Leaf waxes and compound-specific isotopes indicate more humid

Leaf waxes and compound-specific isotopes indicate more humid

Leaf waxes and compound-specific isotopes indicate more
humid conditions in Spain during the LGM
Imke Kathrin Schäfer*, Marcel Bliedtner*, Lorenz Wüthrich*, Daniel Wolf**, Jana Zech*,
Dominik Faust** & Roland Zech*
*Geographisches Institut and Oeschger Centre for Climate Change Research, University of
Bern, Hallertsrasse 12, CH-3007 Bern ([email protected])
** Department of Geography, Technical University Dresden, Helmholtzstrasse 10, DE-01069
Dresden
The Western Mediterranean Region increasingly suffers under the consequences of
global warming, particularly extreme drought periods. To better understand these changes
and to predict future ones, past climate and environmental changes provide a useful
context. Here we present results of leaf wax and compound-specific isotope analyses from
the ~8 m high ((Late Pleistocene)) loess paleosol sequence El Paraíso, Central Spain.
Chain length patterns generally show a dominance of grass-derived n-C31 and n-C33
alkanes, but more deciduous tree-derived n-C27 and n-C29 alkanes at ~2 m depth,
interpreted to reflect more humid conditions during the Last Glacial Maximum (LGM: ~25
ka). Most enriched δ13Cn-alkane values before ~30 ka indicate particularly arid conditions,
followed by more depleted values and more humid conditions during the LGM. The
observed ~2‰ decrease in δ13C since can largely be explained by the increase in
atmospheric pCO2. Compound-specific deuterium analyses show more enriched values
during the last glacial compared to the Holocene, which probably simply reflects the
enrichment of the source water (North Atlantic) and should not be interpreted as enhanced
evapotranspiration. Our results (i) confirm the idea of a more humid LGM in the Western
Mediterranean Region based on lake leves, fluvial records and climate modelling, (ii) show
some controversy with regard to pollen records, and (iii) fuel concerns of more severe
droughts in the near, warmer future.