Department of Earth System Science

Sixty radiocarbon measurements were performed on aragonite from annually banded corals collected from three sites in the Galápagos Islands. Preanthropogenic Δ¹⁴C values of coral that grew around A.D. 1930 averaged −70‰. This is substantially lower than average values previously reported (−51‰) for corals from Florida and Belize in the western North Atlantic Ocean. A decrease of 6‰ was noticed in coral that grew from 1930 to 1954. This decrease could be interpreted as a Suess effect in surface ocean water. The 100‰ increase in Δ¹⁴C for coral that grew from 1954 to 1973 is the result of bomb-produced ¹⁴C that was introduced to the surface ocean waters. The ¹⁴C levels in corals that grew during El Niño years were considerably higher than those for normal years. These higher values are attributed to the absence of up welling at the equator during El Niño events.