Spatial analysis of the intra-annual variation of precipitation isotope ratios and its climatological corollaries

Intra-annual variation in the stable isotope ratios of precipitation imparts a time-dependent isotopic signal to continental hydrological and ecological systems. This variation is forced by seasonal climate cycles, with temperature and precipitation intensity each driving isotopic seasonality in different parts of the globe. In order to better characterize and understand the isotopic seasonality of precipitation and to advance applications such as the inversion of isotope/climate relationships for paleoclimate seasonality reconstruction, these relationships are analyzed using a database of precipitation isotope ratio observations and gridded maps. The results confirm the overwhelming dominance of temperature-and precipitation amount-related isotopic seasonality within specific, well-defined geographic zones and indicate that these zones encompass most of Earth's continental land surface. Analysis of global maps of precipitation isotopic seasonality, however, indicates spatially patterned variation in isotope/climate relationships, including patterns related to continentality in temperature-dominated regions and meridional trends in amount-dominated areas. These features reflect more complex climatological controls on isotope seasonality and suggest limitations and opportunities for paleoclimate reconstruction using isotopic archives.