Monday, February 20, 2012

Abrupt release of methane in the Arctic in late 2011?

Was over 2 Megaton of methane released abruptly from hydrates in the Arctic in late 2011? Satellite images show high levels of methane at various locations in the Arctic over a period of 13 days (November 26, 2011, to December 8, 2011).

Methane was observed at various locations in the Arctic at levels of about 2000 parts per billion. Global levels are about 1820 parts per billion.

What could have caused these high levels in the Arctic?

There are no natural gas pipes at the North Pole that could be leaking, there are no drilling activities taking place, and there are no cows or termites. Since it was winter at the time, there were no algae blooms.

The best way to explain these high levels of methane at the North Pole is that was venting from hydrates at the North Pole and carried by the wind into North America.
Global wind circulation patterns - NSIDC image

In which direction would methane flow?

Polar easterlies are the prevailing wind patterns in the Arctic. When methane emerges at surface levels in the Arctic, these winds will drive it down to 60 degrees North latitude, where it will be further dispersed by the Polar Jet Stream (or Polar front).

How fast can methane be carried by the wind?

In the Arctic, winds have average speeds of 600 to 1032 kilometers per day on the Atlantic side in winter, while maximum wind speeds in the Atlantic region can approach 4320 kilometers per day in winter (Rajmund Przybylak, 2003: The Climate of the Arctic).

By comparison, the distance between Murmansk and Svalbard is about 1000 km (621 miles), as illustrated on the above map.

The animation below shows daily satellite pictures of methane descending down the Arctic, from the North Pole into North America over a period of 13 days (November 26, 2011, to December 8, 2011). Distances traveled daily appear to match average wind speeds for the respective area at this time of the year.

Note: This is a 2.17 MB file; it may take some time for the animation to fully load.

In conclusion, the animation suggests that methane is venting from hydrates in the Arctic at levels up to 2000 parts per billion. These high levels can cover areas as large as Greenland. Total surface of Earth is 510,072,000 square kilometers, and Greenland has a surface of 2,166,086 square kilometers, one 235th that of Earth.

The total methane burden on Earth is about 5 Gt, corresponding with a level of 1820 parts per billion. Thus the burden over an area the size of Greenland would be one 235th of 5 Gigaton, or 21 Megaton. A level of 2000 parts per billion is about ten percent higher than the world's average level of 1820 parts per billion. Thus, the methane that shows up in the animation could result from abrupt release of some 2.1 Megaton of methane from hydrates in the Arctic.

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