Global Outlook for Ice & Snow

Selected regions

and neighbouring parts of Canada) show a mean annual thickness change of –0.5 m water equivalent from the mid 1950s to the mid 1990s, and more than three times as much (–1.8 m water equivalent) from the mid 1990s to 2000–2001 based on a sub-sample of 28 glaciers 26 .

North America

Arctic islands and mountain ranges

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 USA and southwest Canada, accelerated retreat coincid- ed with a shift in atmospheric circulation patterns that occurred during 1976–1977 96,97 .

Figure 6B.12: Glacier shrinking on Cum- berland Peninsula, Baffin Island, Cana- dian Arctic. A new glacier inventory based on satellite data shows that the glacier cover reduced by about 22 per cent be- tween the Little Ice Age (LIA) maximum extent and 2000. Source: Data and figure from F. Svoboda, University of Zurich, Switzerland

Airborne laser altimetry studies on 67 glaciers (repre- senting about 20 per cent of the glacierized area in Alaska

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GLOBAL OUTLOOK FOR ICE AND SNOW