The last ice age lasted more than 100,000 years. It’s an ice-bound eternity in any degree of imagination, but this long winter has not been completely frozen to silence.
During the last ice age, which ended about 12,000 years ago, climate change was a powerful phenomenon, just as it is now, albeit for different reasons.
During the ice age, a series of sudden warming episodes suppressed the cold, and each caused the temperature to rise (to 16 degrees Celsius) in temporary heat waves that flared for decades before disappearing.
These sudden phenomena, called Dansgaard-Oeschger events, occurred dozens of times during the 100 millennia of the Last Glacier. But what made them live at all?
“Many studies have attempted to answer this long-standing question: What part of the climate system first changed when these approximately 30 sudden climate changes [began]? “says the nuclear scientist Emilie Capron from the University of Copenhagen in Denmark and the University of Grenoble in France.
“For example, was it the ocean currents in the North Atlantic, the wind and rainfall patterns in the Northern Hemisphere, or the distribution of sea ice in the North Pole that caused climate change?”
Study author Emilie Capron with a thin, polished piece of iron core. (Sepp Kipfstuhl)
If there is a pattern that promotes these mysterious warms, it remains hidden for now.
In a new study, Capron and her team discovered that when the Dansgaard-Oeschger events unfolded, a series of climatic transitions took place almost in harmony, and that it probably affected the others, and without any observable single trigger – such as’ a card house collapsing. an invisible jerk.
To find out, the researchers analyzed two giant ice cores drilled from the Greenland ice sheet: epic columns of compressed snow that stretched up to 3 kilometers long.
The nuclei retain numerous numerical signals of ancient climatic conditions laid down in prehistory, including isotope ratios that reveal previous temperatures, and gas bubbles that show atmospheric composition, among many other clues.
According to the researchers, the iron data we have – and additional climate simulations performed by the team – indicate a variety of coincident factors that are relatively close to creating the Dansgaard-Oeschger events, and it is not yet possible to know for sure which of these underlying mechanisms may precede the other, or be more fundamentally important.
“There may not be a unique series of changes that propose Dansgaard-Oeschger heatings, nor is there a unique stimulus for these sudden changes,” the authors write in their paper.
“The emerging picture of the Dansgaard – Oeschger warming is one in which the components of the climate system are so tightly linked that it may not be possible to resolve significant clues between them, and consequently it may be evasive to move to a single a sequence of events in authorized data that can adequately describe all the recent glacier-abrupt climate transitions. “
Either way, some of the characteristics of the sudden transitions are common at events – one of which is the level of ice cover, which is currently declining rapidly.
Of course, we are not currently in an ice age, so no one is saying exactly that a Dansgaard-Oeschger event is about to break loose.
Nevertheless, as we well know, our environment is changing rapidly in the midst of the current climate crisis – and factors such as sea ice, which have been deeply involved in sudden disasters in the past, may have very powerful trigger potentials that we do not yet have. not. fully understood.
“The results highlight the importance of trying to limit climate change by, for example, reducing anthropogenic emissions of CO2 and other greenhouse gases, both to reduce the predictable, gradual climate change and to reduce the risk of future sudden climate change,” says co. author and climate physicist Sune Olander Rasmussen from the University of Copenhagen.
“If you do not want the dominoes to tilt, it is better not to push the table on which they stand too much.”
The findings are presented in Nature communication.