In a new study, the authors examined calcite and similar rocks on the walls of several caves in
Next, the researchers measured the proportion of uranium isotopesand thorium in these deposits and found that about 400 thousand years ago, there was no permafrost in almost the entire territory of present-day Canada and Alaska beyond the Arctic Circle. A similar warming has occurred in the past.
On the one hand, our observations and similarmeasurements in Siberia show that the climate of the entire Arctic about 400 thousand years ago became more stable. On the other hand, we did not find evidence that in earlier eras, due to the melting of permafrost, there were sharp surges in the concentration of greenhouse gases.
It is noted that in the same period, similarthe way the climate in Siberia changed. This means that permafrost was unstable for most of the Pleistocene. However, its melting, for still unknown reasons, did not in any way affect the Earth's climate and the concentration of greenhouse gases in its atmosphere.
One of the reasons for such drastic changes, the authors say, could be the periodic disappearance of permafrost, which prevented organic matter from accumulating in large quantities.
However, climatologists do not exclude that methane and carbon dioxide, which were formed in the process of decomposition of the remains of plants and animals, could be absorbed by someone or something.
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