The Indian Ocean Dipole (IOD), an oscillation of sea surface temperatures in the Indian Ocean, is occurring more frequently because of global warming, a new study has said.
The research was done by Nobuko Nakamura and his team from the University of Tokyo, along with Timothy R. McClanahan from Wildlife Conservation Society, and Swadhin K. Behera from the Frontier Research Center for Global Change, Yokohama, Japan.
Recently, the IOD has become a major influence on the weather variations in the Indian Ocean region.
During positive IOD events, abnormally warm sea surface temperatures in the western Indian Ocean are accompanied by severe droughts over the Indonesian region and heavy rainfall over east Africa.
To learn more about IOD patterns, the team of scientists studied a 115-year coral record from Kenya.
They analyzed coral oxygen isotope ratios, which trace rainfall anomalies, to reconstruct IOD variability.
The results add to evidence that the IOD has been occurring more frequently in recent decades.
They found that before 1924, the IOD occurred approximately every 10 years, but since 1960, IOD events have been occurring approximately 18 months to 3 years apart.
The researchers suggested that global warming effects on the western Indian Ocean have driven the observed shift in IOD variability and note that the IOD has replaced the El Nino-Southern Oscillation as the major driver of climate patterns over the Indian Ocean region.