Due to rising sea temperatures below surface, more methane bubbles up off Oregon and Washington coasts. Scientists explained that the warming now affects depths where frozen pockets of the gas can morph into a powerful source of greenhouse gas.
According to a recently published paper in the journal Geochemistry, Geophysics, Geosystems, nearly 170 methane bubble plumes were observed within the past ten years, which is considered a number critical to the stability of frozen methane pockets.
“We see an unusually high number of bubble plumes at the depth where methane hydrate would decompose if seawater has warmed,”
noted H. Paul Johnson, senior researcher involved in the study.
Johnson explained that those bubble plumes are normally the result of decaying sediments. But the boom in their number may suggest that methane is now coming from dormant methane that was frozen for thousands of years.
Methane is a powerful greenhouse gas that influenced Earth climate throughout millennia. It is uncertain whether it has the same effects on rising global temperatures as carbon dioxide has. Yet recent reports show that methane emissions in the Arctic may have contributed to rising temperatures in the area.
Fourteen bubble plumes off the Oregon and Washington coasts were observed within the transition depths. If these bubbles reach surface, they can contribute to the greenhouse effect. Fortunately, much of the bubbling methane is lost in its way toward surface.
Researchers explained that there are many marine microbes that feed on methane and convert it into carbon dioxide. But that fuels oceanic acidification since the excess of carbon dioxide promotes a more acid environment in the sea along shoreline.
But as sea water gets more acid it starts to affect waterways and fisheries along the coast. Plus, if methane continues to be released from frozen deposits, seafloor slopes may become destabilized since there is no frozen methane to keep them glued to one another.
But past studies had also shown that transition depths are warming off the Pacific Northwest coast. According to a 2014 study, the ocean is warming at 0.3 miles depths because of warm water emerged in a climate change-caused hotspot off Siberia and carried by ocean currents to the region.
Methane in seafloor is in solid state because of low temperatures and high pressures. Solid methane is called methane hydrate, a compound that is very sensitive to rising subsurface temperatures. When seawater is too warm hydrate molecules part ways and methane gas is released into the seafloor. But some part of that gas escapes seafloor pores and forms bubble plumes.
Image Source: Wikimedia
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