The Great Siberian Thaw 0122.rtf - In-depth history and analysis
Arctic Permafrost Cauldron 0918.rtf
- Much of the carbon emitted is really old, many 1,000s, even millions of years.
About 24% of Northern Hemisphere land surface was covered by permafrost in 1997. See north polar-view map at left. Soil carbon content tends to be greater toward the poles, where permafrost is most prevalent (and probably deeper).
Permafrost regions contain 1,700-1,900 trillion tonnes of carbon (to 1 meter deep), in the form of frozen organic matter, nearly 2 x that currently in the atmosphere (Tarnocai et al. 2009, updated by Hugelius et al. 2012).
This model projection indicates a 59% loss in near-surface permafrost area by 2100 for the IPCC A1B scenario. The dark grey regions show where taliks may form and permafrost in the top 15 meters of soil may completely thaw (Schaefer et al. 2011).
CO2 and methane (CH4) emissions from thawing permafrost can continue for decades or even centuries, as seen in this plot of estimated annual permafrost emissions in CO2 equivalent for the IPCC A1B scenario. Here, anthropogenic emissions stop in 2100, but permafrost CO2 and methane emissions continue well past 2200 (Schaefer et al. 2011).
Peak permafrost emissions are ~9% of today's human emissions (33 Gt/yr).
IPCC 5th Assessment, Technical Summary
Northern Hemisphere total from US National Climate Assessment, 2013
Projection for average yearly ground temperature at 3.3-foot (1-meter) depth over time, if heat-trapping gases continue to grow (higher A2 emissions scenario), and if they are substantially reduced (lower B1 emissions scenario).
Blue shades represent areas below freezing (where permafrost is present at the surface), while yellow and red shades represent areas above freezing (permafrost-free at the surface) (Markon et al. 2012).
Changes in the size of each Earth system carbon pool in response to the addition of permafrost carbon to the UVic ESCM.
That is, the difference in the size of each carbon pool between simulations with and without permafrost carbon. All values are relative to the size of the frozen permafrost carbon pool. A summation of all the pools adds up to 100% for each year.
Results are given for two emissions pathways (DEPs 4.5 and 8.5) and for 3 climate sensitivities to a doubling of CO2 (2.0, 3.0, and 4.5°C). Soil layers that thaw, but are subsequently returned to a permafrost state, continue to be administered by the active soil carbon pool, leading to the apparent high rate of transfer of carbon to the active soil carbon pool in the 20th century.
Permafrost (not including whatever is under the ice in Greenland and Antarctica) holds about twice as much carbon as the atmosphere does today. In the worst case shown, if current net carbon sinks fail, atmospheric CO2 levels could double from permafrost alone. Then add the effect of human carbon emissions.
Strangely enough, the additional temperature effect of permafrost emissions is not highest in the highest human emission scenario (DEP 8.5), but in the intermediate scenarios. The simplest reason is that CO2 in the air warms the air at a diminishing rate; with more CO2 molecules in the air, the chances are higher that one at a lower altitude will intercept outgoing radiation before one at a higher altitude gets a chance.
MacDougall Permafrost Carbon Emissions, Supplement 0912.pdf
Graphs of modeled future permafrost extent anomaly in CO2 concentration with respect to baseline runs with no permafrost carbon, for each DEP. Which climate sensitivity is assumed in not clear.
Squeezing Carbon Balloon - Kane 1112.pdf - for 2 adjacent plots in northern Sweden
The tundra-heath stores about 7.1 kilograms of carbon per square meter (6.2+0.8), while the birch forest stores about 4.6 kg (2.1+2.5) of carbon / sq m. The tundra-heath plot is on same hillside as the birch forest, 4 kilometers southeast and 190 meters higher.
As tundra systems give way to birch forest, more ecosystem carbon is in aboveground pools, but with a net loss of total ecosystem carbon. Below-ground carbon pools dwarf above-ground pools, especially if one considers carbon deeper in the soil….
Thawing Permafrost to Double Carbon in Air 0113.rtf - summary of study below
Antarctic May Host Methane Stores 0812.rtf
"Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme warming events (hyperthermals) superimposed on a long-term warming trend. The first and largest of these events ... (PETM) is characterized by a massive input of carbon, ocean acidification and an increase in global temperatue of about 5°C within a few thousand years."
"...the magnitude and timing of the PETM and subsequent hyperthermals can be explained by the orbitally triggered decomposition of soil organic carbon in circum-Arctic and Antarctic terrestrial permafrost. This massive carbon reservoir had the potential to repeatedly release thousands of [billions of tonnes] of carbon to the atmosphere-ocean system, once a … threshold had been reached...."
"These results show the potential for high-latitude climate forcing to trigger massive terrestrial carbon release, initiating positive warming feedbacks that can account for the sudden and high elevations of past hyperthermals."
(Xerophytic plants, such as cactus, are adapted to live with very little water.)
At 400 ppm (not shown), global mean surface temperature is ~14.6°C, about the same as today. At 900 ppm CO2 (top & middle 4 panels of 6), global mean surface temperature is 6°C warmer than today and Antarctic summers are too warm to allow glaciation. But ~9/10 as much permafrost remains in high latitudes of both hemispheres (top panel, not middle) as in Earth's total modern inventory, NOT counting modern Greenland and Antarctica, where most permafrost was then.
In the model, the warming-permafrost positive feedback loop eliminates 97-98% of the initial permafrost inventory (bottom 2 panels), releasing ~3,400 billion tons af carbon within 10,000 years [~10 times what humans have released from fossil fuels]. This raises global mean surface temperature another 6°C, leaving 2,680 ppm of CO2 in the air (see bottom left panel).
In the bottom panel, which features 2,680 ppm CO2 and is ~12°C warmer than today, dry vegetation types (scrub and cactus) cover most of Africa (replacing much savanna), South America (replacing savanna and tropical deciduous woodland), and Southeast Asia (replacing tropical broadleaf forest). Warm and temperate deciduous and mixed deciduous-conifer forests cover much of Antarctica and most of Siberia and Canada, replacing most cold conifer forests.
Section Map: Carbon Emissions