layer dwelling planktonic foraminifer Globigerinoides
ruber at the onset of S5 deposition, which is twice as large as the analogous shift at
the onset of S1. The surface-to-intermediate water δ13C gradient in S5 is of the
same magnitude as the total surface-to-deep water δ13C gradient within S1. This
suggests that intermediate waters during S5 may have been as poorly ventilated (thus
strongly isolated) as the deep waters during S1. Taken together, the datasets suggest
that the stronger insolation forcing of the last interglacial maximum (S5), relative
to the Holocene maximum (S1), promoted: (a) more dramatic monsoon-fuelled
freshwater flooding into the eastern Mediterranean; (b) stronger water mass stratification,
and (c) higher Corg MARs. We discuss these findings within the context of other
paleoclimate records from the wider tropical/subtropical belt in the Northern Hemisphere |
|
|
|
|
|
|