The scientific community currently believes that the dinosaurs went extinct due to a meteorite impact approximately 66 million years ago. New research has found that while the dust from this impact briefly cooled the Earth, it also released a large amount of carbon dioxide into the atmosphere, causing the Earth's climate to warm again over the next 100,000 years after the initial cooling.
Researchers from the University of Missouri and their Tunisian counterparts published a report in the latest issue of the American journal Science, stating that by analyzing the oxygen isotope content in fish fossil remains, they inferred that ocean temperatures rose by about 5 degrees Celsius after the meteorite impact and remained elevated for about 100,000 years before returning to normal.
These fossils, including fish skeletons, teeth, and scales, come from northwestern Tunisia. They are distributed within several meters of rock strata, from which a geological history of approximately 250,000 years can be inferred, during the period of the meteorite impact.
Oxygen has many isotopes, with oxygen-16 being the most abundant on Earth, along with some oxygen-18. Climate warming affects the relative proportions of these two isotopes in seawater, and this change is reflected in marine organisms. Analysis shows that after the meteorite impact, the ratio of oxygen-18 to oxygen-16 in seawater decreased by about 1%, meaning that the water temperature rose by about 5 degrees Celsius.
Current theories suggest that meteorite impacts would trigger wildfires that burn vegetation and cause the decomposition and volatilization of carbonates in the Earth's crust, releasing large amounts of carbon dioxide into the atmosphere. For months to decades after the impact, the smoke and dust would block sunlight, leading to cooling and mass extinctions. After the dust settles, the greenhouse effect of carbon dioxide would begin to take hold, causing global warming.
Previous studies have confirmed a brief cooling of the climate following the meteorite impact, but data on a warming process were lacking. This new research provides evidence for related theories and helps to deepen our understanding of the impact's effects on Earth's climate and ecosystems.
