Australia: The Land Where Time Began

A biography of the Australian continent 

Climate Change Science – Permafrost, Methane and Clathrates

At high altitudes and high latitudes there are vast areas of permafrost, ground that is permanently frozen. During warmer seasons the top few centimetres of the permafrost, the active zone, in these areas thaw. Problems are caused for structures such as buildings, as well as roads and other structures.

A very large quantity of methane, CH₄, has accumulated in frozen soils, having formed as a product of bacterial activity and is then released whenever permafrost thaws. Recently methane releases have been occurring and there have been eyewitness reports of methane bubbling to the surface in lakes and the ocean in permafrost areas of the world, especially on the North Slope of Alaska, and off the north Siberian coast.

Vast deposits of methane are known to be present beneath the Arctic Ocean being held in the form of methane clathrates. According to Farmer & Cook it is a matter of when rather than if the clathrates release this methane to the atmosphere, as the Arctic is warming faster than any other part of the world. Most of the methane accumulated about 18,000 years ago during the last Glacial Maximum (LGM) when the sea level was at a low stand. When the massive ice sheets of the glacial phase receded the sea level rose, flooding these areas of continental shelves that are now the floor of shallow ocean water around the coasts of the continents of the present.

When the continental shelves began to flood, as the continental ice sheets began to melt, but before the shelves were completely flooded, there would, according to Farmer and Cook, have been salt or tidal marshes where anaerobic bacteria were breaking down complex hydrocarbons to methane. There is plenty of atmospheric oxygen in dry conditions, with the result that aerobic bacteria would be producing carbon dioxide, CO_2. In the wet areas, such as swamps, wetlands and parts of the ocean, areas where the oxygen levels are too low for aerobic bacteria, anaerobic bacteria break down the complex hydrocarbons to methane. Some of the methane produced is released to the atmosphere, though some is trapped. The methane that enters the atmosphere is gradually broken down to carbon dioxide and water vapour by a series of chemical reactions.

Sources & Further reading

1. Farmer, G. Thomas & Cook, John, 2013, Climate Change Science: A modern Synthesis, The Physical Climate Vol.1, Springer Dordrecht