At the coldest in our history

“Large format science: The 5 lives of the Earth – Ice”

We must imagine a hostile planet, the polar opposite of the one we know today (despite everything we do to it). A world in the grip of chaos and disproportionate climate change. To understand the impact they have had on our future (and that of the fauna and flora), we must delve back into its tormented history. At the time of the supercontinent, Rodinia. Surrounded by water, its lands were arid and devoid of life. Conversely, on the ocean floor of its coastal waters, microscopic bacteria formed microbial mats on which primitive eukaryotes stood. “ Depending on the cells that constitute them, living organisms are either prokaryotes or eukaryotes. », specifies doctor of geobiology Cecila Sanders. “ Unlike prokaryotic cells, eukaryotic cells contain all of their DNA in a central structure, the nucleus. » The presence of these eukaryotes, combined with a slow geological process, gave rise to plants, animals and human beings.

Eukaryotes and all other forms of life have adapted, but through slow evolution. This didn’t happen overnight.

Peter Girguis, Harvard University

From volcanic eruptions to Snowball Earth

Thinned by tectonic forces, Rodinia’s crust eventually leaked molten magma over more than two million square kilometers. Among the consequences of this major event, the decrease in carbon dioxide in the atmosphere. “ Because there was both a lot of basalt and rain, it removed large amounts of carbon dioxide from the atmosphere. “, explains Chris Jackson. A decrease which caused the gradual cooling of the Earth and the appearance of ice in the polar regions. Icy surfaces which will continue to expand to cover almost the entire planet. “ As soon as a surface is covered in ice, it increases the albedo of the planet, specifies a scientist. That is to say its reflective power. The more solar rays are reflected, the more the planet cools and therefore the more water turns into ice. » Hard to believe, but living organisms have managed to survive in this icy universe. “ There were life forms before the Snowball Earth period, and there are still some today, explains biology researcher Jaz Millar from an Icelandic glacier. So there are obviously some who have survived. These holes [à cryoconites] (pointing to one of them) are perfect for micro-organisms, as they allow them to benefit from both sunlight and melt water. » These are undoubtedly not the only places where organisms survived this long period of glaciation, but they undoubtedly participated in it.

For life to truly flourish again, a radical change will be necessary to free it from this prison of ice.

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Susannah Porter, University of California

Ice-albedo feedback mechanism

“The ice-albedo feedback mechanism describes the interaction between the cryosphere (land surface covered with snow and ice) and the global climate. Global warming causes ice to melt, increasing the surface area of ​​water or vegetation. Ice has a high albedo and reflects most of the solar radiation back into space, while water or vegetation absorbs most of it. This warms the surfaces further, causing other snow and ice surfaces to melt. This mechanism does not only operate in the polar regions, but also in the mountains, where the melting of glaciers leads to the same acceleration of warming. This is a positive feedback that further strengthens the active cause. It also works the other way around: a cooling leads to an expansion of snow and ice surfaces and, therefore, an increase in retroactive radiation and further cooling. »
Source: Météo Suisse – Federal Office of Meteorology and Climatology