Large-scale Australian fires have created a huge thermal anomaly in the stratosphere

(ORDO NEWS) — Vast expanses of wildlife and the lives of billions of animals were reduced to ash and smoke during the raging black summer fires in Australia. The resulting haze suffocated major cities, caused fatal emergencies, and turned distant glaciers brown.

Now, researchers have directly traced how some of this burned-out biomass contributed to the largest warming of the stratosphere in three decades and also disrupted the Antarctic ozone hole.

By combining satellite data with surface observations of aerosol behavior in computer models, University of Exeter statistician Lilly Damany-Pierce and her colleagues were able to detect smoke rising high into our planet’s atmosphere.

The fires destroyed more than 5.8 million hectares of land and were so intense that they formed their own weather patterns, including smoke-filled thunderstorms (pyrocumulonimbus) that continued for days on end.

As the researchers explain, these systems and their vortices lifted the smoke to unusually high altitudes, and the sun’s rays heated the dark particles and forced them to rise further, in a process called self-ascension.

The first vortex, detected on December 31, 2019, reached a height of 16 kilometers (nearly 10 miles). Then another plume from January 12, 2020 was eventually detected at an altitude of up to 35 km – far in the stratosphere – and persisted for up to 2 months.

“For a month, the aerosol plume drifted across the South Pacific Ocean and was clearly detected in the stratosphere by the [NASA] CALIOP instrument, as well as by surface lidars and solar photometers operating from the southern tip of South America,” the group writes in their paper.

At this time, there was a sharp jump in the average global temperature in the stratosphere by 0.7 °C (1.8 °F).

The anomalous temperatures persisted for four months, and climate modeling conducted by the researchers showed that these temperatures could not be explained without the release of 0.81 teragrams of smoke particles that satellites detected in the stratosphere.

It was the largest temperature jump in the Earth’s stratosphere since the eruption of Mount Pinatubo in 1991, Damany-Pierce and colleagues note.

While the planet’s surface cooled by about half a degree Celsius due to diffuse clouds of particles blocking sunlight, the absorption of infrared radiation by particles in the stratosphere actually caused a significant warming of this layer of the atmosphere.

Volcanic aerosols released into the atmosphere during such eruptions are also known to deplete the ozone layer, and recent studies have shown that particles from forest fires can do the same.

The chemical reactions that take place on the surface of smoke particles consume ozone molecules. So the researchers mapped the vertical distribution of ozone in the southern hemisphere in 2020 and found even more evidence of smoke-induced ozone depletion.

Smoke particles have extended the duration of the ozone hole over Antarctica and disrupted the Antarctic polar vortex, which usually begins to break down by late spring.

“Ozone depletion serves to increase the strength of the polar vortex by reducing stratospheric heating and balancing the thermal wind, providing a positive feedback that appears to delay the polar vortex’s collapse,” Damany-Pierce and colleagues explain in their paper.

“This, in turn, contributed to the long-lasting ozone hole that was observed in 2020.”

The Antarctic ozone hole hit near-record levels in 2020, and now we know why. The new study shows how these smoke-induced changes then also affected temperatures, strengthening the polar vortex. This resulted in an unusually cool spring of 2020 in the Southern Hemisphere.

Meanwhile, closer to the Earth’s surface, more problematic smoke particles floated over the ocean and fell into the sea, spurring plankton into feeding and reproductive frenzy, resulting in suffocating blooms of these micro-organisms larger than the smoke’s origin continent.

Nearly three years and several massive fires later, it is more disturbing than ever to see the staggeringly large, varied, and far-reaching effects massive wildfire smoke plumes can have.


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