"Carbon dioxide has gone up and down repeatedly over time, and we don't really know why," said Joshua West of the University of Southern California. "Our study suggests that this process may play a meaningful role."
West, colleague Mark Torres and others analysed 7700 river-glacier drainage samples.
"We found glacial rivers are rich in dissolved sulphur, and...we have found that this tends to be because of the weathering of pyrite or fool's gold," said Torres. "When these kinds of rivers flow into the ocean, the sulphur causes the transfer of carbon that was previously stored in rocks and the ocean back into the atmosphere."
West, Torres and colleagues published their findings in PNAS.