New Delhi: When the dinosaurs walked the Earth, the world was a tropical greenhouse. Today, it has ice-capped poles. Scientists have long been puzzled about the massive drop in the temperature of the Earth after the dinosaurs went extinct. New research suggests that this drop in temperatures is because of a decrease in calcium levels in the oceans of the Earth. An international team of researchers have discovered that the concentrations of calcium in the sea dropped by more than half over the last 66 million years. A paper describing the research has been published in Proceeding of the National Academy of Sciences (PNAS).
The research shows that the dramatic shift in calcium levels may have sucked carbon dioxide out of the atmosphere, which is a major greenhouse gas that traps heat, driving a global cooldown. The researchers used fossilised remains of tiny sea creatures dug up from sediments at the seafloor to construct the most detailed record of ocean chemistry so far. The chemical composition of the foraminifera fossils indicated a close link between the amount of calcium in seawater and the level of carbon dioxide in the air. Using sophisticated computer models, the researchers show that high levels of calcium change how much marine life such as corals and plankton can fix carbon.
A Thermostat for the Planet
As the calcium levels decreased across millions of years, it altered how marine organisms produced and buried calcium carbonate in the sea floor. The process scrubs carbon dioxide from the atmosphere and sequesters it. This process acted as a thermostat for the entire planet. The scientists also revealed that the drop in calcium also matched the slowdown in seafloor spreading, the volcanic process through which new ocean floors are constantly created. The chemical exchange between the rocks and sea water was disturbed by the slowing of seafloor production. The research suggests that seawater chemistry has a larger role to play in the climate history of the planet.