A Hitchhiker’s Guide to an Ancient Geomagnetic Disruption
About 42,000 years ago, the Earth was side by side with oddity. Its magnetic field collapsed. Snow sheets have increased in North America, Australia and the Andes. Wind belts migrated to the Pacific and Southern Oceans. Prolonged drought-affected Australia; The largest mammals of that continent went extinct. Man went to the caves to make ocher-colored art. Neanderthals died for good.
Through all of this, a giant Kaurai tree stood tall – until about two millennia later, it died and fell into a swamp, where the chemical records embedded in its flesh were immaculately preserved. A few years ago near Nagawa Springs, northern New Zealand, the tree finally discovered what allowed researchers to fit a tight timeline in what seemed like a previously intriguing but vaguely correlated series of events.
What if, researchers said, the magnetic field crash caused climate change of that era? And to think that the Nagwa Kauri tree was a witness to the whole thing.
“It must have seemed like the end of days,” Chris SM Turnai, a geologist at the University of New South Wales in Sydney, Australia, and part of a larger team describing the findings. In a study published on Thursday in Science. “And this tree went through all that. Which is incredible, actually. “
By comparing tree-ring age data and radioactive carbon concentrations from that kauri tree and three others of similar vintage from recent dating information obtained from two stalagmites in Hulu caves in China, Drs. Twainy and his 32 co-authors were able to point out when. The tree lived and died. This gave them what they call the “calibration curve”, allowing them to convert radiocarbon dating from that period to a calendar year.
The scientists at the disciplines said that the Kaori data was a luminosity and long-awaited addition to the radiocarbon canon.
“For a radiocarbon person, the Kauri records are simply amazing,” Luke C. Said Skinner, a paleontologist at the University of Cambridge, who was not involved in the study. He said that fossil Kaur trees were the main way for scientists to obtain radiocarbon information for so long.
The tree lived through a long disintegration of the magnetic field, known as the Laschamps excursion, when magnetic poles unsuccessfully attempted to switch locations. As a result, Dr. Tern and his co-authors were able to use the new data to describe more accurately when this excursion occurred and discover what else was going on, including the bizarre climate and extinction.
“It was sudden, God, these things are actually happening all over the world together, at the same time,” Dr. Tern said. “It was just an extraordinary revelation.”
That discovery opened up a much-hyped thought experiment. Earth’s magnetic field, which is constantly arising from deep within the planet’s molten outer core, protects against dangerous galactic and solar rays. 42,000 years ago, all those peculiar climatic, biological and archaeological phenomena linked to the ruined magnetic field? Did its fall change the course of life on Earth? And what about other disturbances in the magnetic field, including the time 780,000 years ago when magnetic poles actually created switch locations?
Scientists have been trying to find answers to these questions since the fact of magnetic pole reversal was established several decades ago. As a result, this latest effort has drawn immense scrutiny.
“It’s very brave,” said Katherine G. Constable, a geophysicist at the Scripps Institution of Oceanography in San Diego, who was not involved in the study.
Using global climate model simulations allowing for the interaction of chemistry, Drs. Tern and his colleagues used the timeline generated by the Kaur tree to try to find out what the climate was during the excursion.
The data revealed “slight but significant changes in atmospheric chemistry and climate” according to the paper. Among them: a slightly lower ozone layer; Slightly increased ultraviolet radiation, especially near the equator; A jump in ionization that damages the tissue; And the Auroras as close to the equator as the 40th parallel of latitude, which would run through the continental United States in the Northern Hemisphere and the lower end of Australia to the south.
Adding a period of reduced solar activity, known as the grand solar minima, produced a more dramatic effect in this mixture. A long series of beryllium-10 isotopes in Greenland’s ice core, a peculiar series, originated from the Laschamps excursion 42,000 years ago. Such isotopes are formed when cosmic rays cover the upper atmosphere; In the geological record they indicate a time when the Earth experienced a low magnetic field and, sometimes, solar changes.
In the more extreme computer scenario, the solar effect actually increased ultraviolet radiation by 10 to 15 percent from the norm, and ozone declined the same amount. Those effects were cascaded through the climate system, Drs. Tern said:
“It was basically like a perfect storm,” he said.
Simulations suggest that the weakened magnetic field caused some climate change from 42,000 years ago, and those changes could have widespread effects: signaling the extinction of many large mammals in Australia, hastening the end of Neanderthal, and Maybe give rise. The authors proposed keeping the art in a cave to hide for a long time to avoid ultraviolet rays that damage the skin.
In fact, the effects were striking given that researchers have given a new name to the years leading up to the Laschamps excursion. They call it the Adams Transitional Geomagnetic Event.
“The Adams event appears to represent a major climatic, environmental, and archaeological range that has been previously unrecognized,” the team writes, concluding, overall, that these findings reflect the evolutionary effects of geomagnetic resurgence and deeper geological The record raises important questions about excursions. . “
The new name is a tribute to British comedian Douglas Adams, “The Hitchhiker’s Guide to the Galaxy” and the book and radio series “Last Chance to See,” about extinction. It is also a sign for Mr. Douglas’s famous line that “the answer to life, the universe, and everything” is 42 – which Dr. Turn said he reminded him of the time of the magnetic episode 42,000 years ago.
“It just feels supernatural,” he said with a laugh. “How did he know?”
Interpretation is destined to create controversy. Some scientists reading the paper expressed appreciation for the breathtaking relationships across disciplines.
“One of the strengths of the paper, from the perspective of its scholarly work, is not necessarily the analytical science it does, it is just the degree to which it separates all of these together from its source of information” in New York. Jason E., a climate scientist at the Lamont-Doherty Earth Observatory of Columbia University. Simardon, who was not involved in the study. He called it a “tour day force”.
Similarly, James ET Channell, an emerging professor of geophysics at the University of Florida who was not involved in the study but was a peer reviewer, said scholars had staged the question for half a century as to whether waning affected magnetic fields Does life The paper opens up new avenues of research.
“If we knew enough about the time of the excursion, perhaps we could see this problem,” he said.
But other scientists said that extensive analysis made them wonder if there were other explanations for some of the events during the Laschamps excursion.
“It’s opening a can of worms instead of solving a set of questions,” Dr. Skinner said.
Like many others interviewed, he worried whether naming the Adams event would cause confusion in scientific literature, and whether it was necessary. But he praised the paper for stimulating discussion.
“I was definitely more excited about the subject than I was yesterday,” he said.