NOAA/WDS Paleoclimatology - Line Islands Coral P/Ca Reconstructions from 1981-2002

Variations in ocean productivity are driven largely by nutrient supply to the photic zone, but temporal records of nutrient variability are sparse. Here we show scleractinian coral P/Ca proxy records of variations in phosphate concentrations during El Niño Southern Oscillation (ENSO) cycles in the central equatorial Pacific. Covarying P/Ca records in Porites corals from Christmas and Fanning Islands show a regional ~40% decrease during the upwelling relaxation of the 1997-1998 El Niño, consistent with less frequent nutrient measurements from this area. Similar ~35-45% skeletal P/Ca decreases occur during the 1982–1983 and 1986-1987 El Niño events, which predate satellite color and regional nutrient measurements. After each El Niño event, nutrient increases lag temperature recovery by 4-12months, likely reflecting uptake by massive phytoplankton blooms that followed resumption of upwelling. The results support the utility of coral P/Ca to probe the mechanisms linking ENSO, equatorial upwelling, and carbon cycling in the past.