Changes in the Cryosphere and Global Climate Change
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Changes in the Cryosphere and
Global Climate Change
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• Carbon Dioxide has risen from ~280ppm in 1850 to 379ppm in 2005.
• Warming is now unequivocal– Increase in global average air and
ocean temperatures, rising average sea level, melting ice
• Primary forcings are anthropogenic greenhouse gases– Fossil fuel burning– Deforestation
• Similar increases in methane and nitrous oxide
Global Warming: The Basic Science
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• “Canary in the coal mine”– Ice is one of the most
sensitive parts of the climate system
– Most visible symptom of climate change
– Arctic contains 1/3 of the world’s stored carbon
• Global decline in snow and ice that is accelerating.
Perito Moreno glacier Glacier National Park,
Argentina.
Why the Cryosphere?
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Components
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Snow Cover• Snow cover has decreased in most regions•Decreases due to temperature•Some specific increases due to precipitation•Could cause long-term freshwater shortages
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• Extends and retreats every year
• Arctic sea ice extent: -2.7% per decade
• Minimum extent (in summer): -7.4% per decade
Sea Ice
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• 9/3-9/9: Area of sea ice the size of Florida (69,000 mi2) melts
• Northwest Passage open for first time in human history
Recent Dramatic Events
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Glaciers and Ice Caps• Studied in terms of mass balance•10% of world’s surface covered by glaciers, mostly Greenland and Antarctica•Some date back as far as the last ice age•Rapid and visible melting•Approx. 0.5 SLE 1961-2004; 0.77 SLE 1991-2004; trending higher
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Visible Effects
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• Defined: Glacier Ice greater than 50,000 km2. The big kahuna of glaciers!
• Greenland Ice Sheet: 7.2m SLE!• Antarctic Ice Sheet: 61m SLE!• Ice shelves extend out from connected ice sheets• Melting ice shelves can foreshadow melting ice
sheets• Ice sheets very likely already contributing to sea
level rise
Ice Sheets and Ice Shelves
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Greenland and The Antarctic Ward Hunt Ice Shelf
• 2003-2005: Greenland ice sheet loses 41 mi3 at margins and gains only 14 mi3 at interior.
• Ward Hunt: – Approximately 3,000
years in age– In 2002 it began to
break upAn ice island about 1.5 kilometers long, 250 meters wide, and 30 meters thick moves into the Arctic ocean after the fracturing of the Ward Hunt Ice Shelf in August 2002. (Image courtesy of Warwick Vincent, Université Laval)
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How surface melting accelerates glacier melting
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• The largest part of the cryosphere in terms of surface area
• Permafrost can be ancient; some ground only freezes seasonally
• Human development on top of permafrost– Cities/towns– Oil pipelines– Roads
Frozen Ground
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• Tundra/Permafrost– Contains more carbon
locked away in frozen soil than the entire atmosphere holds today
– Can release its carbon as methane, a more potent greenhouse gas
Frozen Ground
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• Many polar species are particularly vulnerable to climate change because they are specifically adapted to that environment.– Food supply– Invasive new species filling niches– Fresh water supply
• Melting ice also opens up new areas to explore for human development/extraction/hunting, further threatening polar life.
Impacts on Biodiversity
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Case Study: Caribou
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Impacts
Increases in temperature encourage mosquito harassment
Paradoxically, warming is predicted to cause increases in Arctic precipitation, causing increase in snow pack, making
feeding difficult.
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Who else loses?
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Who Benefits from Inaction?• In general, natural resource extraction and refining; new areas open to exploitation•Construction companies;
anyone who can make a profit following coastal disasters• Oppressive governments
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• Some warming has already occurred; more will likely already occur regardless of anything else
• The amount of future warming will depend on a number of different forcings, one of which is human-made emissions
• With regard to predictions of future emissions and warming, it is useful to speak in terms of scenarios
• See “Summary for Policymakers” at WWW.IPCC.CH – last page
Prediction Scenarios
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• Human population distribution– Large numbers near coasts or major rivers
• Coastal ecosystem disruption• Global dilemma– International cooperation required at a time of
serious divisions– Mitigating climate change offers a means of
encouraging cooperation on other issues
Large-scale Implicationsof Sea Level Rise