KlimaNotizen – supplementing information about climate change
What happens when permafrost thaws? A dramatic increase in the greenhouse effect? A look at the facts reveals surprising news and insights – in particular about CO2.
So CO2 is a topic in this newsletter.
Further topics are in the pipeline.
Additional information, comments, ideas and views are welcome.
More information at www.KlimaNotizen.de
Permafrost thawing leads to the formation of moors. Moors are CO2 sinks because they absorb more CO2 than they release.
Water-covered areas release methane. A look at the past shows that it is a moot point whether or not considerable melting would result in a significant accumulation in the atmosphere. More research is necessary.
is permanently frozen ground, such as 85% of the surface of Alaska. During the summer, the upper layer (active layer) may thaw. Some layers contain a lot of water whereas others contain only few water.
Permafrost may be well up to more than 1000 m below the surface.
Permafrost has been mapped for about 50 years.
Deutschlandfunk (German radio station), Forschung aktuell (Research News) (2) :
At several locations in the world however, we try to drill deeper than 100 m in the permafrost to measure temperatures. These measurements show that currently the upper permafrost layer is in some parts of the world warmer than in others. …
Questions: Which climatic factors are crucial for the development of this active layer? Which factors are most important ?
Traditionally, air temperature is considered to be predominant in summer. This seems to be the case in some places, but other places show that there are further factors. We think that the amount of rain in summer, the snow depth in winter and summer are considerable factors, too.
Investigations in Spitzbergen, Greenland and Sweden have shown that local and regional factors are equally important as the air temperature in summer. A comment from Ole Humlum:
If an unusually high amount of snow has fallen in winter, most of the summer period is needed to melt the snow. Then, there is only few time to thaw the active layer. Despite a possibly very warm summer this layer will be thin. So, things are quite complicated. …
Climate models only connecting permafrost with the air temperature in summer take a too short-termed view. …. (2)
„Currently, the thawing layer in summer increases in Alaska and North America, but it decreases in parts of Siberia and Russia.“…
„It can be observed that every 10 to 15 years a part of the northern hemisphere seems to cool whereas another part warms” says the geologist” [Ole Humlum]. This is a result of cyclic changes in the North Atlantic wind flow. (7)
Permafrost areas are sparsely populated worldwide. Increased thawing has serious consequences, such as landslides, for the people in the area. Buildings, streets, railroads, pipelines etc. may only be used when intensive constructional measures are taken or must be given up.
On the other hand, permanent thawing can give way to a civilization of these areas as we had it in Middle Europe in the past. Wetlands dry up and are opened up for settlement and agriculture. Fertile landscapes would emerge that could easily be populated.
... and solid new buildings
How was it in the past ? Is permafrost a modern phenomenon? Temperature variations at various places in the past (4a) suggest comprehensive permafrost thawing in former times.
But then there was no civilization whose achievements could spectacularly sink to the ground and be witness to this development.
Temperatures of the past 8000 years. Example: Greenland
Ice cores are highly exact climate archives and can be found where everything is permanently frozen. The renowned scientist D. Dahl-Jensen et al. published a study (3) about the analysis of the GRIP and Dye 3 ice cores in Greenland including the following diagram in the Science magazine.
The diagram shows that around the year 1000 the surface temperatures in Greenland were one degree higher than today and even two degrees higher for a long period 4000 years ago.
The Alps were probably almost ice-free for several periods in the past 10 000 years. (6)
According to the time and temperature variations shown above, the current warming is not unusual in comparison to the more recent and distant past. Please see also newsletter no. 11 (Greenland) and no. 12 (Alaska).
Carbon dioxide, CO2
The importance of carbon dioxide, CO2 for permafrost thawing has been overestimated in the public.
Flat tarns and ponds expand in the polar landscape and thus modify the conditions of living. New plant species, such as shagnum types immigrate.
Researchers are still puzzling about the effects for our climate. After all moors are “carbon sinks” that absorb the greenhouse gas carbon dioxide. This effect is increased by stronger vegetation because the new plants store more carbon dioxide. Payette says “it has always been feared that additional CO2 is released into the atmosphere when the permafrost ground thaws, because then organic material begins to decompose. But this is compensated by the new vegetation cover. The grasses and moors absorb CO2 from the atmosphere, too. Therefore, the moor does not have to become a carbon source. The amount of released and absorbed CO2 should be more or less balanced.” Data from the European permafrost confirm this assumption. (10)
When water-covered permafrost ground thaws, methane from decomposing plants is released into the atmosphere.
