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From: Edit revsion of event study on Ice Shelf
Date: 11/1/02
Time: 9:47:38 AM
Remote Name: 208.183.225.4
Hey Navigators, I added a few casual chains and other interactions, and a few sentences to the closing. Let me know if there is anyhting else you think needs to be changed. i really would like to post this by about 3:00 today (friday) so please reply. i am going on a ladies retreat with my church this weekend that is why i want to get it posted today. If i do not hear from anyone i will assume it is alright and i will go ahead and post it. thanks for all of your work navigators.
Christa Bolton
Ice Shelf Disintegration and the Four Spheres: The Atmosphere:
The Atmosphere is the gaseous/vaporous envelope surrounding the earth. It consists of several layers: troposphere, stratosphere, mesosphere, and thermosphere with the troposphere at the surface of the earth, and the thermosphere spreading out into space. The portion of the atmosphere we experience, day to day, is the troposphere where 99% of the water vapor in the atmosphere is located and troposphere’s movements produce weather. The stratosphere contains 90% of the ozone layer. This layer protects Earth’s surface from many ultraviolet rays. The ozone absorbs the bulk of the solar ultraviolet radiation in the atmosphere due to its closeness to the Sun. The planet Earth is a natural greenhouse. Some naturally occurring greenhouse gasses permit incoming solar radiation to reach Earth’s surface, but they restrict the outward flow of infrared radiation. Carbon dioxide and water vapor absorb this outgoing infrared energy and re-radiate some of it back to ground level. This greenhouse effect is essential to most life on Earth. Without it the average temperature would be a frigid ––18Cºº, rather than the 14Cºº as it is today. (“”http://encarta.msn.com/encnet/refages/refarticle.aspx?refid+761559991"”) and (Http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/ATM_CHEM/atmospheric_structure.html)
The Hydrosphere:
The hydrosphere is made up of all the Earth's water. The hydrosphere contains all the solid, liquid and gaseous water of the planet. The hydrosphere extends several kilometers below the surface of the Earth and reaches heights of 12 kilometers into the atmosphere. The hydrosphere interacts with, and is influenced by, all other spheres. Water, on Earth, exists in three states: liquid, solid, and visible vapor. It forms oceans, rivers, streams, and lakes. Only a small percentage of the water in the hydrosphere is fresh. Fresh defined here means non-salty. Hydrology is the science that encompasses the occurrence, distribution, movement, and properties of water of the earth and their relationship with the environment and within each phase of the hydrologic cycle. Fresh water supplies originate from precipitation that falls from the atmosphere down to earths surface, from the rivers and streams that flow on the earth's surface, and as groundwater below earth's surface. It is estimated that 97.5% of the total global water is salt water. 68.9% is made up of glaciers and permanent snow and 29.9% is fresh groundwater. The earth's freshwater supplies can be broken down as follows: ice 77%, groundwater 22%, soil moisture. 18%, lakes .32%, rivers and streams .004%, and the atmosphere 0.36%. Sources: (Http://webworld.unesco.org/water/ihp/pulications/waterway/webpc/definition) and (http://distance.una.edu/ess5-8/countline/week10b.html)
The Biosphere: The biosphere, a termed coined by Russian scientist Vladimir Vernadsky in 1929, is the life zone of the Earth and includes all living organisms, including man, and all organic matter that has not yet decomposed. Life began on earth millions of years ago and the biosphere readily distinguishes our planet from all others in the solar system. The biosphere is structured into a hierarchy known as the food chain whereby all life is dependent upon the first tier (i.e. mainly the primary producers that are capable of photosynthesis). Energy and mass is transferred from one level of the food chain to the next with an efficiency of about 10%. At each level, the consumer gets only about 10% of the stored energy of what it consumes. All organisms are intrinsically linked to their physical environment and the relationship between an organism and its environment is the study of ecology. The biosphere can be divided into distinct ecosystems that represent the interactions between a group of organisms forming a trophic pyramid and the environment or habitat in which they live. (http://www.geology.ufl.edu/Biosphere.html) The biosphere is the one place where all the four spheres of the planet work together. The land (lithosphere) interacts with the water (hydrosphere) and it also interacts with the air (atmosphere). Each of these interactions will interact with the biosphere at all times. All of the interactions are affected by the energy that surrounds us. All of those forces work together to create our living world. (http://www.geoghraphy4kids.com/files/land_biosphere.html)
The Lithosphere: The lithosphere contains all of the cold, hard solid land of the planet’s crust or surface, the semi-solid land underneath the crust, and the liquid land near the center of earth. The surface of the lithosphere is very uneven because it includes the mountain ranges (the Rockies and Andes), the plains or flat areas that are found in Iowa, Texas, and Brazil, and the deep valleys of the ocean floor. The lithosphere thins to a few kilometers at ocean spreading centers; thickens to about 100 to 150 kilometers under the ocean basins; and is up to 250-300 kilometers thick under continental shield areas. The crust is an important part of the lithosphere; however, it is composed mainly of mantle rocks. Due to this, authors sometimes state that the lithosphere is the uppermost part of the mantle and they do not include the thin rocks of the crust. (Http://geolsoc.org.uk/template.cfm%3Fname%3Dlithosphere) and (http://distance.una.edu/ess5-8/cintro/spheres.html) .
