Barnes Ice Cap shows ice sheets began re-expanding 2,000 years ago before human warming

Ice Sheet Re-expansion Identified

A study published in Science reveals that the Laurentide Ice Sheet, a major Pleistocene ice sheet, reached its smallest size about 3,600 years ago. Subsequently, it began to re-expand roughly 2,000 years ago, a process interpreted as the onset of a new glaciation period. This re-expansion continued until approximately 1960.

Human Impact on Glaciation

The research indicates that human-caused climate warming reversed the natural re-expansion of the ice sheet around 1960. This suggests that a potential new ice age was underway before being interrupted by anthropogenic climate change.

Evidence from Barnes Ice Cap

The Barnes Ice Cap, located on Baffin Island in the Canadian Arctic, provided the direct physical evidence for these findings. It is the last remnant of the Laurentide Ice Sheet. Nicolás Young, a geologist at Columbia University’s Lamont-Doherty Earth Observatory and lead author, explained that the cap's unique characteristics allowed for the preservation of this historical record.

Cold-Based Ice Preservation

Unlike most warm-based glaciers that slide and erode underlying material, the Barnes Ice Cap is cold-based. This means it is frozen directly onto the bedrock, preventing movement and preserving the ground beneath it. Tundra plants that colonized the ground after the initial retreat were smothered and preserved when the ice re-advanced, allowing researchers to date the re-expansion using two independent methods.