Fine soil particles once encased in ice were discovered in a cave about 20,000 years after the frozen sheet melted. This sediment is significant both for what it tells us about the past and what it could forecast for the future, according to an article in the journal Nature Geoscience.
The sediment found in an Alaskan cave was likely once part of the Cordilleran Ice Sheet, which melted at the end of the last Ice Age. Most of that ice — along with the sediment contained within it — ended up in the oceans. Finding traces of it on land is extremely rare.
“This is the first evidence of land-based meltwater events from this ice-sheet,” Paul Wilcox, a geologist at the University of Innsbruck, Austria, and an author of the paper, said in a press release. “In a way, the cave acted as a kind of time capsule that preserved the sediments for thousands of years.”
Preserving Ice Age Life
Two aspects of the sediment help tell the story of Ice Age life. First, scientists detected plant pollen within the particles. That provides indirect evidence of biological refuges — even during peak ice coverage “[…] in which plants could survive even under extreme climatic conditions,” Daniela Festi, a pollen researcher with GeoSphere Austria and an author of the paper, said in a press release.
The sediment also contained quartz — convenient because the presence of that mineral makes determining the particles’ age possible using a method that can detect when it was last exposed to sunlight. But more importantly, it also shows that the sediment must have been transported quite a distance before being deposited, since the cave is in a limestone region, where quartz would generally be scarce or non-existent.
Read More: How Ice Age Humans Mastered Fire During the Coldest Era in History
Glacial Meltwater and Climate Changes
Dating the sediment allows scientists to look to the past to forecast the future. Although the Cordilleran Ice Sheet almost certainly melted due to a change in the Earth’s position relative to the sun, that alone doesn’t account for the ice’s backward retreat from western North America. Other forces must have contributed.
Data from the last Ice Age show signs that glacial meltwater repeatedly pulsed into the North Atlantic. That cycle likely further disrupted the region’s heat and contributed to further warming.
“This supports the hypothesis that climate changes in the Northeast Pacific were a prerequisite for the shifts observed in the North Atlantic,” Wilcox said in the release.
Understanding how these events happened over space and time could inform us about the future. Continued warming could lead to similar increased freshwater flowing into the oceans. That, in turn, could disrupt circulation systems that impact temperature.
The researchers plan to investigate additional Alaskan caves and compare the sediment archives to each other. That could provide a more detailed picture of the past ice sheet’s melting dynamics — and perhaps provide a glimpse into how a similar event could affect climate in the future.
Read More: Ice Ages: What Causes the Earth to Freeze Over Every Few Million Years?
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature Geoscience. Semi-continuous release of Cordilleran Ice Sheet meltwater between 20,000 and 17,000 years ago
Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
