Siberia's permafrost erosion has been worsening for years
Coastal erosion in the Lena Delta is contributing to the greenhouse
effect

Date:
September 16, 2020
Source:
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine
Research
Summary:
The Arctic is warming faster than any other region on the planet. As
a result, permafrost that is thousands of years old is now being
lost to erosion. As measurements gathered on the Lena River show,
the scale of erosion is alarming.



FULL STORY ==========================================================================
The Arctic is warming faster than any other region on the planet. As a
result, permafrost that is thousands of years old is now being lost to
erosion. As measurements gathered on the Lena River by AWI experts show,
the scale of erosion is alarming: every year, roughly 15 metres of the riverbanks crumble away. In addition, the carbon stored in the permafrost
could worsen the greenhouse effect.


========================================================================== Today, the permafrost soils found on the Arctic coasts of Canada, Russia
and Alaska, frozen for thousands of years, are increasingly eroding away
due to the effects of waves and river currents -- especially because the
warm season there is steadily growing longer. As experts from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI)
have determined, this thawing has now taken on enormous proportions. By conducting a detailed analysis of historical satellite images from
Siberia, Matthias Fuchs and his team were able to show that permafrost
erosion in the Lena Delta has steadily worsened since the 1960s. Whereas
in the 1960s the river, at a width of ca. 1.7 kilometres, gnawed away an average of five metres of land per year, between 2015 and 2018 that number
rose to nearly 16 metres. In total the banks -- more in some places,
less in others -- lost between 322 and 679 metres from 1965 to 2018.

The researchers focused their efforts on the 1.5-kilometre-long
Sobo-Sise Cliff, a steep yedoma cliff from which permafrost plummets
into a branch of the Lena River. At its highest point, it is 27 metres
tall -- as tall as a several- storey house. As Matthias Fuchs explains,
"Major quantities of permafrost have been eroding away across the Arctic
for many years now. Nevertheless, the Sobo- Sise Cliff is definitely
a hotspot. There are very few other regions where the loss of land is
so substantial." The worrisome aspect: the fact that the thawing and
permafrost loss have intensified so massively in the last several years.

Fuchs and his colleagues not only analysed satellite data; they also
took a closer look at how much carbon and nitrogen are released every
year by the erosion. The cliff's permafrost, which is ca. 50,000 years
old and formed during the last Ice Age, consists of 88 percent ice. The remainder is mainly peat, silt and sand. Especially the peat, which
consists of partially decomposed ancient mosses and sedges, contains a
great amount of carbon and nitrogen, formerly stored in the plants. The
AWI experts collected soil samples on site and then analysed their
carbon and nitrogen content in the lab. "It's amazing that the Sobo-Sise
Cliff contains so much organic material, even though it's predominantly composed of ice. On average, we find roughly 26 kilograms of carbon and
two kilograms of nitrogen per cubic metre." That means from 2015 to 2018
alone, ca. 15,000 metric tons of carbon and at least 1,000 metric tons
of nitrogen landed in the Lena River, where they were washed away.

"Carbon and nitrogen are important nutrients for microorganisms,"
Fuchs explains. "Due to the erosion and thawing of permafrost,
microorganisms now enjoy access to both." And this can have a number of consequences. When the microbes break down the carbon, they release carbon dioxide -- just like we humans do when we breathe. When that happens,
the loss of permafrost worsens the greenhouse effect by 're-mobilising'
carbon that was previously stored away. In addition, the intensive input
of carbon and nitrogen in the Lena is changing the nutrient supply in
its waters. "This could significantly influence, or even transform,
the river's natural food webs," says Fuchs.

The researchers can't yet say precisely what the consequences will be. To
do so, in future studies they'll need to examine the nutrient flows in,
and the biology of, the Lena river in more detail. But with their latest efforts and their assessment of the permafrost erosion, which has just
been published in the journal Frontiers in Earth Science, the AWI experts
have provided an important basis for additional investigations.


========================================================================== Story Source: Materials provided by Alfred_Wegener_Institute,_Helmholtz_Centre_for_Polar_and
Marine_Research. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Matthias Fuchs, Ingmar Nitze, Jens Strauss, Frank Gu"nther,
Sebastian
Wetterich, Alexander Kizyakov, Michael Fritz, Thomas Opel,
Mikhail N.

Grigoriev, Georgii T. Maksimov, Guido Grosse. Rapid
Fluvio-Thermal Erosion of a Yedoma Permafrost Cliff in the
Lena River Delta. Frontiers in Earth Science, 2020; 8 DOI:
10.3389/feart.2020.00336 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200916113452.htm

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