It was. Huybers and Langmuir spliced two databases of volcanic eruptions worldwide over the last 40,000 years.
Eruption levels stayed low until around 12,000 years ago, then suddenly they suddenly shot up. The melting ice released so much pressure that the newly liberated volcanoes erupted at up to six times their normal rate, the researchers estimated.
The inferno lasted for 5,000 years and could have pumped enough CO2 into the atmosphere to raise concentrations between 40 and 50 parts per million, the researchers estimate. Changes in ocean chemistry probably released the rest.
The study was published in the journal Earth and Planetary Science Letters.
If the researchers are right, the picture for the future is unclear. Melting glaciers in Iceland, Alaska, the Andes and Antarctica could lead to regional increases in volcanic eruptions.
"The Vatnajokull glacier in Iceland, the largest in Europe, is retreating quite rapidly. It's definitely been a question in my mind: 'What would happen to the volcanoes underneath the ice as it thins?'" said Joseph Licciardi of the University of New Hampshire in Durham. "But the major removal of weight since the last glacial maximum has probably already occurred. The ice is already so thin."