“We see an unusually high number of bubble plumes at the depth where methane hydrate would decompose if seawater has warmed,” said lead author H. Paul Johnson, a University of Washington professor of oceanography. “So it is not likely to be just emitted from the sediments; this appears to be coming from the decomposition of methane that has been frozen for thousands of years.”<p>Methane has contributed to sudden swings in Earth’s climate in the past. It is unknown what role it might contribute to contemporary climate change, although recent studies have reported warming-related methane emissions in Arctic permafrost and off the Atlantic coast.