Cave reveals hidden climate clues from the last Ice Age

New evidence from an Alaskan cave reveals Ice Age meltwater pulses and offers fresh insights into past climate shifts and glacial refugia.

In a new study published in Nature Geoscience, an Austrian research team including Daniela Festi (GeoSphere Austria), Paul Wilcox, and Michael Meyer (University of Innsbruck) presents the first terrestrial evidence of glacial meltwater pulses from the Cordilleran Ice Sheet during the last Ice Age. These sediments, discovered in a remote cave on Alaska's Prince of Wales Island, offer rare insight into the semi-continuous release of meltwater into the Pacific Ocean between 20,000 and 17,000 years ago — a period marked by major climate transitions.

Using optically stimulated luminescence (OSL) dating, the researchers established the age of the cave deposits and found that they had remained undisturbed for thousands of years. Remarkably, the sediments also contained pollen, hinting that the cave may have been near a glacial refugium — an ice-free area where life could persist during peak glaciation. These findings help reconstruct the timing and drivers of postglacial warming and contribute vital data for understanding how sudden freshwater inputs can influence global climate systems.

This work underscores the importance of paleoclimate archives for decoding Earth's climatic past and refining predictions of future change. The research also highlights the Pacific region’s previously underappreciated role in triggering global climate shifts — a perspective that could be key in assessing the risks of modern-day ice sheet melt and ocean circulation changes in a warming world.

Understanding climate change in Austria means looking far beyond its borders. While the long-term current warming of the planet is unequivocally driven by human-generated greenhouse gas emissions, natural ocean phenomena like El Niño in the Pacific or large-scale ice melting events can influence how these changes unfold in different parts of the world. These natural climate patterns do not drive the ongoing global warming trend, but they can intensify or moderate its local effects. By studying these global connections, scientists are improving forecasts for Austria — and helping to shape smarter adaptation strategies that specifically address the impacts of human-caused climate change.