Maximum covariance analysis (MCA) and isometric feature mapping (Isomap) are
applied to investigate the spatio-temporal atmosphere–ocean interactions
otherwise hidden in observational data for the period of 1979–2010. Despite an
established long-term surface warming trend for the whole northern hemisphere,
sea surface temperatures (SST) in the East Pacific have remained relatively
constant for the period of 2001–2010. Our analysis reveals that SST anomaly
probability density function of the leading two Isomap components is bimodal.
We conclude that Isomap shows the existence of two distinct regimes in surface
ocean temperature, resembling the break and active phases of rainfall over
equatorial land areas. These regimes occurred within two separated time
windows during the past three decades. Strengthening of trade winds over
Pacific was coincident with the cold phase of east equatorial Pacific. This
pattern was reversed during the warm phase of east equatorial Pacific. The El
Niño event of 1997/1998 happened within the transition mode between these two
regimes and may be a trigger for the SST changes in the Pacific. Furthermore,
we suggest that Isomap, compared with MCA, provides more information about the
behavior and predictability of the inter-seasonal atmosphere–ocean
interactions