Predict their future the antarctic glaciers It is undoubtedly a great challenge for science, but the most important thing above all is to know How will it affect global sea level?. The worst of all is that the latest news we have at our disposal is not at all positive, since the Hektoria glacier It has retreated 8 km in just two months, which is an unprecedented speed in the modern era.
Where we start from. Normally, the retreat of glaciers It is measured in hundreds of meters per year. It is one of the clearest metrics we have to be able to ‘measure’ global warming, and that is why now what a team from the University of Colorado Boulder has just recorded on the Hektoria glacier, on the eastern peninsula of Antarctica, plays in a completely different league.
The measurement. In just two months during 2023, the Hektoria lost almost half of its mass. In total, 8 kilometers of ice disappeared. A speed of collapse that has never been seen in modern history and that, according to the authors of the study, is more typical of the end of the last ice age. Something that doesn’t add up in this case.
Hektoria is relatively small by Antarctic standards (about 300 km², less than the city of Malaga), but its collapse was so sudden that it left researchers stunned.
A coincidence. Ironically, the research team wasn’t even studying Hektoria. They were analyzing satellite and remote sensing data for another project when Ochwat realized that the glacier had essentially disappeared from the images.
The measurements. This is where technology comes into play. The team had to combine data from multiple satellites to understand what had happened and, above all, how quickly he did it. “If we only had one image every three months, we couldn’t say that the glacier lost two and a half kilometers in two days,” explains Ochwat. In this case, by combining images from different satellites you can fill in the time gaps and confirm with evidence in hand how quickly the ice has been melting.
But the key was not only in the images. They also used seismic instruments that have the ability to detect a series of “glacial earthquakes” that occurred exactly during the period of rapid melting. And these earthquakes are not measured for the sake of it, but to confirm something crucial: the glacier was anchored to the bedrock (and not floating) just before breaking.
This is fundamental both for science and for the entire planet, since ice that is floating (such as an ice shelf) does not raise sea level when it melts, any more than an ice cube does in a glass of water. But ice that rests on land (or anchored to a seabed) and falls into the sea does contribute to the global rise in sea level by increasing its volume.
Your Achilles heel. The collapse was not due to simple superficial melting. The cause was topographic, since many Antarctic glaciers rest on deep canyons or underwater mountains. The Hektoria, however, had the misfortune of resting on an “ice plain”: an area of bedrock that was exceptionally flat and below sea level.
This flat topography caused a gigantic section of the glacier to begin floating all at once, rather than gradually. The moment the glacier lost its anchorage to the ground (its “line of support”), it was exposed to the forces of the ocean, and therefore everything began to advance very quickly.
The process was brutal, since it all began with the warmest ocean water that seeped underneath and began to open cracks from the bottom of the glacier upwards. At the same time, the glacier already had cracks on the surface. Eventually, the lower and upper cracks met and the glacier literally disintegrated.
A warning for future glaciers. The Hektoria case is a first-rate warning. Scientists know that there are numerous glaciers in Antarctica that also rest on these types of ice plains. Until now, it was thought that their collapses would be centuries-long processes. Hektoria shows that they can be months, which should set us off due to the implications it would have on sea level.
And while the collapse of a small glacier like Hektoria won’t dramatically change global sea level, it alone does demonstrate that a rapid collapse mechanism, until now theoretical or believed to be typical of past geological eras, is perfectly possible today. If this same mechanism is activated in much larger glaciers, sea level rise could accelerate very considerably and much sooner than expected.
Images | Cassie Matias
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