Historical climate effects of permafrost peatland surprise researchers


Date:
June 17, 2021
Source:
University of Helsinki
Summary:
Peatlands are an important ecosystem that contribute to the
regulation of the atmospheric carbon cycle. A multidisciplinary
group of researchers investigated the climate response of a
permafrost peatland located in Russia during the past 3,000
years. Unexpectedly, the group found that a cool climate period,
which resulted in the formation of permafrost in northern peatlands,
had a positive, or warming, effect on the climate.



FULL STORY ========================================================================== Peatlands are an important ecosystem that contribute to the regulation of
the atmospheric carbon cycle. A multidisciplinary group of researchers,
led by the University of Helsinki, investigated the climate response
of a permafrost peatland located in Russia during the past 3,000
years. Unexpectedly, the group found that a cool climate period, which
resulted in the formation of permafrost in northern peatlands, had a
positive, or warming, effect on the climate.


==========================================================================
The period studied, which began 3,000 years ago, is known as a climate
period of cooling temperatures. The climate-related effect of permafrost formation brought about by the cooling was investigated particularly by analysing the ancient plant communities of the peatland, using similarly analysed peatland data from elsewhere in Russia, Finland and Sweden as
a comparison.

"Our studies demonstrated that the effect of permafrost peatlands on the climate can be difficult to predict. Studies encompassing longer periods
of time are valuable, as they help us to understand future change,"
says researcher Minna Va"liranta from the Faculty of Biological and Environmental Sciences, University of Helsinki.

The study linked data on ancient plant communities with information about
how rapidly contemporary northern peatlands bind and sequester carbon,
or how rapidly peat accumulates. In addition, data on carbon emissions
to the atmosphere were utilised. These factors constitute what is known
as the peatland's radiative forcing, which has either a warming effect on
the climate when the peatland emits more carbon into the atmosphere than
it binds from it, or a cooling effect when the peatland serves as a carbon
sink and binds more carbon from the atmosphere than it releases into it.

Rather unexpectedly, the researchers found that a cool climate period,
which resulted in the formation of permafrost in northern peatlands,
had a warming effect on the climate. This was caused by the habitats
of the plant communities living in the permafrost peatlands drying
up, after which they no longer bound carbon from the atmosphere very effectively. In fact, a reverse process took place in which previously
formed peat, which used to store carbon, was released back into the
atmosphere as a result of accelerated decomposition and degradation.

Moreover, the permafrost processes even created bare peat surfaces
entirely devoid of vegetation in the peatlands. Such surfaces emit, in
addition to carbon dioxide, also nitrous oxide, a potent greenhouse gas,
into the air.

These emissions clearly increased the peatland's warming effect on
the atmosphere.

Other typical peatland surfaces do not emit significant quantities of
nitrous oxide into the atmosphere, which is why such emissions have been considered insignificant. The study demonstrated that such bare peat
surfaces have previously been much more prevalent. However, it appears
that this type of surfaces have regained their plant cover over time, consequently reducing the extent of bare surfaces.

Climate change can drive the development of permafrost peatlands in
unforeseen directions "This was the first study in which the long-term development of bare peat surfaces was investigated. Consequently, further research is needed in order to better forecast the fate of such surfaces typical of permafrost peatland and the future development of permafrost peatlands in general," says Va"liranta.

The climate effects of the greenhouse gas emissions of the peatlands
studied were associated with changes in plant life, which, in turn,
are determined by the peatland's hydrological balance. The researchers
predict that the thawing of the permafrost may lead to rising peatland
water levels and, therefore, substantial methane emissions that will
warm the climate further. At the same time, global warming is thought to accelerate carbon intake from the atmosphere due to the intensification of
the basic production processes of plants. In other words, photosynthesis
is binding carbon dioxide from the air with increasing efficiency.

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


========================================================================== Journal Reference:
1. Minna Va"liranta, Maija E. Marushchak, Juha-Pekka Tuovinen, Annalea
Lohila, Christina Biasi, Carolina Voigt, Hui Zhang, Sanna Piilo,
Tarmo Virtanen, Aleksi Ra"sa"nen, Dmitry Kaverin, Alexander
Pastukhov, A.

Britta K. Sannel, Eeva-Stiina Tuittila, Atte Korhola, Pertti J.

Martikainen. Warming climate forcing impact from a sub-arctic
peatland as a result of late Holocene permafrost aggradation and
initiation of bare peat surfaces. Quaternary Science Reviews,
2021; 264: 107022 DOI: 10.1016/j.quascirev.2021.107022 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/06/210617133751.htm

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