Photo: Jon Aars/NPI
Melting sea ice may influence global patterns of ocean
Ice in the Sea
circulation; increasing melting of sea ice in combina-
tion with increased freshwater influx from melting
glaciers and ice sheets may result in major changes to
ocean circulation.
In the last three decades there have been declines in Sea ice is vital habitat for organisms ranging from tiny
the extent of Arctic sea ice of 8.9 per cent per decade bacteria, algae, worms and crustaceans to sea birds,
in September and 2.5 per cent per decade in March. penguins, seals, walrus, polar bears and whales. Some
The retreat of sea ice is particularly noticeable along sea-ice dependent animals are already at risk and the
the Eurasian coast. Sea-ice thickness has declined predicted declines in sea ice may lead to extinctions.
in parts of the Arctic since the 1950s and both the Shrinking sea ice is forcing coastal Arctic indigenous
extent and the thickness of Arctic sea ice are pro- people to adopt different methods of travel and to
jected to continue to decline with the possibility of change their harvesting strategies. Further loss of sea
a mainly ice-free Arctic Ocean in summer by 2100 ice threatens traditional livelihoods and cultures.
or earlier. Increasing extent of open water in polar regions will pro-
Antarctic sea ice is projected to decline in extent at a vide easier access to economic activities such as explora-
similar rate as in the Arctic, but it is not expected to tion and exploitation of petroleum resources, and ship-
thin as much. borne tourism, with accompanying benefits and risks.
Declines in the extent of sea ice accelerate the rate The Northern Sea Route along Russia’s Arctic coast is
of melting because more sunlight is reflected by the currently navigable for 20–30 days annually. Predictions
bright surface of snow and sea ice than by the dark sur- are that by 2080 the navigable period will increase to
face of open water. This is the same feedback process 80–90 days. This, combined with the potential of future
that results from decline of snow-cover extent on land. opening of the Northwest Passage through Canada’s wa-
This feedback process affects climate globally. ters, will likely have a major impact on world shipping.
CHAPTER 1 HIGHLIGHTS 11