Eurasian contribution to the last glacial dust cycle: how are loess sequences built?

Denis-Didier Rousseau,Anders Svensson,Niklas Boers,Jorgen Peder Steffensen,Adriana Sima,Matthias Bigler

doi:10.5194/cp-13-1181-2017

Abstract

Abstract. The last 130 000 years have been marked by pronounced millennial-scale climate variability, which strongly impacted the terrestrial environments of the Northern Hemisphere, especially at middle latitudes. Identifying the trigger of these variations, which are most likely associated with strong couplings between the ocean and the atmosphere, still remains a key question. Here, we show that the analysis of δ18O and dust in the Greenland ice cores, and a critical study of their source variations, reconciles these records with those observed on the Eurasian continent. We demonstrate the link between European and Chinese loess sequences, dust records in Greenland, and variations in the North Atlantic sea ice extent. The sources of the emitted and transported dust material are variable and relate to different environments corresponding to present desert areas, but also hidden regions related to lower sea level stands, dry rivers, or zones close to the frontal moraines of the main Northern Hemisphere ice sheets. We anticipate our study to be at the origin of more sophisticated and elaborated investigations of millennial and sub-millennial continental climate variability in the Northern Hemisphere.

Highlights

During the last glacial interval, abrupt climate changes have been documented worldwide in different types of records, but especially in ice cores (Dansgaard et al, 1969, 1982; Johnsen et al, 1992, 1972, 2001)
The last 130 000 years have been marked by pronounced millennial-scale climate variability, which strongly impacted the terrestrial environments of the Northern Hemisphere, especially at middle latitudes
We investigate in this study the 18 Greenland interstadials (GIs), labeled from 17.1 to 2 (Rasmussen et al, 2014), which have been identified during the MIS 3 and 2 (59–14 ka b2k) interval

Summary

Introduction

During the last glacial interval, abrupt climate changes have been documented worldwide in different types of records, but especially in ice cores (Dansgaard et al, 1969, 1982; Johnsen et al, 1992, 1972, 2001). High-resolution studies of the temperature signal in older interstadials show the occurrence of sub-millennialscale elements like precursor events of about centennial duration before the interstadial itself, rebound events exhibiting abrupt cooling towards stadial conditions, and cooling events occurring towards the end of the interstadial (Capron et al, 2010) These sub-millennial events make the understanding of the climate variability during these interstadials even more complicated than a simple warming followed by a two-step cooling. After briefly describing the abrupt changes observed in the very-high-resolution δ18O and dust records from NGRIP (NGRIP, 2004), we compare the dust particle sedimentation rates over Europe and China as expressed in key loess sequences (Fig. 1) This is a complementary study of Rousseau et al (2017), which essentially focused on paleosol development.

Findings

Discussion

Conclusion