May 31. (EUROPE PRESS) –
An analysis of rocks near Antarctica’s Thwaites Glacier have unexpectedly revealed that the ice sheet was thinner in the last few thousand years than it is today.
This finding, presented by researchers from the British Antarctic Survey (BAS), shows that the region’s glaciers were able to regrow after an earlier shrinkage.
The contribution of Antarctic ice melt to global warming is currently the largest source of uncertainty in predictions of how much and how fast sea level will rise in the coming decades and centuries. Together with his immediate neighbor, the Thwaites Glacier currently dominates the Antarctic contribution to sea level rise.
To understand how this important glacier will respond to climate changes expected in the next century, scientists need to know how it behaves under a wide range of climatic conditions and over long time scales. Since satellite observations only go back a few decades in time, we must look at the geological record to find this information.
Using specially designed drills to cut through both the ice and the underlying rock, the team recovered rock samples from deep within the ice sheet next to Thwaites Glacier. They then measured, in those rock samples, specific atoms that form when rocks on Earth’s surface are exposed to radiation from outer space. If ice covers those rocks, these particular atoms no longer form. Therefore, their presence may reveal periods in the past when the ice sheet was smaller than it is today.
Keir Nichols, a glacier geologist at Imperial College London and lead author of the study, says it’s a statement : “The atoms we measured exist only in trace amounts in these rocks, so we were reaching the limits of what is currently possible and there was no guarantee that it would work. We are excited that this is the first study to reveal recent history .of an ice sheet using bedrock collected directly beneath it”
The team discovered that the rocks they collected were not always covered in ice. Their measurements showed that, over the past 5,000 years, the ice near Thwaites Glacier was at least 35 meters thinner than it is now. In addition, their models demonstrated that their growth since then, Getting the ice sheet to the size it is today took at least 3,000 years.
This discovery reveals that the retreat of the ice sheet in the Thwaites Glacier region can be reversed. The challenge for scientists now is to understand the conditions necessary for that to be possible.
Joanne Johnson, BAS geologist and co-author of the study, says: “At first glance, these results seem like good news: Thwaites Glacier was able to regrow from a smaller configuration in the geologically recent past. However, our study shows that this recovery took more than 3,000 years, in a climate that was probably not as warm as what we expect for centuries to come.”
“If we want to avoid the impacts of sea level rise on our world that will result from the continued retreat of the West Antarctic Ice Sheet, that time frame is much longer than we can afford to wait.”
