Late Quaternary Climate Reconstruction and Lead-Lag Relationships of Biotic and Sediment-Geochemical Indicators at Lake Bolshoe Toko, Siberia

Larisa Nazarova,Gregor Pfalz,Tim Kröger,Lyudmila A Pestryakova,Bernhard Diekmann,Ulrike Herzschuh,Liudmila Syrykh,Boris K Biskaborn

doi:10.3389/feart.2021.737353

Abstract

Millennial-scale climate change history in eastern Siberia and relationships between diatom diversity, paleoclimate, and sediment-geochemical lake system trajectories are still poorly understood. This study investigates multi-proxy time series reaching back to the Late Pleistocene derived from radiocarbon dated Lake Bolshoe Toko sediment cores, southeastern Yakutia, Russia. We analyzed diatoms, elements (XRF), minerals (XRD), grain-size, organic carbon, and included chironomid analyses and published pollen-data for quantitative paleoclimate reconstruction. Changes in diatom species abundances reveal repeated episodes of thermal stratification indicated by shifts from euplanktonicAulacoseiratoCyclotellaspecies. Chironomid and pollen-inferred temperature reconstruction reveal that the main shift between these diatom species is related to the onset of Holocene Thermal Maximum (HTM) at 7.1 cal ka BP. Comparison to other paleoclimate records along a north-south transect through Yakutia shows that the HTM was delayed as far south as the Stanovoy mountains. Relationships between sediment-geochemistry, paleoclimate variability and diatom species richness (alpha diversity) was tested in a moving temporal offset approach to detect lead-lag relationships. Sediment-geochemical data, mainly uniform during the Holocene, revealed strongest positive or negative correlations ahead of species richness changes. Mean July air temperature (TJuly) reconstructions correlate with both Hill numbers and relative assemblage changes indicated by sample scores of multidimensional scaling analysis (MDS) over the entire time series. We found that sediment organic carbon revealed distinct positive correlations, i.e., centennial-scale delay to increases in diatom effective richness (Hill numbers N0 and N2). We conclude that a lag of deposited organic carbon concentrations behind changes in diatom alpha diversity reveals that species richness can augment the production and thus sequestration of organic matter in comparable lake systems.

Highlights

Over the past few decades, boreal and high elevation regions warmed faster than elsewhere (Mountain-Research-Initiative et al, 2015) and was strongest in northern Russia
The last strong warming of the atmosphere in a comparable setting took place after the Pleistocene-Holocene transition, referred to as the Holocene Thermal Maximum (HTM) that progressed in a non-uniform spatiotemporal event (Kaufman et al, 2004; Renssen et al, 2012)
High resolution of pollen-based summer temperature reconstruction TJuly provides evidence for Younger Dryas cooling between ca. 12.9 and 11.7 cal ka BP and possibly an interim warm period

Summary

Introduction

Over the past few decades, boreal and high elevation regions warmed faster than elsewhere (Mountain-Research-Initiative et al, 2015) and was strongest in northern Russia In order to assess the dimensions of modern landscape changes in Siberia, information about ecosystem changes during comparable climate warming episodes of the past provide valuable clues. Knowledge about trends within this event was successively gained from paleolimnological records across a north-south transect through Siberia (Biskaborn et al, 2012; Biskaborn et al, 2016). These and our new record rely on radiocarbon dating and sediment-geochemical parameters that provide the background information on the sedimentation history necessary to reliably compile and evaluate paleoenvironmental bioindicator records (Biskaborn et al, 2013b; Wang et al, 2015; Heinecke et al, 2017)

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