small plots, track others remotely, and draw
inferences about the rest—unlike Arctic sea ice,
which can be measured in its entirety by satel-
lite. “You can go online and track exactly what
happened to sea ice,” said permafrost expert Ted
Schuur of Northern Arizona University. “With
permafrost, we’re barely looking. We barely have
the tools to measure what’s happening.”
One type of permafrost has researchers par-
ticularly concerned: the 20 percent or so that
contains immense deposits of solid ice. Some
of that ice formed when water percolated down
through soils and froze as it hit permafrost;
some was created over thousands of years
during Arctic winters, when the ground con-
tracted and cracked into polygonal patterns. In
spring, meltwater filled those crevices, which
later refroze. Over time the buried ice grew into
massive wedges enveloped by permafrost soil.
Duvanny Yar is shot through with them.
Such a structure can unravel swiftly. When
permafrost disintegrates, buried ice melts too.
As water drains, it transports heat that spreads
the thawing, and it leaves behind tunnels and
air pockets. The ground sinks to fill those
cavities, creating surface depressions that fill
with rain and meltwater. The water deepens
the pools and chews through their icy banks,
until puddles grow to ponds and ponds become
lakes. That causes more ground to warm and
more ice to melt.
“Abrupt thaw,” as scientists call this process,
changes the whole landscape. It triggers land-
slides; on Banks Island in Canada, scientists doc-
umented a 60-fold increase in massive ground
slumps from 1984 to 2013. It topples forests.
Merritt Turetsky, an ecologist with Canada’s
University of Guelph, has tracked abrupt thaw
in a black spruce forest near Fairbanks for the
past 15 years. Flooding there, she has found, is
destabilizing tree roots and trunks. Turetsky sus-
pects all the trees in her “drunken forest” will tip
over soon and get swallowed by new wetlands.
“There are still little pockets of land, but you
have to wade through some pretty wet spots to
reach them,” she said.
All permafrost thaw leads to greenhouse gas
emissions. But standing water accelerates the
threat. The gas that bubbles from the oxygen-
deprived mud under ponds and lakes is not
only carbon dioxide but also methane, which
is 25 times as potent a greenhouse gas as CO 2.
Ecologist Katey Walter Anthony of the Univer-
sity of Alaska Fairbanks has been measuring
the methane coming from Arctic lakes for two
decades. Her latest calculations, published in
2018, suggest that new lakes created by abrupt
thaw could nearly triple the greenhouse gas
emissions expected from permafrost.
It’s not clear how much of this message has
reached policymakers. Last October the IPCC
unveiled a new report on the more ambitious of
two temperature goals adopted at the 2015 Paris
conference. The planet already has warmed by
about one degree Celsius (1.8 degrees Fahren-
heit) since the 19th century. Capping global
warming at 1.5 degrees Celsius rather than two
degrees, the report said, would expose 420
million fewer people to frequent extreme heat
waves, and it would halve the number of plants
and animals facing habitat loss. It also might
save some coral reefs—and as much as 770,000
square miles of permafrost. But to achieve the
1.5-degree goal, according to the IPCC, the world
would have to cut greenhouse gas emissions
45 percent by 2030, eliminate them completelyTHE THREAT BELOW 91