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Title: Arctic Glaciers Face 'Terminal' Decline As Microbes Accelerate Ice
Melt

Link: https://news.slashdot.org/story/25/08/15/2027...

Scientists in Svalbard warn Arctic glaciers are in "terminal" decline, with
microbe-driven biological darkening accelerating ice melt and potentially
triggering major climate feedback loops. The Guardian reports: Recent
research implicates snow and ice-dwelling microbes in positive feedback loops
that can accelerate melting. With more than 70% of the planet's freshwater
stored in ice and snow -- and billions of lives sustained by glacier-fed
rivers -- this has profound implications everywhere. Yet not all polar
microbes amplify global heating. Emerging evidence suggests that certain
populations are -- for now -- applying a brake to methane emissions. [...]
Microbes that live in surface ice and snow produce dark-colored pigments to
harness sunlight and shield themselves from damaging UV light. They also trap
dark-colored dust and debris. Together, these factors darken snow and ice,
causing it to absorb more heat and melt faster -- a process known as
"biological darkening." Microbes also respond to global changes, such as
increased nutrients from air pollution, wildfire smoke or wind-blown dust
from receding glaciers and expanding drylands. "The snowpack chemistry is now
different to preindustrial era snow," Edwards says. Rising temperatures and
longer melt seasons caused by global heating further accelerate the growth of
ice-darkening microbes. Together, these factors have the potential to trigger
an amplifying positive feedback loop: ice-darkening microbes nudge up
temperatures and accelerate melt, exposing more nutrient-rich debris that
encourage the growth of yet more microbes, which darken the surface further
still. Each summer, a biologically darkened zone, visible from space,
covering at least 100,000 sq km, appears on the south-western part of the
Greenland ice sheet. According to a 2020 study, microbes there are
responsible for 4.4 to 6.0-gigatons of runoff, representing up to 13% of
total melt, from an ice mass that holds enough water to raise global sea
levels by more than 7 meters. These effects are acknowledged in IPCC reports
but not yet incorporated into climate projection models. Across the European
Alps, Himalayas, central Asia and beyond, at least 2 billion people depend on
glacial meltwater for drinking water, agriculture and hydropower. Yet even if
the world meets Paris targets, half these glaciers will not survive this
century.

Read more of this story at Slashdot.

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