Climate change in Antarctica San Jose State University Meteorology 112 April 5, 2010 Antarctic Ice Shelves ► Most common Ice Shelf: Giant floating platform of ice formed from glaciers located along coastlines ► 50-600 meters thick ► Can last for thousands of years ► 10 major ice shelves in Antarctica Antarctic Major Ice Shelves Antarctic Peninsula Ice Shelves ►Ice shelves are retreating in the southern section of the Antarctic Peninsula due to increasing temperatures. ►Ice shelves disintegrate into small iceberg pieces caused by melt water and ice cracks ►Without ice shelves, glaciers accelerate up to 8 times their original speed ►March 20, 2002: Ice Shelf the size of Rhode Island breaks up and releases 720 billion tons of ice into the ocean Larsen Ice Shelf Break How Ice Shelves are Collapsing Snow Coverage 98% of Antarctica’s surface is covered with various forms of snow and ice ► In winter the sea around the Antarctic freezes (sea water usually begins to freeze at 28°F or -1.8°C) eventually covering an area larger than the continent itself ► The Antarctic Ice Sheet is a thick with a maximum depth of nearly 3 miles (15,000 feet). This ice sheet contains over 5 million cubic miles (30 million cubic km) of ice ► Precipitation Pattern ► ► Average yearly total precipitation is about two inches. It is essentially a dessert Average precipitation on the coast is 20 to 50 inches of snow (7 to 16 inches of water equivalent). The Antarctic Peninsula has highest precipitation of the continent, (36 inches water equivalent) Vegetation Spore plants: Mosses and Lichens Vegetation is limited to less than 2% of Antarctica's landmass Almost entirely cryptogamic (reproduction by way of spores) Angiosperms Only two species of seed bearing plants live in Antarctica: Antarctic hair grass and Pearlwort Only live in the maritime climate areas of the continent The effects of Climate Change on Vegetation Higher levels of harmful UV-B rays stunned plant growth in grass and pearlwort. In other words, less branching and fewer leaves per shoot led to reduced plant size and biomass. Furthermore, leaves were thicker in UV-B exposed plants and had accelerated plant development with greater numbers of reproductive structures in both angiosperm species. The effects of CO2 on Antarctic vegetation have not been researched thoroughly enough to witness any adverse effects. Temperature rises have led to the invasion of alien species from South America. Then and Now Temperature rises have also led to the expansion of species ranges in Antarctica. “Long term monitoring of continental Antarctic terrestrial vegetation is crucial for accurate measurement and predictions of vegetation dynamics Water Resources Water Resources Antarctica holds 70 percent of the world's fresh water in the form of ice. Contains a vast network of subglacial lakes and rivers. Lake Vostok, one of Earth's biggest lakes, lies under Russia's Vostok Station. Thought to hold microorganisms that are millions of years old. The affects on ecologies in terms of changing water resources have not been thoroughly researched. Subglacial Lakes Caused by geothermal heating from the earth's core. Subglacial lakes are thought to have a significant effect on the flow of ice sheets. May act as lubricants to hasten the speed of ice sheet runoffs and subsequently, the rise in sea levels around the world. Antarctic Ozone Hole ► Ozone hole begins to develop in spring when the sun returns to Antarctica ► Occurs between (August-November) ► First detected by scientist in 1985 and has continued to increase in the years of observation ► Not technically a “hole”, but a diminishing or thinning of the ozone layer Function & Characteristics ► Absorb UV radiation UV-a, UV-b, UV-c UV-b high energy 95% absorbed ► Upper stratosphere ► Composed of O3 ► Measured in Dobson Units Conc. of O3 molecules ► 2.6x1016 ► Average molecules per sq.cm thickness 300 DU or 3mm thick 100 DU or 1mm thick Causes of Depletion ► Chlorofluorocarbon (CFC) ► Presence of UV, Chlorine dissociates from (CFC’s) Produces chlorine radicals Decompose ozone molecules ► Polar stratospheric clouds Occur in winter at -80 °C CFC reacts with nitric acid to liberate chlorine Other factors: ► Methyl bromide ► Aerosols & refrigerants ► Agricultural pesticides The Polar Vortex Effect ► Large scale cyclone centered at poles ► Ozone depletion causes cooling of 6°C in stratosphere ► Intensifies westerly winds and prevents outflow of cold air ► Results in: Cooler temperatures in the eastern region and warmer