Calibration of the δ18O isotopic paleothermometer for central Greenland, using borehole temperatures

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Abstract
We calibrate theδ18O paleothermometer for central Greenland using borehole temperatures, a thermal model forced by a measuredδ18O record and a formal inverse technique. The calibration is determined mostly by temperature fluctuations of the last several centuries, including the Little Ice Age. Results are generally insensitive to model variables, including initial condition, basal boundary condition, parameterization of snow thermal properties, ice thickness and likely errors in temperature and isotope measurements. Results of this borehole calibration also seem to be in agreement with modern spatial gradients ofδ18O and temperature. We suggest that calibrations of isotopic paleothermometers using borehole temperatures are a useful paleoclimate tool, because they are independent of spatial gradients and include the effects of prehistoric temperatures over ice sheets.