Selected regions
and neighbouring parts of Canada) show a mean annual
North America
thickness change of –0.5 m water equivalent from the
mid 1950s to the mid 1990s, and more than three times
Arctic islands and
as much (–1.8 m water equivalent) from the mid 1990s
mountain ranges
to 2000–2001 based on a sub-sample of 28 glaciers
26
.
By far the largest area of glaciers and ice fields are found in
Canada (about 201 000 km
2
)
88
, followed by Alaska (about
75 000 km
2
)
89
with about 700 km
2
in the rest of the USA
90
.
Glaciers and ice fields are concentrated in the High Arctic
(Figure 6B.12) and western cordillera.
Glaciers reached their Little Ice Age maximum extent
between the early 18th and late 19th century in Alaska
91

and in the mid to late 19th century in Canada and the
continental USA
92
. Subsequently, a general retreat of
glaciers developed, particularly at lower elevations and
southern latitudes
91
. There are exceptions to this trend:
southern cordilleran and Alaskan coastal glaciers slowed
their retreat or advanced in response to cooler summers
and heavier snowfall in the 1950s to 1970s
93,94
. Since that
time the glaciers have continued to retreat and the re-
treat has accelerated since the 1970s. In the western cor-
dillera they have now lost about 25 per cent of their area
since the Little Ice Age
90,95
. In the northwest continental
Figure 6B.12: Glacier shrinking on Cum-
berland Peninsula, Baffin Island, Cana-
USA and southwest Canada, accelerated retreat coincid-
dian Arctic. A new glacier inventory based
ed with a shift in atmospheric circulation patterns that
on satellite data shows that the glacier
occurred during 1976–1977
96,97
.
cover reduced by about 22 per cent be-
tween the Little Ice Age (LIA) maximum
Airborne laser altimetry studies on 67 glaciers (repre-
extent and 2000.
senting about 20 per cent of the glacierized area in Alaska Source: Data and figure from F. Svoboda, University of Zurich, Switzerland
134 GLOBAL OUTLOOK FOR ICE AND SNOW