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Ice Sheets ESS Compilation B > A > E > H > B>A Human activities have increased the levels of greenhouse gases in the atmosphere and have thus augmented global temperatures (1). Greenhouse gases include water vapor, carbon dioxide, and methane, and they are part of the Greenhouse Effect. The Greenhouse effect is a naturally occurring phenomenon that helps regulate the temperatures on Earth. However, since the industrial revolution, humans have rapidly increased the amount of greenhouse gases in the atmosphere, thus increasing their effectiveness in keeping Earth warm. For example, the burning of fossil fuels (coal, natural gas, oil) has caused concentration of carbon dioxide in the atmosphere to increase from about 280ppm in pre-industrial times to 386ppm in 2008 (2). Furthermore the Figure 1: Atmospheric concentrations of carbon dioxide and transformations of forests to cattle ranches methane (IPCC, 2007). and rice paddies have increased the amount of methane in the atmosphere. Methane concentrations have risen from 700 ppb in pre-industrial times to 1775ppb in 2005 (3) (see Figure 1). Thanks to the human actions and their consequential influence on the Greenhouse Effect, over the past century average global temperature has risen 1.3oF and will reach an increase of 3oF to 7oF by 2100 if emission of greenhouse gases remain at the current rates (1). Arctic temperatures, however, have been affected far more dramatically than the global average. Winter warming has exceeded 4 oC in some Arctic regions. In response to these higher temperatures, extent of arctic ice has also been declining (13). Each year in the Arctic in the beginning of summer, the ice cap covering the North Pole, start to recede and regenerate at the onset of winter. According to Ocean Conservancy, scientists have been measuring the ice caps in the middle of the summer since 1979. The scientists report that, “In 2005 the extent of sea-ice was 20% lower than 1979”, which is certainly a troubling trend (see Figure 2). Then, just two years later, in 2007, the cap receded to a level 43% lower than the 1979 Figure 2: Seasonal and annual Northern Hemisphere sea ice measurement—a rate that startled everyone, extent. (University of Illinois, 2008) including scientists. If this trend continues, the North Pole could be entirely devoid of summer sea ice by 2050” (10). The increase in global temperatures can cause sea levels to rise due to the natural expansion of seawater as it warms and the melting of land-based ice (see Figure 3). According to Roach (2006), sea levels globally have risen an estimated 0.1 inch a year over the past decade (4). Many scientists fell that it is possible for global sea levels would rise and estimated 20 -21 feet if all of the ice on Greenland were to melt into the North Atlantic Ocean. Greenpeace organization estimates that the Antarctic ice sheet holds enough frozen water ( 60% of Earth’s freshwater is stored in these sheets) to make sea levels rise 203 feet (7). This rise in sea level will greatly affect coastal ecosystems. As sea level rises, existing coastal marshes and mangrove ecosystems will be eroded away. Rising water levels will create new wetlands, however it is anticipated that these new systems will be significantly smaller due to human structures (see Figure 4). By 2080, as 3 (EPA,into 2009) much as 33% of the world’s coastal ecosystems couldFigure be flooded open water systems (1). The EPA estimates that a two-foot rise in sea level would lead to 17-43% of American wetlands being lost. Furthermore, according to the Nature Conservancy, some of the most atrisk ecosystems from sea level rise are mangroves. Mangroves systems with little sedimentation and on low relief islands are especially in danger. Mangroves are especially important to the biosphere because they provide a habitat and nursery area for many animals, and also produce oxygen through photosynthesis. Though the process the mangroves absorb carbon dioxide and expels oxygen into the Figure 4: Wetland ecosystem loss by rising sea level atmosphere. If the mangroves die off, there will be less carbon dioxide absorbed, thus increasing the amount of carbon dioxide emitted into the atmosphere. As stated earlier, the more carbon dioxide there is in the atmosphere, the warmer global temperature will become. References: 1. Intergovernmental Panel on Climate Change (IPCC). (2007). Changes in Atmospheric Constituents in Radiative Forcing. Climate Change 2007: The Physical Science Basis. Cambridge University Press: Cambridge, U.K. 2. Hofmann, D.J., Butler, J.H., Tans, P.P. (2009). A new look at atmospheric carbon dioxide. Atmospheric Environment 43(12), 2084-2086 3. University Corporation for Atmospheric Research (UCAR). (2007). Climate and global change. Windows to the Universe. Retrieved from http://www.windows.ucar.edu/tour/link=/earth/climate/climate.html 