Thawing permafrost releases greenhouse gas from depth
After 2020 heat wave: methane concentrations in Siberian air point to gas emission from limestone

Date:
August 2, 2021
Source:
University of Bonn
Summary:
Geologists compared the spatial and temporal distribution of methane
concentrations in the air of northern Siberia with geological
maps. The result: the methane concentrations in the air after last
year's heat wave indicate that increased gas emissions came from
limestone formations.



FULL STORY ==========================================================================
In a study led by the University of Bonn (Germany), geologists compared
the spatial and temporal distribution of methane concentrations in the
air of northern Siberia with geological maps. The result: the methane concentrations in the air after last year's heat wave indicate that
increased gas emissions came from limestone formations. The study is
published in the journal Proceedings of the National Academy of Sciences (PNAS).


==========================================================================
What effect did the heat wave of summer 2020 have in Siberia? In a study
led by the University of Bonn (Germany), geologists compared the spatial
and temporal distribution of methane concentrations in the air of northern Siberia with geological maps. The result: the methane concentrations in
the air after last year's heat wave indicate that increased gas emissions
came from limestone formations. The study is published in the journal Proceedings of the National Academy of Sciences (PNAS).

Permanently frozen permafrost soils cover large areas of the northern hemisphere, especially in northern Asia and North America. If they
thaw in a warming world, this can pose dangers, because CO2 and
methane are released during thawing -- and amplify the anthropogenic
greenhouse gas effect. "Methane is particularly dangerous here because
its warming potential is many times higher than that of CO2," explains
Prof. Dr. Nikolaus Froitzheim from the Institute of Geosciences at the University of Bonn. Pessimists therefore already spoke of an imminent
"methane bomb." However, most previous projections showed that greenhouse
gases from thawing permafrost will contribute "only" about 0.2 degrees
Celsius to global warming by 2100. This assumption has now been challenged
by a new study by Nikolaus Froitzheim and his colleagues Jaroslaw Majka (Krakow/Uppsala) and Dmitry Zastrozhnov (St. Petersburg).

Most previous studies only dealt with emissions from the decay of plant
and animal remains in the permafrost soils themselves. In their current
study, researchers led by Nikolaus Froitzheim made a comparison between
methane concentrations in Siberian air, determined by satellite-based spectroscopy, and geological maps. They found significantly elevated concentrations in two areas of northern Siberia -- the Taymyr Fold Belt
and the rim of the Siberian Platform. What is striking about these
two elongated areas is that the bedrock there is formed by limestone
formations from the Paleozoic era (the period from about 541 million
years ago to about 251.9 million years ago).

In both areas, the elevated concentrations appeared during the extreme
heatwave in summer 2020 and persisted for months after. But how did the additional methane occur in the first place? "The soil formations in the observed areas are very thin to nonexistent, making methane emission from
the decay of organic soil matter unlikely," says Niko Froitzheim. He and
his colleagues therefore suggest that fracture and cave systems in the limestone, which had been clogged by a mixture of ice and gas hydrate,
became permeable upon warming. "As a result, natural gas being mainly
methane from reservoirs within and below the permafrost can reach the
Earth's surface," he says.

The scientists now plan to investigate this hypothesis by measurements
and model calculations to find out how much and how fast natural gas may
be released. "The estimated amounts of natural gas in the subsurface of
North Siberia are huge. When parts of this will be added to the atmosphere
upon thawing of the permafrost, this could have dramatic impacts on the
already overheated global climate," emphasizes Niko Froitzheim.

The universities of Bonn, Uppsala and AGH Krakow as well as the Karpinsky Russian Geological Research Institute in St. Petersburg were involved
in the study.

========================================================================== Story Source: Materials provided by University_of_Bonn. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Nikolaus Froitzheim, Jaroslaw Majka, Dmitry Zastrozhnov. Methane
release
from carbonate rock formations in the Siberian permafrost
area during and after the 2020 heat wave. Proceedings of the
National Academy of Sciences, 2021; 118 (32): e2107632118 DOI:
10.1073/pnas.2107632118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210802160702.htm

--- up 12 weeks, 3 days, 22 hours, 45 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)