Reconstruction of temperature, accumulation rate, and layer thinning
from an ice core at South Pole using a statistical inverse method
Abstract
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 (Δage), and from high-resolution measurements of water
isotopes, used to calculate the water-isotope diffusion length. Both
Δage 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 °C at the South
Pole. The sensitivity of δ180 to temperature is 0.99 ± 0.03 ‰/°C,
significantly greater than the spatial slope of ~0.8
‰/°C 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.