At least twice in the history of the Earth, almost the entire planet has been enclosed in snow and ice. These dramatic events of the “Earth Globe” happened quickly, about 700 million years ago, and evidence suggests that the successive global ice age became the basis for the further explosion of complex multicellular life on Earth.
Scientists have considered several scenarios of what may have brought the planet to each ice age. Although no motion process has been identified, it is assumed that what caused the temporary freezes should have done so in a way that pushed the planet to a critical threshold, such as reducing sunlight or atmospheric carbon dioxide to a level sufficient to set the global ice expansion.
But MIT scientists now say that the Earth of snowballs was most likely the product of “ice-induced speed.”; That is, they found that the Earth could turn into a global ice age, when the level of solar radiation it receives changes rapidly in a geologically short period of time. The amount of solar radiation should not fall to a certain limit point; as long as the decrease in sunlight is faster than the critical rate, there will be a temporary icing or Snowball Land.
These findings are published in Proceedings of the Royal Society A, suggest that everything that caused the Earth’s ice age most likely included processes that rapidly reduced the amount of solar radiation coming to the surface, such as widespread volcanic eruptions or biologically caused clouds that could significantly block the sun’s rays. .
These findings may apply to the search for life on other planets. The researchers sought to find exoplanets in the habitat – the distance from their star, which would be within the temperature range that could support life. A new study suggests that these planets, like Earth, may also temporarily freeze if their climate changes dramatically. Even if they lie within a residential area, Earth-like planets may be more susceptible to global ice ages than previously thought.
“You could have a planet that’s well in a classic residential area, but if the sunlight changes too quickly, you can get a globe,” says lead author Konstantin Arnsheid, a graduate student in the Earth, Atmospheric and Planetary Sciences Department of MIT (EAPS). ). “It emphasizes that this is a concept that there are many more nuances in the concept of suitability.”
Arnscheidt is a co-author with Daniel Rothman, a professor of geophysics at EAPS and co-founder and co-director of the Lorenz Center.
Regardless of the specific processes that have caused past glaciation, scientists generally agree that Earth’s snow is caused by a “runaway” effect that involves albedo ice feedback: When sunlight decreases, ice expands from the poles to the equator. As more ice covers the globe, the planet becomes more reflective or higher albedo, which further cools the surface to increase the amount of ice. Eventually, if the ice reaches a certain degree, it becomes a runaway process that results in global glaciation.
The world’s ice ages on Earth are temporary due to the carbon cycle of the planet. When the planet is not covered with ice, the level of carbon dioxide in the atmosphere is somewhat controlled by the weathering of rocks and minerals. When the planet is covered with ice, weathering is greatly reduced, so that carbon dioxide accumulates in the atmosphere, creating a greenhouse effect that eventually thaws the planet from its ice age.
Scientists generally agree that the formation of a snow globe has something to do with the balance between incoming sunlight, albedo ice feedback, and the global carbon cycle.
“There are many ideas about what caused these global glaciations, but they all really come down to some implicit modification of the incoming solar radiation,” Arnscheidt said. “But in general it has been studied in the context of the threshold crossing.”
He and Rothman had previously studied other periods in Earth’s history when the rate or rate at which certain climate changes occurred played a role in causing events such as past mass extinctions.
“In the course of this exercise, we realized that there is an immediate way to make serious sense by applying such ideas of speed sketch to Snowball Earth and population,” says Rothman.
“Beware of speed”
Researchers have developed a simple mathematical model of the Earth’s climate system that includes equations to reflect the relationship between incoming and outgoing solar radiation, Earth’s surface temperature, atmospheric carbon dioxide concentration, and the effects of weathering on atmospheric carbon dioxide absorption and storage. The researchers were able to adjust each of these parameters to observe the conditions under which the Earth of the Snowball is generated.
Eventually, they found that a planet freezes faster if incoming solar radiation decreases rapidly at speeds above the critical speed, rather than to a critical threshold or a certain level of sunlight. There is some uncertainty as to what this critical velocity would be, as the model is a simplified representation of the Earth’s climate. However, according to Arnsteidt, the Earth will have to experience about a 2 percent drop in sunlight for about 10,000 years to move into the global ice age.
“It is reasonable to assume that past glaciations are caused by geologically rapid changes in solar radiation,” says Arnscheit.
The specific mechanisms that may have quickly overshadowed the sky over tens of thousands of years are still being discussed. One possibility is that widespread volcanoes may have released aerosols into the atmosphere, blocking incoming sunlight. Another thing is that primitive algae may have developed mechanisms that contributed to the formation of reflective clouds. The results of this new study allow scientists to consider processes that rapidly reduce the inflow of solar radiation as more likely triggers for the ice ages of the Earth.
“Even though humanity will not provoke icing on our current climate trajectory, the existence of such a ’caused by the rate of overlap’ worldwide can still be a cause for concern,” Arnscheidt said. “For example, it teaches us that we need to be wary of the rate at which we change the Earth’s climate, not just the scale of change. There may be other similar rates of overturning that can be triggered by anthropogenic warming. is an important goal for further research. ”
Researchers reveal clues to the dramatic chapter of the Earth’s geological history
Ways to global glaciation, Proceedings of the Royal Society A, royalsocietypublishing.org/doi… .1098 / rspa.2020.0303
Provided by the Massachusetts Institute of Technology
Citation: A burst of incoming sunlight may have caused the “Snowball Land” (2020, July 28), obtained July 28, 2020 from https://phys.org/news/2020-07-plunge-incoming-sunlight-triggered-snowball .html
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