4. Roach, J. (2006). Greenland Ice Sheet Is Melting Faster, Study Says. National Geographic News. Retrieved from : http://news.nationalgeographic.com/news/2006/08/060810-greenland.html 5. (2006). Study Previews Ice Sheet Melting, Rapid Climate Change. Retrieved from : http://www.sciencedaily.com/releases/2006/03/060312210108.htm 6. (2004) A Chilling Possibility. Retrieved from: http://science.nasa.gov/headlines/y2004/05mar_arctic.htm 7. http://www.greenpeace.org/international/campaigns/oceans/globalwarmingoceans 8. http://pubs.usgs.gov/fs/fs2-00/ 9. http://www.theglobaleducationproject.org/earth/global-ecology.php 10. http://www.oceanconservancy.org/site/News2?page=NewsArticle&id=10341 11. http://earthobservatory.nasa.gov/Features/Water/water_2.php 12. http://www.oceanconservancy.org/site/News2?page=NewsArticle&id=10341 13. University of Illinois Polar Research Group (2008). The Cryosphere Today. Retrieved from http://arctic.atmos.uiuc.edu/cryosphere/ E>H>A The water in our world's oceans is constantly moving whether it is pushed and pulled by tides or blown by waves. Through the force of the Great Ocean Conveyor Belt (also called the thermohaline circulation) the ocean is gradually circulating around the globe. One of the most well known parts of the Great Ocean Conveyor is the Gulf Stream and North Atlantic Drift, which helps give Europe a somewhat moderate climate. Because it is powered by distinctions in water temperature and salinity, the melting of a large part of the Arctic ice could switch off, slow down or divert the Great Ocean Conveyor. Salt water freezes at a lower temperature than fresh water. At the poles, ocean salinity is about 35 ppt, and sea water begins to freeze at -1.8 degrees Celsius (5). As the sea water freezes, salt is excluded and concentrated into liquid droplets of extremely saline brine, which are expelled back into the ocean. The formed ice will eventually be fresh enough to drink as the brine drains out (5). This expelled brine causes the water around the sea ice to be extremely saline and denser than Figure 5: The global oceanic conveyer belt, is a unifying concept surrounding water, causing it to sink. This that connects the ocean's surface and thermohaline (deep mass) cold and dense polar water moves along the circulation regimes, transporting heat and salt on a planetary ocean bottom towards the equator, where scale. it warms and rises, and travels along the surface back to the poles (see Figure 5). However, as sea ice melts and introduces fresh water to polar oceans, thermohaline circulation can be disrupted. Australian scientists feel that the melting ice could release too much fresh water and could get in the way with the formation of dense "bottom water," which sinks 4-5 kilometers to the ocean floor. A slowdown in the system known as "overturning circulation" (2009) could have a great affect on the way the ocean carries heat around the globe. Unfortunately, if the ocean water salinity drops too low, the Great Ocean Conveyor will not be able to make water cold and salty enough to sink. “Only a few places around Antarctica and in the northern Atlantic create water dense enough to sink to the ocean floor, making Antarctic "bottom water" crucial to global ocean currents”. The interplay between ocean and atmosphere is one of the keys to understanding Earth’s climate. Wind not only helps redistribute heat around the world and help drive ocean surface currents. Currents in turn redistribute the heat the ocean carries and play a major role in shaping global temperature and rainfall patterns. For example, Europe is relatively warm because ocean currents circulate heat from the equator up the east coast of North America, and westward to Europe. As the warm surface water cools as it reaches Europe, heat is released to the atmosphere (5). As phenomenon such as El Niño demonstrate, even subtle shifts in winds and surface currents can profoundly impact temperature and rainfall patterns both locally and globally. References: 1. Byrnes, M. (2009).Southern Ocean current faces slowdown threat. Retrieved from : http://www.asoc.org/Portals/0/pdfs/Southern%20Ocean%20current%20faces%20slowdown%2 0threat.pdf 2. Ewing, B (2009). Warming oceans could shift earth’s axis. Retrieved from: http://news.nationalgeographic.com/news/2008/03/080314-warming-quakes.html 3. http://www.greenpeace.org/international/campaigns/oceans/globalwarmingoceans 4. http://www.theglobaleducationproject.org/earth/global-ecology.php 5. University of Colorado at Boulder National Snow and Ice Data Center. All About Sea Ice. Retrieved from: http://nsidc.org/seaice/index.html E>L>A>H>H>L It is well known that the rising global temperatures cause ice to melt. The resulting meltwater percolates down the cracks of the ice. However, what happens in the invisible region underneath where the ice meets rock, soil, and water is still largely unknown. Moreover, Greenland