Ice Shelves: Ice shelves formed from glaciers and ice sheets flow over the edge of the continent of Antarctica and float in the surrounding ocean. These shelves of thick freshwater ice are extensions of the grounded ice sheet and flow from the land to the sea where parts (icebergs) break off, or are calved. (http://www.meteor.iastate.edu/gcp/sealevel/ross.html) The weight of Antarctica’s ice is so enormous that it has forced the continent tow thirds of a mile into the earth. Under the massive forces of their own weight, the ice sheets deform and drag themselves outward. Very large glaciers called ice streams flow through them continually. Transporting ice from the center of the continent to the sea. (Http://nsidc.org/cryosphere/coldfacts.html) The rate at which an ice shelf flows is dependent on the ice thickness and temperature, and the shape of the surrounding lands, which it flows past. (http://web.pdx.edu/~chulbe/science/Larsen/larsen2002.html) When ice streams reach the coast and push out into the open sea, they pass over a rocky landscape and anchor themselves to the irregular rocks to form a hinge. The ice will continue to grow outward and as a result, a large shelf of ice is attached to the continent. (Http://www.asoc.org/general/iceshelve.htm) Ice shelves gain mass by a flow from grounded ice sheets and glaciers and new snow accumulation on their surfaces. They lose mass primarily by iceberg calving and secondarily by melting. Ice shelves balance between gravity-driven horizontal spreading and stresses at the grounding lines and the calving seaward front. The small thin ice shelves that fringe the Antarctic Peninsula are sustained primarily by new snow accumulation; larger ice shelves such as the Ross Ice Shelf are sustained mainly by flow from inland ice sheets. Thickness of these ice shelves is approximately 200m. Changes in winter accumulations or summer melting are of fundamental importance to the health of fringing ice shelves. (http://nsidc.org/iceshelves/larsen1995/index.html) The Larsen Ice Shelf, located on the Antarctic Peninsula, was about 220 meters thick and is believed to have existed for at least 400 years. Recent satellite imagery has shown that the northern section of the ice shelf has broken and separated from the continent in the largest single event in a thirty-year series of the ice shelf retreats in the Antarctic Peninsula. (Http://nside.org/iceshelves/larsen1995/index.html) The Larsen Ice Shelf has had a greater increase in temperatures than the rest of the continent, and has been warming five times faster than the global average. (http://www.climatehotmap.org/antarctica.html) The shelf has lost about 2200 square miles of ice over the last five years. However, the Ross Ice Shelf, located closest to New Zealand, has been cooling and gaining mass as it thickens since the glacial streams flowing over it have slowed down. Giant icebergs have calved (broken away) from the Ross Ice Shelf in March 2000, March 2002, and May 2002. (http://www.exploratorium.edu/climate/cryosphere/data5.html) The disintegration of the Larsen B Ice Shelf in west Antarctica (closest point to South America) sent thousands of small icebergs adrift in the Weddell Sea. This was the largest single loss in a series of recent events leading to the break down of this ice shelf (http://www.exploratorium.edu/climate/cryosphere/data5.html) and followed the warmest summer on record around the Antarctic Peninsula. The area lost in this most recent event dwarfs Rhode Island in size. In terms of volume, the amount of ice released in this short time is 720 billion tons, enough ice for about twelve trillion 10kg bags! (Http://www.colorado.edu/PublicRelations/NewsReleases/2001/1008.html) and (http://nsidc.org/iceshelves/larsen1995index.html). (http://web.pdx.edu/~chulbe/science/Larsen/larsen2002.html) While iceberg calving is normal for ice shelves, disintegration is not. Farther south, at the same time as the disintegration, a large iceberg broke off the ice shelf seaward front. (http://nsidc.org/iceshelves/larsen1995/index.html) The disintegration break up lasted for 35 days from January through late March 2002. Scientists attribute the collapse to its warming by 2.5 degrees Celsius (4.5 degrees Fahrenheit) since 1945. Other breakup events of the Larsen Ice Shelf include the disintegration of the Larsen A section in 1995 reducing the shelf by 770 square miles, and the collapse of the Larsen B and Wilkins Ice Shelves between March 1998 and March 1999 reducing the shelves by 1150 square miles. (http://www.climatehotmap.org/antarctica.html; http://earthobservatory.nasa.gov/Study/LarsenIceShelf/) Disintegration of the ice shelf does not contribute to an increase in sea levels since the ice shelf is already floating prior to the collapse. However, ice shelves do serve as natural barriers to the flow of ice from glaciers. Thus, continued disintegration could lead to a rise in sea levels if glaciers were able to dump ice into the ocean more quickly, (http://yosemite.epa.gov/oar/globalwarming.nsf/content/NewsandEventsScienceandPolicyNews.html; http://nsidc.org/iceshelves/larsen1995/index.html) perhaps as much as by 19 feet (five meters). (http://www.climatehotmap.org/antarctica.html; http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2002/200203188307.html)
