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Cold And Darkness After Asteroid Impact Killed The Dinosaurs

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The extinction of the dinosaurs is largely blamed on a giant asteroid that hit the Earth thousands of years ago. Now, a new study revealed how the darkness and cold that followed after the impact largely contributed to the mass extinction of the prehistoric animals.

Aftermath Of The Chicxulub Asteroid Impact

Global temperatures dropped after the massive Chicxulub asteroid hit Earth about 66 million years ago and the resulting extreme cold may have significantly reduced the odds of survival of the dinosaurs that managed to survive the impact. The findings highlighted the importance of climate in the survival of life forms on Earth.

In a new study which was published in the journal Geophysical Research Letters on Jan. 13, Potsdam Institute for Climate Impact Research (PIK) researcher Julia Brugger and colleagues used computer simulations to create a map that showed how the world's temperatures changed after the asteroid struck.

Droplets Of Sulphuric Acid Blocked Sunlight

The researchers looked at how tiny droplets of sulphuric acid in the atmosphere influenced life on Earth. The droplets formed after the impact when sulphur dioxide combined with oxygen in the atmosphere.

These droplets of sulphuric acid reflected the sunlight away. As a result, the sunlight was blocked for many years causing many plants on Earth to die which had profound impact on the food web.

Period Of Cold And Climate Change

The computer simulations showed the droplets led to a period of cold and drastic changes to global temperatures. Prior to the impact, the Earth experienced the hottest global temperatures for a period spanning about 200 million years.

From 27 degrees Celsius, the average tropical temperature dropped to just 5 degrees Celsius. The global annual mean surface temperature likewise got colder by at least 26 degrees Celsius.

The dinosaurs thrived in a lush climate but following the asteroid impact, the annual average temperature plummeted to below freezing for a period of about three years. The ice caps expanded and it took the climate about 30 years to recover.

"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," said study author Georg Feulner, from PIK, adding that the long-term cooling had more important impact than the local events which include wildfires, tsunamis and extreme heat near the impact site.

Cold Disturbed The Marine Ecosystem

The cold also severely disturbed the marine ecosystem, which also had unwanted consequences. Surface water became denser and heavier because of the cold temperature and thus sank into depths. Warmer waters from deeper ocean layers though rose to the surface and carrying nutrients that may have boosted algal bloom. The algae could have produced toxic substances that may have further affected life at the coast.

"The surface cooling triggered vigorous ocean mixing which could have resulted in a plankton bloom due to upwelling of nutrients," Brugger and colleagues wrote. "These dramatic environmental changes suggest a pivotal role of the impact in the end-Cretaceous extinction."

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