By Emma Conkle
Nov. 28, 2025
To an onlooker, it may have seemed like Tricia Hall Collins and her research partner, Katie Westbrook, were blasting into the surfaces of boulders in a rainy Norwegian field, but what they were actually doing could change the way we understand climate change.
“That our glacier records are showing a global response gets at what underlying mechanisms can be used to warm up the whole Earth,” said Hall Collins, a PhD student at the University of Maine. “If we are not understanding those underlying mechanisms correctly, we can’t model them correctly to project our current global warming.”
Hall Collins presented her new records at the annual Comer Climate Conference in southwestern Wisconsin, where leading climate scientists gather to collaborate on climate change solutions.
Using an isotope of beryllium called beryllium-10, Hall Collins was able to date pieces of erratic boulders and moraines at Lysefjord glacier in southwestern Norway. This isotope collects at predictable rates once the boulder is ice-free. This helped her create a chronology of the glacier’s movements during three significant periods of warming and cooling following the last Ice Age. Scientists are able to compare past chronology to current climate trends, showing the more rapid pace of climate change now.
Moraines, natural ridges of sediment and boulders that accumulate as glaciers retreat, and erratic boulders, large rocks deposited randomly by glaciers, are indicators of periods when glaciers melt. Moraines reveal where the glacier’s retreat periodically stopped.
To source samples, Hall Collins and Westbrook climbed atop boulders, drilled into them, and used electric charges to blow off rock fragments.
Periods known as Heinrich Stadial 1 and the Younger Dryas, about 18,000–14,700 years ago and 12,900–11,700 years ago respectively, were understood to be periods of cold temperatures in the North Atlantic and warm temperatures in Antarctica. But Hall Collins’ new data from the Lysefjord glacier demonstrates there were also periods of warm temperatures in the North Atlantic due to glacial retreat, or melting.
During the Bølling–Allerød Interstadial period (14,700–12,900 thousand years ago), which occurred at the same time as the Antarctic Cold Reversal, it was believed that the North Atlantic was warm while Antarctica was cold. However, Hall Collins’ data shows that the glacier likely readvanced and stabilized during a supposed warming period.
“These glaciers are responding to atmospheric temperatures primarily, which means globally, the atmosphere is getting warm during the Heinrich Stadial 1 and Younger Dryas,” said Hall Collins.
Aaron Putnam, an associate professor at the University of Maine and Hall Collins’ advisor, said, “The initial warming event that caused that ice to retreat into that fjord by 16,000 years ago that Tricia showed–to me, that being simultaneous between the hemispheres says there was energy being put in both hemispheres that was available to melt ice, and I can’t see any way around it.”
Hall Collins’ data supplements an ongoing debate over broad atmospheric changes after the last Ice Age among paleoclimatologists, or scientists who study Earth’s past climate. The debate is reassessing the case for global patterns with new research, while some scientists hold to hemispheric models that differ from what the Earth is currently experiencing.
“We’re seeing patterns. We’re seeing relations. The model and the data together are telling us things that matter,” said Richard Alley, a professor of geosciences at Penn State University, about Hall Collins’ data.
Why does this matter to the Earth’s current climate?
According to Putnam, Earth is now in a period of transient warming, a time when the ocean and atmospheric systems are out of equilibrium. Heat builds in that system, warming the planet.
“Those things that we suspect were probably operating during the last Ice Age termination, well, they seem to be kicking in now, too, or have already kicked in,” Hall Collins said.
The last major transient warming event was the one that ended the mini ice age of the Younger Dryas more than 11,000 years ago. Studying how the climate responded during that time can help us predict and understand how the Earth will respond to current climate warming events that are exceeding the Younger Dryas’ pace of warming.