A team of international scientists are alarmed that methane gas is seeping out from under the Arctic sea-bed which indicates that the increased ocean temperatures have spread out below, in fact, reaching the sea-bed level. About 250 clouds of methane emissions have been detected as rising from the sea-bed around the Norwegian region. Methane gas was evident from depths ranging from 150m-400m.
Yet we cannot really fathom the impact of these methane emissions if we do not have a clear perception where this methane gas emanates from. Perhaps, we should take a closer look just where exactly in the ocean floor, is methane gas coming from?
The methane gas that the researchers are concerned about is gas trapped inside ocean floor sediments that remain stable under water depths of beyond 500 meters. Gas hydrates filled in the porous gaps of these sediments rendering them as practically hydrate-cemented with zero permeability, hence these sediments became known as permafrost. Large amounts of methane gas are trapped inside these non-porous permafrost formations. If temperature and pressures under these water depths remain unchanged or stable, the permafrost sedimentation remains stable and the methane gas stays trapped inside them.
The layers of ocean floor sedimentation or permafrost are likewise rendered as tightly sealed while containing trapped gasses inside, including methane.
Hence, if scientists are telling us that methane gas is seeping out from Arctic sea-beds, then it leaves us with the understanding that the effects of global warming has affected the temperature and pressure below depths of 500 meters. Simply stated, the warmth of the ocean temperature has reached and melted the gas hydrates that sealed-off the porous gaps at 0°C below the freezing point of water. This has caused permafrost to thaw off and is now releasing trapped methane gas in the process.
What are Gas Hydrates?
Gas hydrates are natural gasses which include methane and they combine with water, under pressures already beyond the freezing point of 0°C. This combination of gas and water will take the form of crystalline solids similar to ice particles and are called gas hydrates or clathrates. They are commonly found underneath a permanently frozen land mostly in the polar areas and around 500 meters deep below the Earth’s continental margin near the sea-floor sediments of the ocean floor.
These gas hydrates have molecular size properties, which make them capable of sealing-off the porous gaps of ocean floor sedimentations. These hydrate-cemented sedimentations create the permafrost.
Other gasses that form into gas hydrates are hydrogen sulfide, carbon dioxide, and numerous hydrocarbons with low-carbon number.
Environmental Impact of Thawed Out Permafrost
The possibility of global warming thawing out multitudes of frozen layers of sediments will result to the release of high concentrations of methane and other gasses. By this alone, we could imagine the degree of temperature capable of thawing out permafrost that is sustained at 0°C below the freezing point of water.
There are also risks involved in setting up drilling platforms, pipelines and wells in the sea-floor as great amounts of gasses are unleashed. In addition, since most methane in gas hydrates are biogenic in nature or bacteria generated methane, the simultaneous release of these biogenic gasses poses possible environmental risks.
In sea water, methane gas reacts with the oxygen content of the water and will form into carbonic acid that will contribute in large amounts to the ocean’s acidification. Extreme levels of acidification pose grave threats to marine biodiversity.
As a source of fuel, methane gas if considered from worldwide occurrences of gas hydrates will account for 1x104 gigatons of carbon at the least, based on conservative estimates. This is said to be twice the figure of carbon found in all of the Earth's fossil fuels.