Eastern Mediterranean surface water temperatures and d18O composition during deposition of sapropels in the late Quaternary


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amackensen [ at ] awi-bremerhaven.de

Abstract

Water column stratification increased at climatic transitions from cold to warm periods during the lateQuaternary and led to anoxic conditions and sapropel formation in the deep eastern Mediterranean basins. Highresolutiondata sets on sea-surface temperatures (SST) (estimated from U37k0 indices) and d18O of planktonicforaminifer calcite (d18Ofc) across late Pleistocene sapropel intervals show that d18Ofc decreased (between 1 and4.6%) and SST increased (between 0.7 and 6.7 C). Maximal d18Oseawater depletion of eastern Mediterraneansurface waters at the transition is between 0.5 and 3.0%, and in all but one case exceeded the depletion seen in awestern Mediterranean core. The depletion in d18Oseawater is most pronounced at sapropel bases, in agreementwith an initial sudden input of monsoon-derived freshwater. Most sapropels coincide with warming trends ofSST. The density decrease by initial freshwater input and continued warming of the sea surface pooled freshwater in the surface layer and prohibited deep convection down to ageing deep water emplaced during cold andarid glacial conditions. An exception to this pattern is glacial sapropel S6; its largest d18Oseawater depletion(3%) is almost matched by the depletion in the western Mediterranean Sea, and it is accompanied by surfacewater cooling following an initially rapid warming phase. A second period of significant isotopic depletion is inisotope stage 6 at the 150 kyr insolation maximum. While not expressed as a sapropel due to cold SST, it is inaccord with a strengthened monsoon in the southern catchment.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
5490
DOI 10.1029/2000PA000617

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Emeis, K. C. , Schulz, H. , Struck, U. , Rossignol-Strick, M. , Erlenkeuser, H. , Howell, M. W. , Kroon, D. , Mackensen, A. , Ishizuka, S. , Oba, T. , Sakamoto, T. and Koizumi, I. (2003): Eastern Mediterranean surface water temperatures and d18O composition during deposition of sapropels in the late Quaternary , Paleoceanography, 18 (1) . doi: 10.1029/2000PA000617


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