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Climate reconstructions based on GDGT and pollen surface datasets from Mongolia and Baikal area: calibrations and applicability to extremely cold–dry environments over the Late Holocene
Climate of the Past ( IF 3.8 ) Pub Date : 2021-06-16 , DOI: 10.5194/cp-17-1199-2021 Lucas Dugerdil , Sébastien Joannin , Odile Peyron , Isabelle Jouffroy-Bapicot , Boris Vannière , Bazartseren Boldgiv , Julia Unkelbach , Hermann Behling , Guillemette Ménot
Climate of the Past ( IF 3.8 ) Pub Date : 2021-06-16 , DOI: 10.5194/cp-17-1199-2021 Lucas Dugerdil , Sébastien Joannin , Odile Peyron , Isabelle Jouffroy-Bapicot , Boris Vannière , Bazartseren Boldgiv , Julia Unkelbach , Hermann Behling , Guillemette Ménot
Our understanding of climate and vegetation changes throughout
the Holocene is hampered by representativeness in sedimentary
archives. Potential biases such as production and preservation of the markers
are identified by comparing these proxies with modern environments. It is
important to conduct multi-proxy studies and robust calibrations on each
terrestrial biome. These calibrations use large databases dominated by forest
samples. Therefore, including data from steppe and desert–steppe sites becomes
necessary to better calibrate arid environments. The Mongolian Plateau,
ranging from the Baikal area to the Gobi desert, is especially characterized
by low annual precipitation and continental annual air temperature. The
characterization of the climate system of this area is crucial for the
understanding of Holocene monsoon oscillations. This study focuses on the
calibration of proxy–climate relationships for pollen and glycerol dialkyl
glycerol tetraethers (GDGTs) by comparing large Eurasian calibrations with a
set of 49 new surface samples (moss polster, soil and mud from temporary dry
ponds). These calibrations are then cross-validated by an independent dataset
of top-core samples and applied to four Late Holocene paleosequences (two
brGDGT and two pollen records) surrounding the Mongolian Plateau: in the Altai
mountains, the Baikal area and the Qaidam basin, to test the accuracy of local
and global calibrations. We show that (1) preserved pollen assemblages are
clearly imprinted on the extremities of the ecosystem range but mitigated and
unclear on the ecotones; (2) for both proxies, inferred relationships depend
on the geographical range covered by the calibration database as well as on
the nature of samples; (3) even if local calibrations suffer from reduced
amplitude of climatic parameters due to local homogeneity, they better reflect
actual climate than the global ones by reducing the limits for saturation
impact; (4) a bias in climatic reconstructions is induced by the
over-parameterization of the models by the addition of artificial correlation; and
(5) paleoclimate values reconstructed here are consistent with Mongolia–China
Late Holocene climate trends and validate the application of local
calibrations for both pollen and GDGTs (closest fit to actual values and
realistic paleoclimate amplitude). We encourage the application of this
surface calibration method to reconstruct paleoclimate and especially
consolidate our understanding of the Holocene climate and environment
variations in arid central Asia.
更新日期:2021-06-16