GLACIER LA PEROUSE – On our first lunch at a blue gravel campsite near this Alaskan glacier named after a French explorer, scientist Ben Gaglioti and I had a visitor.
As we sat on bleached wooden slabs, I held in my left hand a rectangular cookie with peanut butter smeared on top.
We heard a loud hum. A hummingbird hovered in front of my cracker. As I stood still, the hummingbird probed the peanut butter, twice, with its needle beak. The cracker transferred the vibration to my left hand, tickling my fingers.
As the bird walked away, I looked at Ben to confirm the experience.
âI think you have superpowers now,â he said.
So began our 11-day tour of this glacier located on the outer coast of Glacier Bay National Park and Preserve. It’s a place where many bears live, the thunder of falling blue ice and a thumb-sized bird that first tasted peanut butter.
Gaglioti was there to continue exploring a “ghost forest” that he and others had discovered years earlier. He studies ancient landscapes for his work as an ecologist at the Center for Water and Environmental Research at the University of Alaska at Fairbanks.
This ghost forest, a few hundred meters from the swollen tongue of the La PÃ©rouse glacier, is where we camped.
We hung our food in dry sacks using a rope that we had thrown over a thick gray rod that was once a towering Sitka spruce top, bristling with thousands of bright green needles. It was before the glacier crushed it.
Gaglioti and his colleagues – including Dan Mann of the UAF and Greg Wiles of the College of Wooster in Ohio – used core samplers to learn when these trees died, which told them how long the glacier had advanced for. shear the powerful stems.
Scientists matched the growth rings with still living rainforest trees nearby. They discovered that the La PÃ©rouse glacier bulldozed these trees between 1850 and 1866.
After a year of absence linked to the pandemic, Gaglioti was happy to climb the giant rocks of an outlet stream towards the La PÃ©rouse glacier. Explorer William Dall in 1874 named the glacier for the French ship commander who sailed here in 1786. La Perouse fled Alaska shortly after losing 21 men to tidal currents at the mouth of the nearby bay of Lituya. He named the island in Cenotaph Bay, a word that means “empty tomb”.
Gaglioti wanted to find out what these trees, crushed during a cold period known as the Little Ice Age, can tell us about how the forest is responding to extreme climate change. Not just the warming we are feeling now, but also the extreme temperature swings that have occurred on several occasions in the past.
These dead trees we camped among – some of them are 600 years old when the glacier cut them down – hold a long-term record in their growth rings. Scientists compare them to records kept in living trees, including giant spruces, hemlocks and Alaskan yellow cedars that have sprouted high enough to be safe from glacier advances.
Gaglioti will use dendrochronology – taking pencil-thin carrots of living and dead trees as well as slices of dead cedars that he removed with a handsaw – to see how trees reacted to changes in temperature due to the proximity to ever-changing ice.
In the hummingbird camp of dead trees, gray and fine gravel shaded with green by some pioneer plants, we often felt the cold breath of the nearby glacier; in the middle of the summer, we had dinner wearing woolen hats.
Gaglioti believes the retreat of the glacier combined with the recent warming of air temperatures in Alaska may be a double dose of increased heat that the trees are responding to. Their reaction may be a predictor of how trees in the southeast respond to global warming and its eventual acceleration.
To gather information, Gaglioti and I scoured the thick, soft, and slippery rainforest nearby to collect temperature sensors that he installed in dead trees and the ground a few years ago. He also cored a few dozen trees, and, with a Japanese steel hand saw blade, cut a few wooden biscuits which he will bring back to the UAF to study in detail.
With slight grizzly signs and blue skies above us, we took our close encounter with the hummingbird as a promise of good things to come. We still had 11 days to go in a place with no boot prints except for our own Xtratufs.