Articles | Volume 10, issue 1
Clim. Past, 10, 21–39, 2014
Clim. Past, 10, 21–39, 2014

Research article 08 Jan 2014

Research article | 08 Jan 2014

Quantitative reconstruction of precipitation changes on the NE Tibetan Plateau since the Last Glacial Maximum – extending the concept of pollen source area to pollen-based climate reconstructions from large lakes

Y. Wang1,2, U. Herzschuh1,2, L. S. Shumilovskikh3, S. Mischke2,4, H. J. B. Birks5,6,7,8, J. Wischnewski1,2, J. Böhner9, F. Schlütz3,10, F. Lehmkuhl11, B. Diekmann1, B. Wünnemann12, and C. Zhang13 Y. Wang et al.
  • 1Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Telegrafenberg A43, 14473 Potsdam, Germany
  • 2Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Str. 24, 14476 Potsdam, Germany
  • 3Department of Palynology and Climate Dynamics, Albrecht-von-Haller Institute for Plant Sciences, University of Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
  • 4Institute of Geological Sciences, Free University Berlin, Malteserstr. 74-100, 12249 Berlin, Germany
  • 5Department of Biology, University of Bergen, Thormøhlensgate 53A, 5006 Bergen, Norway
  • 6Bjerknes Centre for Climate Research, Allegaten 55, 5007 Bergen, Norway
  • 7Environmental Change Research Centre, University College London, London, WC1E 6BT, UK
  • 8School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK
  • 9Institute for Geography, University Hamburg, Bundesstr. 55, 20145 Hamburg, Germany
  • 10Institute of Geographical Sciences, Free University Berlin, Malteserstr. 74-100, 12249 Berlin, Germany
  • 11Department of Geography, RWTH Aachen University, Templergraben 55, 52056 Aachen, Germany
  • 12School of Geography and Oceanography, Nanjing University, Hankou Road 22, 210093 Nanjing, China
  • 13Centre for Arid Environment and Paleoclimate Research, School of Resources and Environmental Sciences, Lanzhou University, 730000 Lanzhou, China

Abstract. Pollen records from large lakes have been used for quantitative palaeoclimate reconstruction, but the influences that lake size (as a result of species-specific variations in pollen dispersal patterns that smaller pollen grains are more easily transported to lake centre) and taphonomy have on these climatic signals have not previously been systematically investigated. We introduce the concept of pollen source area to pollen-based climate calibration using the north-eastern Tibetan Plateau as our study area. We present a pollen data set collected from large lakes in the arid to semi-arid region of central Asia. The influences that lake size and the inferred pollen source areas have on pollen compositions have been investigated through comparisons with pollen assemblages in neighbouring lakes of various sizes. Modern pollen samples collected from different parts of Lake Donggi Cona (in the north-eastern part of the Tibetan Plateau) reveal variations in pollen assemblages within this large lake, which are interpreted in terms of the species-specific dispersal and depositional patterns for different types of pollen, and in terms of fluvial input components. We have estimated the pollen source area for each lake individually and used this information to infer modern climate data with which to then develop a modern calibration data set, using both the multivariate regression tree (MRT) and weighted-averaging partial least squares (WA-PLS) approaches. Fossil pollen data from Lake Donggi Cona have been used to reconstruct the climate history of the north-eastern part of the Tibetan Plateau since the Last Glacial Maximum (LGM). The mean annual precipitation was quantitatively reconstructed using WA-PLS: extremely dry conditions are found to have dominated the LGM, with annual precipitation of around 100 mm, which is only 32% of present-day precipitation. A gradually increasing trend in moisture conditions during the Late Glacial is terminated by an abrupt reversion to a dry phase that lasts for about 1000 yr and coincides with "Heinrich event 1" in the North Atlantic region. Subsequent periods corresponding to the Bølling/Allerød interstadial, with annual precipitation (Pann) of about 350 mm, and the Younger Dryas event (about 270 mm Pann) are followed by moist conditions in the early Holocene, with annual precipitation of up to 400 mm. A drier trend after 9 cal. ka BP is followed by a second wet phase in the middle Holocene, lasting until 4.5 cal. ka BP. Relatively steady conditions with only slight fluctuations then dominate the late Holocene, resulting in the present climatic conditions. The climate changes since the LGM have been primarily driven by deglaciation and fluctuations in the intensity of the Asian summer monsoon that resulted from changes in the Northern Hemisphere summer solar insolation, as well as from changes in the North Atlantic climate through variations in the circulation patterns and intensity of the westerlies.

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