Last summer, 2011, there were reports of the ocean bubbling from
tankers traveling through the Chukchi Sea north of Russia. The Chukchi Sea is north
of Siberia, a section of the Arctic Ocean, and one of the last places in
the Arctic to receive extensive research. It runs along the coast of
northeastern Siberia which is home to the East Siberian Arctic Shelf
(ESAS). The ESAS is the shallowest portion of the Arctic Ocean with an
average depth of 50m.
In response to the freighter's reports a team
from the University of Alaska Fairbanks that had been studying the area
for the past decade launched an expedition to the region. What they
found were plumes of methane bubbling from the ocean up to a km across.
These areas had not been explored yet by the team. Areas close to it
however had only had plumes tens of meters across. Why does this
matter?
Methane is one of the more potent greenhouse gases (GHGs)
that occur naturally on Earth in large quantities. Over 20 years
methane has 72 times more warming potential than carbon dioxide and 25
times more over 100 years. Scenarios from the SRES, SREX, and the two
latest comprehensive climate change reports from the IPCC, the TAR and
AR4, don't include methane emissions outside of anthropogenic sources
(agricultural emissions due to livestock and rice and other industry).
As a result, the effects of methane emissions from many natural sources
has not been quantified and the effect of such large additions of
methane into the atmosphere is unknown.
The ESAS is home to the
largest concentration of methane hydrates or clathrates in the world.
Clathrates are solid crystal structures created under pressure near the
bottom of the ocean or within the sediment. Beneath the sediment
clathrates extend until the geologic heat from the Earth becomes too
much for the solid crystal structure to be maintained. 80% of the
world's clathrates are located in the ESAS. It is estimated that around
1750Gt of methane are stored within the ESAS.
In 2010 Shakhova
et. al estimated that it was possible for a 50 Gt release of methane from
the clathrates of the ESAS to happen at any time. 50 Gt of methane is
enough to double the amount of carbon in the atmosphere, pushing us into the region of dangerous climate change.
In
earlier periods, methane release from clathrates played a role in
massive extinctions. In fact, the largest extinction known to date,
occurred in conjunction with massive methane releases from clathrates.
The Permian-Triassic extinction killed off 70% of terrestrial
vertebrates, 90% of marine life. and is the only know mass extinction of
insect life. During that period carbon supersaturated the oceans
turning the ocean from a carbon sink to a carbon source. Oxygen levels
are presumed to have been at such a low proportion that some forms of
life could not be supported. Massive wildfires roamed the continents.
This
is an extreme example of the ability methane has of wreaking havoc on
our climate system. There is not nearly as much methane deposited in
hydrates as there had been at that time. It is also believed that the
release of the hydrates was caused by the seismic activity of volcanoes
located in Siberia. Both of these point toward changes in climate not
being as drastic as the Permian extinction. Any change caused by the
release of large amounts of methane from the ESAS however would be swift and
have a large impact on the climate system.
What is most worrisome
about this latest development in the ESAS is that the Arctic is already
warming quicker than the rest of the world. Some of this warming is
unaccounted for. It has been acknowledged that there is a feedback
mechanism that inherently speeds the loss of Arctic ice as it melts. As
the ice melts and breaks apart it becomes surrounded by water which has
a lower albedo (or reflectivity). Heat energy is more easily trapped
by surfaces with low albedo, causing the water surrounding the ice to
heat up faster, causing the ice to melt quicker. This vicious cycle
does not account for all increases in warming however.
Recently,
NASA performed flyovers of the oceans spanning from one pole to the
next. They flew over the Arctic five times and discovered that methane
levels from the Arctic ocean were .5% higher than background levels.
(See my entry from April 24, 2012.) The higher methane levels were
concentrated where there were leads in the ice, meaning the methane was
coming from the ocean and not already present in the atmosphere. This
discovery may account for the additional warming we are experiencing in
the Arctic. The source of this methane has not been identified yet.
This leaves us with the question, "What is happening in the Arctic?"
It would seem to me that the increasing levels of
methane are indicative of a positive feedback beginning in the Arctic.
The ocean water that is coming in contact with the permafrost on the
ESAS is 12-17 degrees Celsius warmer than the ice that had previously
covered it. With the greater release of ESAS methane Arctic waters will
become supersaturated with carbon, become warmer more easily, turn the
ocean into a source, and aid the release of additional clathrates in
Arctic. GHG emissions must be limited NOW in order to prevent this...
References
Kort,
E., Wofsy, S., Daube, B., Diao, M., Elkins, J., Gao, R., et al. (2012).
Atmospheric observations of Arctic Ocean methane emissions up to 82
north.
Nature Geoscience,
5, 318-321.
"Methane releases from Arctic shelf may be much larger and faster than anticipated."
National Science Foundation - US National Science Foundation (NSF).
Version 10-036 . N.p., 4 Mar. 2012. Web. 11 May 2012.
.
Romm, Joe. "Science stunner: Vast East Siberian Arctic Shelf methane stores destabilizing and venting | ThinkProgress."
ThinkProgress.
N.p., 4 Mar. 2012. Web. 11 May 2012.
.
Shakhova, N.E, V.A Alekseev, and I.P Semiletov. "Predicted methane emission on the East Siberian Shelf."
Doklady Earth Sciences 430.2 (2010): 190-193.
Shakhova,
N., Semiletov, I., Sergienko, V., Pipko, I., & Dudarev, O. (2012).
On carbon transport and fate in the East Siberian Arctic
land–shelf–atmosphere system.
Environmental Research Letters,
7, 1-13.
Shen, S, J.L Crowley, Y Wang, S.A Bowling, D.H Erwin, P.M Sadler, and C Cao. "Calibrating the end-Permian mass extinction."
Science 334 (2011): 1367-1372.
