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polar ecosystems.docx

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Life Sciences
Luc Bernier

March 6 , 2013 Life Sci 2H03: Environmental Life Sciences Polar Ecosystems Polar Ecosystems - areas in black are always covered in ice - forecast of expected response - melting of process Positive Feedback of Melting Polar Systems - bright surface of ice and snow cover: high albedo - with melting leads to more sunlight absorbed by land and sea, bringing warmer temperatures and less ice and snow - melting of ice and snow - positive feedback - thawing of permafrost leads to increase of methane, warmer temperatures, less ice and snow, more sunlight absorbed by land and sea and warmer temperatures Patterns of Snow Cover - determined by:  timing  magnitude  and rate of melting  length of the season - as we move to higher latitudes the temperatures become cooler, less moisture in the atmosphere, it is less mild but persists for longer periods of time - snow pack goes through different stages in the evolution What Controls the Snow Accumulation Patterns - many factors including:  ground temperature  vegetation (allows for wind protection)  initial conditions: is there a lot of wind and what were the temperatures in the atmosphere - snow cover in NH: in winter months the extent of snow cover is greater, when we move to spring summer the snow cover is at tis minimum - extent from year to year varies Snow: Trends - snow cover has declines I the Northern Hemisphere: particularly in spring and summer - results of the influence of climate change - graph of estimates of snow cover in the spring from 1930-2000s - spring decline: 7.5% since 1922, IPCC - approximately 1.3% decrease in the spring per decade - reinforcing positive feedback Snow: Future Outlook - trend will continue - major reductions in snow cover projected for mid-latitudes - yellow to red: less snow - blue: increase snow - areas around the great lakes: less snow - due to warming of temperatures can hold more moisture converted into snow flakes which precipitate in the polar regions - by the end of the 21 century - reduction especially in lower latitudes: 75-98%, almost no snow during the winter season Snow: Impacts - in Arctic ecosystems, snow: important ecological factor - changes in snow cover affect plants and animals adapted to it - ex.: birds develop nest on vegetation covered in snow - deer and caribou dig for vegetation, their preferred food source is likely to disappear - eating and breeding habits - caribou populations are shrinking especially in the Canadian Arctic What Drives the Formation of Sea Ice? - seasonal changes in radiation - more sea ice leds to higher albedo o - forms at -1.9 C - heat from the ocean (as it has a high heat capacity) will release heat to overlying atmosphere and moderate the climate - with sea ice, air is no longer receiving the warm heat - sea salt is expelled from the sea water and will allow sea ice to form - increasing albedo - influence ocean circulation - witout sea ice we are increasing warming as heat is expelled to the atmosphere What Drives the Formation of Sea Ice? - Arctic sea-ice: cover shrinking by 8.9% per decade per summer - 2.5% per decade in winter - becoming thinner - based on satellite observation - trend might be faster as we only have data from 1980 - by the end of the century Arctic ocean could be entirely free of sea ice during the summer -
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