A research on the cold and the darkness that killed the dinosaurs

Image from the simulation of the climate changes the followed the asteroid impact (Image courtesy Potsdam Institute für Climate Impact Research (Pik))
Image from the simulation of the climate changes the followed the asteroid impact (Image courtesy Potsdam Institute für Climate Impact Research (Pik))

An article published in the journal “Geophysical Research Letters” describes a research on the climate consequences of the impact caused by the large asteroid that struck the Earth about 66 million years ago. A team of researchers of the Potsdam Institute for Climate Impact Research (PIK) created computer models to simulate these events and concluded that the atmospheric dispersion of sulfuric acid droplets may have darkened the planet’s skies resulting in the surface cooling.

Since Luis Alvarez proposed the theory of the impact of an asteroid as a cause of the dinosaurs extinction, more and more scientists from different disciplines have been trying to reconstruct those events. The team led by Julia Brugger of the PIK tried to simulate them using climate models that bring together data on the atmosphere, oceans and sea ice. The results indicate that the gases containing sulfur evaporated following the impact were the main cause of the darkening of the skies and the subsequent cooling.

Generally, the idea is that the impact of an asteroid generate various types of dust that can be projected into the atmosphere and these are the cause of the darkness. Instead it’s possible that the main cause was a sulfate aerosols, especially sulfuric acid but also other sulfur compounds. According to the simulations, the cooling was truly remarkable, so much that in the tropics the average temperature fell from 27° to just 5° Celsius.

In many areas of the Earth the average temperature fell below the freezing point of water and this situation lasted for 3 years. Subsequently the skies started clearing but according to the simulations it took about 30 years for the global climate to return to the conditions that preceded the impact. In the meantime, however, the ecosystems were upset hitting particularly animals such as dinosaurs, adapted to warm climates.

These events were catastrophic for many living species but brought an advantage to others. For example, the surface waters of seas and oceans cooled and consequently sank into the depths. The deeper waters that were protected from the cooling ascended to the surface carrying many nutrients. This was a boon for several species of toxic algae, which prospered hitting other species within their ecosystems. The extinction of ammonites might be due to these consequences.

This research is inevitably based on estimates of conditions in that period and the subsequent results of the simulations. Verifying these results is difficult because the remaining traces are limited. There’s also the problem of the various factors that contributed to those climate changes: for example, an article published in October 2015 in the journal “Science” described a study that illustrated the role of volcanism in the great extinction.

The research will continue. They’re very interesting because they’re investigating a moment of the history of life on Earth critical to the current situation considering that the dinosaurs extinction allowed mammals to become dominant. They also show the enormous influence of an event such as an asteroid impact, an ever present danger.

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