Here we developed a composite pollen-based record of altitudinal vegetation changes from Lake Fúquene (5° N) in Colombia at 2540 m elevation. We quantitatively calibrated Arboreal Pollen percentages (AP%) into mean annual temperature (MAT) changes with an unprecedented ~60-year resolution over the past 284 000 years. An age model for the AP% record was constructed using frequency analysis in the depth domain and tuning of the distinct obliquity-related variations to the latest marine oxygen isotope stacked record. The reconstructed MAT record largely concurs with the ~100 and 41-kyr (obliquity) paced glacial cycles and is superimposed by extreme changes of up to 7 to 10° Celsius within a few hundred years at the major glacial terminations and during marine isotope stage 3, suggesting an unprecedented North Atlantic – equatorial link. Using intermediate complexity transient climate modelling experiments, we demonstrate that ice volume and greenhouse gasses are the major forcing agents causing the orbital-related MAT changes, while direct precession-induced insolation changes had no significant impact on the high mountain vegetation during the last two glacial cycles
Genetically meaningful decomposition (unmixing) of sediment grain‐size distributions is accomplished with the end‐member modelling algorithm. Unmixing of the loess grain‐size distributions of a Late Quaternary loess–palaeosol succession from the north‐eastern Tibetan Plateau indicates that the loess is a mixture of three end‐members representing very fine sandy, coarse silty and medium silty loess. The unmixing approach potentially enables the unravelling of sediment fluxes from multiple dust sources, opening the way to significant advances in palaeoclimatic reconstructions from loess grain‐size distribution data. However, as laser‐diffraction size analysis is a volume‐based technique, the proportional contributions of the modelled end‐members might deviate (significantly) from weight proportions. Hence, calibration of the end‐member volume proportions to weight proportions must be established before one can calculate the source‐specific dust fluxes. This paper reports the findings of a sediment‐mixing experiment which enables calibration of the modelled mixing patterns established for the Tibetan loess–palaeosol succession.
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