A new study published in the journal “Science” reveals that this country of ice has already melted in the past under the influence of temperatures close to ours today.
Greenland is home to the second largest ice cap in the world after Antarctica. But this island has not always been covered with a layer of ice more than a kilometer thick. An American team of researchers has just proved that a major melting of Greenland has already taken place, 416,000 years ago, due to a long natural global warming. Greenland had then lost between 20% and 70% of its ice cover and was covered with forests, in which mammoths lived.
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Researchers can be sure of this melting of Greenland in the past thanks to the study of an ice core, in which they found traces of leaves, mosses, and sediments that are known to have been exposed to the sun. What makes this discovery even more fascinating is that this ice core was taken from a secret US army base in the 1960s. It had not revealed all its secrets at the time, then it was forgotten in laboratory freezers for 50 years, before being found in 2017.
30,000 years of warming
However, in the meantime, the techniques for dating the ice have progressed, which is what has recently made it possible to establish this melting of Greenland, 400,000 years ago. This caused at the time a rise in sea level to water of at least 1.5 m, and perhaps even more than 5 m.
We can make a connection with our current situation because 400,000 years ago, the temperature on earth was similar to what we know today. We were indeed in an interglacial period (which is a period of natural warming) but with a big difference. It is that at the time the concentration of CO2 in the atmosphere was about 30% lower than today. However, CO2 acts as a heating blanket for the earth.
At the time, natural warming was therefore very gradual, spreading over 30,000 years. Nothing to do with today’s which is much faster. We must therefore expect a melting of Greenland, in the coming centuries, alert scientists, with the submersion of many coastal regions. This work is a new alert on the urgency of reducing greenhouse gas emissions.