Not all ice ages are equally brutal. In the most extreme glaciation events known to science, ice spreads from the Earth’s polar regions and extends all the way to lower latitudes, literally changing the planet’s surface again.
Evidence for such epic transitions can be found in the geological record, most recently in formidable glaciations during the cryogenic period. Scientists think that these extreme cooling events had global potential and ramifications: a phenomenon called “Snowball Earth”.
But what on Earth can come out of a devastating and relentless cold that most – or all – of our planet end up covered in a frozen sphere of ice and snow? While the exact trigger is still unknown, researchers have now opened up a new theoretical explanation for how such a thing could happen.
“There are many ideas for what caused these global glaciation, but they all reduce to some implicit modification of incoming solar radiation,” says planetary science researcher Constantin Arnscheidt from MIT.
“But it has generally been studied in the context of threshold crossing.”;
In other words, the conventional explanation for how Snowball Earth can happen is that, in some kind of cataclysmic cast of shadow, a reduced amount of sunlight will be able to reach the surface of the planet, which resulting in one of the Earth proceeding to freeze.
Another hypothetical explanation, relating to the carbon cycle, would be the opposite of the global warming crisis facing the Earth now: what would happen if our planet had so little carbon dioxide? to capture heat in the atmosphere that we have completely lost the Earth’s temperate climate, with its heat drifting into space?
“Although there remains a debate about the specific characteristics of low-latitude glaciation in the Earth’s geological past, there is a general understanding that glaciation begins when changes in radiative or CO2 flows exceed the limit. critic, “Arnscheidt and his co-author, MIT Geophysicist Daniel Rothman, explain it in a new paper.
While the theory has focused on such critical limits before, researchers have welcomed a new way to think about the precursors of the Snowball Earth: what would happen if a critical hit was not met (in terms of solar radiation, for example) , but a critical rate of change achieved?
In the new modeling, the researchers simulated the Earth’s dynamic systems in glaciation scenarios – mainly the feedback interaction of the ice albedo and the carbonate-silicate cycle.
The first is an example of a positive response. As the Earth grows and approaches Snowball Earth, the icy ice sheet and ice end up reflecting more sunlight away from the planet, which in turn accelerates the cooling effects already found in the process.
However, as the Earth becomes a meal, our usual carbonate-silicate cycle is disrupted. With Earth’s rocks sealed under ice, they are less able to absorb atmospheric carbon, and thus get stuck in the heat trap in the air. That is why – still at a distance from Earth from the Sun – our planet is theoretically not stuck in a permanent Snowball Earth state, despite the realization of the ice-albedo response.
With these types of factors embedded in their models, the researchers examined whether rate-induced tipping could lead to a Snowball World event. In the right circumstances, she did.
In the simulations, Arnscheidt and Rothman found that if solar radiation drops fast enough for a long time, that in itself may be enough to release Snowball Earth – and all that could be about a 2 percent reduction in sun that has reached the surface for 10,000 years, researchers estimate.
In the great scheme of things (read: the age of about 4.5 billion years of the Earth), that’s not long. But what can the Earth hide from the Sun like that, for 10,000 years at a time?
No one really knows, but it’s plausible that something like a planetary-scale volcanic winter loosened by volcanic eruptions could be enough clouds in our atmosphere. Alternatively, some kind of biological phenomenon in the ancient past of the Earth, such as an increase in moisture-producing algae, can generate condensation clouds that can eventually freeze them and anything else in oblivion. .
Of course, all these ideas are pretty much there. But that doesn’t mean we shouldn’t go looking for what might have made Snowball Earth happen, or exploring how quickly this ancient and icy story might have resurfaced.
Especially because they are now moving so fast in the opposite direction, the researchers say.
“It teaches us that we have to be careful of the speed with which we are modifying the Earth’s climate, not just the magnitude of change,” says Arnscheidt.
“There may be other points of rate change that could be caused by anthropogenic warming.”
The findings are reported in Proceedings of the Royal Society A.