Model evaluation of the coherence of a common source water oxygen isotopic signal recorded by tree-ring cellulose and speleothem calcite

Oxygen isotopic compositions (O-18) of tree rings and speleothems inherit O-18 of precipitation (O-18(ppt)) and are used to reconstruct past variations in the amount of precipitation or temperature. Integration of O-18 records of both the proxies for a multiproxy climate reconstruction necessitates understanding of the extent to which the initial O-18(ppt) is modified in both the proxies before getting preserved in them. A forward modeling approach, assuming both the proxies have access to a common source water O-18 signal, is employed to assess the expected maximum correlation between the O-18 records of the two proxies on interannual time scale and the factors influencing the correlation. Variations in the leaf temperature, relative humidity, O-18 of atmospheric water vapor introduce variations in O-18 of tree-ring cellulose, while the variations in the cave temperature and oxygen isotopic equilibrium/disequilibrium conditions between calcite and drip water influence O-18 of speleothem calcite. Variation introduced by these factors in O-18 of individual proxies as compared to the variation in O-18(ppt) is crucial in deciding the correlation between O-18 records of the two proxies. When the former is higher than or comparable with the latter, finding one to one correspondence between the O-18 records of the two proxies could be challenging. Modeling exercise revealed a favorable climatic condition at Jagdalpur (19.08 degrees N, 82.03 degrees E), a potential tropical location for tree ring and speleothem-based climate reconstruction, for inheriting a common source water O-18 signal in both the proxies. O-18 records of tree ring and annually resolved speleothem from Jagdalpur could be integrated for the multiproxy climate reconstruction.