temperatures at the Antarctic Peninsula (Larsen, Ross, Wilkins, Ice Shelf's) Promotes accelerated warming and increase in sea ice Past Events ► Deepest ozone hole: September 30, 1994 Levels fell to 73 DU ► Largest ozone hole: September 1, 2006 10.6 million sq. miles Antarctica ► (5.4 million sq. miles) Effects of Ozone Depletion ► Increased surface warming ► Promotes increased melting Potential to increase sea levels ► Affects marine ecosystems Increased UV will result in less phytoplankton Building block of oceanic food chain Adverse effects on other species Human Impact on Antarctica ► ► ► ► ► The burning of fossil fuels has led to a rapid increase of CO2 in the atmosphere, which has contributed to warming of the atmosphere and melting of the ice in Antarctica. The Antarctic Peninsula is one of the most rapidly warming locations on Earth. The Antarctic Peninsula is warming 5x faster than the global average. In March 1994, the fastest sustained atmospheric warming since 1947 was observed in the Antarctic Peninsula-a 0.5 degrees Celsius per decade. The British Antarctic Survey (BAS) spokesperson Dr John King stated at the time: "The rise is the fastest we have on record ... people should be looking to the future for the consequences could be quite dire." The annual melt season on the peninsula has increased by 2 to 3 weeks in the last 20 years. 87% of the glaciers along the west coast of Antarctica have retreated in the last 50 years. Two Decades of Temperature Change in Antarctica -0.5 -1 -1.5 -2 Year 1997 1995 1993 1991 1989 1987 1985 1983 1981 1979 1977 1975 1973 1971 1969 1967 1965 1963 1961 1959 1957 Temperature (C) Mean Yearly Antarctic Surface Temperatures 1957-1998 1.5 1 0.5 0 What We Can Do To Slow Down Global Warming ► ► ► ► ► One of the main greenhouse gases is carbon dioxide (CO2). As trees grow they take in CO2 from the air and when the wood dies the CO2 is returned to the air. When we cut down trees and burn wood CO2 is added to the atmosphere. For example in 1987 an area of the Amazon rain forest the size of Britain was burned, adding 500 million tones of CO2 to the atmosphere. Deforestation not only adds CO2 to the atmosphere, but it means there are fewer trees to absorb CO2. To combat global warming we need to stop deforestation and plant more trees. To reduce fossils fuels, the U.S. should commit to reducing greenhouse gas emissions. People can help slow global warming by being more energy conscious. Television, lights and computers use electricity that is created mainly from burning coal. Cars-especially SUVs- are also major sources of CO2. States, like California, should pass tougher emission regulations on cars. References Nasa Earth Observatory http://earthobservatory.nasa.gov/IOTD/view.php?id=2288 ► National Snow and Ice Data Center http://nsidc.org/arcticseaicenews/faq.html#antarctic http://nsidc.org/sotc/iceshelves.html ► U.S. Geological Survey http://www.usgs.gov/newsroom/article.asp?ID=2409 ► Intergovernmental Panel on Climate Change http://www.ipcc.ch/ipccreports/tar/wg1/416.htm ► Antarctica Connection http://www.antarcticconnection.com/antarctic/weather/sno w-ice.shtml ► References (cont.) ► ► ► ► Carbon Dioxide Analysis Center http://cdiac.ornl.gov/epubs/ndp/ndp032/ndp032.html Johnson, Brian Fisher. "ANTARTICA GETTING WARM ALL OVER." Earth (00168556) 54.4 (2009): 27. Academic Search Premier. EBSCO. Web. 27 Mar. 2010 Ecophysiology of Antarctic vascular plants. By Alberdi, Miren; Bravo, León A; Gutiérrez, Ana; Gidekel, Manuel; Corcuera, Luis J PHYSIOLOGIA PLANTARUM 115: 479–486. 2002 Living on the edge- Plants and global change in continental and maritime antarctica, by Robinson, Sharon A.; Wasley, Jane; Tobin, Alyson K Global Change Biology; Dec2003, Vol. 9 Issue 12, p16811717, 37p References (cont.) ► ► ► ► ► Kapitsa, A., Ridley, J.K., Robin, G. de Q., Siegert, M.J. & Zotikov, I. Large deep freshwater lake beneath the ice of central East Antarctica. Nature, 381, 684-686. (1996) Remy, F., Frezzotti, M. (2006). Antarctica Ice Sheet Mass Balance. C.R. Geosciences. Volume 338, pages 1084-1097 Siegert, Martin J.1 Progress in Physical Geography; Jun2005, Vol. 29 Issue 2, p156-170, 15p Troshichev, O., Gabis, I., (2004). Effects of solar irradiation on dynamics of ozone hole. Journal of Atmospheric and Solar-Terrestrial Physics. Volume 67. pages 93-104. Wingham, D.J., Siegert, M.J., Shepherd, A.P. and Muir, A.S. Rapid discharge connects Antarctic subglacial lakes. Nature, 440, 1033-1036 (2006).
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