A Bat’s-Eye View of Holocene Climate Change in the Southwest: Resolving Ambiguities in Cave Isotopic Records

Abstract:

In dry environments, speleothems provide an outstanding archive of information on past climate change, particularly since lakes are typically absent or intermittent. Speleothem stable isotopes are widely used for climate reconstruction, but the isotope-climate relationship is complex in arid-region precipitation, and within-cave processes further complicate climate interpretations. Our isotope results from 3 southeastern Arizona caves, spanning the past 3.5-12 kyr, collectively indicate a weakening monsoon from 7kyr to present. These records exhibit substantial multidecadal-multicentury variability that is sometimes shared, and sometimes independent among caves. Strategies to overcome ambiguities in isotope records include long-term monitoring of cave dripwaters, multi-site comparisons, and multiproxy measurements. Monthly dripwater measurements from two caves spanning several years highlight substantial seasonal biases that create distinct differences in the climate sensitivity of individual cave records. These biases can lead to lack of correlation between records, but also creates opportunities for seasonally specific moisture reconstructions. New preliminary analyses suggest that elemental data can help to unravel the multivariate signal contained in speleothem oxygen isotope records.