• Fast-melting alpine permafrost may contr

    From ScienceDaily@1:317/3 to All on Mon Mar 14 22:30:38 2022
    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

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