Sea Ice: Sea ice is the thin, fragile, solid layer of ice (water in a frozen state) floating on the ocean’s surface, that forms in the North (Arctic) and South (Antarctic) Polar regions. It forms a boundary between the relatively warm ocean and the cooler atmosphere. The sea ice helps to regulate the water’s temperature, salinity, and currents. Sea ice is seasonal and responds quickly to changes in the air temperatures. The extent of sea ice can now be monitored daily thanks to microwave sensors on satellites. (http://www.exploratorium.edu/climate/cryosphere/data4.html) There are many different kinds of sea ice: first year ice, ridges, and multi-year ice. Sea ice will float because it is less dense in the solid phase than it is in the liquid phase. If sea ice were denser in the solid phase, it would cause it to sink to the bottom of the ocean causing the oceans to freeze to their beds. This would cause the animals and plants that live on the ocean floor to die. (http://southport.jpl.nasa.gov/polar/iceinfo.html) Sea ice is also an interesting habitat for a variety of organisms; often inaccessible to scientist to be able to further an on site study of this habitat. Penguins, whales and phytoplankton all can live on sea ice. (http://www.awi-bremerhaven.de/Eistour/index-e.html) For the purpose of this sphere study we will focus on ice shelf disintegration and its effects on the four spheres of the Earth: atmosphere, hydrosphere, biosphere, and lithosphere:
Event > Sphere Reactions: E>A: In 1994, the British Antarctic Survey (BAS) released data demonstrating that the average temperature on the Antarctic Peninsula had warmed by 4.5 degrees Fahrenheit since 1947. The building of sea ice (event) increases the reflection of more solar radiation than bare land surface back into stratosphere and mesosphere (atmosphere) because water and earth being darker than ice, absorb more sunlight and warm the whole planet. As the sea ice doubles in size, the reflection rate increases causing a rise in temperature of our atmosphere and more global warming. (http://www.enn.com/enn-news-archive/1999/04/040999/iceretreat_z583.asp http://www.asoc.org/general/iceshelve.htm. Meltdown: Satellites Show Accelerated Polar Ice Threat by Robert Roy Britt Sunday Report: Melting Releases Riddles on Global Warming Los Angeles Times, 04/01/01
E>A: Researchers at the University of Colorado at Boulder recently discovered that air temperature in Antarctic rose 18 degrees Fahrenheit in just a few decades. The largest warming ever recorded in the Southern Hemisphere. That temperature change is only now making its way to the bottom of the two-mile thick icecap, where it may be affecting how the ice flows. The region has now entered a vicious cycle of polar warming: rising average temperatures, fewer cold years and longer summer melting have resulted in the warming of Antarctica’s waters. This has resulted in a decrease in sea-ice extent. (http://www.enn.com/enn-news-archive/1999/04/040999/iceretreat_z583.asp http://www.asoc.org/general/iceshelve.htm. Meltdown: Satellites Show Accelerated Polar Ice Threat by Robert Roy Britt Sunday Report: Melting Releases Riddles on Global Warming Los Angeles Times, 04/01/01
E>A With a loss of sea ice a dice shelves, reduced albedo (reflective power) causes a change in the absorption heat and carbon dioxide, which means more warming. This has caused two ice shelves to break up and melt faster than anyone expected. A warming trend in the region has caused the annual melt season to increase by two or three weeks over the last 20 years. The Larsen B and Wilkens ice sheets on the Antarctic Peninsula have lost nearly 3,000 sq. km of their total area in 1998. Scientists expected the two shelves to fail soon, but the current disintegration is occurring at an even faster rate than earlier breakups because of the warming trend. Scientists believed the Larsen B ice shelf has existed for a t least 400 years. It is roughly the size of Connecticut. The local climate is inching toward an average summertime temperature just above 32 degrees Fahrenheit-melting point of water. (http://www.enn.com/enn-news-archive/1999/04/040999/iceretreat_z583.asp http://www.asoc.org/general/iceshelve.htm. Meltdown: Satellites Show Accelerated Polar Ice Threat by Robert Roy Britt Sunday Report: Melting Releases Riddles on Global Warming Los Angeles Times, 04/01/01
E>A: Sea ice helps modify the transfer of heat, mass, and momentum between the atmosphere and the ocean. It acts a physical barrier to the exchange of gases, such as carbon dioxide, oxygen and water vapor. Sea ice behaves as an insulating cover between the cold atmosphere and the considerably warmer ocean. During the winter, the loss of heat to the atmosphere over sea ice is ““two orders of magnitude smaller”” than loss of heat over open ocean. Sea ice also reflects solar radiation back to space rather than allowing the ocean surface to absorb it. (““"http://www.antcrc.utas.edu.au/aspect/seaiceintro.html””")
E>A: Removal of permanent ice packs would significantly increase precipitation in the Arctic Ocean and North Atlantic. (““"http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html””")
E>H: Changing the volume of an ice shelf does not change the sea level because floating ice already displaces a volume of water equal to the volume of water it contains. However, if ice currently resting on the continental surface were to flow into the ocean more rapidly as a result of the removal of the fringing ice shelves, then sea levels would rise. (http://nsidc/iceshelves/larsen1995/index.html)
E>H Scientist say the melting of the West Antarctic ice sheet will cause sea levels to rise at a rate of 1cm per decade for a total of 20ft. over the next 7,000 years. Scientist from the University of Maine and University of Washington studying this process, predict the 360,000 square mile ice sheet will completely melt due to global warming. (http://seattletimes.nwsource.com/news/health-science/html98/melt)
E>H: The breaking ice shelves could be loaded with all types of pollutants etc. As the glaciers disintegrate and return to a liquid form, they could pollute the water supply. (http://nsidc/iceshelves/larsen1995/index.html)
E>H: Warm summer temperatures on the Ross Ice Shelf in Antarctica could have very dire consequences because that ice shelf is part of the braking system for some very large glaciers. According to Ted Scambos of the University of Colorado at Boulder, "If we begin to get significant water ponding there, and the shelf is eventually destroyed, we would likely have ice. http://www.colorado.edu/PublicRelations/NewsReleases/2001/1008.html.
