Climate Change› Greenhouse Science & Climate Impacts
Which of the following statements are correct about the deposits of ‘methane hydrate?
- 1. Global warming might trigger the release of methane gas from these deposits.
- 2. Large deposits of ‘methane hydrate’ are found in Arctic Tundra and under the seafloor.
- 3. Methane in atmosphere oxidizes to carbon dioxide after decade or two
Select the correct answer using the code given below.
Answer d.
Option (d), all three statements are correct. Methane hydrate is methane locked in an ice-like water cage that is stable only under cold, high-pressure conditions, so warming can release it; it occurs in Arctic permafrost and marine sediments; and atmospheric methane oxidises to carbon dioxide within roughly a decade. Methane hydrate (clathrate) is a crystalline solid in which a cage of water molecules traps a methane molecule; it stays solid only where temperature is low and pressure high, chiefly beneath Arctic permafrost and in continental-margin seafloor sediments a few hundred metres down. Warming of permafrost or ocean-bottom waters destabilises the cage and can release methane — the feared 'clathrate gun' positive feedback. In the atmosphere methane is destroyed mainly by reaction with the hydroxyl radical (OH), giving it a lifetime of about 9-12 years, at the end of which it has been oxidised to carbon dioxide and water; that is why methane is far more potent than CO2 over 20 years but much shorter-lived, and why cutting methane brings quick climate returns.
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