Large-scale atmospheric circulation influences the ice core d-excess record from the central Tibetan Plateau

摘要

Deuterium excess (d-excess), as a secondary parameter of water stable isotopes, inherits the meteorological information from moisture source to the site of interest. Understanding the climatic implications of d-excess in ice cores from the Tibetan Plateau (TP) is critical for reconstructing the paleoclimate. Here we present an annually-dated ice core record retrieved from the central TP and analyze the correlations between the ice core d-excess record and local and regional climate variables in the past decades (1948-2011). Our results show poor correlations between d-excess and local meteorological parameters, deemphasizing the local control on the interannual variations in d-excess records. However, significant correlations exist between the d-excess record and the relative humidity over the eastern Arabian Sea and Bay of Bengal. In addition, our results indicate that d-excess is positively correlated with temperature in the Nino 3.4 region, demonstrating that large-scale atmospheric circulation through ENSO cycle affecting the interannual d-excess signal in ice cores from the central TP. Mechanically speaking, in annual scale, the higher (lower) temperature that occurs in the eastern tropical Pacific Ocean in El Nino (La Nina) years is accompanied by the ascending branch of the Walker circulation weakening (enhancing) in the Indian Ocean region, leading to lower (higher) relative humidity value in the moisture source regions of the Arabian Sea and Bay of Bengal, and subsequently producing higher (lower) d-excess value in the central Tibetan ice core records. This finding will enhance the understanding of the climatic significance of ice core d-excess in the Asian monsoon region.