It’s hard to believe after a lifetime of watching documentaries on La 2 about frozen cliffs, sharp snow-capped mountains and penguins used to moving in freezing temperatures, but Antarctica has not always been the snowy expanse we’re used to.
Throughout the Mesozoic era – between 252 and 66 million years ago – it is believed that its temperature was warmer and during the Cretaceous – 145-66 million years ago – it was home to a tropical forest. What is Antarctica today also remained connected for millions of years with South America and Australia, creating a large area through which both fauna and flora could move. Como recoge Live Science, scientists do not know exactly when Antarctica became an isolated continent, a concept, that of “isolation”, even subject to debate.
The influence of ocean currents
Now an investigation published in Nature Communications sheds new light on the circumstances that completely changed the appearance of Antarctica and favored its current appearance: a vast block of ice. Its authors conclude that one of the keys must be sought during the passage from the Eocene to the Oligocene, about 34 million years ago —The day before yesterday in geological terms— when the Drake Passages and the Tasmanian Passages were opened. The first was created between Antarctica and South America; the second, between Antarctica and Australia.
The continent has moved south, but one of the keys to understanding its current appearance is in the seas. More specifically, in how changes affected the organization of ocean currents, crucial in turn for the temperature. The new steps made it easier for cold water to flow around Antarctica and be isolated from warmer currents.
“The opening of the Drake Passage and the Tasman Passage allowed the Antarctic Circumpolar Current to fully form”Explains Libby Ives of the University of Wisconsin-Milwaukee, in statements to Live Science collected by Live Science. To analyze the impact of the Drake passage, the team of researchers used high resolution simulations and he analyzed the influence of oceanic eddies and how — as the pass gradually deepened — they stopped bringing warm water to the south.
“When at least one entrance (Tasmania or Drake) is shallow (300 m), the turns [oceánicos] they carry warm waters to Antarctica. When the second gate decreases below 300 m, these gyrations weaken and cause a spectacular cooling (average of 2 to 4 °, up to 5 °) of the surface waters of Antarctica ”, highlights the study, which concludes: “Our results show that tectonic changes are crucial for climate change in the Southern Ocean.”
Images: Christopher Michel (Flickr)