Indian Ocean affects climate

A CLIMACTIC phenomenon in the Indian Ocean that causes drought in Australia has been linked to climate change. In a study published yesterday, researchers from Australian National University (ANU) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) found that the Indian Ocean Dipole (IOD) is more likely to be in a positive state as a result of global warming.

The IOD measures sea surface temperatures between the western and eastern parts of the Indian Ocean. A “positive” state is when waters near the Horn of Africa are warmer than average while those near Australia are cooler, resulting in less rainfall and high temperatures.

The research team found that the positive IOD events had become stronger and more frequent since the 1960s. The Australian drought last year, one of the worst in the nation’s history, occurred at a time when the IOD was at a record positive, causing flooding in eastern Africa.

“The rain bands are moving away to where the (sea) temperature is maximum,” Wenju Cai, director of the Centre for Southern Hemisphere Oceans Research at the CSIRO, told the Australian Broadcasting Corporation.

“Rain bands and convection always move to regions where the ocean temperature is the maximum.”

According to projections produced by Cai, Australia will experience twice as many drought-causing extreme IOD positives if global temperatures warm by 1.5ºc.

“If we look at climate models, they produce this increasing frequency and intensity of positive Indian Ocean Dipole events and project that, as the climate continues to warm, we will see those trends continuing,” said Nerilie Abram from the ANU Research School of Earth Sciences. “That is going to increase the risk that we will have these very dry and hot years and those are the years where we precondition our landscape to burn.”