Temperature and leaf wax delta H-2 records demonstrate seasonal and regional controls on Asian monsoon proxies

Orbital-scale precipitation isotope records can elucidate climate forcing mechanisms and provide benchmarks for climate model validation. The ability to differentiate the influence of temperature, seasonality, and vapor transport history on precipitation isotope proxies is critical to both objectives. We present a 300 k.y. leaf wax hydrogen isotope record from the South China Sea with the effects of local condensation temperature removed (delta H-2(wax-T)). delta H-2(wax-T) reflects annually integrated precipitation delta H-2 in the Pearl River catchment of southeast China. Depleted delta H-2(wax-T) lags minimum precession (P-min) by 1.0 +/- 0.7 k.y., reflecting the influence of maximum summer insolation and minimum winter insolation, with a minor influence of global ice volume, which lags P-min by 3.3 +/- 0.4 k.y. In contrast, annually integrated cave delta O-18 minima in central China, 1000 km north of our site, lag P-min by 2.7 +/- 0.3 k.y., in phase with ice volume minima. This phase indicates that precipitation delta O-18 in central China is more strongly influenced by ice volume forcing at the precession band, with a lesser influence of Northern Hemisphere insolation. Our new delta H-2(wax-T) data demonstrate that precipitation isotopes in Asia have strong regional variability. Interpreting water isotope records within the context of regionally varying temperature, seasonality, and sensitivity to changing glacial boundary conditions is imperative to understanding Asian hydroclimatic change.</p