ice sheet spills out through gaps in the mountain rim, and the glaciers cover deep narrow valleys. According to van der Veen and other scientist, Greenland valleys have higher than usual geothermal gradients. As a result, it may be geothermal heat rather than global warming that causes some of the Greenland glaciers to have higher than usual flow rates. Furthermore, in parts of the world, glaciers have been receding since 1895 and with an increasing pace since 1930 and to date there are no obvious explanations for this and the dates have no clear counterpart in temperature or carbon dioxide records. When the ice accumulates, there can be a delay in the bedrock sinking for thousands of years which cause the ice sheets to be positioned at a higher elevation and more positive ice mass that results in the ice growing faster. However, during ice melting, the bedrock rebound can also be delayed for thousands of years but ice sheets are positioned at lower, warmer elevation which causes negative ice mass balance which results in the ice melting faster. The flow of ice is generally slow also known as glacially slow. In Greenland, the Upernivek Glacier in Greenland flows at about 40 meters per day. As the ice sheet melts and reaches a lower altitude, due to depressed land surface, where the temperature is higher, it starts to melt and evaporate at the same time, a process called ablation. If growth and melting are at a balance, the ice would be described as being stationery. If precipitation exceeds melting, the ice would be described as growing and if melting exceeds precipitation the ice would be described as receding (2). As ice sheets melt, they can release pent-up energy and trigger massive earthquakes, according to new study. Roughly 10,000 years ago a series of large earthquakes shook Scandinavia along fault lines that are now quiet. Each earthquake occurred in roughly the same time period of the melting of the thick ice sheets from the last ice age. Scientists think that the melting of the ice sheets triggered the earthquakes by releasing the pressure that had been building up on Earth’s crust, and triggered these earthquakes by releasing pressure that had built up in Earth's crust. References: 1. Inman, M. (2008). Melting Ice Sheets Can Cause Earthquakes, Study Finds. National Geographic News. Retrieved from: http://news.nationalgeographic.com/news/2008/03/080314-warming-quakes.html 2. http://earthobservatory.nasa.gov/Newsroom/view.php?id=31651 3. http://icecap.us/images/uploads/OllierPaine-NoIceSheetCollapse-AIGNewsAug.2009.pdf A>H>E>H>L The hydrologic cycle, also called the water cycle is a model that describes the movement and storage of water between Earth’s four spheres. On Earth, water can be stored in any of the following reservoirs: atmosphere (water vapor), oceans, lakes, streams, rivers, groundwater, soil, snowfields and ice sheets (glaciers and icebergs). Earth’s water can be continuously cycled through threes reservoirs through process like condensation, precipitation, evaporation, sublimation, transpiration, infiltration, groundwater flow and melting. According to www.physicalgeography.net, 2.05 percent of Earth’s water is stored in ice caps and glaciers and water lasts in glaciers for 20 to 100 years. Meltwater contains both fluvial and glacial processes, therefore certain distinctive landforms are found in glacial ablation environments or rather areas that have been affected by the erosion of glaciers. They can be formed either by the erosion of ice or streams or a combination of the two. Sediment that becomes deposited by glacial meltwater is called stratified drift. Deposits of sediments from outwash streams are a little different. Outwash streams are comprised mostly meltwater, and because of this are tied much closely to glacial ablation. It is with this that outwash streams change with local climate conditions. Table 8a: Hydrologic Cycle Table 8b-1: Inventory of water at the Earth's surface. Reservoir Oceans Volume (cubic km x 1,000,000) Percent of Total 1370 97.25 Ice Caps and Glaciers 29 2.05 Groundwater 9.5 0.68 0.125 0.01 Lakes Soil Moisture 0.065 0.005 Atmosphere 0.013 0.001 Streams and Rivers 0.0017 0.0001 Biosphere 0.0006 0.00004 Table 8b-2: Typical residence times of water found in various reservoirs. Reservoir Average Residence Time Glaciers 20 to 100 years Seasonal Snow Cover 2 to 6 months Soil Moisture 1 to 2 months Groundwater: Shallow Groundwater: Deep 100 to 200 years 10,000 years Lakes 50 to 100 years Rivers 2 to 6 months Block diagram of the glacial drainage system. References: 1. http://www.physicalgeography.net/fundamentals/8b.html 2. http://earthobservatory.nasa.gov/Features/Water/water_2.php 3. http://www.teachersdomain.org/resource/ipy07.sci.ess.watcyc.icesimulate/ E>L>B>A>H The cryosphere is composed of all of the frozen water found in the hydrosphere. The two components that comprise it are the continental