Integrating paleolimnological hydrogen and oxygen isotope records during the Holocene on the Tibetan Plateau

Abstract

Stable isotopes are effective proxy indicators for past climate and environment changes. Paleolimnological hydrogen and oxygen isotopes have been used to reconstruct changes in precipitation isotopes and continental climates. However, the stable hydrogen and oxygen isotope records from lakes are rarely compared and integrated directly to study past changes in climate and environment due to their different fractionation pathways. Combined studies on hydrogen and oxygen isotopes would provide much more information than single isotope records. Here, we reanalyzed published lacustrine hydrogen and oxygen isotope records across the Tibetan Plateau, to investigate how both isotope records reveal the influences of the Indian summer monsoon and the westerlies on the Plateau throughout the Holocene. Principal component analysis (PCA) shows that the first principal component (PC1) of 16 lacustrine hydrogen isotope records resembles that of 28 oxygen isotope records. The PC1s of the hydrogen and oxygen isotope records were generally low at 12–6 ka BP, followed by gradual increase since 6 ka BP, suggesting the influence of the Indian summer monsoon. Reconstruction of Holocene precipitation isotopes showed that the slopes of segmented precipitation isotope lines generally followed changes in monsoon intensity. The PC2s for hydrogen and oxygen isotope records remained relatively low at ∼8–4 ka BP, coinciding with moisture variation in westerlies dominated regions. The millennial-scale variations in both hydrogen and oxygen isotope records, revealed by the PC3-PC6, likely responded to the ice drift events in the North Atlantic Ocean, as well as differences in the isotope fractionation pathways at specific sites. The reanalysis of stable hydrogen and oxygen records across the Tibetan Plateau suggests that the water vapor source is the most important factor affecting the isotope variation, though the isotopic fractionation processes may differ significantly. Our results revealed nonlinear variations of monsoon and westerlies on the Tibetan Plateau during the Holocene. This review shows that integration of the stable hydrogen and oxygen isotope records would provide comprehensive understanding of the atmospheric circulation on the Tibetan Plateau.