Fig. 16.18 (a) Time-series of the North Atlantic Oscillation (NAO) index estimates
for 1950 to 2000. NAO is the atmospheric pressure difference between Iceland and
Portugal, plotted here as anomalies. (From NOAA.) General effects of low NAO (b)
and high NAO (c) on ocean current patterns in the North Atlantic.
(^) (After Mann & Lazier 1991.)