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Download (0°C) for at least two years. Permafrost is typically characterized by
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lecture 12 Regional climate change: The Arctic and California About a quarter of the Northern Hemisphere's land contains permafrost, defined as soil that remains below 32°F (0°C) for at least two years. Permafrost is typically characterized by an active surface layer, extending anywhere from a few centimeters to several meters deep, which thaws during the summer and refreezes during the winter. The deeper permafrost layer remains frozen. The active layer responds to changes in climate, expanding downward as surface air temperatures rise. Recent warming has degraded large sections of permafrost across central Alaska, with pockets of soil collapsing as the ice within it melts. The results include buckled highways, destabilized houses, and "drunken forests"—trees that lean at wild angles. In Siberia, some industrial facilities have reported significant damage. Further loss of permafrost could threaten migration patterns of animals such as reindeer and caribou. This sinkhole near Fairbanks, Alaska, formed due to the melting of a large ice pocket within permafrost that is gradually thawing as temperatures warm. (Photo courtesy Vladimir Romanovsky, Geophysical Institute, University of Alaska Fairbanks.) Regions containing permafrost within the top 11 feet of soil could decrease by as much as 90% across the Arctic over the next century, based on simulations by the NCAR Community Climate System Model. Shown are areas with near-surface permafrost in the CCSM simulations for 1980-1999 (light blue) and 2080-2099 (dark blue). The latter projection is based on the UN Intergovernmental Panel on Climate Change's A1B emissions scenario, often called the "business as usual" scenario. (Image courtesy David Lawrence.) From space, we can monitor the melting areas of the worlds major ice sheets. The melting of Greenland is accelerating… area of California Extent of September Arctic Sea Ice, 1978-2005. The loss of ice since 1978 is about 1.3 million square km. If current rates of decline continue, the Arctic could be ice-free by century’s end. 1.3 million square km = Arctic researchers see early warming signals 1979 2000 Based on satellite data, these images show summertime Arctic sea ice. The ice cover shrunk by about 20 percent over that time. Oct 17, 2003 MISR What about California? The Union of Concerned Scientists recently published an assessment of climate change in California. They based their assessment on the results from two global climate models, one with a relatively low sensitivity to CO2 doubling (PCM), and the other with a relatively high sensitivity (HADCM3). They looked at outcomes in California for two scenarios. One is “business as usual” scenario, that envisages fossil fuel emissions increasing at approximately the same rate as present for the remainder of the 21st century. The other is a lower emissions scenario, where emissions continue to increase but at a lower rate, stabilizing around 2050, then declining to levels below the present level by 2100. There are therefore two scenarios for each model, giving a range of possible outcomes for California. The global models’ resolutions are on the order of 200 km. Regional details have been supplied by a regional climate model. Rising Temperatures California statewide Projected average summer temperature changes Source: A Luers/Union of Concerned Scientists Most precipitation over the Sierras falls in wintertime, where it is stored in the snow pack. The snowpack comprises approximately half the total water storage capacity of California, the other half being contained mainly in human-made reservoirs. As the snow melts, water flows to reservoirs, where it makes its way through aqueducts to agricultural and urban areas. This shows aqueducts for water resource re-distribution in California Precipitation Projections Statewide, Winter 150 Precipitation Change (mm) 100 HadCM3 A1 HAD higher PCMhigher A1 PCM HAD lower HadCM3 B1 PCM PCMlower B1 50 0 -50 ~30% reduction -100 -150 1960 1980 2000 2020 Source: A Luers/Union of Concerned Scientists 2040 2060 2080 2100 Percent of Water Year Runoff The Sierra snow pack has been steadily shrinking over the past century… 70% 70% 65% 65% 60% 60% 55% 55% 50% 50% 45% 45% 40% 40% 35% 35% 30% 30% 25% 25% 20% 20% 15% 15% 10% 10% 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 Water Year (October 1 - September 30) Sacramento River Runoff (1906-2001) April to July as a Percent of Total Runoff Source: California Protection Agency, Environmental Protection Indicators for California, 2001 Diminishing Sierra Snowpack % Remaining, Relative to 1961-1990 This shows how the more sensitive global model projects snowpack to change in the Sierras. The change in snowpack is significant because it comprises approximately half the total water storage capacity of California, the other half being contained mainly in human-made reservoirs. Source: A Luers/Union of Concerned Scientists Decreasing Wine Grape Quality Temperature Impacts 1961-1990 Current Conditions 2070-2099 LOWER (B1) PCM Wine Country Cool Coastal Northern Central Valley HadCM3 HIGHER (A1fi) PCM HadCM3 Optimal Impaired Marginal Impaired Impaired (mid) Optimal Optimal Optimal Optimal (mid-high) (mid-high) (high) Impaired (low) Marginal Impaired Impaired Impaired Impaired Wine Country (Sonoma, Napa Counties) Cool Coastal (Mendocino, Monterey Counties) Northern Central Valley (San Joaquin, Sacramento Counties) Source: A Luers/Union of Concerned Scientists Changes in Vegetation Distribution 2070-2099, relative to 1961-1990 HadCM3-A1 HadCM3 higher HadCM3-A1 HadCM3-B1 HadCM3-B1 HadCM3 lower PCM-A1 PCM-A1 PCM higher PCM-B1 PCM-B1 PCM lower Alpine/Subalpine Forest Alpine/Subalpine Forest Evergreen Conifer Forest Temperature-Evergreen Conifer Forest driven Mixed Evergreen Forest Mixed Evergreen Forest Mixed Evergreen Woodland Mixed Evergreen Woodland Grassland Fire-mediated Grassland Shrubland Shrubland Desert Desert -100 -50 0 50 100 Change in Total Cover (%) -100 Source: A Luers/Union of Concerned Scientists -50 0 50 Change in Total Cover (%) 100