E>B Giant icebergs calved from ice shelves can cause a risk to navigation (and thus people) as they drift into open water. (http://www.cnn.com/2002/TECH/space/05/09/iceberg.satellite/index.html)
E>B The growth of phytoplankton in the southwestern part of the Ross Sea had been reduced by the large icebergs that calved from the Ross Ice Shelf in 2000. Data from satellites showed a decrease in volume of these tiny plants by about 40% between March of that year and December 2001. After breaking away, the icebergs grounded on the sea floor about 100 kilometers from the ice shelf blocking the path of sea ice from flowing out to the open seas. Plankton requires the open water and direct sunlight to survive. (http://www.newscientist.com/hottopics/climate/climate.jsp?id=ns99992203) Phytoplankton, rich in chlorophyll, is the base of the local food chain for marine mammals and birds. Less plankton could lead to reduced numbers of these organisms.
E>B Krill is a tiny shrimp-like crustacean. They feed on sea ice algae or phytoplankton, and juveniles especially seek protection from predators in the cracks of the ice. They provide the staple diet for many fish, birds, and mammals in the Southern Ocean. (http://www.awi-bremerhaven.de/Eistour/index-e.html) Loss of sea ice would mean less krill and could have a disastrous effect on the regional food chain.
E>B Adelie penguins are found on the sea ice surrounding Antarctica where sea ice lasts throughout the winter and well into the spring thaw. During winter, the penguins dive to catch krill in the cracks in the ice. When the sea ice is reduced, suitable feeding sites become scarce or too far away for the birds, thus reducing their survival. If the sea ice were diminished, there would be less Adelie penguins. (http://www.bbc.co.uk/nature/earth/warnings/antarctic_all.shtml) The annual melt season has increased by 2 to 3 weeks in just the last twenty years. The Adelie penguin populations have shrunk by 33% over the past 25 years due to the loss of their winter sea ice habitat (http://www.climatehotmap.org/antarctica.html)
E>B Scientists have proposed that the amount of krill, tiny crustaceans, relates to the amount of sea ice. Sea ice offers protection to the krill and provides them with a food source in the form of ice algae, which grows in small cracks on the underside of the sea ice. Krill and Salpa thompsoni, or salps, are competitors. Large numbers of salps inhibit krill reproduction. Warmer temperatures favor larger numbers of salps and less numbers of krill, while colder temperatures and more sea ice favor krill. Salps prefer open sea environments, thus warmer temperatures and less sea ice. They reproduce asexually in early spring consuming phytoplankton, which in turn limits the amount available to krill, which inhibits their reproductive development and spawning. Krill reproduce later, and salps are predators of krill larvae. Years of less sea ice have resulted in smaller amounts of krill and larger amounts of salps. However, during years of extensive sea ice coverage, krill seem to spawn early. Krill are an essential part of the diets of whales, penguins, squid, seals, seabirds, and fish, while salps are not. Decreased amounts of krill could have a great effect on the Antarctic food chain (http://earthobservatory.nasa.gov/Study/UpperCrust/)
E>B Reduced sea ice and ice shelves affect native plants and animals, which in turn provide food and resources to people. (http://www.climatehotmap.org/antarctica.html)
E>B Arctic sea ice is a critical part of the ecosystem for Arctic organisms such as polar bears, seals, and walruses that depend on it for their habitat as they rest, forage, mingle, and breed there. Reduced amounts of this sea ice could have an adverse effect on these animals and their survival. (http://earthobservatory.nasan.gov/Study?ClimateClues/; http://nsidc.org/sotc/sea_ice.html)
E>B Shipping companies moving raw materials such as oil or coal out of the Arctic must work around the sea ice, thus shipping during times of limited sea ice. Less ice would enable them to ship goods for longer periods throughout the year. More ice makes it treacherous to navigate through barely open pathways. (http://nsidc.org/sotc/sea_ice.html)
E>B At least four seal species (Weddell, Crabeater, Leopard, and Ross seals) use sea ice for resting and hunting, as well as a place to give birth and seek refuge from predators. (http://www.awi-bremerhaven.de/Eistour/index-e.html) Decreased amounts of sea ice could adversely affect these species.
