Impact Induced Snowball Earth
Interesting paper:
Impact-induced initiation of a Snowball Earth: A model study
Minmin Fu, Dorian S. Abbot, Christian Koeberl, Alexey Fedorov
Science Advances, 10 eadk5489 (2024) 9 February 2024
Basically, these folks used a climate model of the Earth configured various way, and tried to replicate what a large meteorite impact might do to that climate model. In this paper, “model” apparently means something like “simulation we can run for a to see what it’s climate does”. This “model” is more like an engineer’s finite element model, than it is a set of equations you plug numbers in and calculate some value(s) from.
They looked at modern climate and geography, and the inferred climate and geography of some earlier geological periods to see if a dinosaur-killing meteorite would put the planet into a Snowball Earth configuration.
The authors seem to have bracketed some uncertain aspects of the Earth in the past, like atmospheric CO2 levels, and what a large meteor impact would throw into the atmosphere.
Running their models/simulations indicate that an impact during the last glacial maximum period, and during the Tonian period could easily trigger a Snowball Earth. During the Cretaceous and the pre-industrial modern Earth, impact effects on the atmosphere doesn’t throw the world into a snowball state, but does cause some increase in glaciation. Which validates their model a little: not until 2014 did someone detect an impact winter, much less increased glaciation at the end of the Cretaceous Period.
The eerie part of the paper is that it takes less than 10 years from impact to glaciers at the equator and a Snowball Earth.
“PI” is pre-industrial earth atomosphere. “LGM” is Last Glacial Maximum, about 20-26,000 years ago.
I gather that geologists mostly think that at least a couple of periods of Snowball Earth happened, but the cause(s) are still mysterious. Meteor impact competes with volcanic sulfur emissions, silicate weathering of a large igneous province, a supercontinent that formed in the tropics causing a perturbation in the carbon cycle, even a complicated biological interaction with anoxic deep ocean water. These are as varied as proposed causes of the Ordovician extinction.
The Yarrubbba impact structure is of roughly the right age to have caused a Snowball Earth, if this paper’s model is at all correct. And that’s where my questions all pile up. I’m not a climatologist, so I have idea how good climate models are, whether you can “perturb” the model with different climates and atmospheric compositions and whatever, and still get a simulation that might match reality.