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| Titel |
Reconstructing Holocene palaeo-environmental conditions in the Baltic: A
multi-proxy comparison from the Little Belt (IODP Expedition 347, Site
M0059) |
| VerfasserIn |
Ulrich Kotthoff, Elinor Andrén, Thomas Andrén, Jeanine Ash, Thorsten Bauersachs, Anne-Sophie Fanget, Wojciech Granoszewski, Jeroen Groeneveld, Nadine Krupinski, Odile Peyron, Caroline Slomp, Anna Stepanova, Jonathan Warnock, Niels van Helmond, Expedition 347 Science Party |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132937
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| Publikation (Nr.) |
 EGU/EGU2016-13492.pdf |
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| Zusammenfassung |
| Some of the largest marine environmental impacts from ongoing global climate change are
occurring in continental shelf seas and enclosed basins, including severe oxygen depletion,
intensifying stratification, and increasing temperatures. In order to predict future changes in
water mass conditions, it is essential to reconstruct how these conditions have changed in the
past against the background of climate changes. The brackish Baltic Sea is one of the
largest semi-enclosed basins worldwide, and its sediment records provide a unique
opportunity to analyse palaeo-environmental and climate change in central and
northern Europe. IODP Expedition 347 recovered an exceptional set of sediment cores
from the Baltic Sea which allow high-resolution reconstructions in unprecedented
quality.
We present a comparison of commonly-used proxies to reconstruct palaeoecosystems,
-temperatures, and -salinity from IODP Site M0059 in the Little Belt over the past ∼8000
years. Our aim is to reconstruct the development of the terrestrial and marine ecosystems in
the research area and the related environmental conditions, and to identify potential
limitations of individual proxies.
The age model for Site M0059 is based on 14Cdating, biostratigraphic correlation with
neighbouring terrestrial pollen records, and sediment stratigraphy. Sedimentary
organic carbon content and the bulk elemental composition have been measured,
and can be used to determine the depositional environment and degree of oxygen
depletion (e.g., Mo, Corg/Ptot). Pollen is used as proxy for vegetation development
in the hinterland of the southern Baltic Sea and as a land/air-temperature proxy.
Comparison with dinoflagellate cysts, insect remains, and green algae remains from the
same samples provides a direct land-sea comparison. The application of the modern
analogues technique to pollen assemblages has previously yielded precise results for late
Pleistocene and Holocene datasets, including specific information on seasonality,
but pollen-based reconstructions for Northern Europe may be hampered by plant
migration effects. Palynomorph analyses are therefore complemented with analyses of
lipid palaeothermometers, such as TEX86 and the long chain diol index (LDI), to
reconstruct variations in Baltic Sea surface temperatures (SST). In addition, the
MBT/CBT proxy is used to infer past changes in mean annual air temperatures
(MAAT).
Benthic foraminiferal δ18O and δ13C measurements (monospecific) and foraminifera and
ostracod faunal assemblage analyses allow us to estimate bottom water salinity and
environmental changes qualitatively and quantitatively. Low bottom water salinity (∼23 in
bottom waters) and varying diagenesis in the Little Belt’s organic-rich sediments complicates
the application of benthic foraminiferal Mg/Ca as a palaeotemperature proxy. Reliable
bottom water temperatures, however, are reconstructed using clumped isotope analyses of
mollusc material. In addition, diatoms and the diol index (DI) are analysed to determine
variation in salinity of the Baltic Sea’s surface waters over the investigated time
period.
The results of this inter-proxy comparison study will be used to reconstruct gradients
between different settings, e.g. how water column stratification developed, possibly if and
how changes in seasonality occurred, and to identify the circumstances under which specific
proxies may be affected by secondary impacts. |
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