Amazon Basin Fire Risk has been Linked to North Atlantic Hurricane Activity

As the ten-year anniversary of Hurricane Katrina approaches, researchers from the University of California, Irvine (UCI) and NASA recently discovered a new link between the dry Amazon basin and moisture pulled from the Amazon by the whirl of North Atlantic storm activity.

"The ocean conditions that led to a severe hurricane season in 2005 also reduced atmospheric moisture flow to South America, contributing to a once-in-a-century dry spell in the Amazon. The timing of these events is perfectly consistent with our research findings," notes James Randerson, Chancellor's Professor of Earth system science at UCI and senior author on the paper, in a statement.

Lead author Yang Chen found that, in addition to the east-west influence of El Niño on the Amazon, the tropical North Atlantic controls north-south fire activity. This played a major role in finding the connection between the high wildfire risk in the Amazon basin and the hurricanes that devastate North Atlantic shorelines. While warm ocean waters help hurricanes develop, gather strength and speed to North American shores, they also shift a large belt of tropical rainfall, known as the Intertropical Convergence Zone, to the north. This draws moisture away from the southern Amazon, leading to a heightened fire risk there, the statement said.

Essentially, less rain falls in the southern Amazon when very warm sea surface temperatures in the North Atlantic draw away from the global balance of moisture. As a result, that part of the Amazon's groundwater is not recharged. Then, in the next dry spell, plants cannot draw on the groundwater to evaporate and transpire water from their stems and leaves, according to the statement.

In the study, the scientists examined historical storm and temperature data regarding the sea surface from the National Oceanic & Atmospheric Administration, and fire data collected by NASA satellites. From all this they were able to see a striking pattern: a progression over the course of several months from warm waters in the tropical region of the North Atlantic to a dry southern Amazon and more catastropic hurricane landfalls in North and Central America, noted the release.

The scientists published their findings in the journal Geophysical Research Letters.

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