Ice is melting everywhere—and at an accelerating
rate. Rising global temperatures are lengthening melting seasons,
thawing frozen ground, and thinning ice caps and glaciers that,
in some cases, have existed for millennia. These changes are
raising sea levels faster than earlier projections by scientists,
and threatening both human and wildlife populations.
Since the industrial revolution, human activity has released
ever-increasing amounts of carbon dioxide and other greenhouses
gases into the atmosphere, leading to gradual but unmistakable
changes in climate throughout the world—especially at the
higher latitudes. Average surface temperatures in the Arctic
Circle have risen by more than half a degree Celsius (0.9 degrees
Fahrenheit) per decade since 1981. The extent of Arctic sea ice
cover has decreased by 7-9 percent per decade. And the three
smallest extents of summer ice ever seen there have all occurred
since 2002. According to the latest forecasts, the Arctic could
be ice-free in the summer by the end of this century.
The Arctic melt season has lengthened by 10–17 days,
shrinking the amount of ice buildup that remains from year
to year. As
sea ice thins and recedes from coastlines, indigenous hunters
and fishers are finding themselves cut off from traditional
hunting grounds. Coastal communities face more violent and
weather, rising sea levels, and diminishing access to food
sources. Polar bears, unable to cross thin or nonexistent
ice to hunt
seals, will soon face a severely reduced food source. Scientists
fear that with continued melting, the bears may become extinct
by the end of the century. Seals, walruses, and seabirds
will also lose key feeding and breeding grounds along the ice
Arctic permafrost has warmed by up to 2 degrees Celsius in recent
decades, with soils thawing to greater depths. By the end of
this century, the southern permafrost boundary is projected to
shift northward by several hundred kilometers, changing regional
vegetation patterns. An estimated 15 percent of the Arctic tundra
has already been lost since the 1970s—an area roughly three
times the size of California. As permafrost thaws, unstable ground
shifts or subsides, damaging buildings, roads, pipelines, and
other infrastructure in areas such as Alaska.
The Greenland ice sheet is the largest land ice mass in the
Northern Hemisphere. It holds enough fresh water to raise
sea level by 7.2 meters (24 feet) if it were to melt completely,
a result expected if the regional temperature rises 3 degrees
Celsius. Scientists project that concentrations of greenhouse
gases will be high enough by 2100 to push temperatures past this
threshold. Satellite data show Greenland’s ice has been
melting at higher elevations every year since 1979. A conservative
estimate of annual ice loss from Greenland is 50 cubic kilometers
(12 cubic miles) per year, enough water to raise the global sea
level by 0.13 millimeters a year.
The Amundsen Sea region in the West Antarctic has experienced
some of the world’s greatest temperature change, with annual
temperatures up 2.5 degrees Celsius over the past 60 years. The
glaciers flowing into the sea from the Antarctic continent have
been getting thinner for the past 15 years, and ice shelves in
the region have decreased by more than 13,500 square kilometers
since the 1970s. Since the collapse of the Delaware-sized Larsen
B Ice Shelf in 2002, satellites have shown a two- to sixfold
increase in the speed of glaciers flowing toward the former ice
shelf. While most glaciers typically move a few centimeters to
several hundred meters annually, these glaciers are currently
moving as much as 1.5 kilometers each year.
Ice melting is not limited to the poles. According to glaciologist
Lonnie Thompson of Ohio State University, all but 13 of the 2,000
glaciers in southeast Alaska are retreating. Montana’s
Glacier National Park may have no glaciers left by 2030, and
the ice cap on Tanzania’s Kilimanjaro may disappear completely
In South America, Andean glaciers have been melting three
times faster in recent years than they were in the mid-20th
Bolivia’s Chacaltaya, once home to the world’s highest
ski slope, is estimated to be a mere 2 percent of its former
size. It lost two thirds of its mass in the 1990s alone and may
disappear completely by 2010. Shrinking glaciers may mean a loss
of power in Peru, where 70 percent of electricity comes from
hydroelectric turbines powered by the annual runoff from glaciers.
In fact, millions of people living in Asia and South America
rely on glacial runoff for drinking water and irrigation. If
the glaciers disappear, severe water shortages are sure to
follow. Meanwhile, rapidly filling glacial lakes in both the
Himalayas threaten to break their banks and flood towns below.
In Europe, shrinking glaciers and snow cover in the Alps
are undermining the continent’s ski and tourism industries.
By 2025, Alpine glaciers are likely to contain only half their
1970s volume, dwindling to 5 percent by the end of the century.
Pollution from European cities does not help the situation: scientists
have measured black carbon concentrations atop these mountains
high enough to double the area’s absorption of sunlight.
Such widespread glacial melting has local as well as global
effects. Global sea level has risen 10–20 centimeters in the past
century. According to the Intergovernmental Panel on Climate
Change, up to 1 meter of sea level rise is projected by 2100,
with half the rise attributed to melting ice and half to thermal
expansion. As sea level rises, inundation and loss of coastal
land will force millions of people to relocate.
Warming and melting could force local plant and animal species
to adapt or relocate—an increasingly difficult proposition
as wildlife habitats are fragmented by expanding human populations.
Changes to the food base of ecosystems, such as decreases of
algae and plankton in the Arctic Ocean, could have a ripple effect
all the way up to the top predators, including the people who
hunt and fish these animals.
Most disturbing, many of the effects of ice melting are self-reinforcing.
As ice disappears, land and open water are exposed. When sunlight
strikes ice and snow, approximately 80 percent is reflected
back into space and 20 percent is absorbed as heat. The opposite
true for land and open water—20 percent is reflected and
80 percent is absorbed. This decrease in reflectivity, or albedo,
creates a positive feedback loop, perpetuating the temperature
rise and ice melting. Additionally, soot from faraway sources
has darkened snow and ice, further decreasing albedo.
Melt water on top of glaciers and ice sheets contributes
to fracturing and destabilization of the ice masses and
as the water lubricates the underside of the ice. Thawing tundra
releases trapped carbon dioxide and methane from newly created
wetlands, contributing to further warming. Finally, increased
fresh water from melting glaciers and sea ice could alter ocean
circulation patterns and destabilize regional climate patterns,
perhaps weakening the Gulf Stream and North Atlantic currents
that moderate Europe’s climate. Warmer waters may also
decrease the ocean’s ability to act as a carbon sink. If
no action is taken to halt global warming, these positive feedbacks
could quickly send climate change spiraling out of control.
Melting ice is a harbinger of more change to come. Perhaps
in the future, children will look back on the fabled polar
of the icy North Pole the way we imagine woolly mammoths
in the last Ice Age. Only this time, we will know who
is to blame.