The thermocline is centered between 100-200 m, with equatorial weakening indicative of the presence of the Equatorial Undercurrent. Conversely, temperature variations in the surface layer are typically only 0.1 -0.3 C. Notably, SST variations tend to be larger than those at 50 m, which is a point that will be discussed in detail in section 5. Variations associated with these eigenfunctions are determined by multiplication of the EOFs with their corresponding time series. Percent variance explained by each EOF is indicated. Hatching indicates negative eigenvector values.
Variations are in phase in latitude by out of phase between the surface layer and the thermocline.
Hence in this analysis we will focus mainly on the first EOF, which accounts for most of the temperature variability during the period from December 1986 to April 1987. We also performed an EOF decomposition of the overlapping wind record from December 1986 to April 1987 in Figure 2 . Percent variance explained by each EOF is indicated. This issue is examined in greater detail in section 5, where the analysis focuses on the longer equatorial mooring record with its finer vertical resolution in the surface layer.