Arctic News: Methane Erupting From Arctic Ocean Seafloor

Monday, March 13, 2017

Methane Erupting From Arctic Ocean Seafloor

Seafloor methane often missed in measurements

Large amounts of methane are erupting from the seafloor of the Arctic Ocean. These methane eruptions are often missed by measuring stations, because these stations are located on land, while measurements are typically taken at low altitude, thus missing the methane that rises in plumes from the Arctic Ocean. By the time the methane reaches the coast, it has typically risen to higher altitudes, thus not showing up in low-altitude measurements taken at stations on land.

The image below shows the highest mean global methane levels on March 10 over the years from 2013 through 2017, for selected altitudes corresponding to 945 mb (close to sea level) to 74 mb.

The table below shows the altitude equivalents in feet (ft), meter (m) and millibar (mb).

57,016 ft	44,690 ft	36,850 ft	30,570 ft	25,544 ft	19,820 ft	14,385 ft	8,368 ft	1,916 ft
17,378 m	13,621 m	11,232 m	9,318 m	7,786 m	6,041 m	4,384 m	2,551 m	584 m
74 mb	147 mb	218 mb	293 mb	367 mb	469 mb	586 mb	742 mb	945 mb

The signature of seafloor methane

Above image shows that, over the years, methane levels have risen strongly high in the Troposphere, up into the Stratosphere. This looks like the signature of methane that originated from the seafloor of the Arctic Ocean. The image below further explains why.

The Tropopause separates the Troposphere from the Stratosphere. The Troposphere ends at a height of some 9 km (5.6 mi; 30,000 ft) at the poles, and at a height of some 17 km (11 mi; 56,000 ft) at the Equator.

As said, methane is erupting from the seafloor of the Arctic Ocean concentrated in plumes, unlike methane from wetlands and agriculture that is typically emitted over a wide area. Since seafloor methane is rising in plumes, it hardly shows up on satellite images at lower altitude either, as the methane is very concentrated inside the area of the plume, while little or no increase in methane levels is taking place outside the plume. Since the plume will cover less than half the area of one pixel, such a plume doesn't show up well at low altitudes on satellite images,

Methane over the Arctic typically does show up on satellite images at altitudes between 4.4 km and 6 km (14,400 ft and 19,800 ft). Seafloor methane will show up better at these higher altitudes where it spreads out over larger areas. At even higher altitudes, methane will then follow the Tropopause, i.e. the methane will rise in altitude while moving closer to the equator.

NOAA image

In conclusion, methane originating from the seafloor of the Arctic Ocean can strongly contribute to high methane levels that show up over the Equator at higher altitudes, but this methane can be misinterpreted for methane originating from tropical wetlands.

Methane levels as high as 2846 ppb

[ click on images to enlarge ]

On March 14, 2017, methane levels were as high as 2846 ppb, as illustrated by the image on the right. While the origin of these high levels looks hard to determine from this image, the high levels showing up over the East Siberian Arctic Shelf (ESAS) later that day (image underneath) give an ominous warning that destabilization of methane hydrates is taking place.

The images also show that high methane levels are showing up at many other places, e.g. over Antarctica where hydrate destabilization also appears to be taking place, which could also be the cause of noctilucent clouds as discussed in earlier posts (see links at end of this post).

Why is methane erupting from the Arctic Ocean?

Why are increasingly large quantities of methane erupting from the seafloor of the Arctic Ocean? The main driver is warming of the Arctic Ocean that is destabilizing once-permanently-frozen sediments that contain huge amounts of methane in the form of hydrates and free gas.

Ocean heat is increasingly entering the Arctic Ocean from the Atlantic Ocean, as illustrated by the images below. Self-reinforcing feedbacks, in particular sea ice decline, further speed up warming of the Arctic Ocean.

[ from earlier post ]

Self-reinforcing feedback loops

[ click on images to enlarge ]

Meanwhile, the next El Niño event has already started, at a time when sea surface temperature anomalies over the Pacific Ocean are very high as illustrated by the image on the right showing sea surface temperature anomalies east of South America as high as 5.3°C or 9.5°F (compared to 1981-2011) on February 28, 2017.

Greater contrast between sea surface temperatures and temperatures on land has contributed to flooding in California and South America.

Importantly, more water vapor in the atmosphere results in more warming, since water vapor is a potent greenhouse gas.

[ click on images to enlarge ]

Above images shows ECMWF (European Centre for Medium-Range Weather Forecasts) plumes with strong positive anomalies in all three El Niño regions (on the right).

In other words, temperatures in 2017 look set to be very high, which spells bad news for the Arctic where temperature anomalies are already several times higher than in the rest of the world.

Arctic sea ice looks set to take a steep fall, as illustrated by the image below.