Arctic Climate Change
3. How will Arctic warming affect the rest of the planet?
- 3.1 How can the reflection of sunlight on snow and ice affect the climate?
- 3.2 How can Arctic warming affect ocean currents?
- 3.3 How could Arctic warming contribute to greenhouse gas emissions?
- 3.4 How can climate change cause sea level rise?
- 3.5 How will changes in the arctic affect the rest of the world?
Arctic warming and its consequences have worldwide implications
The Arctic influences global climate through three major
feedback mechanisms, all of
which could be affected by global warming. These mechanisms
involve the reflection of sunlight, ocean currents, and
greenhouse gas releases.
3.1 How can the reflection of sunlight on snow and ice affect the climate?
As snow and ice are bright white, most of the solar energy
that reaches them is reflected back to space. This is one reason
why the Arctic remains so cold. As air temperatures are
increasing, snow and ice now tend to form later in the autumn
and melt earlier in the spring. The darker land and water
surfaces, which absorb more of the sun's energy, are thus longer
uncovered. This warms the surface further, which, in turn,
causes faster melting, creating a ‘positive feedback loop’ that
amplifies and accelerates the warming trend
(see also Question 4.2).
This is one reason why
climate change is
particularly rapid in the Arctic.
With Arctic warming, forests are projected to expand northward
into areas that are currently
tundra. Forests are darker
than tundra and mask snow cover on the ground, reducing the
reflection of sunlight and further increasing warming. However,
the resulting warming could be partly offset by larger expanses
of forests absorbing more
3.2 How can Arctic warming affect ocean currents?
One of the ways the sun's energy is transported from the
equator toward the poles is through the globally interconnected
movement of ocean waters primarily driven by differences in heat
and salt content, known as the
(“thermo” for heat and “haline” for salt).
At present, the
Gulf Stream current that
flows from the Gulf of Mexico to the coasts of Europe warms the
winds and provides much of the moisture that falls as
precipitation over northwestern Europe. As the water moves
northward, it becomes cooler, saltier and denser. As a result,
surface water eventually becomes heavier than the water(s) below
it and sinks deep into the ocean. This process drives the global
(sometimes referred to as the “conveyor belt”) which pulls warm
waters northward. Part of this global circulation is known as
the Gulf Stream, providing some of the heat that keeps Europe
warmer in winter than regions of North America at the same
latitude. Climate change
could interfere with the formation of the cold, dense water that
drives oceanic circulation and thus bring about further changes
would have several major global effects:
- The decreasing transport of
contained in water from the surface to the deep ocean. This
would contribute to further increases in the level of
CO2 in the
atmosphere and thus to
further warming (due to CO2).
- Regional cooling, for instance in Europe. This could
result from the slowing of the northward transport of heat
by Atlantic Ocean currents, even while the rest of the
planet warms rapidly.
- Reduced sinking of cold, dense water in the Arctic.
This would, in turn, reduce the amount of
nutrients carried back
toward the surface elsewhere in the world that sustain
marine life living near the surface.
3.3 How could Arctic warming contribute to greenhouse gas emissions?
Greenhouse gases are
exchanged between the
atmosphere and Arctic soils
and sediments. These processes can also be affected by global
climate change and in turn
Carbon is currently trapped as
organic matter in the
permafrost (frozen soil) of
the Arctic. During the summer, when the top layer of permafrost
thaws, and plant material on dry land or ponds decomposes,
methane – a very potent
greenhouse gas – and
are released. Higher temperatures lead to an increase in the
rate of decomposition and gas production, and possibly to a
feedback loop with more
warming that results in more releases, causing more warming, and
(see also Question 3.1).
The replacement of Arctic vegetation by denser and faster
growing vegetation from the south could in part offset this
effect through a greater uptake of carbon.
In the Arctic, vast amounts of methane are trapped in
permafrost and in cold
ocean sediments in a solid icy form (as methane hydrates or
clathrates). A rise in temperature within the soil could
initiate the release of methane from permafrost to the
atmosphere. This release is
a less certain outcome of
climate change than the
other emissions discussed here because it would probably require
greater warming and take more time to occur. If such releases
were to take place, the climate impacts could be very large.
Currently, the direct effect of the Arctic Ocean on the level
in the atmosphere is
limited. This is due to the presence of
sea ice that limits the
absorption of CO2 by the water and its uptake by
organisms living near the water surface. A reduced ice cover
could significantly increase the amount of carbon taken up by
the Arctic Ocean. While these changes are likely to be important
regionally, the total area affected is not large enough to
significantly reduce global CO2 concentrations in the
3.4 How can climate change cause sea level rise?
There are 3 100 000 km3 of ice on Arctic lands
around the world, containing enough water to raise the global
sea level by 8m. Most Arctic
ice caps have been in
decline since the early 1960s, with this trend speeding up in
the 1990s. In some areas, the increase in precipitation has
outpaced the melting so that a small number of glaciers,
especially in Scandinavia, have gained mass during some recent
The Greenland Ice Sheet
is the largest area of ice on Arctic lands. Part of the top
layer of ice of this
ice sheet is melting during
summer and the area where this is happening increased by about
16% between 1979 and 2002, (which represents) an area roughly
the size of Sweden.
Projections from global climate models suggest that the
contribution of Arctic
glaciers to global
sea-level rise will accelerate over the next 100 years. By 2100,
the melt of these glaciers will have contributed to a rise of
roughly four to six centimeters or even more according to recent
estimates. In the longer term, the Arctic contribution to global
sea-level rise is projected to be much greater. Some climate
models project that local warming over the
Greenland Ice Sheet will
eventually lead to its complete disappearance, with a resulting
sea-level rise of about seven meters.
Climate change causes sea
level to rise in two ways:
- First, and most significantly, water expands as it
warms, and this is projected to be the largest component of
sea-level rise over the next 100 years.
- Secondly, warming increases melting of
ice sheets, adding to
the amount of water flowing into the oceans.
Global average sea level rose almost 3mm (0.12 inches) per
year during the 1990s. This is about one millimeter (0.04
inches) more per year than during the decades before that.
Global average sea level is projected to rise 10 to 90cm (4 to
36 inches) between 2000 and 2100, with the rise speeding up with
time. Over the longer term, much larger increases in sea level
Sea-level rise is projected to have serious implications for
coastal communities and
river deltas and harbors. A
number of the world’s most populous cities such at Calcutta and
Bangkok will be severely affected.
3.5 How will changes in the arctic affect the rest of the world?
Arctic wildlife resources such as seals, reindeer, birds and
fish have long been sold on world markets. Arctic seas contain
some of the world's oldest and most productive commercial
fishing grounds, which provide significant catches for many
Arctic countries, as well as for the rest of the world.
Moreover, the Arctic has significant oil and gas reserves, and
the mineral reserves in parts of Russia and Canada provide large
quantities of raw materials to the world economy. Marine access
to resources is likely to be enhanced in many places in a warmer
Arctic with less sea ice,
but access by land is likely to be hampered due to a shortening
of the season during which the ground is sufficiently frozen to
Climate-related changes in Arctic
ecosystems will have
consequences not only at local level but also on a global scale
because of the many links between the Arctic and the rest of the
planet. Many species from
around the world migrate to the Arctic in summer and depend on
it for breeding and feeding.
Climate change will alter
some of their habitats
Expansion of the forests towards the North, for instance, may
reduce the size of tundra
areas, which are important breeding grounds for hundreds of
millions of migratory birds. Indeed, a number of bird
species are projected to
lose more than 50% of their breeding area during this century,
including several globally endangered seabird species.