A study found that the East Antarctic Ice Sheet has survived higher temperatures than we’ve created.
One of the biggest potential dangers of increasing climate change is sea level rise caused by the melting of the polar ice caps. As our planet heats up, large ice sheets in Greenland and Antarctica will melt, potentially triggering several feet of increased sea level rise. If the entire Antarctic ice sheet melts into the ocean, it could lead to dozens of feet of sea level rise, likely enough to wipe out entire cities.
Of course, it’s important to remember that ice sheets are complex and predicting how they will react is difficult—there’s a wide range of possibilities. Perhaps the best way for scientists to predict how ice sheets will behave in the future is by learning how they behaved in the past, so one group of scientists traveled to the East Antarctic Ice Sheet to learn its history.
Specifically, the researchers were interested in what happened to the ice sheet during the Pliocene epoch, the geologic period from about 5.4 million years ago to around 2.5 million. During the Pliocene, global temperatures were a few degrees warmer than they are today, which means this era is a good model for what our world might look like in a few decades, if climate change remains unchecked.
To determine just what happened to the ice sheet during this period, the researchers drilled deep into the rock beneath it. The scientists were looking for samples of certain isotopes, beryllium-10 and aluminum-26. These particular isotopes are created from the impact of cosmic rays from space. When these cosmic rays hit the atoms in the soil, they trigger atomic reactions that produce these isotopes.
The key fact here is that cosmic rays can’t penetrate ice. If there was ice over the ground during the Pliocene, the cosmic rays wouldn’t have reached the ground and these isotopes shouldn’t be present in the soil. But if the ice sheet melted significantly, the researchers would find higher levels of these isotopes.
This scientific task is not as easy as it sounds. “Isolating these rare isotopes from grains of ancient sand is like finding a very small needle in a very large haystack,” said study author Paul Bierman. “But measuring them gives us a powerful view of Antarctica’s past that has never been seen before.”
In the end, the researchers found only trace amounts of the isotopes, suggesting that the ice sheet was present throughout the entire Pliocene. This is good news for us, because it means the ice sheet will also likely survive the next few decades of climate change as well.
“Based on this evidence from the Pliocene, today’s current carbon dioxide levels are not enough to destabilize the land-based ice on the Antarctic continent,” said study author Jeremy Shakun.
But that doesn’t mean we no longer have to worry about sea level rise. This study only focused on land-based ice, but the ice sheet also consists of a great deal of ice over the ocean. “Marine-based ice very well could and in fact is already starting to contribute to sea level rise,” said Shakun, “and that alone holds an estimated 65 feet of sea-level rise.”