E>B With the disintegration the melting water would lower temperature causing the living things in the water surrounding the melting to be exposed to colder water temperatures and even untimely death due to the extreme cold. (http://www.learnz.org.nz/old/98/seaice2.htm; and http://www.awi-bremerhaven.de/Eistour/pinguine-e.html )
E>B When the breaking away of an iceberg happens and disintegration begins the moving ice can block or close off certain places on the ice shelves. Emperor penguins, which are entirely dependent on the sea ice to breed and rear their young, may be unable to reach their breeding grounds because of this and therefore unable to breed. This will result in a decrease in the Emperor penguin population. (http://www.enn.com/news/en-stories/2002/01/01102002/s_46027.asp; and http://www.awi-bremerhaven.de/Eistour/pinguine-e.html)
E>B Ice Shelf Disintegration could cause trade for food to shut down which would result in less imports of food that the living population needs. Hunger could result. With the disintegration of the ice shelf, the shipping lanes would be pushed further back. Ships could not sail into or on the melting ice shelves. If ships could not reach their destination then trade could not happen which would result in no trade (that trade could be food) and if food could not get through, then hunger and starvation could result. (http://www.learnz.org.nz/old/98/seaice2.htm; and (http://www.coolantarctica.com/Antarctica%20fact%20file/antarctic.../seaaice%20formation.ht)
E>L The disintegration of ice shelves can change the coastal grounding line that they are attached to and also the surrounding islands or rocks. When the glaciers move out over the ocean, they pass over rocky terrain and anchor to the rocks to form a hinge. They also attach to the land surface of the continent and form a grounding line. The ice shelves float up and down with the ocean and grate against the rocks. This causes the rocks to become smoother and eventually break apart. The sediments that result from this will then settle on the bottom of the ocean or they will be carried away by the iceberg that develops when the ice breaks away. If the erosions continue, the rocks will break apart and will not be able to provide a breaking system for the ice shelf. The ice shelves prevent the discharging of glaciers in the ocean. The grounding line may also be affected. When the Ninnis Glacier Tongue on the eastern coast of Antarctica broke away it changed the coastline overnight. When the tongue disintegrated it cracked at the grounding line and moved away from the land. This caused pieces of rock and sediments to be pulled away from the grounding line, therefore changing the shape of the coastline. http://earthobservatory.nasa.gov/Study/Ninnis/
E>L The disintegration of the ice shelves will cause the Antarctic continent to rise above sea level. The Antarctic icecap contains about 90 percent of the ice that exists in the world and 70 percent of the world’s fresh water. The weight of the ice in the Antarctic is so great in many areas that it pushes the land below sea level. This process is known as isostasy. If the ice shelves were to collapse, this could cause severe problems because the ice shelf acts as a braking system for some of the very large glaciers. With rising temperatures and global warming, the glaciers would start to flow at faster rates into the oceans. http://www.usatoday.com/weather/antarc/aiceshet.htm http://www.antarctica.ac.uk/Key_Topics/IceSheet_SeaLevel/
E>L The disintegration of the ice shelves can cause pollutants to be carried to other lands and contaminate the soil. Sea ice seems to be a key element in the transport of contaminants. If the water is contaminated and frozen into ice these contaminants will be released into the ocean as the ice thaws, re-freezes, and thaws again. As the sea ice flows into warmer water and melts, the contaminated sediments can flow to nearby shores and pollute the soil. This could then prevent plants from being able to grow, etc. and as rain washes the soil into the ocean, the ocean could then be polluted as well. ( Http://www.ecology.com/ecology-today/tracking-air-pollution/ )
E>L The land may rise or sink as the ice shelves disintegrate. Isostatic rebound occurs when a load is imposed on or removed from the lithosphere. The surface tends to either rise or sink as the lithosphere rises or sinks into the asthenosphere. Loads may include lakes, oceans, ice, sediment, or volcanoes. The rising and sinking of the lithosphere may continue until isostatic equilibrium is reached. http://www.umich.edu/~gs265/isost.html . The event may cause a peripheral bulge. Isostatic depression itself is only possible if the asthenosphere can flow away from the depressed area and if the lithosphere is able to move vertically, either along fractures or by elastic bending. Geological evidence indicates that lithospheric bending dominates over fracturing and we can therefore use flexural models to predict the shape of the depression and surrounding areas (or vice versa). Instead of all areas around a load becoming depressed, the flexural rigidity of the lithosphere (among other things) causes some areas to actually be elevated during this same time. This is known as the peripheral bulge, which forms a ring around the outside of the load. (Http://www.umich.edu/~gs265/isost.html )
E>L Coastal flooding may result as the ice melts. Some estimates of how much flooding there would be include 35 meters ocean rise to 75 meters rise. Still other estimates state a rise of 60-110 meters. This flooding could cause coastal erosion which could result in the loss of coastal cities as buildings and homes are destroyed. (Http://maxpages.com/globalwarming) And (http://www.pog.su.se/sea/04_coastal.htm)
Sphere>Event Interactions:
A>E: Intense global warming of more than 0.5 degrees Celsius per decade over the last thirty years has lead to the decline of sea ice. Computer generated models suggest that if greenhouse gases continue to warm the Earth, permanent ice packs will likely melt and will be replaced with seasonal winter ice. http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html””")
A>E: Major changes in the Arctic air circulation patterns have also affected sea ice. Over the central Arctic Ocean, average sea level pressure has dropped, and high latitude storms have increased. This has resulted in considerably warm spring and summer air masses over the Arctic Ocean area, which melts some sea ice and pushes the remaining ice away from the shore. (““"http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html””")
A>E: A lengthening warm season is also contributing to sea ice decline. When there are open areas of water, called ““leads““, darker areas of the ocean reflect less sunlight, therefore, warm up and melt even more ice. (““"http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html””")
H>E Increases in ocean water temperatures and ocean currents might increase the rate of discharge of ice sheets into the ocean. If ice flows in to the ocean more rapidly than melting, then sea level increases would occur more rapidly. Heavy rains from storms also would erode ice sheets, gradually over a period of time. (http://Earthsky.com/2000/es000209.html)
H>E According to Slawek Tulaczyk, an assistant professor of earth sciences, ice streams flowing across ice sheets may slow down and stop moving altogether. Stoppage of the ice streams may lead to thinning and shrinking of the ice shelves they nourish, most notably the large Ross Ice Shelf that covers the Ross Sea. Loss of the ice shelf over the Ross Sea could, in turn, trigger changes in global ocean circulation and climate( www.ucse, edu/currents/00-01/01-01/ice.html).
