Mean values of the oxygen-isotope ratio relative to standard mean ocean
water (δ18O, in ‰) reported for 46 sites on the Greenland ice sheet are
compiled together with data on mean annual surface temperature, latitude,
δ18O elevation, and mean annual shortest distance to the open
ocean denoted by the 10% sea-ice concentration boundary. Stepwise regression
analyses, with δ18O as the dependent variable, define two robust models. In the
forward mode at the 99.9% confidence level, only temperature enters the
model. In the backward mode at the 95% confidence level, only temperature,
latitude and distance to the open ocean remain in the model. Inversions of
the models on the basis of 160 gridpoint locations 100 km apart in the area
delimited by the surface equilibrium line produce four contoured
distributions of δ18O. Two distributions are based on the bivarrate model and two
on the multivariate model. The second distribution for each model is
obtained substituting mean annual surface-temperature values obtained from
the Nimbus-7 Temperature Humidity Infrared Radiometer (THIR) database. All
four distributions are considered valid, and differences between them are
evaluated using contoured anomaly maps. It is suggested that the inversion
of the multivariate model using THIR data provides the more reliable pattern
for studies of atmospheric advection or for the derivation of ice-flow
adjustments for δ18O series obtained from deep-core or ablation-zone sites.