Warming May Have Canceled an Ice Comeback in North America

For most of the last glacial period, the Laurentide Ice Sheet covered much of northern North America and reached well into what is now the United States. As it melted over several thousand years, it left behind a few shrinking remnants, including the Barnes Ice Cap on Baffin Island in the Canadian Arctic. Those leftovers were not destined to stay small forever.

Over the past several thousand years, slow shifts in Earth's orbit have gradually cooled high northern latitudes. Around 2,000 years ago, that long cooling trend may have been enough to start the remnant ice growing again. Ice masses that small are highly sensitive to changes in summer temperature and snowfall, so even modest cooling can tip them toward expansion.

The new picture suggests that this comeback was probably interrupted. Warming driven largely by greenhouse gas emissions has pushed summer temperatures in the region upward, melting away the snow that would otherwise have built up into ice. In effect, the headline's blunt phrasing captures the finding: a regrowth that the natural climate was already preparing appears to have been halted by human-caused warming.

The result is a reminder that ice responds to climate on timescales people can observe within a human lifetime. A new ice age is not on the horizon, but the same sensitivity that could have driven regrowth now works in the other direction, and small ice caps across the Arctic are already retreating. Researchers see these remnants as sensitive indicators of how the climate system is changing.