H>E: As more of the ice shelves disappear, the water temperature in the oceans would continue to rise. As a result, more of the shelf would continue to disappear. According to Professor Bill Budd of Australia’s Antarctic Co-operative Research Center, atmospheric warming can lead to surface melting, that in turn, can cause the shelf to break. Budd and his research associates also have evidence of warming of the ocean below floating ice, which shows that even one, or two tenths of a degree make a significant difference. Therefore, both atmospheric temperature and the water temperature can greatly affect the composition of the ice shelves. (http://ens.lycos.com.ens/html.)
B>E Living things emit lots of energy and chemicals into the environment. One such chemical, carbon dioxide, a greenhouse gas, could play a role in the melting of ice or helping it to disintegrate at a quicker pace due to the emitting of carbon dioxide or other chemicals. (http://www.geology.ufl.edu/Biosphere.html; and http://igbp.kva.se/cgi-bin/php/scienchistory.show.php?section_id=11&article_id=146)
B>E Manmade drilling machines or boat routes, etc. can contribute to the cause of ice shelf disintegration through the use of machinery and boats to get through to certain places that the ice shelves may block. They may be trying to reach trade routes, people, etc. but in trying to make a way in the ice it disturbs the natural balance of things and allows for pieces to be broken from the ice shelf that normally would not be done by nature causing further disintegration to the ice shelf (http://www.coolantarctica.com/Antarctoca%20fact%20file/antarctic...ht; and http://southport.jpl.nasa.gov/polar/iceinfo.html) B>E Once again, according to Carnegie Mellon University in Pittsburgh, Pennsylvania, people have been the main cause of global warming. This is due to burning coal, oil, and natural gas. These things release carbon dioxide gas into the atmosphere. This may warm the earth (hence, global warming) and cause the ice shelves to disintegrate. (http://www.eces.) L>E Along the edge of the coastal line are rocks that could cause the ice shelves to break apart. The glaciers often grind past these rocks and cause cracks and crevices to appear in the ice. If the ice plows into the rocks, the ice shelf could be destroyed.http://earthobservatory.nasa.gov
Casual Chains:
A>B>H>E>A The concentration of greenhouse gases in the atmosphere, especially carbon dioxide, has been increased by the human combustion of fossil fuels, exacerbated by deforestation. Humans have added other greenhouse gases such as methane, CFCs, and nitrous oxide to the atmosphere. The combined effect of these additional gases will be a rise in global temperatures, predicted by climate models to be between 1Cºº and 4Cºº by the end of this century. Global warming is not expected to be uniform over the globe because of the complex interactions within and between the lithosphere, hydrosphere and atmosphere. Some of the most profound changes are expected at the higher latitudes. Exposed ocean and bare earth, caused by the loss of ice and snow from melting, will result in increased absorption of solar energy (a positive feedback). Conversely, this situation will increase heat fluxes from the ocean to the atmosphere caused by the decrease in sea ice (a negative feedback) This requires us to study the Antarctic climate processes contributing to the climate system, and determine the response of the Antarctic to past climate change and compare past and present changes to estimate how many of the changes have anthropogenic causes. Many important Antarctic processes involve ice, snow and sea ice. Ice and snow, snow particularly, with its albedo limits absorption of solar energy, and sea ice acts as a blanket preventing latent heat transfer between the ocean and atmosphere. (“”Http://encarta.msn.com/encnet/refpages/refarticle.aspx?refid=761559991"”)
A>H>E Researchers propose that the ice shelf disintegration is caused by increased melt water ponds on the ice shelf surface due to the extended melt seasons in summer, as the temperatures increased. Water from these ponds fills in the crevasses in the ice surface causing them to continue through the ice shelf thickness due to the added weight of the water in the crack. With these fractures in place, the ice shelf is vulnerable to rapid break up from winds, tides, or another melt season. Satellite imagery has supported this theory as ponds were seen to contract, indicating water was draining to the sea, prior to the last disintegration event. (http://web.pdx.edy/~chulbe/science/Larsen/larsen20002.html; http://nsidc.org/sotc/iceshelves.html) Thus the mean summer temperature may be more indicative of ice shelf destruction than the previously thought mean annual temperature. Summer temperatures above freezing are more likely to promote ice shelf retreat. (http://earthobservatory.nasa.gov/Newsroom/NasaNews/20010200102264406.html)
E>A>H>B>H>A Removal of permanent ice packs would significantly increase precipitation in the Arctic Ocean and North Atlantic. Such precipitation, combined with melted sea ice, would result in the reduction of salinity of the ocean water. The North Atlantic Conveyor, which is the main driving force for the Gulf Stream and global ocean circulation. Furthermore, this could be severely reduced by these changes in salinity, global marine life would be disrupted, and the ocean would have a reduced ability to remove greenhouse gases from the atmosphere. (““"http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html””")
A>B>E>H Nature recently published an extensive review of climate and ice sheet stability which reveals that human-induced global warming might compound cyclical melting within the West Antarctic Ice Sheet, causing the sheet to collapse over the next one hundred to one thousand years. The author of the article, Dr. Michael Oppenheimer, concludes, :Atmospheric accumulation of greenhouse gases over the next 100 years could irreversibly affect the future of the WAIS." "The future of WAIS, " he added, "will be determined by internal responses of the ice sheet to millenia-scale trends in global climate and sea level, couple with changes in the accumulation and discharge of ice due to global warming." Dr. Oppenheimer does not conclude that the West Antartic Ice Sheet will collapse, only that it could. He believes that we might still be able to avert catastrophe if we reduce greenhouse gases now. Dr. Oppenheimer's data suggests that collapse of the West Antarctic Ice Sheet would likely raise sea levels by 20 feet (four to six meters). It could take more than 10,000 years for the ice sheet to reform. (http//www.asoc.org/general.iceshelve/htm)
