Indian Ocean causes drought and heatwaves in South America


JULY 8, 2019 – by University of New South Wales

https://phys.org/news/2019-07-indian-ocean-drought-heatwaves-south.html
The marine heatwave that accompanied the South American drought of 2013/14 was one of the strongest ever recorded for the area. Trends show that these marine heatwaves are getting longer, more intense and cover larger areas. Credit: Dr. Regina Rodrigues

New research has found the record-breaking South American drought of 2013/14 with its succession of heatwaves and long lasting marine heatwave had its origins in a climate event half a world away—over the Indian Ocean.

The findings published in Nature Geoscience by an international research team with authors from the Federal University of Santa Catarina in Brazil, Australia’s ARC Centre of Excellence for Climate Extremes and NOAA in the US suggest this may not have been the first time the Indian Ocean has brought extraordinary heat to the region.

It all started with strong atmospheric convection over the Indian Ocean that generated a powerful planetary wave that travelled across the South Pacific to the South Atlantic where it displaced the normal atmospheric circulation over South America.

You can think of these atmospheric waves as being similar to an ocean swell generated by strong winds that travel thousands of kilometres from where they were generated. Large-scale atmospheric planetary waves form when the atmosphere is disturbed and this disturbance generates waves that travel around the planet.

“The atmospheric wave produced a large area of high pressure, known as a blocking high, that stalled off the east coast of Brazil,” said lead author Dr. Regina Rodrigues.

“The impacts of the drought that followed were immense and prolonged, leading to a tripling of dengue fever cases, water shortages in São Paulo, and reduced coffee production that led to global shortages and worldwide price increases.”

That impact wasn’t just felt on land as the high-pressure system stalled over the ocean.

(Continued)

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Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.