Climate change in Antarctica

San Jose State UniversityMeteorology 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 in response to future temperature regimes around the world”

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 molecules per sq.cm

►Average 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

Mean Yearly Antarctic Surface Temperatures 1957-1998

-2

-1.5

-1

-0.5

0

0.5

1

1.5

1957

1959

1961

1963

1965

1967

1969

1971

1973

1975

1977

1979

1981

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1985

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1997

Year

Tem

per

atu

re (

C)

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/snow-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, p1681-1717, 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).