Researchers at Columbia University, in a study published in the journal Nature, say new evidence from New Zealand suggests the deep freeze up north bypassed much of the Southern Hemisphere.
"Glaciers in New Zealand receded dramatically at this time, suggesting that much of the Southern Hemisphere was warming with Antarctica," study author Michael Kaplan, a geochemist at Columbia's Lamont-Doherty Earth Observatory, said. "Knowing that the … cooling in the Northern Hemisphere was not a global event brings us closer to understanding how Earth finally came out of the ice age."
Ice core data show warming of the Southern Hemisphere starting 13,000 years ago coincided with rising levels of the heat-trapping gas carbon dioxide.
The new study links this spike in CO2 to the impressive shrinking of glaciers in New Zealand.
Scientists estimate the glaciers shrank by half over 1,000 years in response to the local climate warming as much as 2 degrees F.
Researchers theorize that a weakening Gulf Stream at the start of the last ice age drove the north into freezing temperatures while simultaneously affecting the planet's wind patterns and ocean currents, pushing warm air and seawater south.