E>B >A The fresh water from the melted ice stays at the top of the salt water where diatoms (a silicate covered phytoplankton) flourish. The Ross Sea is an example of where this occurs. Another species of phytoplankton, Phaeocystis Antarctica, is a nearly twice as productive carbon dioxide using organism –– thereby very beneficial to us. ““Should the phytoplankton community shift from P. Antarctica to diatom dominance in response to enhanced upper ocean stratification, the capacity of the biological community to draw down atmospheric carbon dioxide could diminish dramatically.”” Increased levels of carbon dioxide could be devastating to the biosphere. (Arrigo in http://earthobservatory.nasa.gov/Study/Polynyas/)
E>A>B If the sea ice were diminished through melting from warmer temperatures, there would be less Adelie penguins. Due to the warmer temperatures on the Antarctic Peninsula, the colonies of the Adelie penguins have diminished and are being replaced by colonies of other penguin species such as the gentoos and chinstraps which are not so dependent on the sea ice. (http://www.bbc.co.uk/nature/earth/warnings/antarctic_all.shtml)
E>A>H As more of the ice shelves disappear, the water temperature in the oceans would continue to rise. As a result, more of the shelf would continue to disappear. According to Professor Bill Budd of Australia's Antarctic Co-operative Research Center, atmospheric warming can lead to surface melting that in turn, cause the shelf to break. Budd and his research associates also have evidence of warming of the ocean below floating ice, which shows that even one or two tenths of a degree make a significant difference. In other words, both atmospheric temperature and the water temperature can greatly affect the composition of the ice shelves. (http://ens.lycos.com/ens/2002L-03-19-03.html.)
E>H>B Ice shelf disintegration would greatly raise the freshwater levels in the ocean while disturbing the salt levels in the ocean. Sea ice, while made of seawater, is surprisingly unsalty. The salt dissolves when the ice is formed; so when the sea ice is formed the melting would put fresh water into the salty ocean water and this would disturb the salt levels in the ocean. With the salt levels disturbed, the ocean sea life could be harmed or even die from the changes in the salt levels. (http://www.learnz.org.nz/old/98/seaice2.htm; and http://www.awi-bremerhaven.de/Eistour/index-e.html)
A>E>H Ice streams are fast moving river like currents of ice that move through an ice sheet, carrying large volumes of ice out into ice shelves. A complete collapse of an ice sheet is unlikely at this point. However, due to global warming ice streams may accelerate their flow, increasing the discharge of ice and contributing to the disintegration of the entire ice sheet. (http://www.learnz.org.nz/old/98/seaice2.htm; and http://www.awi-bremerhaven.de/Eistour/index-e.html)
E>H>L>B The disintegration of sea ice can cause pollutants to be carried to other lands causing the soil to become contaminated. Dirty sea ice has been observed coming from the arctic ice shelves. Sea ice seems to be a key element in the transport of contaminants. Sea ice can incorporate contaminants if the water from which it freezes is contaminated, if the contaminated sediments are frozen into the ice, if it picks up pollutants from the surface ocean micro layer during drift, and if pollutants are deposited on its surface from atmospheric deposition, such as acid rain. Accumulated contaminants are released into the ocean as the ice thaws, refreezes and thaws again. As the sea ice flows into warmer water and melts, the contaminated sediments can flow to nearby shores interacting with the soil. The uppermost or O horizon of the soil represents organic debris, decomposed leaves, branches, and grass stalks from the growing plants. The A1 horizon is dark in color and contains humus, finely divided organic material, which has been worked into the earth by the activities of soil animals, especially earthworms. If the pollutants from the sea ice affect the soil, it would not be able to support plant life. (Acidic water could even cause chemical burns on the plant leaves) The pollutants in the ground would also affect the soil animals. The A1 and O layers combined are called topsoil and the soil animals play a key role in soil formation. (http://arcus.org./RAISE/RAISE.pdf) (http://www.pages.unibe.ch/calendar/calextras/Images2000.html) (http://rainbow.Ideo.columbia.edu/edf/text/enviice.html) (http://antcrc.utas.edu.au/aspect/seaiceglossary.html)
Summary: There has been much controversery over ice shelf disintegration. Although the process of disintegration takes long periods of time they do indeed cause much damage to some aspect of each sphere. Exposed ocean and bare earth, caused by the loss of ice and snow from melting, will result in increased absorption of solar energy. Therefore, the situation will increase heat fluxes from the atmosphere caused by the decrease in sea ice. Thus, it will have an impact on the atmosphere as well as the other spheres. Ice shelf disintegration greatly affects the biosphere. Continued loss of sea ice can adversely affect the regional and in time the global biosphere as food chains are disrupted and habitats lost. Ice shelf disintegration greatly affects the hydrosphere. ““The total volume of the ice sheet covering Antarctica is estimated to be 29 million cu km (7 million cu mi), or about 90 percent of the world’s ice. If the ice sheet melted, the oceans of the world would rise by 60 m (200 ft). Ice shelf disintegration can greatly affect the lithosphere by increasing landmass. Some 11 percent of the ice sheet consists of ice shelves——massive floating slabs of permanent ice fringing the continent——that are anchored to the rock and extend into the surrounding ocean. The largest, Ross Ice Shelf, is about the size of France. The Antarctic ice sheet has an average thickness of 2,160 m (7,090 ft); its greatest recorded depth is more than 4,700 m (15,400 ft).”” (Microsoft®® Encarta®® Reference Library 2002. ©© 1993-2001 Microsoft Corporation.)
