Ice Across Biomes graphic descriptors

Changes in sea-ice extent in the northern hemisphere

Graphic thumbnail: changes in sea-ice extent in the northern hemisphere

This line graph shows a declining trend in the extent of sea ice in September in the Northern Hemisphere from 1979 to 2010. The ice extent declined at a relatively slow rate between 1979 and 1995 (from approximately 7.2 million square kilometres to 6 million square kilometres), then began to decrease at a faster rate. The year with the least ice cover was 2007 (4.3 million square kilometres). The 2010 sea-ice extent was only slightly above this, at 4.9 million square kilometres.

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Deterioration in southern Hudson Bay polar bear body condition

Graphic thumbnail: deterioration in southern Hudson Bay polar bear body condition

This bar chart shows the decline of mean body condition index in polar bears captured around southern Hudson Bay. From 1984 to 1986 the mean body condition index of captured polar bears was approximately 0.75. From 2000 to 2005 the mean body condition index was approximately zero.

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Cumulative loss of ice thickness for three mountain glaciers and an Arctic ice cap

Graphic thumbnail: cumulative loss of ice thickness for three mountain glaciers and an Arctic ice cap

This graphic contains both a map and a line graph. The map shows three things: first, the overall distribution of glaciers and ice caps in Canada; second, the location of two groups of glaciers that are discussed in the text – Nahanni glaciers in the Taiga Cordillera Ecozone+ and Yukon glaciers, located mainly in the western Boreal Cordillera Ecozone+; and third, the location of three glaciers and one ice cap for which data are displayed in the line graph – the Devon Ice Cap (Northwest Sector) in the Arctic Ecozone+, Place Glacier at the eastern edge of the Western Interior Basin Ecozone+, Helm Glacier in the Pacific Maritime Ecozone+, and Peyto Glacier in the Montane Cordillera Ecozone+. The line graph shows the cumulative loss of ice thickness for these three mountain glaciers and one Arctic ice cap from 1959 to 2007. The overall trend for these four ice masses is a decline, with a less steep decline for the Arctic ice cap than for the three mountain glaciers. The total reduction in average ice thickness over the period of measurement for each ice mass was: 4 metres water equivalent for the Devon Ice Cap (Northwest Sector), 24 metres for Peyto Glacier, 37 metres for Place Glacier, and 38 metres for Helm Glacier.

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Trends in the timing of spring ice break-up on large lakes

Graphic thumbnail: trends in the timing of spring ice break-up on large lakes

This map shows trends in lake ice break-up on 39 large lakes in Canada from 1970 to 2004. Significantly earlier break-up trends, at a rate of more than 5 days per decade, are shown for two lakes on Baffin Island. Trends for these two lakes are based on remote sensing data from 1984 to 2004. Other significant trends for earlier break-up are shown for five lakes in southcentral Canada, three lakes in the Boreal Shield Ecozone+, and two lakes in the Prairie Ecozone+. There are also many lakes shown with non-significant trends to earlier break-up, ranging from fewer than 2.5 days per decade to more than 5 days per decade. There were no significantly later break-up trends at any of the lakes monitored over this time period.

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Change in Great Lakes ice cover

Graphic thumbnail: change in Great Lakes ice cover

This bar graph shows the percent change in mean maximum ice cover on each of the Great Lakes from 1970 to 2008. Mean maximum ice cover decreased on all the Great Lakes. The reduction in ice cover for each lake was: 35.6% for Lake Superior, 17.7% for Lake Huron, 43.4% for Lake Michigan, 39.9% for Lake Ontario, and 19.2% for Lake Erie.

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Permafrost zones

Graphic thumbnail: permafrost zones

This map of Canada shows the extent of the country’s four permafrost zones. The continuous permafrost zone covers the northernmost regions of Canada, including the Arctic Archipelago and extending south to cover the southern shore of Hudson Bay. Within the continuous permafrost zone, locations for case study sites discussed in this section are shown: Alert in Nunavut, Boniface River on the Ungava Peninsula in northern Quebec, and an additional northern Quebec study site south of Boniface River. The second zone is the extensive discontinuous permafrost zone which forms a thin band following the southern border of the continuous zone. This zone includes the Central Mackenzie Valley, the site of a case study discussed in this section. The third zone is the sporadic permafrost zone, a thick band south of the extensive discontinuous zone, reaching from the Pacific to the Atlantic coast and extending south of James Bay. And, lastly, the mountain permafrost zone is found in the Coast Mountains of British Columbia, in the Rocky Mountains, in Newfoundland, and on the Gaspé Peninsula in Quebec.

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Permafrost temperatures in the Central Mackenzie Valley

Graphic thumbnail: permafrost temperatures in the Central Mackenzie Valley

This line graph displays the trends in permafrost temperatures at 10 to 12 metres depth from 1984 to 2008. Two locations, Fort Simpson and Northern Alberta, show relatively stable permafrost temperatures, hovering between approximately -0.2 and -0.1 degrees Celsius. The permafrost temperature at Wrigley increased at a rate of 0.1 degrees Celsius per decade, rising from below -0.8 to above -0.7 degrees Celsius. The permafrost temperature at Norman Wells increased at a rate of 0.3degrees Celsius per decade, changing from approximately -1.5 to close to -1.1 degrees Celsius.

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Permafrost temperatures at Alert, Nunavut

Graphic thumbnail: permafrost temperatures at Alert, Nunavut

This graph displays an overall increasing trend of permafrost temperatures at Alert from 1978 to 2008, measured at 15 metres depth. Manual measurements in the first years of the period of record were conducted approximately monthly. After 2000 data points are monthly averages based on measurements from dataloggers. These monthly values show the seasonal fluctuations in permafrost temperature and the lower-magnitude year-to-year fluctuations. The monthly values are overlain with a line that plots the mean annual ground temperature, showing an increasing trend from approximately -15.3 degrees Celsius in 1978 to -13.9degrees Celsius in 2008.

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Changes in land cover with loss of permafrost, northern Quebec

Graphic thumbnail: changes in land cover with loss of permafrost, northern Quebec

This line graph shows the decline of permafrost and two associated trends in land cover from 1957 to 2003 at a study site in northern Quebec. The percent of the study site with permafrost decreased from 80% to 13%. The percent of the site covered by ponds increased from 18% to 37%, while fens increased from 2% to 50% of land cover over the period of the study.

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