... Methane has a 20 times stronger effect than CO2. Torben Christensen from the GeoBiosphere Science Centre at Lund University in Sweden says “measurements in Northern Sweden show that the methane release in the subarctic has increased significantly during the past 30 years, in some places an increase by 60 per cent can be observed.” This is due to increased plant decomposition, because today the moors are more often covered by water and the plants begin to decay. According to estimations from Lund University this negative factor outweighs the increase carbon dioxide absorption. So this negative influence will be stronger with higher temperatures in the atmosphere. (10)
Considerations to put possible fears into perspective.
The amount of methane in the atmosphere is very small (1.75 ppmv) whereas the amount of the trace gas CO2 (360 ppmv) is much higher.
It is unclear whether the methane released from permafrost ground leads to an accumulation in the atmosphere. Research has not yet found a definite answer here (7).
A look at the past can help.
The variations of methane concentration in the atmosphere of the past 10 000 years (11) show that even in warmer periods than today, methane concentrations were not much higher (0.55-0.75 ppmv) – and ,for different reasons, at a considerably lower level than today (1.75 ppmv).
Here, the relatively short lifetime of methane in the atmosphere (12 years) has a positive effect.
For several years now the methane concentration in the atmosphere (12) remains static which is a mystery to researchers.
When looking at the temperatures in the past, today’s thawing processes do not seem to be unusual. They may continue and expand as a result of a warming, but it is also possible that a reversed trend toward cooler conditions will occur. Nobody can say that for sure.
A significant increase in the greenhouse effect on the atmosphere due to thawing processes seems to be less probable. More research is necessary.
3 April 2005
Last modifications: 3 April 2005
Translation: Silke Kamprich
Last modifications: 11 April 2005
1. nsidc.org: Permafrost and Frozen Ground
2. DLF.de v. 21.7.2003:
Väterchen Frost auf dem Rückzug
3. SCIENCE 1998 VOL 282 www.sciencemag.org
D. Dahl-Jensen, K. Mosegaard, N. Gundestrup, G. D. Clow, S. J. Johnsen, A. W. Hansen, N. Balling
Past Temperatures Directly from the Greenland Ice Sheet
4. Arktische Konferenz - Arctic Climate Impact Assessment (ACIA)
Impacts of a Warming Arctic: Arctic Climate Impact Assessment
ACIA, Impacts of a Warming Arctic: Arctic Climate Impact Assessment. Cambridge University Press, 2004, http://www.acia.uaf.edu
4a. Chapter 2: Arctic Climate - Past and Present, 18.104.22.168. Early to mid-Holocene
5. Feng Sheng Hu, Emi Ito, Thomas A. Brown, B. Brandon Curry¶, and Daniel R. Engstromi
Pronounced climatic variations in Alaska during the last two millennia
6. BMBF-Studie: "Herausforderung Klimawandel - Bestandsaufnahme und Perspektiven der Klimaforschung" von 2003, S. 43:
“...Rekonstruktionen belegen,dass die Alpen während der letzten zehntausend Jahre wiederholt nahezu frei von Gletschern waren....”
7. Welt v. 14.08.2003
Klimarisiko aus dem ewigen Eis
... Denn Klimasimulationen zeigen, dass der Permafrost durch die globale Erwärmung schmelzen und große Mengen des Treibhausgases Methan freisetzen könnte. Manche Forscher sehen bereits erste Anzeichen dafür. "Aber für belastbare Aussagen wissen wir viel zu wenig", hält Ole Humlum dagegen. Erst seit wenigen Jahren laufe eine systematische Forschung mit Bohrungen in den Permafrost hinein und einem Netz von Messpunkten rund um den Nordpol. ...
10. Deutschlandfunk v. 17.12.2004: Unbekannte im Polarkreis
If the facts change, I'll change my opinion.
KlimaNotizen will dazu beitragen, dass die öffentlichen Diskussionen zur allgemeinen Klimaentwicklung ausgewogener werden.
Die Inhalte angeführter Links und Quellen werden von diesen selbst verantwortet.
Diese Site dient ausschließlich wissenschaftlichen Zwecken