A Multiproxy Approach to Calibrating Speleothem Paleoclimate Reconstructions using Modern Isotopic and Remotely Sensed Data

Abstract:

Tropical island nations, such as Barbados, are particularly vulnerable to extreme event impacts as changes in interannual storm frequency and intensity could influence groundwater supplies and their climatic resilience. Creating high resolution paleoclimate records for these areas aids in determining the intensity and cyclicity of possible future climate extremes. This study presents a high-resolution, isotopic hydroclimatological analysis of Barbados’ rainfall and groundwater in relation to atmospheric influences during storms. Through this calibration of interannual precipitation variability under a modern climatic regime, we can better understand the climatic influences driving our interpretation of paleoclimate reconstructions from speleothems. Weekly samples of dripwater, rainfall, groundwater, and 10-minute precipitation amounts were collected from July, 2012 to October, 2013 at Harrison’s Cave in Barbados. These samples underwent isotopic analysis for oxygen and deuterium isotopes. Weekly to monthly rainfall totals were compiled from Harrison’s Cave and several island wide stations. In addition, Tropical Rainfall Measuring Mission (TRMM) satellite data were used to compare against oxygen isotope values to provide a multiproxy approach at reconstructing rainfall variability used in the calibration model. At a weekly resolution, the amount effect is not represented at the study site; however, using weather station and remotely sensed data, at an island wide scale the amount effect signal is strongest at monthly timescales. TRMM data accurately reflect the influence of the amount effect at this resolution, thus providing the possibility of a new proxy for rainfall amount when calibrating speleothem paleoclimate records. The amount-weighted precipitation and groundwater values indicate homogenization of the aquifer indicate speleothem record changes in interannual variability. When compared to data from previous studies, the average annual dripwater oxygen isotope values are the same (­–3‰), thereby indicating minimal changes in the climatic environment over a decadal scale. When applied to speleothem climate reconstructions, using high resolution, modern multiproxy calibration techniques can aid in interpreting the paleoclimate record.