Reconstructing deglacial warming of monsoonal East Asia using branched tetraether membrane lipids and clumped isotopes of land snails in the Chinese Loess Plateau

Abstract:

The Chinese Loess Plateau (CLP) is one of the best continuous paleoclimate archives on land, and its sediments host a long record of East Asian Monsoon (EAM) climate variability. However, most of the currently available paleorecords represent a mixed signal of temperature and precipitation, mostly due to a lack of methods that are able to deconvolve temperature and EAM precipitation signals. This hampers our full understanding of the influence of (future) warming on EAM precipitation.

Here, we combine temperature-sensitive soil bacterial membrane lipids, named branched glycerol dialkyl glycerol tetraethers (brGDGTs), and clumped isotopes (expressed as Δ₄₇) of land snail shells stored in the Yuanbao section, located on the western edge of the CLP, to reconstruct a continuous, high-resolution, absolute air temperature record for monsoonal East Asia over the last deglaciation.

Our record shows that air temperature follows Northern Hemisphere insolation, and the difference between the start of Last Glacial period and the Holocene Climate Optimum is around 9 °C based on brGDGT records. The preliminary temperature reconstructed by clumped isotopes of snail shells from the same loess core records similar trend with that based on brGDGTs. Notably, deglacial atmospheric warming leads the onset of monsoon precipitation, represented by magnetic susceptibility. Similarly, this offset was also found in Mangshan section on the eastern edge of the CLP with a relatively shorter warming lead period, thus suggesting the existence of a spatial gradient in the response time of monsoon precipitation to atmospheric warming.