Reconstruction of the undiffused seasonal oxygen isotope signal in centralGreenland ice cores

The climatologically important seasonal signal in ice core oxygen isotope r ecords is altered by diffusion with time. Here we use the diffusion model o f Whillans and Grootes [1985] to calculate the effects of isotopic diffusio n in nine shallow ice cores recovered over a 150 x 150 km grid centered on Summit, Greenland. Two different computational methods give similar results for the back-diffused delta(18)O seasonal extrema. Although back diffusing the ice core delta(18)O records improves the correlations between the indi vidual ice core oxygen isotope and Greenland coastal temperature records; t he correlations remain poor, particularly for the low-accumulation sites. S tacking the back-diffused isotopic records from several cores results in mu ch higher correlations, with a strong winter linkage between west coast sta tions and central Greenland. These correlations are also significantly grea ter than the correlations between the stacked measured (diffused) isotopic profiles and coastal temperatures. Our results indicate that the use of ice core isotopic records to identify anomalous seasons requires that diffusio n effects be accounted for.