Daily δ18O and δD of precipitations from 2007 to 2009 in Guangzhou, South China: Implications for changes of moisture sources

Oxygen and hydrogen stable isotopes (delta O-18 and AD) in precipitation collected in every event from 2007 to 2009 in Guangzhou, South China, are presented in this paper. The total correlation between delta O-18 and delta D is obtained as delta D = (8.46 +/- 0.13) delta O-18 + (15.0 +/- 0.9). More negative delta O-18 and delta D generally occur during summer and autumn, while less negative or even positive delta O-18 and delta D occur during winter and spring. Significant negative correlations between precipitation delta O-18 and temperature, and between precipitation delta O-18 and precipitation amount are observed. Regression line changes from year to year are likely due to changes in moisture sources for the precipitation. The moisture contributed by adjacent seas or local evaporation account for the main precipitation during winter and early spring, while summer monsoon brings huge amounts of moisture from remote seas associated with higher temperature and larger precipitation amounts. Seasonal variations of the precipitation D-excess provide more details for changes in moisture sources. Higher D-excess values during winter and early spring are estimated to correspond to a lesser proportion of remote moisture, while lower D-excess values during summer and autumn correspond to larger remote moisture transported by summer monsoons. This generally agrees with the results of model analysis on single isobaric backward trajectories for air parcels during specific time periods. Results of this study imply that precipitation delta O-18 and delta D, as well as some related paleoclimate proxies such as delta O-18 in speleothem and tree ring, and delta D in plant-derived organic compounds and tree ring, currently cannot indicate changes in temperature or precipitation amount separately, but should be comprehensive proxies for monsoon climate. (C) 2011 Elsevier B.V. All rights reserved.