or land ice and sea ice. Continental ice can be found mainly in Greenland and Antarctica however you can also find smaller ones in China and South America. Valley glaciers which are part of continental ice can actually be found on every continent except Australia. Continental ice forms when snow accumulates on the surface of land and over time compresses under the weight of snow on the surface. Snow accumulates during the winter from precipitation and accumulates from the weight of the new snow. As the snow melts, water filters into the snow and fills in the available air space and freezes at the snow-ice boundary. The continental ice formation and flow process is generally very slow and the build up or decay of ice sheets like valley glaciers can take decades or centuries. Sea ice is formed by the freezing of sea water. Ocean water is salty, and when it freezes the salt is left in the water and leaves the rest of the water around it denser and with a higher salinity. River and lake ice is frozen mainly from fresh water generally and is therefore is not salty. Melting of ground ice leads to thermokarst erosion- the ground surface subsides as ice melts, causing depressions. These depressions tend to form melt lakes. Bacteria breaking down this newly exposed organic-rich substrate carry out methanogenesis in the anaerobic environment of the melt lake. Bubbling up methane from anaerobic methanogeneis in thermokarst lakes could increase methane emissions to the atmosphere by 15-40%. Because methane is a powerful greenhouse gas, this could provide a positive feedback to global warming, leading to further ice melt (Walter, et al, 2006) References: 1. Post, E., Forchhammer, M.C., Bret-Harte, M.S., Callaghan, T.V., Christensen, T.R., Elberling, B., Fox, A.D. (2009). Ecological dynamics across the Arctic associated with recent climate change. Nature 325, 1355-1358. 2. Schiele, E. (2009). Melting Ice Sheets Impact. Retrieved from: http://www.bbc.co.uk/climate/impact/glaciers.shtml 3. Walter, K.M., Zimov, S.A., Chanton, J.P., Verbyla, D., Chapin, F.S. (2006) Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming. Nature 443, 71-75. 4. United States Environmental Protection Agency (EPA). (2009). Frequently asked questions about Global Warming and Climate Change: Back to basics. Retrieved from http://www.epa.gov/climatechange/downloads/Climate_Basics.pdf 5. University of Illinois Polar Research Group (2008). The Cryosphere Today. Retrieved from http://arctic.atmos.uiuc.edu/cryosphere/ 6. http://earth.rice.edu/mtpe/cryo/cryosphere.html B>A> E> L>H> A>B Human activities have increased the levels of greenhouse gases in the atmosphere and have thus augmented global temperatures. Greenhouse gases include water vapor, carbon dioxide, and methane, and they are part of the Greenhouse Effect. The Greenhouse effect is a naturally occurring phenomenon, that helps regulate the temperatures on Earth. However, since the industrial revolution, humans have rapidly increased greenhouse gases and thus have rapidly increased their effectiveness in keep planet earth warmer. For example, the burning of fossil fuels (coal, natural gas, and oil) has caused concentration of carbon dioxide in the atmosphere to increase from about 280ppm in pre-industrial times to 386ppm in 2008. Furthermore the transformations of forests to cattle ranches and rice paddies have increased the amount of methane into the atmosphere. Methane concentrations have risen from 700 ppb in pre-industrial times to 1775ppb in 2005. Thanks to the human actions and their consequential influence on the Greenhouse Effect, over the past century average global temperature has raised 1.3oF and will reach an increase of 3oF to 7oF by 2100 if emissions of greenhouse gases remain at the current rates. Several of the studies on climate changed propose that the greatest amount of temperature increases are occurring or will occur over Earth’s poles, where the largest ice sheets are located. In fact, data records on Antarctica’s show that the continent’s average surface temperature has increased about .05 degrees Celcius per decade since 1957. Not surprisingly, another scientific study conducted by Johannessen from 1978 to 1995 indicates that the arctic sea ice has been decreasing about 2.7% per decade. There is a strong link between global temperature increase and ice sheet decline, leading many scientists to believe that global warming may be the underpinning cause of the melting. For example, a five nation scientific team claims that a small increase in carbon dioxide, a greenhouse gas that triggers global warming, may affect the stability of the West Antarctic Ice Sheet and may even cause it to disappear over time, in approximately 1000 years. Furthermore, research by NASA Goddard scientists show that when the temperatures are warmer, the ice sheets of Greenland are moving quicker. Higher temperatures melt ice sheets first