Melting ice reveals secret buried in the Rocky Mountains not seen for 6,000 years

Melting alpine ice in the Rocky Mountains has led to the discovery of a 5,900-year-old whitebark pine forest.

Over 30 trees are estimated to have been found by scientists during an archaeological survey on the Beartooth plateau in Wyoming.

The newly uncovered trees are located at 3,100 metres sea level which is 180 metres higher than the present tree line.

But what does this recent find mean for researchers?

According to Cathy Whitlock at Montana State University, it "offers us a window into past conditions at high elevations since you won't see Whitebark pine (Pinus albicaulis) growing at this elevation today - that's because the climate was warmer back when these trees grew".

It is thought the trees lived 5950 to 5440 years ago when temperatures were gradually decreasing and to establish this timeline of the forest's history and age, the team analysed their rings and used carbon dating.

Gregory Pederson

What was causing this temperature decline?

To answer this question, we look to Antarctica and Greenland where ice core data revealed that volcanic eruptions in the northern hemisphere going on for centuries impacted the decrease in temperatures due to the production of aerial sediment to reduce sunlight and as the temperature got colder, the conditions meant it was too cold for the forest.

This is backed up by climate models that show the temperature drop 5,100 years ago was caused by continuous volcanic eruptions in Iceland, according to team member Joe McConnell at the Desert Research Institute in Nevada.

After taking a closer look at the trees, researchers noted how they were in great condition which suggests that despite dying, they were well-preserved. Although there isn't enough evidence to say avalanche coverage helped with this, the trees do have marks which align with the expansion of the present ice patch.

McConnell noted how the ice patch increased in size due to the lower temperatures and consequently “the fallen trees were entombed in ice and protected from the elements for the next 5000 years".

Why can we see the forest now?

Rising temperatures have led to the ice melting and revealing the previously hidden trees and as temperatures are expected to continue to increase in the years to come, Whitlock says the current tree line is "likely to shift upslope with increasing temperatures in the coming decades".

“This discovery was possible because of anthropogenic climate change – rising temperatures are now exposing areas that have been buried by ice for millennia,” she added. “While such discoveries are scientifically interesting, they are also a sad reminder of how fragile alpine ecosystems are to climate change.”

Kevin Anchukaitis at the University of Arizona reflected on how this discovery is a "valuable ‘time capsule’" which can "not only about these mountain forests 6000 years ago, but about the climate conditions that allowed them to exist".

This isn't the first discovery researchers have unearthed from Rocky mountain ice patches. Previously, "fragments of wooden shafts used for arrows and darts" were found, Whitlock said.

A key finding was a shaft over 10,000 years old, and Whitlock noted how this shows us how "people have been hunting in high-elevation environments for millennia".

Elsewhere, a massive ocean was discovered beneath the Earth's crust.

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