As geological puzzles go, it is a pretty good one. within the global greenhouse conditions of the first Eocene (56-48 million years ago), how did huge numbers of giant glendonite crystals manage to form?
These rare carbonate crystals - that require temperatures not up to 4 degrees Celsius to make - are composed of the mineral ikaite and located in their tens of millions on the Danish islands of Fur and Mors. they need been dated to 56-54 million years ago.
"Why we discover glendonites from a hot period when temperatures averaged above 35 degrees, has long been a mystery," says geologist Nicolas Thibault, from the University of Copenhagen in Denmark. "It should not be possible."
After an in-depth qualitative analysis of glendonite samples by Thibault and a world team of researchers, employing a technique called clumped isotope thermometry to trace temperatures back a lot of years, we may have an answer: the Eocene was perhaps not as uniformly warm as previously thought.
The idea of colder Eocene spells has been recommending previously, but the evidence has been inconclusive up to now. The new chemical breakdown helps researchers argue the case for cooler conditions, with models suggesting the glendonites formed in waters below 5 degrees Celsius (41 degrees Fahrenheit) at a depth of around 300 meters (984 feet).
Sedimentary layers of ash on the island of Fur point to the likelihood that volcanic eruptions may perhaps are accountable for these chillier episodes within the Eocene, localized around specific regions, which might help to elucidate the cooler waters and therefore the rock record.
"There was probably an outsized number of volcanic eruptions in Greenland, Iceland, and Ireland during this era," says Thibault.
"These released sulfuric acid droplets into the stratosphere, which could have remained there for years, shading the earth from the sun and reflecting sunlight away."
"This helps to clarify how regionally cold areas were possible, which is what affected the climate in early Eocene Denmark."
The new study backs the hypothesis that colder Eocene periods are more likely than the choice – which is that the science is wrong about the kind of temperatures that ikaite-based rock is ready to make at.
Next, the team wants to determine similar investigations distributed to determine how widespread the cooling discovered within the Danish Basin actually was. Other geological records – including those from the Arctic – suggest this dip in temperature wasn't happening everywhere in the world through the Eocene.
As with any discovery about our climate past, the study goes to assist scientists to project our climate future.
We might not have the sky obliterated by volcanic ash anytime soon, but a quickly changing climate are a few things we are hunting – a bit like parts of the planet was over 50 million years ago, long before humans arrived on the scene.
"Our study helps solve a mystery about glendonites, moreover as demonstrating that cooler episodes are possible during otherwise warmer climates," says Thibault.
"The same is said for today, as we wise up to the chance of abrupt global climate change."
No comments:
Post a Comment