El Nino's Impact May Reach Beyond Pacific - Brief Article

USA Today (Society for the Advancement of Education), June, 2000

OCEANOGRAPHY

People living along the Pacific coast have learned to respect the awesome power of El Nino--the periodic warming and cooling of the Pacific Ocean that can bring torrential rainfall or extreme drought every three to seven years. Now, Robert B. Dunbar, professor of geological and environmental sciences, Stanford (Calif.) University, and Julia E. Cole, professor of geosciences, University of Arizona, Tucson, have discovered that El Nino's influence may stretch well beyond the Pacific into the waters of the Indian Ocean.

Using underwater drills, Dunbar's team removed 12-foot-long core samples from a living colony of coral growing in the waters of Kenya's Malindi Marine Park. Like trees, coral skeletons form annual growth rings that accumulate over hundreds of years. The Malindi core samples provide a record of growth dating back to 1801.

As they grow, coral skeletons take up a mixture of different types of the chemical element oxygen. One type is heavier than the other, and, as the coral experiences seasonal and long-term changes in water temperature, the relative proportion of heavy and light oxygen in the skeleton also changes. By measuring how much heavy oxygen is present in each growth ring, scientists can determine past fluctuations in water temperature.

When Dunbar and Cole analyzed the quantity of heavy oxygen in the Malindi samples, they made a remarkable discovery: Surface temperatures in the western Indian Ocean have risen and fallen roughly every 10 years in a pattern almost identical to the periodic warming and cooling that occurred in the tropical Pacific.

The Malindi corals also revealed that the surface temperature of the Indian Ocean has risen approximately 2.3 [degrees] F since 1801. "This is a big increase," Dunbar says, noting that the largest rise occurred in the late 20th century--possibly the result of an artificial greenhouse effect caused by people burning gasoline and other fossil fuels.

Dunbar and his colleagues plan to continue their research to determine if El Nifo has any effect on the severity of monsoon rainfall along the Indian Ocean coastline. Eventually, scientists may be able to predict severe monsoon seasons months in advance, a breakthrough that could benefit millions of coastal residents who face severe flooding in Kenya, India, and nearby countries.