Scientists have detected an ancient river landscape that dates back millions of years and is now buried under more than a mile of ice in Antarctica, reports a new study.
The find offers scientists a glimpse into a lost Antarctica shaped by plants and rivers, as well as a way to predict the impact of climate change on this continent.
Antarctica is almost entirely covered by ice sheets, making it by far the most frigid and otherworldly landmass on Earth. Tens of millions years ago dinosaurs, and many other creatures roamed the faraway continent. It was then a warmer part of Gondwana. Antarctica was a lush, green land with tundra eco-systems even after Gondwana broke up. It only became largely glaciated in the last 20 millions of years. The continent is no longer as hospitable. While there are still some tough life forms, such as the Emperor penguin and other hardy species, its heyday has long passed.
Now, scientists led by Stewart Jamieson, a glaciologist at Durham University in the United Kingdom, have used satellite observations to peer under two kilometers (1. 25 of the East Antarctic Ice Sheet. This approach allowed the team to detect “an extensive pre-glacial relic landscape that was preserved under the central EAIS, despite the millions of years of glacial cover.” It also suggests there may be “other, yet unknown, ancient landscapes underneath the EAIS,” as per a Tuesday study in Nature Communications.
“We’ve had a longtime interest in, effectively, the shape of the land beneath the ice sheet in Antarctica, and in particular, how the shape of that landscape interacts with the ice itself in terms of controlling it, but also in terms of recording how it has behaved in the past, so that it leaves a signature, or a fingerprint,” Jamieson said in a call with Motherboard.
“We’re trying identify the places where we see a clear picture of the landscape beneath the ice and map that out,” Jamieson continued. “The East Antarctic Ice Sheet has existed for 34 million years. This is a long-lived piece of ice, and we are trying to see if there’s anything we can learn about its stability.
To probe the ancient and thick slab of ice that covered this landscape, Jamieson had to find a way to peer through it. The EAIS is a good place to get some insights into the subglacial terrains of these regions, but it’s expensive and covers only a small area.
To gain a broader perspective, researchers used data from the Canadian satellite constellation RADARSAT. These spacecraft can detect tiny anomalies in the surface of the ice that hint at the topography below. From space, for example, mountains buried beneath the ice sheet may produce subtle bumps that would be impossible to detect from the surface or from above.
Jamieson used this technique to fill in some of the missing gaps of survey observations taken in recent decades. These results showed the remnants of an ancient landscape, roughly equal to the area of Wales. It was created by rivers which once flooded in the distant past. The researchers think that this ancient world might date back more than 34 million years old, making it older than the EAIS.
“The implications are that it must be an ancient landscape, carved out by rivers long before the glacier itself formed,” Jamieson said. “That’s why we can say that the landscape itself is likely older than 34 million years. That’s a time when the climate was a bit warmer. There was vegetation and plants growing on Antarctica and there wasn’t big-scale ice.”
“Although in a lot of areas, landscapes like this would be scrubbed away by glacial erosion that’s happening underneath the ice sheet, in this particular location, glacial erosion doesn’t seem to be switched on,” he added. It’s because the water layer that normally lubricates the interface of the ice with the bed is missing. It’s not filing off the landscape. It’s just frozen sitting there, like a protective cap. Because we can still see a river imprint, we think it must have basically been doing that for pretty much all of ice sheet history in Antarctica.”
It’s tantalizing to imagine this ancient terrain, once resplendent with life, that is now entombed in intricate detail under the ice sheet. In the future, it may even be possible to drill down through the EAIS to procure a sample of the landscape, which could help to confirm its ancient age.
In the meantime, though, Jamieson and his colleagues hope to extract more details about the terrain using remote-sensing methods so that they can reconstruct the evolution of the ice sheet over time. The study states that the EAIS “is known to be sensitive” to climate changes and ocean heating in the past, and could potentially do so again. This information, then, can help scientists better understand the impact of climate change on this huge sheet. Jamieson noted that
“A thawing of the area will not happen any time soon, as the study landscape is located more than 200miles inland. “But the key point is that between the coast where the ice margin sits now, and our landscape, is the zone in which we would expect that maybe there will be some possibility for the ice margin to retreat in the future. Computer simulations and modeling of the future will help us investigate the issue in greater detail.
“What’s the likely future of the edges of the ice sheets, the one that impacts us and future generations to come? The initial retreat and the speed at which it can occur will be important to us. We want to avoid a retreat. It’s still a possibility that we can avoid that retreat, but it does involve some pretty rapid action on emissions.”
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