A composite image of researchers at the glacier. (Cathy L. Connor)
The Mendenhall Glacier, which flows from the 1,500-square-mile Juneau Ice Field, has been retreating since the mid-1700s, according to the USDA Forest Service. But in the past 50 years, reports LiveScience, relics of an old forest have begun appearing amid the melted ice. In the past year or so, trees still upright and with roots and bits of bark still intact have been exposed by the retreating flow.
Researchers based at the University of Alaska Southeast (UAS) are studying the emerging forest; they have determined that the trees’ ages range from about 1,200 to 2,350 years old, reports the Juneau Empire. The trees are likely spruce, UAS geology professor Cathy Connor said, though this hasn’t been verified.
"There are a lot of them, and being in a growth position is exciting because we can see the outermost part of the tree and count back to see how old the tree was," Connor told LiveScience. "Mostly, people find chunks of wood helter-skelter, but to see these intact upright is kind of cool."
The trees were likely protected by a four-to-five-foot layer of gravel, which spills out from streams of an advancing glacier’s meltwater in the summer, according to LiveScience. The gravel protected the trees from the glacier’s powerful motion, snapping branches and treetops as it advanced.
Mendenhall is one of 38 large glaciers originating in the Juneau Ice Field, nearly all of which are retreating. Since 2005, LiveScience reports, the glacier has retreated about 170 feet per year, with an expected large retreat this year due to an unusually warm summer.
So far, the Juneau Empire reports, trees are the only remnants of the forest being exposed. But the team hopes to find other vegetation to help better explain the area’s history.
"These are relict stories, and piecing them together with radiocarbon dating and stratigraphic work would help piece together the chapters of the story," Connor told LiveScience.
MORE: Glaciers In Retreat
Grinnell Glacier, Glacier National Park (1938 and 2009)
A side-by-side comparison of Grinnell Glacier in Montana's Glacier National Park. The black-and-white photo on the left dates from 1938, while the color photo on the right was taken in 2009. (T.J. Hileman and Lindsey Bengtson, USGS)