Dinosaurs died out from utter cold, and in darkness, suggests a new study published in Geophysical Research Letters.
Death by Cold & Dark—No, It’s Not Vampires
Dinosaurs were once great predators walking on God’s green earth. They later mysteriously disappeared—that was 66 million years ago. What really caused them to die out, thus paving the way for humans to inherit the planet? One of the most predominant theories suggests that they went extinct following the collision of a massive asteroid with the Earth; Mexico’s Chicxulub crater is said to bear the evidence of the crash. What really happened? A team of climate scientists used simulations to explain how the asteroid led to the death of the dinosaurs.
Real Killer: Sulphuric Acid
According to the researchers, the asteroid impact resulted in the formation of tiny droplets of sulphuric acid in the atmosphere, which obstructed the light of the sun from reaching the ground. Living organisms, then, paid the consequences of being on a cold, dark Earth. Furthermore, the cooling effect would have caused ocean waters to mix vigorously, thereby also affecting marine life.
“The big chill following the impact of the asteroid that formed the Chicxulub crater in Mexico is a turning point in Earth history,” says lead author Julia Brugger from the Potsdam Institute for Climate Impact Research (PIK). “We can now contribute new insights for understanding the much debated ultimate cause for the demise of the dinosaurs at the end of the Cretaceous era.”
The computer simulation used by Brugger and her team was a climate model depicting the atmosphere, the ocean, and sea ice. Moreover, they used data from other studies that explain how the temperature of the planet’s surface plummeted to around 5 degrees Celsius and even less because of the deprivation of sunlight and heat as a consequence of sulphur gases emanating from powerful asteroid impacts.
“It became cold, I mean, really cold,” says Brugger.
Brugger says that the minimum decrease of the average surface air temperature of the planet was 26 degrees Celsius; the thermometer would have hit negative temperatures, leading to the expansion of the ice caps. The dinosaurs were not used to such environmental conditions—and, so, they died out.
“The long-term cooling caused by the sulfate aerosols was much more important for the mass extinction than the dust that stays in the atmosphere for only a relatively short time. It was also more important than local events like the extreme heat close to the impact, wildfires or tsunamis,” explains co-author Georg Feulner.
Ocean circulation was also affected at that time. As surface water decreased in temperature, they increased in density, and thus in weight as well. This water would have then gone to lower depths while its warmer counterpart would have risen to the surface—a process normally accompanied by the movement of nutrients which would have boosted algal populations; the latter are likely to have produced substances toxic to coastal life. Marine species like ammonites might, thus, have gone extinct.
Silver Lining: Humans Got to See the Light of the Day
As the dinosaurs succumbed to the cold in the dark, other species were eventually allowed to bloom, such as mammals.