The last ice age persisted for over 100,000 years. An ice-bound eternity of any stretch of the imagination, but this long winter has not been completely frozen in silence.
During the last ice age, which ended about 12,000 years ago, climate change has existed as a powerful phenomenon, as it is now, albeit for various reasons.
Throughout the ice age, a series of episodes of sudden warming punctuated the cold, each sending temperatures rising (up to 16 degrees Celsius) in temporary heat waves that burned for decades before disappearing.
These sudden phenomena, called Dansgaard-Oeschger events, have occurred dozens of times over the last 100 millennia of the Last Glacier. But what made them sparkle in life?
“Many studies have tried to answer this long-standing question: what part of the climate system has changed the first time these 30 or so sudden climate changes [began]? “says ice core scientist Emilie Capron of the University of Copenhagen in Denmark and the University of Grenoble in France.
“Was it, for example, the ocean currents in the North Atlantic, the wind and precipitation patterns in the northern hemisphere, or the spread of sea ice in the Arctic that triggered climate change?”
The author of the study Emilie Capron with a thin piece, polished with ice core. (Sepp Kipfstuhl)
If there is a pattern that precipitates these mysterious warmings, it remains hidden for the time being.
In a new study, Capron and her team found that when the Dansgaard-Oeschger events took place, a series of climate transitions took place almost in unison, each probably influencing the other and without a single distinct trigger. – just like a house of books collapsing in an invisible gust.
To find out, the researchers looked at two huge ice cores drilled from the Greenland ice sheet: epic columns of compressed snow that stretch up to 3 kilometers long.
The core retains many chemical signals of ancient climatic conditions established in prehistory, including reports of isotopes revealing past temperatures and gas bubbles showing the atmospheric composition, among many other clues.
According to the researchers, the basic ice data we have – and the complementary team-led climate simulations – suggest a variety of overlapping factors combine in the immediate vicinity to create the Dansgaard-Oeschger events and it is not yet possible to know for sure which of these underlying mechanisms may precede the others or be fundamentally more important.
“There may not be a single sequence of changes that represent Dansgaard-Oeschger warm-ups and no single trigger in itself for these sudden changes,” the authors write in their paper.
“The emerging picture of Dansgaard-Oeschger heating is one in which the components of the climate system are so closely linked that it may not be possible to resolve significant gaps and gaps between them and, as a result, it may be evasive to look for a single sequence of proxy data events that can adequately describe all sudden climatic transitions of the last glacier. “
However, some of the hallmarks of sudden transitions are common between events – one of which is the level of sea ice cover, which is rapidly declining today.
Of course, we are not in an ice age at the moment, so no one is saying exactly that a Dansgaard-Oeschger event is about to be triggered.
However, 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 past catastrophes, may have extremely strong trigger potentials that we do not have. we have yet to fully understand.
“The results underscore the importance of trying to limit climate change, for example, by reducing anthropogenic emissions of CO2 and other greenhouse gases, both to reduce predictable, gradual climate change and to reduce the risk of sudden sudden climate change,” he says. co. -author and climate physicist Sune Olander Rasmussen from the University of Copenhagen.
“If you don’t want dominoes to tip over, it’s best not to push the table you’re sitting on too long.”
The findings are reported in Communications about nature.