USGS/NASA Landsat data

This ice-covered Icelandic volcano may emit more carbon dioxide than all of the country’s other volcanoes combined

Despite being mostly smothered by a glacier averaging 200 meters thick, one of Iceland’s largest and most active volcanoes still manages to belch surprisingly large quantities of carbon dioxide (CO2) into the atmosphere, new research reveals.

To help lift the veil on Katla (center right, above), which lies near the southernmost tip of Iceland, researchers flew a sensor-laden aircraft around the peak at low altitude three times in 2016 and 2017. At some points near the volcano, CO2 levels were about 8% higher than normal. Using computer simulations, the team identified a few possible sources of the excess CO2, including locations on the western flank of the volcano where meltwater full of dissolved gases emerges from beneath the peak-covering glacier. Other potential sources include some of the sinkholelike features that pepper the glacier near its peak.

Based on the team’s models and data, Katla is emitting somewhere between 12,000 and 24,000 metric tons of carbon dioxide each day, the researchers report online this week in Geophysical Research Letters. That’s several times higher than previous estimates of emissions from all of Iceland’s volcanoes combined—which may be vastly underestimated because only two of that nation’s subglacial volcanoes have had their emissions measured in detail.

Scientists estimate that volcanoes worldwide emit, on average, about 1.5 million metric tons of CO2 per day (only about 2% of the amount that human activity causes). Yet that estimate may be far too low because it’s based on measurements from only 33 of the world’s most volcanically active peaks (only three of which are ice-covered), among the 1500 or so that have erupted in the past 10,000 years. More data gathered from Iceland—as well as Antarctica, which is home to dozens of ice-smothered volcanoes—may help scientists come up with a better estimate for volcanic CO2 emissions.

*Correction, 23 September, 9:50 a.m.: In the fourth paragraph, the amount of carbon dioxide emitted daily by the world’s volcanoes has been updated. In our original article, a word was missing.