University of Southampton
A team of scientists has discovered a surprising mechanism that could explain how the Earth cooled drastically after the age of the dinosaurs.
In a new study, a team of scientists has solved a 66-million-year-old mystery: how the Earth went from a hot planet and tropical, with a greenhouse effect, for the world covered in ice that we know today.
published at the beginning of the month in Proceedings of the National Academy of Sciencessuggests that Earth’s long-term cooling will have been influenced by a steady decline in calcium dissolved in sea water.
The international team of researchers, led by the University of Southampton, discovered that calcium levels in the oceans decreased by more than 50% over the last 66 million years, a change significant enough to modify the How the oceans interact with the atmospherea.
According to the study’s conclusions, this chemical evolution of seawater could have reduced the amount of carbon dioxide circulating in the air.
Since carbon dioxide retains heat, its removal from the atmosphere will have gradually weakened the greenhouse effect of the planet, allowing global temperatures drop.
Second David Evansresearcher at the University of Southampton and lead author of the study, the results highlight seawater chemistry as an active force in climate modeling: Rather than simply reacting to climate change, changes in the oceans themselves may have helped drive it.
“Our results show that dissolved calcium levels I was fine at the beginning of the Cenozoic Era, shortly after dinosaurs roamed the planet, compared to today,” explains Evans.
“When these levels were high, the oceans worked differentlystoring less carbon in seawater and releasing carbon dioxide into the air”, adds the researcher, quoted by .
“As these levels decreased, CO₂ was extracted from the atmosphere and Earth’s temperature followed this trendlowering our climate by 15 to 20 degrees Celsius”, details David Evans.
“As dissolved calcium levels decreased over millions of years, this altered the way these organisms produced and buried calcium carbonate on the seafloor,” he added. Xiaoli Zhouresearcher at Tongji University, China, and co-author of the study.
“The process effectively extracts carbon dioxide from the atmosphere and isolates it. This change could have changed the composition of the atmosphereeffectively lowering the planet’s thermostat.”
The results of the study also allowed us to conclude that the decrease in calcium coincided closely with the slowdown in seafloor expansionthe volcanic process that continually creates new ocean floors.
“As the rate of ocean floor production slowed, the chemical exchange between rocks and seawater changed, leading to a gradual decline in dissolved calcium concentrations,” he explains. Yair Rosenthalprofessor at Rutgers University, in the USA, and also co-author of the study.
“The chemistry of seawater is seen as something that responds to other factors that lead to changes in our climate, instead of being herself because. But our data suggests that we must look to changing seawater chemistry to understand our planet’s climate history,” he added.
“It may be that changes in these deep Earth processes are ultimately responsible for much of the major climate change that have occurred throughout geological time”, concludes Rosenthal.
