Transcript Antarctic Ice Shelves - San Jose State University

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
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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

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Vegetation is limited
to less than 2% of
Antarctica's
landmass
Almost entirely
cryptogamic
(reproduction by
way of spores)
Angiosperms
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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

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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

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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
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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
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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
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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
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References (cont.)
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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.)
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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).