New Delhi: Scientists have identified a possible geological explanation for why Antarctica became covered by a massive ice sheet millions of years before the Arctic with slow moving forces deep inside Earth helping raise East Antarctica high enough for permanent snow and ice to survive.
The international study published in the journal Science, suggests that so called “mantle waves” gradually lifted large parts of East Antarctica over more than 100 million years. The rising landscape created high plateaus and mountain ranges where temperatures were cold enough for glaciers to form, even when the global climate was significantly warmer than it is today.
Researchers said Antarctica began developing a major ice sheet around 34 million years ago while large ice sheets in the Northern Hemisphere emerged only about five million years ago.
The study found that the separation of Antarctica and Africa during the Jurassic Period triggered geological processes deep within the planet. Slow moving mantle waves subsequently travelled beneath the continent, contributing to the uplift of the East Antarctic plateau and the Gamburtsev Mountains.
Computer simulations tracing 100 million years of landscape evolution suggested that by about 45 million years ago, large areas of East Antarctica had risen above roughly 2 kilometres in elevation a critical threshold where temperatures could become cold enough for mountain glaciers to develop and expand.
The researchers said the findings help explain why falling atmospheric carbon dioxide alone cannot account for the different timing of glaciation at Earth’s two poles.
As the Antarctic ice sheet expanded, its bright surface reflected more sunlight back into space, creating an ice-albedo feedback that further cooled the region. The researchers estimate that this process may have reduced global temperatures by around 1°C.
Another feedback mechanism also strengthened the cooling. As temperatures dropped, the atmosphere held less water vapour, weakening the greenhouse effect and allowing further cooling.
The study suggests that major climate transitions may depend not only on changes in the atmosphere but also on geological processes that prepare landscapes for glaciation.
The East Antarctic Ice Sheet is now the largest on Earth and contains enough frozen water to raise global sea levels by about 52 metres if it were to melt completely.
Researchers said the findings could improve understanding of ancient ice ages and future climate tipping points by showing how Earth’s deep interior can influence the timing and location of major climate changes.