Global heating is “supercharging” the Indian Ocean Dipole (IOD) mechanism that made the climate system increasingly stronger, devastating, and more frequent to contribute to this year’s disasters, including bushfires in Australia and floods in Africa.
As the surface temperatures of sea rise, the phenomenon known as Indian Ocean dipole, which hit this year’s record threatens to occur with more regularity and in a more devastating form, scientists and humanitarian officials said.
The years in which the sea surface off the coast of Africa warms up, resulting in more rains, will be a matter of most concern while temperatures off Australia fall, leading to drier weather.
Similar to the El Niño and La Niña in the Pacific, it may cause abrupt changes in weather patterns on either side of the ocean.
Caroline Ummenhofer, a scientist at Woods Hole Oceanographic Institution in Massachusetts and a key figure in an initiative to understand the dipole’s importance, said unique factors were at play in the Indian Ocean compared with other tropical regions.
The Atlantic and the Pacific Ocean can disperse heating water by ocean currents and winds. However, the giant Asian landmass to the north of the Indian Ocean makes it vulnerable to retaining heat. “It’s quite different to the tropical Atlantic and tropical Pacific events. There you have steady easterly trade winds. In the Indian Ocean that’s not the case,” Ummenhofer said.
“There is a certain season where you have easterly winds. Otherwise you have seasonally reversing monsoon wind, which makes for very different dynamics.”
According to recent research, ocean heat has increased dramatically over the past decade, creating the possibility for warming water in the Indian Ocean that may affect one of the most critical climate patterns in the world, the Indian monsoon.
“There has been research suggesting that Indian Ocean dipole events have become more common with the warming in the last 50 years, with climate models suggesting a tendency for such events to become more frequent and becoming stronger,” Ummenhofer said.
She said warming appeared to be “supercharging” mechanisms already existing in the background. “The Indian Ocean is particularly sensitive to a warming world. It is the canary in the coalmine seeing big changes before others come to other tropical ocean areas.”
This year, the dipole was at least one of the contributing factors in the bushfires as per Australian climatologists. Jonathan Pollock, of Australia’s Bureau of Meteorology, said this dipole was “up there as one of the strongest” on record.
Gemma Connell, of the UN’s Office for the Coordination of Humanitarian Affairs, is concerned over the impact of stronger and frequent Indian Ocean dipole events that Africa would face.
“What we are seeing from the current record events is large-scale flooding across the region. Entire swathes are underwater, affecting 2.5 million people,” she said.
“And putting it in the broader picture of the climate crisis, this flooding is coming on the back of two droughts. What we are seeing, and what we are going to see more of, is more frequent climatic shocks coming. And all that is on top of the violence and conflict that has already displaced many of the people involved.
“In Kenya, for example, the region hardest hit has been around Lake Turkana, where there are already global malnutrition rates above 30% following drought. People are trying to cope with back-to-back shocks and their resilience has been eroded.”
Although climate scientists are racing for developing predictive modeling, there is a dispute over whether stronger Indian Ocean dipole events will bring a wetter or a drier climate for Africa, and that is another concern for Connell and other humanitarian officials.
“As non-meteorologists trying to plan ahead, we’re being faced with complex and changing scenarios. We’re just running to keep up. Looking now at southern and eastern Africa, with failed rainy seasons and then flooding, none of it looks normal,” she said.
“The new normal is a severe weather events. Looking at the Indian Ocean dipole’s effects, you have to see this is as a preview of what can be expected in other parts of the world. And while I’m not surprised that attention of the world is elsewhere, that is still unforgivable given how many are suffering from a phenomenon the rest of the world helped create.”