Interannual and decadal variability in tropical Pacific chlorophyll from a statistical reconstruction: 1958-2008

Historical understanding of marine biological dynamics has been limited by sparse in situ observations and the fact that dedicated ocean color satellite remote sensing only began in 1997. From these observations, it has become clear that physical oceanography controls biological variability over seasonal to interannual time scales. To quantify how multidecadal, climate-scale patterns impact biological productivity, the strong correlation with sea surface temperature and sea surface height is utilized to reconstruct a retrospective 51-yr time series of surface chlorophyll, the pigment measured by ocean color satellites. The canonical correlation analysis statistical reconstruction demonstrates greatest skill away from land and within about 10 degrees of the equator where chlorophyll variance is greatest and predominantly associated with El Nino-Southern Oscillation dynamics. Differences in chlorophyll patterns between east or central Pacific El Nino events are observed, with larger declines east of 180 degrees for east Pacific events and west of 180 degrees for central Pacific events. Additionally, small but significant decadal variations in chlorophyll patterns are observed corresponding to the Pacific decadal oscillation. Decadal changes in chlorophyll west of 180 degrees are consistent with increased stratification, whereas changes between 110 degrees-140 degrees W may be related to long-term shoaling of the nutrient-bearing equatorial undercurrent.