Two articles in the journal Paleoceanography, following another publication in early 2003 in Nature, challenge the most widely advanced theory to explain the formation of the Antarctic ice sheet 32 million years ago. For decades, climatologists believed that the separation of the Antarctic and Australian lands 35 million years ago removed the warm sea currents in place, causing the original cooling of the kilometer-long ice cover that covers today the South Pole. But the analysis of samples taken in 2000 from the coast of the island of Tasmania (which was in the past a bridge connecting the two continents) suggests another scenario.
In fact, researchers from Purdue University (Indiana) and various American and international institutes (Sweden, Canada, the Netherlands and the United Kingdom) have found the trace in sediments dating from the Eocene (between -54 and -35 million years ago), fossils of microorganisms associated with cold water. A discovery incompatible with the hypothesis of a hot current preventing glaciation until the continents break up. The team also notes that two million years elapsed between the opening of the waters between Tasmania and Antarctica and the rapid glaciation phenomenon (in a few thousand years). For scientists, the most plausible explanation for the enigmatic warmth of this region during the Eocene and its subsequent cooling would be a massive and rather sudden drop in the levels of carbon dioxide in the air. The same ones had already put forward this theory following the analysis of fossils found in El Kef in Tunisia (work published in spring 2004). This theory, which remains to be confirmed, reinforces fears linked to current global warming; it implies that changes in the atmosphere can have a significant impact in a relatively short geological period. 03/01/05
(New Theory of Antarctic Ice Cap)