Reconstruction Of Temperature, Accumulation Rate, And Layer Thinning From An Ice Core At South Pole, Using A Statistical Inverse Method

Data from the South Pole ice core (SPC14) are used to constrain climate conditions and ice-flow-induced layer thinning for the last 54,000 years. Empirical constraints are obtained from the SPC14 ice and gas timescales, used to calculate annual-layer thickness and the gas-ice age difference (Delta age), and from high-resolution measurements of water isotopes, used to calculate the water-isotope diffusion length. Both Delta age and diffusion length depend on firn properties and therefore contain information about past temperature and snow-accumulation rate. A statistical inverse approach is used to obtain an ensemble of reconstructions of temperature, accumulation-rate, and thinning of annual layers in the ice sheet at the SPC14 site. The traditional water-isotope/temperature relationship is not used as a constraint; the results therefore provide an independent calibration of that relationship. The temperature reconstruction yields a glacial-interglacial temperature change of 6.7 1.0 degrees C at the South Pole. The sensitivity of delta O-18 to temperature is 0.99 0.03 degrees C-1, significantly greater than the spatial slope of 0.8 degrees C-1 that has been used previously to determine temperature changes from East Antarctic ice core records. The reconstructions of accumulation rate and ice thinning show millennial-scale variations in the thinning function as well as decreased thinning at depth compared to the results of a 1-D ice flow model, suggesting influence of bedrock topography on ice flow.Key PointsAn inverse method using a firn model with isotope diffusion provides self-consistent temperature, accumulation rate, and thinning historiesGlacial-interglacial temperature change at the South Pole was 6.7 +/- 1.0 K. The delta O-18/T sensitivity is 0.99 +/- 0.03 permille/KReconstruction of ice thinning shows millennial-scale variations in thinning function and decreased thinning at depth compared to 1-D model