Position and orientation of the westerly jet determined Holocene rainfall patterns in China

Abstract

Proxy-based reconstructions and modeling of Holocene spatiotemporal precipitation patterns for China and Mongolia have hitherto yielded contradictory results indicating that the basic mechanisms behind the East Asian Summer Monsoon and its interaction with the westerly jet stream remain poorly understood. We present quantitative reconstructions of Holocene precipitation derived from 101 fossil pollen records and analyse them with the help of a minimal empirical model. We show that the westerly jet-stream axis shifted gradually southward and became less tilted since the middle Holocene. This was tracked by the summer monsoon rain band resulting in an early-Holocene precipitation maximum over most of western China, a mid-Holocene maximum in north-central and northeastern China, and a late-Holocene maximum in southeastern China. Our results suggest that a correct simulation of the orientation and position of the westerly jet stream is crucial to the reliable prediction of precipitation patterns in China and Mongolia.

The Eurasian Modern Pollen Database (EMPD), Version 2

“…These problems also extend to the recent release of data by Herzschuh et al (2019) from China and Mongolia. This data represents most of the modern pollen data held in the Chinese Pollen Database (CPD) (Ni et al, 2010;Zheng et al, 2014).…”

“…Some large independent surface sample datasets covering the Eurasian region have been published and made available since EMPD1, most notably , Marinova et al (2018) and Herzschuh et al (2019). Both and Marinova et al (2017) already include a large amount of data from the EPD and EMPD1, but also data that has not been publicly released before.…”

“…This data represents most of the modern pollen data held in the Chinese Pollen Database (CPD) (Ni et al, 2010;Zheng et al, 2014). The Herzschuh et al (2019) dataset includes 2559 modern pollen samples, and is of major importance as the first significant amount of publicly available data from this region. However, the data is only provided as percentages based on a summary of the taxa from each sample, and also includes digitized data.…”

“…We were therefore unable to include it in the EMPD2. The Herzschuh et al (2019) data is available from PANGAEA, along with the Tarasov et al, (2011) dataset of 798 samples mainly from Japan and Eastern Russia, which are also provided as percentages for a limited selection of taxa. We hope that the raw count data for the full assemblage will be made available in the near future.…”

Relationships between low-temperature fires, climate and vegetation during the last 430 kyrs in northeastern Siberia reconstructed from monosaccharide anhydridesin Lake El’gygytgyn sediments

“…show that MAs attached to aerosols would derive from modern day tundra and larch taiga in the Chukotka region, several hundreds of km away from the lake, transported by north-to south-westerly winds during the main fire season in July and August, in agreement with modern climatology(Mock et al, 1998). Yet, El'gygytgyn MA influx records represent centennial-scale averages integrating over multiple fire events under multiple synoptic 315 conditions that varied in the past, such as changing jet stream position and orientation(Herzschuh et al, 2019).…”