Resources: (http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2002/200203188307.html) (http://earthobservatory.nasa.gov/Newsroom/NasaNews/20010200102264406.html) (http://earthobservatory.nasan.gov/Study?ClimateClues/ ) (http://earthobservatory.nasa.gov/Study/LarsenIceShelf/ ) (http://earthobservatory.nasa.gov/Study/Polynyas/) (http://earthobservatory.nasa.gov/Study/UpperCrust/) (http://igbp.kva.se/cgi-bin/php/scienchistory.show.php?section_id=11&article_id=146) (http://nsidc.org/iceshelves/larsen1995/index.html) (http://nsidc.org/sotc/sea_ice.html ) (http://southport.jpl.nasa.gov/polar/iceinfo.html) (http://web.pdx.edu/~chulbe/science/Larsen/larsen2002.html) (http://yosemite.epa.gov/oar/globalwarming.nsf/content/NewsandEventsScienceandPolicyNews.html) (http://www.awi-bremerhaven.de/Eistour/index-e.html) (http://www.awi-bremerhaven.de/Eistour/pinguine-e.html ) (http://www.bbc.co.uk/nature/earth/warnings/antarctic_all.shtml ) (http://www.climatehotmap.org/antarctica.html) (http://www.cnn.com/2002/TECH/space/05/09/iceberg.satellite/index.html) (http://www.coolantarctica.com/Antarctoca%20fact%20file/antarctic...ht) (http://www.coolantarctica.com/Antarctica%20fact%20file/antarctic.../seaaice%20formation.ht) (http://www.exploratorium.edu/climate/cryosphere/data4.html) (http://www.exploratorium.edu/climate/cryosphere/data5.html) (http://www.exploratorium.edu/climate/cryosphere/index.html) (http://www.geoghraphy4kids.com/files/land_biosphere.html) (http://www.geology.ufl.edu/Biosphere.html) (http://www.learnz.org.nz/old/98/seaice2.htm) (http://www.meteor.iastate.edu/gcp/sealevel/ross.html) (http://www.newscientist.com/hottopics/climate/climate.jsp?id=ns99992203) (Microsoft®® Encarta®® Reference Library 2002. ©© 1993-2001 Microsoft Corporation.) (Http://www.antcrc.utas.edu.au/aspect/seaiceglossary.html) (http://bsxisgb.nbs.ac.uk) (http://whyfiles.org/091beach/5.html) (http:encarta.msn.com/encnet/refgapes/refarticle.aspx?refid=761559991) http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html http://asoc.org/general/iceshelve.htm http://www.enn.com/enn-news-archive/1999/04/040999/iceretreat_z583.asp http://wwwnsf.gov/pubs/1999/nsf98016htm/nsf98106m6.html “Meltdown: Satellites Show Accelerated Polar Ice Threat” by Robert Roy Britt. Sunday Report: Melting Releases Riddles on Global Warming Los Angeles Times, 04/01/01. Http://www.eurekalert.org/pub_releases/2002-03/uoca-ais031802.php http://maxpages.com/global warming http://www.pog.su.se/sea/04_coastal.htm http://earthobservatory.nasa.gov http://www.umich.edu/~gs265/isost.html http://www.ecology.com/ecology-today/tracking-air-pollution http://www.usatoday.com/weather/antarc/aiceshet.htm http://webworld.unesco.org/water/ihp/publications/waterway/wepc/difinition http://distance.una.edu/ess5-8/countline/week10b.html http://nsidc.org/crosphere/coldfacts.html http://www.colorado.edu/PublicRealtions/NEwsRelease/2001/1008.html http://www.ucse,edu/currents/00-01/01-01/ice.html http://ens.lycos.com/ens/2002L-03-19-03.html http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/ATM_CHEMM/atmospheric_structure.html (http://nsidc/iceshelves/larsen1995/index.html
Submitted by Team Navigators: (Christa Bolton, Chris Higginbottom, Dorinda South, Stacie White, and Joshua Winters ) UNA GE601