Scientists have discovered that Iceland’s Sólheimajökull glacier, which covers the active volcano, Katla, is releasing up to 41 tons of methane every day through its meltwater during the summer months — equal to the methane produced by more than 136,000 belching cows.

The research, published this week in the journal Scientific Reports, is the first major examination into whether melting glaciers could be a potential major source for methane as the climate warms, particularly those situated on or next to active volcanoes.

“This is a huge amount of methane lost from the glacial meltwater stream into the atmosphere,” Peter Wynn, a glacial biogeochemist at Lancaster University and co-author of the study, said in a statement. “It greatly exceeds average methane loss from non-glacial rivers to the atmosphere reported in the scientific literature. It rivals some of the world’s most methane-producing wetlands and represents more than twenty times the known methane emissions of all Europe’s other volcanoes put together.”

Wynn and his colleagues collected meltwater samples from the front of the Sólheimajökull glacier and compared their methane concentrations with samples collected from nearby rivers and sediment. They used a mass spectrometer to identify that the methane from Sólheimajökull was being produced by microbial activity in the bed of the glacier, sped up by the heat of the glacier’s underlying volcano.

The scientists say their findings reveal a previously unknown source of methane emissions that could further disrupt the global climate system. “Both Iceland and Antarctica have many ice-covered, active volcanoes and geothermal systems,” Rebecca Burns, a geochemist and lead author of the study, said in a statement. “The recent International Panel on Climate Change (IPCC) report highlights that current trajectories indicate global warming is likely to reach 1.5º C between 2030 and 2052, with greatest perceived climate sensitivity at higher latitudes. If methane produced under these ice caps has a means of escaping as the ice thins, there is the chance we may see short term increases in the release of methane from ice masses into the future.”