World’s oceans warmest on record, releasing methane
August 17th, 2009 by Jim JustThe planet’s ocean surface temperature was the warmest on record for July, breaking the previous high mark established in 1998 according to an analysis by NOAA’s National Climatic Data Center. The global ocean surface temperature for July 2009 was the warmest on record, 0.59°C (1.06°F) above the 20th century average of 16.4°C (61.5°F). This broke the previous July record set in 1998. The July ocean surface temperature departure from the long-term average equals June 2009 value, which was also a record.
July 2009 was the 33rd consecutive July with an average global land and ocean surface temperature above the 20th century average. The last July with global temperatures below the 20th century average occurred in 1976.
The combined average global land and ocean surface temperature for July 2009 ranked fifth warmest since world-wide records began in 1880.
Warming oceans are threatening to set off a vicious positive feedback loop. The National Oceanography Centre, Southampton (UK) reports a new study shows the warming of an Arctic current over the last 30 years has triggered the release of methane, a potent greenhouse gas, from methane hydrate stored in the sediment beneath the seabed. Scientists found more than 250 plumes of bubbles of methane gas rising from the seabed of the West Spitsbergen continental margin in the Arctic, in a depth range of 150 to 400 meters. The results indicate that the 1° warming of the northward-flowing West Spitsbergen current over the last thirty years has caused the release of methane by breaking down methane hydrate in the sediment beneath the seabed.
Methane hydrate is an ice-like substance composed of water and methane which is stable in conditions of high pressure and low temperature. At present, methane hydrate is stable at water depths greater than 400 meters in the ocean off Spitsbergen. However, thirty years ago it was stable at water depths as shallow as 360 meters. The scientists claim this is the first time that such behavior in response to climate change has been observed in the modern period.
Methane is over 20 times more effective in trapping heat in the atmosphere than carbon dioxide (CO2) over a 100-year period – but its short-term impacts (i.e., over a 25-year period) are much greater. Methane in the atmosphere is eventually oxidized, producing carbon dioxide and water. It remains in the atmosphere for approximately 9-15 years, with a “half life” of about seven years.
Professor Tim Minshull expressed surprise at the findings:
Our survey was designed to work out how much methane might be released by future ocean warming; we did not expect to discover such strong evidence that this process has already started.
Professor Graham Westbrook issued a stark warning:
If this process becomes widespread along Arctic continental margins, tens of megatonnes of methane per year – equivalent to 5-10% of the total amount released globally by natural sources – could be released into the ocean.