Smoke from massive forest fires in Australia has caused algae blooms

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The catastrophic forest fires that ravaged Australia in the continent’s summer of 2019-2020 were among the worst in the country’s history. Now, scientists have discovered that these fires may have released much more global warming carbon dioxide gas than previously thought, and have discovered the first conclusive link between smoke from forest fires and major blossoms of the forest fires. plankton in the ocean.

The so-called Australian black summer witnessed the burning of around 74,000 square kilometers of eucalyptus forests, an area almost as large as Syria. Researchers suspected the fires had released large amounts of carbon dioxide into the atmosphere, but weren’t sure exactly how much.

By examining high-resolution satellite measurements of carbon monoxide concentrations after forest fires, environmental researcher Ivar van der Velde of the Vrije Universiteit Amsterdam and his colleagues deduced the carbon dioxide emissions triggered by the fires on the basis of previously observed relationships between carbon monoxide and carbon dioxide emissions. They estimated that the fires triggered around 715 million metric tonnes of greenhouse gases from November 2019 to January 2020. This was more than double the previously estimated amount, exceeding normal annual fire emissions by 80%. and fossil fuels in Australia.

“Given current trends in global warming, we say it is entirely possible that the frequency, duration and magnitude of forest fires in South East Australia, and perhaps elsewhere, will only increase in the future, “said van der Velde. “This will contribute to an even faster rise in carbon dioxide levels than expected.”

In addition, by analyzing satellite observations, robotic ocean floats and atmospheric chemistry data from research stations, the researchers tracked the spread of aerosols from forest fires. They discovered iron-laden nutrients in smoke-fertilized seaweed in the Southern Ocean thousands of miles downwind of the fires. This has led to plankton blooms so intense and extensive that the associated increase in photosynthesis may have temporarily offset a significant fraction of the carbon dioxide emissions from the fires.

“Australian wildfires have a very distant impact on marine ecosystems,” said biogeochemist Nicolas Cassar of Duke University.

Major forest fires such as those raging not only in Australia but also in the western United States, Siberia, the Amazon, the Mediterranean and elsewhere are expected to occur more often with droughts and warming brought on by the climate change, said biogeochemist Weiyi Tang at Princeton University. . In the future, research vessels downwind of these fires can study how the oceans may react – whether the carbon emissions absorbed by algae are buried safely in the depths, or if plankton quickly release them into the sea. ‘atmosphere, Cassar said.

Van der Velde, Tang, Cassar and their colleagues detailed their findings in of them studies online September 15 in the journal Nature.

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