Fast-melting alpine permafrost may contribute to rising global
temperatures
Date:
March 14, 2022
Source:
University of Arizona
Summary:
Using lake sediment in the Tibetan Plateau, a team of researchers
was able to show that permafrost at high elevations is more
vulnerable than arctic permafrost under projected future climate
conditions.
FULL STORY ==========================================================================
From the ancient sludge of lakebeds in Asia's Tibetan Plateau, scientists
can decipher a vision of Earth's future. That future, it turns out,
will look very similar to the mid-Pliocene warm period -- an epoch
3.3 million to 3 million years ago when the average air temperature
at mid-latitudes rarely dropped below freezing. It was a time when
permanent ice was just beginning to cling to the northern polar regions,
and mid-latitude alpine permafrost -- or perpetually frozen soil --
was much more limited than today.
========================================================================== Global permafrost today contains a whopping 1,500 trillion grams of
carbon.
That's twice as much as what's stored in the atmosphere. Alpine
permafrost, which is found closer to the equator at high elevations,
isn't as well studied as arctic permafrost but contains 85 trillion grams
of carbon. When melted, it can release carbon dioxide and methane --
greenhouse gases that influence global temperature.
Alpine permafrost is expected to melt at a faster rate than arctic
permafrost under current global warming conditions, according to new
research published in Nature Communications, and this may contribute
even more to rising global temperatures.
"Atmospheric carbon dioxide concentrations today are similar, or maybe
even higher, than the mid-Pliocene because of the burning of fossil
fuels, and so scientists point at that time period as an analog for our
current and near- future climate," said paper co-author Carmala Garzione,
dean of the University of Arizona College of Science. "We're not feeling
the full effects of the rise in atmospheric carbon dioxide yet because
our Earth system takes time to adjust." "We wanted to estimate the
stability of modern permafrost globally in a warmer- than-today climate scenario," said Feng Cheng, the paper's lead author and a professor at
Peking University in China. Cheng formerly worked with Garzione as a postdoctoral fellow. "Our findings were very surprising and highlight
the fact that we need to put more effort into monitoring the stability
of the permafrost in the alpine region." The team used carbonate -- a
family of minerals -- that formed in a Tibetan Plateau lake to estimate temperatures during the Pliocene period (5.3 to 2.6 million years ago) and
the Pleistocene period (between 2.6 million and 11,700 years ago). When
algae grows in lakes, it absorbs carbon dioxide from the water and, as
a result, decreases lake acidity. That decrease drives the lake to form
finely grained carbonate minerals that settle at the lake bottom. The
atoms in that carbonate reflect the temperature at which the carbonate
formed, and can be used like a time-traveling thermometer.
The Tibetan Plateau, which sits at an elevation over 15,400 feet, is
the largest alpine permafrost region on Earth, but others can be found
in the Mongolian Plateau in central Asia, the Canadian and American
Rocky Mountains, the southern stretches of the Andes, and other mountain
ranges worldwide at elevations where the air temperature is consistently
below freezing.
The team also modeled the paleoclimate on Earth during the Pliocene. They
found that not only was the average temperature of much of the Tibetan
Plateau above freezing in the Pliocene, but the same was true for many
of the alpine regions across the globe.
Ultimately, the modeling suggests that under current levels of atmospheric carbon dioxide, 20% of arctic permafrost land area and 60% of alpine
permafrost land area will be lost in the future. High altitude alpine
regions are more sensitive than high latitude arctic regions to warming
under higher atmospheric carbon dioxide conditions.
"The Pliocene is an important period as an ancient analog for how Earth
will adjust to the carbon dioxide that humans have already released to the atmosphere," Garzione said. "We need better and broader studies of the vulnerability of alpine regions under global warming scenarios. There's
been a lot of focus on the stability of arctic permafrost, because it
covers more land area and contains a huge reservoir of organic carbon
trapped in permafrost, but we also need to be aware that alpine regions
stand to lose more permafrost proportionally and are important in
understanding of potential carbon release under global warming scenarios."
========================================================================== Story Source: Materials provided by University_of_Arizona. Original
written by Mikayla Mace Kelley. Note: Content may be edited for style
and length.
========================================================================== Journal Reference:
1. Feng Cheng, Carmala Garzione, Xiangzhong Li, Ulrich Salzmann,
Florian
Schwarz, Alan M. Haywood, Julia Tindall, Junsheng Nie, Lin
Li, Lin Wang, Benjamin W. Abbott, Ben Elliott, Weiguo Liu,
Deepshikha Upadhyay, Alexandrea Arnold, Aradhna Tripati. Alpine
permafrost could account for a quarter of thawed carbon based on
Plio-Pleistocene paleoclimate analogue.
Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-29011-2 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220314181454.htm
--- up 2 weeks, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)