A team of researchers has put forward a theory about the cause of planet-wide ice ages that have occurred in the distant past, known as “Snowball Earth” events. Their study suggests that these periods of extreme ice cover could have been abruptly triggered by large asteroids colliding with Earth.
The new findings, published in the journal Science Advances, aim to provide an explanation for some of the most significant climate shifts in Earth’s history. The study involved researchers from Yale University, the University of Chicago, and the University of Vienna.
According to climate modelers, if the Earth becomes cold enough, the high reflectivity of its ice and snow could lead to a feedback loop, creating more ice and lowering temperatures until the entire planet is covered in ice. These conditions persisted at least twice during Earth’s Neoproterozoic era, between 720 and 635 million years ago.
Despite the understanding of this process, the cause of these global glaciation events, or “Snowball Earth” periods, has remained uncertain. Most theories have revolved around the decline of greenhouse gases in the atmosphere triggering the onset of ice ages.
Lead author Minmin Fu, a Richard Foster Flint Postdoctoral Fellow at Yale’s Department of Earth and Planetary Sciences, explained the rationale behind the study: “We decided to explore an alternative possibility. What if an extraterrestrial impact caused this climate change transition very abruptly?”
To test this alternative possibility, the researchers utilized a sophisticated climate model that accounts for atmospheric and ocean circulation, as well as sea ice formation, under various conditions. The same type of model is commonly used to forecast future climate scenarios.
Applying their model to the aftermath of a hypothetical asteroid impact during different time periods, the researchers found that an asteroid strike was unlikely to trigger global glaciation in warmer climates such as the Cretaceous and preindustrial periods. However, in the Last Glacial Maximum and Neoproterozoic scenarios, where temperatures were already cold enough to be considered an ice age, an asteroid impact could potentially push Earth into a “Snowball” state.
Co-author Alexey Fedorov, a professor of ocean and atmospheric sciences at Yale’s Faculty of Arts and Sciences, highlighted a surprising result from their study: “What surprised me most in our results is that, given sufficiently cold initial climate conditions, a ‘Snowball’ state after an asteroid impact can develop over the global ocean in a matter of just one decade. By then, the thickness of sea ice at the Equator would reach about 10 meters, compared to a typical sea ice thickness of one to three meters in the modern Arctic.”
The researchers noted that the chances of an asteroid-induced “Snowball Earth” period in the future were unlikely due to human-caused warming, despite the potential devastating impact of other asteroid strikes.
The study was co-authored by Dorian Abbot of the University of Chicago and Christian Koeberl of the University of Vienna.
