A positive feedback is define as “processes that amplify climate change”, such as reduced absorption of CO2 by the oceans and the ice-albedo effect. As time goes on, scientists are finding more and more of these positive feedback mechanisms, further increasing the warming effect. One of the long predicted positive feedback mechanisms is the release of methane in the Arctic by permafrozen seas and soils – a natural process exacerbated by global warming. Recent research from Spitsbergen (an area off the Arctic where climate change is occurring at unprecedented rates) suggests that this methane escape is a growing cause for concern:
Scientists say they have evidence that the powerful greenhouse gas methane is escaping from the Arctic sea-bed. Researchers say this could be evidence of a predicted positive feedback effect of climate change. As temperatures rise, the sea-bed grows warmer and frozen water crystals in the sediment break down, allowing methane trapped inside them to escape.
The research team found that more than 250 plumes of methane bubbles are rising from the sea-bed off Norway. The joint British and German research team detected the bubbles using a type of sonar normally used to search for shoals of fish. Once detected, the bubbles were sampled and tested for methane at a range of depths.
Writing in Geophysical Research Letters, the team says the methane was rising from an area of sea-bed off West Spitsbergen, from depths between 150m and 400m.The gas is normally trapped as “methane hydrate” in sediment under the ocean floor. “Methane hydrate” is an ice-like substance composed of water and methane which is stable under conditions of high pressure and low temperature.
As temperatures rise, the hydrate breaks down. So this new evidence shows that methane is stable at water depths greater than 400m off Spitsbergen. However, data collected over 30 years shows it was then stable at water depths as shallow as 360m. (Read More at BBC News)