Figure 15 – Comparison of stacked isotope record from the Summit Greenland ice cores with sea level pressure measured in Iceland and the Azores. These sites are used in calculating the North Atlantic Oscillation (NAO) index. Note that the pressure in the Azores is inverted. Correlation coefficients is 0.256 (with Iceland) and 0.248 (with Azores). Taken from White et al. (1997).