An international research team led by Silvia Spezzaferri from the University of Freiburg has discovered why the Antarctic polar ice cap is melting faster on the western side of the continent than on the eastern side. New drillings and sophisticated modeling have shown that this phenomenon can be traced back to the original formation of the ice sheet 34 million years ago.
In recent years, Antarctica’s perpetual ice has begun to melt faster than previously thought due to global warming, particularly in the western part of the continent. According to the work of an international research team led by the Alfred Wegener Institute (AWI), the cause of this differential melting could lie in the past, almost 34 million years ago, when the polar ice cap formed. Sediment samples from drill cores in combination with complex climate and inland ice modeling showed that the ice sheet did not spread over the entire continent as previously assumed, but was limited to the eastern region and only advanced westward 7 million years later. This discovery explains why the ice melt on the two sides of Antarctica appears to be so different.
A continent covered in forest
Around 34 million years ago, our planet experienced one of the most fundamental climate changes: the transition from a world with a greenhouse effect, in which little or no continental ice accumulated, to a world in which large, permanent ice sheets existed. It was during this second period that the Antarctic ice sheet formed. Until now, however, scientists did not know how this happened due to a lack of reliable data and samples from key regions such as West Antarctica in particular.
One drill hole changes everything
Using a drill core taken with the deep-sea drilling platform MARUM-MeBo70 off the Pine Island Glacier on the coast of the Amundsen Sea in West Antarctica, the scientists were able to trace the history of the formation of Antarctica’s icy continent for the first time. To their surprise, no signs of the presence of ice were found in this region during Antarctica’s first major glaciation phase. West Antarctica therefore remained ice-free during the first glacial maximum. At that time, this part of the continent was covered with dense deciduous forests and had a cool, temperate climate that prevented the formation of ice.
Icing first in the east
In order to better understand where the first permanent ice formed in Antarctica, the researchers combined the newly available data with existing data on air and water temperatures and ice deposits. The modeling confirmed the geologists’ drilling results: The basic climatic conditions for the formation of permanent ice only prevailed in the coastal regions of East Antarctica and northern Victoria Land. There, the moist air masses reached the steeply rising Transantarctic Mountains, which favored the accumulation of permanent snow and the subsequent formation of the ice sheet. From there, the ice sheet quickly extended to the hinterland of East Antarctica. It was not until about seven million years later that conditions allowed the ice sheet to reach the west coast of Antarctica. ’These results clearly show how cold it must have been for the ice to advance and cover West Antarctica,’ says Hanna Knahl, a paleoclimate modeler at the AWI.
The study also provides new information that allows climate models to more accurately simulate how permanent ice sheets affect the dynamics of the global climate, i.e. the interaction between ice, oceans and the atmosphere. These new insights are valuable as we could be faced with such fundamental climate change again in the near future.
Ice sheet-free West Antarctica during peak early Oligocene glaciation , Science, 4 Jul 2024,
