A spatial reconstruction of Siberian Last Glacial Maximum climate from pollen data

Abstract

The Last Glacial Maximum (LGM, around 21.000 years before present) was a period with significantly colder global mean temperature, large Northern Hemisphere ice sheets, and lower CO2 concentrations. Siberia was affected by a lower sea level which led to a closed Bering strait and a northward shift of the Arctic Ocean coastline. However, unlike other high-latitude areas, Siberia was not covered by a terrestrial ice sheet at that time. Climate simulations with LGM boundary conditions show large inter-model differences especially in Northern Siberia, which impede a direct analysis of Siberian LGM climate from simulations. Preserved pollen samples provide information on the LGM vegetation and climate state.We reconstruct mean temperature of the warmest month and mean annual precipitation from a network of pollen samples using weighted averaging partial least squares transfer functions. Combining these local reconstructions with a multi-model ensemble of PMIP3 climate simulations in a Bayesian framework, we obtain the first probabilistic spatial reconstruction of Siberian LGM climate. Our reconstruction shows less cold summer temperature anomalies along the coastlines than in Western Siberia, and a weaker precipitation reduction in Eastern Siberia compared to Western Siberia. Finally, we quantify the mismatch between each ensemble member and the proxy data. By examining common features among similarly performing simulations, we find that most simulations with a comparatively warm and wet Siberian climate score better.Our data constrained state estimate is well-suited for future analyses of Siberian LGM climate. Potential applications include the investigation of reasons for the absence of a Siberian ice sheet during the LGM, the quantification of land-atmosphere carbon fluxes, and the estimation of past afforestation rates.

Northeast Siberian Permafrost Ice‐Wedge Stable Isotopes Depict Pronounced Last Glacial Maximum Winter Cooling

“…Deduced annual mean surface air temperatures over land show LGM cooling of about −6°C on a global scale between 23 and 19 Kyr BP, but noticeably little cooling or even warming in West Beringia compared to the late Holocene. A similar pattern has been found for LGM summer temperatures around 21 Kyr BP in West Beringia based on pollen records and modeling efforts (Weitzel et al., 2021). Similar‐to‐modern LGM summer temperatures between 20 and 18 Kyr BP have been reported by V. D. Meyer et al.…”

“…temperatures around 21 Kyr BP in West Beringia based on pollen records and modeling efforts (Weitzel et al, 2021). Similar-to-modern LGM summer temperatures between 20 and 18 Kyr BP have been reported by V. D. Meyer et al (2017) on Kamchatka Peninsula in far-east Russia based on biomarker proxy data from marine sediments.…”

“…The substantial LGM winter cooling under highly continental conditions as reflected in the Bol’shoy Lyakhovsky ice‐wedge stable isotope record complements the results of recent LGM climate modeling studies. Modeled annual LGM temperatures (Tierney et al., 2020) and summer‐season LGM temperatures (Weitzel et al., 2021) as well as biomarker‐based summer‐season temperature reconstructions (V. D. Meyer et al., 2017) indicate only slightly colder or even warmer LGM conditions than today in East Siberia (West Beringia) for periods slightly post‐dating the present winter‐season record. By highlighting the seasonal biases of the different studies, the apparent differences imply the need for well‐dated regionally constrained seasonal‐scale temperature reconstructions and climate model output for holistically assessing the climate conditions of particular time periods such as the LGM.…”

“…The substantial LGM winter cooling under highly continental conditions as reflected in the Bol'shoy Lyakhovsky ice-wedge stable isotope record complements the results of recent LGM climate modeling studies. Modeled annual LGM temperatures(Tierney et al, 2020) and summer-season LGM temperatures(Weitzel et al, 2021) as well as biomarker-based summer-season temperature reconstructions (V. D Meyer et al, 2017). indicate only slightly colder or even warmer LGM conditions than today in East Siberia (West Beringia) for periods slightly post-dating the present winter-season record.…”