National Geographic USA - 09.2019

870 gigatons

of carbon

in atmosphere

1,600 gigatons

in permafrost

Active layer

Permafrost

A LANDSCAPE

REVOLUTION

As ice buried within frozen ground melts, the

meltwater moves through the permafrost, thawing it

further and causing the ground above it to slump.

Ponds form and later drain, hastening the collapse of

even more frozen soils. The process is called abrupt

thaw, and it’s accelerating the release of trapped

carbon—and visibly changing the Arctic.

BURNING TUNDRA

Tundra fires, once rare, are becoming

more common as a warming climate

greens the Arctic. Fires thaw the top

layer of soil and rapidly degrade

the permafrost below.

How polygonal permafrost forms—and thaws

Growing ice wedges push soil

upward, forming

polygonal patterns.

Water fills in the cracks, which freeze

and expand, form-

ing ice wedges.

JASON TREAT, MATTHEW W. CHWASTYK, AND RYAN WILLIAMS, NGM STAFF SOURCES: DAVID OLEFELDT AND OTHERS, NATURE COMMUNICATIONS, 2016;

MERRITT TURETSKY AND OTHERS, UNIVERSITY; TED SCHUUR, NORTHERN ARIZONA UNIVERSITY; EPANATURE, 2019; RÓISÍN COMMANE, COLUMBIA

JASON TREAT, RYAN WILLIAMS, AND EVE CONANT, NGM STAFFART: TOMÁŠ MÜLLER. SOURCES: KEN TAPE AND ANNA LILJEDAHL, UNIVERSITY OF ALASKA FAIRBAN

Greater than 400

300-400

200-299

100-199

Less than 100

GradualthawAbruptthaw

Carbon content (in tons per acre)in permafrost susceptible to:

Powering 43.5 average U.S. homes for a year releases

about 400 tons of carbon.

ARCTIC OCEAN

ATLANTIC OCEAN

PACIFIC

OCEAN

Hudson

Bay

Gulf of

Alaska

BaffinBay

LabradorSea

BeaufortSea

E. SiberianSea

Bering Sea OkhotskSea of

Gre

enl

an

d^ S

ea

Ka

ra

Se

a

BarentsSea

No

rw

egi

an^

Sea

Ambarchik Bay

BaikalLake

PLEISTOCENEPARK

Cherskiy

Fairbanks

Kaktovik

Newtok

Lakselv

S I B E R I A

ElizabethQueen

Islands

Parr

y^ Is.

Baffin

Isla

nd

Banks I.

Victoria I.

Batagaikacrater

Broo

ks^ Ra.

NORTH

AMERICA

A

S

I

A

EU

R

O

P

E

CANADA

ICELAND

(U.S.)

NORWAY

DENMARK

RUSSIA

SW

EDE

N

FINL

AND

GREE

NLA

ND

(KALA

ALLIT

NUN

AAT)

(DEN

MAR

K)

ALASKA

North Pole

ARCTIC CIR

CLE

0 °

60 °

30 °E

30 °W

60 °

60 °

90 ° 90 °

120 °

120 °

150 °W 180 ° 150 °E

The active layer freezes in winter,

creating cracks

deep in the soil.

THE THAW SPEEDS UP

The unexpectedly rapid collapse of ice-rich permafrost

in the Arctic could pump billions of additional tons of

methane and carbon dioxide into the atmosphere every

year—a threat that has yet to be fully accounted for in

climate models. Scientists are discovering destabilized

landscapes where permafrost that once thawed a few

inches a year can now abruptly thaw up to 10 feet within

days or weeks, creating wetlands in once frozen regions

and accelerating emissions from up to 1,600 gigatons

of carbon still locked underground.

Thawing fast and slow

Twenty percent of permafrost is ice rich and at risk of abrupt

thaw, which could double

the amount of greenhouse

gases released.

SCENES OF THAWING