A glacier isn’t the kind of thing you’d expect to get away from you. After all, only the world’s fastest-flowing glaciers can match a snail’s pace. But we know it’s possible for glaciers to have tipping points that, once crossed, result in an unstoppable change. Once unstable, they can lose a lot of ice before finding another stable configuration.
Looking back through the history of the Antarctic ice sheets, we know that they have been susceptible to warming in the past. The West Antarctic Ice Sheet is especially vulnerable because a great deal of the continent beneath it is below sea level. If the ice shrinks back from the higher elevation areas, the entire ice sheet can collapse, as it may have done several times in the last million years. Some of the West Antarctic glaciers that prevent this collapse have behaved dynamically in the recent past—and, as we saw this week, there’s evidence that we may be committed to seeing a repeat performance.
The amount of ice present there today could raise global sea level roughly several meters if it all melted. But across the continent, the East Antarctic Ice Sheet is much larger, holding the equivalent of 55 meters of sea level rise as ice. Fortunately, it’s perched securely above sea level. Researchers are less concerned with the potential for tipping points there. There are, however, exceptions. Some East Antarctic glaciers have melted back considerably in the past. The key is to figure out how much ice they can lose and how fast they can lose it.