THAW SLUMPS
When permafrost thaws near a hillside
or a stream or river, it can trigger
a landslide. These so-called thaw slumps
quickly expose more permafrost,
rapidly accelerating further thawing.SPREADING LAKES
Lakes that once froze solid are now
partially liquid in winter and widening
as permafrost thaws. The warmth allows
microbes to feed on organic material
year-round, releasing greenhouse gases.New foragers
As shrubs spread out and
grow taller, they attract large
herbivores such as moose, which in turn affect vegeta-
tion growth patterns.New life in the waterWarmer water and new
aquatic habitats may
allow fish such as salmon
to become established in the Arctic.Ice wedgesFormed over millennia, as soil
froze and cracked in winter
and filled with water in spring,
they’re now degrading in as little as a few years.Permafrost polygons
The distinctive,
puzzle-like pattern of
some Arctic landscapes is shaped by ice wedges
beneath the surface.Active layer
The top layer of soil thaws
and refreezes annually. This
layer is deepening across the Arctic as permafrost turns
into unfrozen soil.Wedges melt, the soil above them
collapses, and
water accumulates.The active layer grows, wedges
shrink, and the
landscape drains.BEAVER PONDS
A warming tundra has more and larger
shrubs, which attract beavers. They dam
up creeks, creating new ponds and lakes.
That speeds up permafrost collapse
and alters the landscape.KS