What is coral dating
The chemicals in each layer reflect conditions in the ocean when the layer formed.
Like the scaly coverings of foraminifera and other marine organisms, the ratio of heavy and light oxygen in coral growth bands provide a record of temperature and rainfall during the growing season.
This slow-down in growth appears in the growth layers pulled from core samples just as drought shows up in the growth rings of trees.
The climate record left in coral reefs is detailed, but limited.
The lower graph shows change in oxygen-18 isotopes measured in coral cores on Tarawa Island.
First, coral reefs don’t exist everywhere in the world.
They can only tell scientists about climate in warm, tropical waters.
Scientists have discovered some deep water coral that may yield a detailed climate record of other regions, but the work is still in its early stages. The record they preserve only covers the lifetime of the individual—a few hundred years, then an older coral from the reef has to be found to stretch the record further back.
Piecing together a continuous record can be very difficult and requires numerous samples from both living and fossil corals.a meteorological measurement of the intensity of El Niño.