A study has cemented the link between an intense global warming episode 56 million years ago and volcanism in the North Atlantic, with implications for modern climate change.
Roughly 60 million years ago, circulation changes deep within our planet generated a hot current of rock — the Iceland plume — causing it to rise from the heart of Earth’s mantle.
When the mantle rock pierced the bottom of the North Atlantic Ocean, lava spurted across Scotland, Ireland, and Greenland, scabbing into spectacular columned landscapes like the Giant’s Causeway in Northern Ireland and Scotland’s Fingal’s Cave (pictured).
That opening salvo was followed 4 million years later by a second gigantic pulse of hot mantle rock, which once again rode up the Iceland plume.
It swelled under the seafloor and lifted a wide region of ocean floor between Greenland and Europe into the air, forming a temporary land bridge connecting Scotland and Greenland.
Under the surface, the mantle blob melted, turning from solid rock to fluid magma.
The magma then bled, bruise-like, through sediments. As the magma spread, it formed thousands of horizontal sheets known as sills that cooked organic matter in the sediments.
This cooking produced methane and carbon dioxide gas that burst through vents in the seafloor.
As sheet after sheet of magma bled into the expanding bruise for millennia, more and more gas bubbled from the ocean like a boiling pot.
Evidence indicates that suspiciously close in time to all that igneous activity, the planet warmed by 5 degrees Celsius (9 degrees Fahrenheit).
In this ancient warming event, known as the Paleocene-Eocene Thermal Maximum, or PETM, the land suffered intense downpours, while ocean acidification and heat drove many marine species extinct.
Many land animals went extinct as well and were replaced by dwarf species. The Arctic had alligators, giant tortoises, and vegetation typical of Florida today, and sea levels were around 300 feet higher than now.
The PETM has preoccupied climate scientists since its discovery in the early 1990s because of its parallels to today’s climate change, including a temperature jump, ocean acidification, a huge shift in the atmospheric carbon level, and a profound effect on life.
To produce those effects, a massive reservoir of carbon — around 10 trillion tons by recent estimates — must have been pumped into the sky.
But what was that carbon store? How could it be released so fast, and could a similar carbon reservoir be poised to amplify our current warming today?
“If we can understand … the closest analog that we’ve got in the past hundred million years, then we’re going to be in better shape to think about what’s going to happen in our lifetimes,” said Stephen Jones, a geologist at the University of Birmingham in the United Kingdom.
Because many of the North Atlantic’s volcanic features, which scientists collectively call the “North Atlantic Igneous Province,” formed concurrently with the PETM, they are a candidate for the cause of the warming.
But coincidence isn’t causation, and there have been good scientific reasons to doubt that the volcanic activity could have caused climate change.
Recently, a paper by Jones and his collaborators in Birmingham removed the last major doubt and showed that igneous activity was indeed the principal driver of the warming.
The Wrong Kind of Carbon
Although a great deal of North Atlantic volcanism happened close in time to the PETM, scientists were initially skeptical that it could have driven the warming.
Sedimentary layers that formed at the time had the wrong kind of carbon — they were rich in the isotope carbon-12, indicating an organic carbon source rather than a volcanic one.
The leading theory was that fluctuations in Earth’s orbit around the sun melted a type of frozen methane just beneath the seabed called methane clathrates.
Yet scientists found scant evidence that enough clathrates existed in the pre-PETM world, or that they could have melted fast enough to drive the warming.
A possible missing link between the North Atlantic Igneous Province and organic carbon was spotted in 2004 in seismic scans through the seabed off the coast of Norway.
When Henrik Svensen of the University of Oslo and colleagues analyzed recorded echoes from air blasts produced by oil exploration ships, they saw vents leading upward from sills that formed around the time of the PETM.
They reasoned that the vents resulted from hot sills baking organic detritus, which is rich in carbon-12. This would have generated methane and carbon dioxide.
The gases would have erupted through the seabed and ocean and into the atmosphere, driving the PETM. More vents have since been spotted on both sides of the Atlantic, and samples have been drilled from one of them.
Similar vents in Siberia and in South Africa have been linked to global warming in different periods of Earth’s history — the Permian and the Jurassic respectively.
Still, few thought that igneous activity could act fast enough. Geologists thought the sills formed over a few million years, whereas fossilized sediments show it took just a few thousand years to start the PETM.
The Birmingham team has closed that gap. They found that with the Iceland plume, as Jones put it, “you can turn the tap on … in five to ten thousand years.”
Read rest at Quanta Magazine
and the Greatest Flood of them all the Noah Flood and the Ark and Animals coming in couples
Instead of taking millions of years to develop a geological global warming, it could happen as quickly as 4,000-5,000 years.
We better listen to Greta and take action NOW!!! In 12 years it will be too late!!
From the article, “To produce those effects, a massive reservoir of carbon — around 10 trillion tons by recent estimates.” Note that the authors are assuming carbon dioxide is the control knob. They are taking the effects and then calculating the amount of carbon dioxide needed.