One of the key glaciers in West Antarctica, as far as the stability of the ice sheet there, Pine Island Glacier, was the site of an enormous 225-square mile iceberg calving in 2015. New research from Ohio State University has determined that this event was even more notable than first thought, as it was the result of a deep, subsurface crack that had formed approximately 20 miles inland — nowhere directly near the calving event.
What this means is that the the West Antarctic Ice Sheet is becoming more unstable far inland, rather than just at the edges in, or near, direct contact with the ocean — very likely due to mechanisms similar to those witnessed in Greenland in recent years. As the bottom of the West Antarctic Ice Sheet actually lies below sea level, relatively warm ocean water can make it far inland, unseen, slowly eroding the foundations — causing increased ice sheet flow, mobility, breakage, and general instability.
The fact that the observed rift that led to the calving of the enormous iceberg in 2015 had actually opened at the bottom of a “valley” corroborates this — as the ice sheet was very likely weakened under this “valley” before the rift formed as a result of the intrusion of warmer sea water underneath it.
“It’s generally accepted that it’s no longer a question of whether the West Antarctic Ice Sheet will melt, it’s a question of when,” stated study leader Ian Howat, associate professor of earth sciences at Ohio State. “This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes.”
This matters because West Antarctica’s ice sheet, if it were to melt completely, would raise global average sea levels by around at least 10 feet — which would result in the inundation of a great many major cities, the salinization of numerous important aquifers, large displacements of peoples, and general geopolitical instability.
Eventually, of course, the ice sheet of West Antarctica will melt — owing to what’s already been set in motion, there’s likely no way to stop it — but the speed at which it will melt is really something of an unknown, as is the speed at which the Greenland ice sheet will collapse completely. The new researchers suggests, though, that it may be far sooner than some generally estimated. I suppose that climate change may well result in the re-greening of Antarctica within just a millennia or two, as some on the peripheries of the field have previously suggested. That’s a thought, huh?
The press release provides more specifics:
“… but it wasn’t until Ohio State University researchers were testing some new image-processing software that they noticed something strange in satellite images taken before the event. In the images, they saw evidence that a rift formed at the very base of the ice shelf nearly 20 miles inland in 2013. The rift propagated upward over 2 years, until it broke through the ice surface and set the iceberg adrift over 12 days in late July and early August 2015. …
“The origin of the rift in the Pine Island Glacier would have gone unseen, too, except that the Landsat 8 images Howat and his team were analyzing happened to be taken when the sun was low in the sky. Long shadows cast across the ice drew the team’s attention to the valley that had formed there.”
“Rifts usually form at the margins of an ice shelf, where the ice is thin and subject to shearing that rips it apart,” lead study author Ian Howat noted. “However, this latest event in the Pine Island Glacier was due to a rift that originated from the center of the ice shelf and propagated out to the margins. This implies that something weakened the center of the ice shelf, with the most likely explanation being a crevasse melted out at the bedrock level by a warming ocean.”
“The really troubling thing is that there are many of these valleys further up-glacier,” Howat concluded. “If they are actually sites of weakness that are prone to rifting, we could potentially see more accelerated ice loss in Antarctica.”
It may well be the case that there is significant sea level rise within the lifetimes of those reading this as a result of instability and melting of the Greenland and West Antarctica ice sheets — probably something that should be kept in mind when making various important life decisions.
The new findings are detailed in a paper published in journal Geophysical Research Letters.