Did You Know?

Oct0ber-November 1995

This is an article from WaveLength Magazine, available in print in North America and globally on the web.

Coral reefs record climate

Coral reefs are made up of living coral animals growing on a foundation of dead coral. Scientists have found that, just like tree rings, coral growth rings can be used as a record of climate that extends back into the past

Water temperature affects coral metabolism and growth, so as the climate of a given region shifts, this change is recorded in a pattern of bands in the coral reef based on growth conditions which spur changes in coral species composition changes and other characteristics.

Earth's climate is often affected by the El Nino -- a warm water phenomenon in the tropical Pacific. But there are other consistent patterns of change in Earth's climate that originate over more temperate latitudes. For example, over North America, changing weather patterns often correspond to a shift in the position of the jet stream. When the jet stream has an orientation that's more north-south than east-west, it can bring cold dry Arctic air masses from Canada to the Gulf of Mexico for a period of decades or more.

The growth patterns in the reefs in the Gulf of Mexico were studied recently with respect to shifts in climate. A decrease in coral growth appears to coincide with colder temperatures from the late 1950s to the late '80s. Since, reliable climate records made by meteorologists go back only 100 years or so, researchers believe that coral can be used to trace the history of climate change from decade to decade going back for a period of centuries.