Periodicity in δ18O value of global precipitation: Insight into the controlling factors

A large number of local and regional meteorological parameter controls the δD and δ18O value in precipitation. In this study, we have tried to distinguish and define the regions over the globe where δ18O is a function of a single climatic parameter or convolution of the several climatic parameters by the wavelet approach. The interannual variability of δ18O in precipitation at 138 stations all over the globe is examined through wavelet analysis. Wavelet transform results in a significant inter-annual continuous spectrum when δ18O at a station is a controlled by a single parameter. Stations showing good correlation with local meteorological parameter, i.e., local temperature in mid-high latitude regions or precipitation amount in the tropical areas, have a continuous wavelet spectrum at annual scale. In contrast, stations showing no correlation with local meteorological parameters have complex wavelet spectrum with no annual scale periodicity, and here δ18O is most likely to depend upon the regional parameter rather than local. Such station mainly lies between45°N-45°S. In both tropics and mid-latitude, some stations are showing breaks in inter-annual periodicity throughout the time series are carrying the signature of regional parameters.

The Stations where the δ18O is mainly controlled by a single local parameter, are having continuous wavelet spectrum and geological materials from these regions can be used to construct the past climate more accurately.