Ice-Free Arctic Of PETM (55 MYA) Likely Linked To Methane Hydrate Release

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The last time massive amounts of greenhouse gases were released into the atmosphere, the North Pole was an ice-free expanse of open ocean that was teeming with tropical organisms, a study has found. Scientists have discovered that the complete disappearance of the Arctic sea ice, 55 million years ago, coincided with a dramatic increase in concentrations of carbon dioxide or methane in the atmosphere - which must have caused global warming.

After analysiing the sediments on the floor of the Arctic Ocean, an international team of researchers working for the Arctic Core Expedition (Acex) came to the conclusion that the region was once extremely warm, unusually wet, and ice-free.

The scientists also found that the Arctic is currently experiencing one of the fastest temperature rises on record, with more sea ice melting each summer than at any time in hundreds and possibly thousands of years. The Acex research team drilled frozen sedimentary cores from the ocean floor, which can be dated to 55 million years ago, a period known as the palaeocene-eocene thermal maximum (PETM). Surface temperatures in some parts of the world were then 8C (15F) higher than now.

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"The magnitude of the carbon input at the PETM outset is truly enormous. If it were all volcanic, you'd need something like a Vesuvius-sized eruption each day for centuries, which seems very unlikely," Dr Dickens said. Another possibility is that there was a sudden release of massive amounts of methane and carbon dioxide that had been locked away in the deep ocean in a frozen form known as ocean gas hydrates. Even today, it is estimated that there is more carbon locked away as ocean gas hydrates than all of the oil and gas reserves of the world combined.

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http://news.independent.co.uk/environment/article1218041.ece