around the outside and it takes a very long time for it to affect the middle. Jim Swenson, a scientist and teacher, explained that this is similar to a piece of cloth that is cut at one border with scissor, so that if the cloth is shaken or rubbed the handing threads at the edge are ready to come apart. It does not come apart in the middle, just on the edges. Similarly, when heat is added to the exterior of the ice, the water molecules on the outside that were once glued together as ice, begin to turn to water molecules and join together. By melting, the molecules use up some of the heat energy, thus protecting the interior. But some of the heat energy gets near and melts the interior. As one Copenhagen scientist explains, “the areas lying near the coast begin to decrease in size, because the ice is melting at the edge. When the ice melts at the edge, it slowly causes the entire ice sheet to 'collapse' and become lower.” Thus there are many examples and strong evidence to show that increasing global temperatures have resulted in ice sheet retreat. Ice sheets, long expanses of snow and ice, have very high albedos, or an ability to reflect incoming solar radiation back into space. However, as ice sheets melt and turn into ocean landscapes, the earth begins to absorb almost four times as much solar energy. High latitude ocean albedo is typically near 10%; while snow or ice covered albedo at the same latitude can reach as high as 60% (Hartmann 1994). This is because snow and ice are a lighter color than the ocean’s surface, and the lighter the colors reflect more wavelength of light than darker colors. Think about a really hot Florida day, would one be hotter wearing a black shirt or a white shirt? Black, of course, because it absorbs more wavelengths of light. So, if the ice turns to ocean, more solar radiation will be absorbed, and the warmer the temperatures on earth will become. This will lead to more ice melting and the less solar radiation will be reflected and the cycle begins all over again. This process is called the ice-albedo feedback and is particularly alarming in the context of ice sheet melting because it could potentially rapidly increase the speed of their retreat. Loss of Arctic ice and snowpack from global warming and the ice-albedo feedback severely threatens the viability of species which depend on sea ice for hunting, reproducing, or avoiding predators (Post et al, 2009). Polar bears are considered by wildlife biologists to be “highly pagophilic,” literally meaning they are “ice-loving” and indicating the extreme dependence the species has on ice. Polar bear populations have declined by 22% in Canada’s Hudson Bay and by 50% in Alaska’s Beufort Sea (Post et al, 2009). The USGS has projected that 75% of the polar bear population will be gone by 2050 due to ice loss Polar bears resting on sea ice (Glick, 2007). Canadian Wildlife Service has also documented polar bears displaying decreased weight and lowered reproductive rates in Canada’s James and Hudson Bays. The average weight of a mature female bears fell from 650 pounds in 1980 to 507 pounds in 2004(Glick, 2007). The number of recorded drowned polar bears has also shown a disturbing increase. This is attributed to retreating ice forcing bears to swim increasingly long distances to reach ice large enough on which to rest (Glick, 2007). Melting ice has also lead to increased cub mortality as dens collapse and either crush or reduces insulation and exposes newborns to hypothermia and predation (Post et al, 2009). Den collapse is also a growing cause of mortality for ringed seals, which also create birth dens within ice or snow pack (Post et al, 2009). However, other animals benefit from retreating ice sheets. Earlier spring melt will lengthen growing seasons. Plant species have already be found to flower up to 20 days earlier over the last decade. Ice melt has also favored reindeer populations as winter mortality decreases and reproductive rates increase (Post et al, 2009). Polar species are often highly adapted ice cover. As ice retreats, however, invasive species can immigrate into newly ice-free areas and outcompete specialized species. For example, red foxes are currently displacing Arctic foxes from their traditionally ice and snow-covered territories. Finally, milder ice-free conditions also allow new parasites and insects to invade Arctic ecosystems. For example, the winter moth is currently moving northward and feeding on birch forests traditionally outside its range (Post et al, 2009). http://www.nytimes.com/2008/01/08/science/earth/08gree.html ^ Deser, C., J.E. Walsh, and M.S. Timlin (2000). "Arctic Sea Ice Variability in the Context of Recent Atmospheric Circulation Trends". J. Climate 13: 617–633. doi:10.1175/1520- 0442(2000)013<0617:ASIVIT>2.0.CO;2. http://ams.allenpress.com/perlserv/?request=getabstract&doi=10.1175%2F1520-0442(2000)013%3C0617:ASIVIT%3E2.0.CO%3B2&ct=1. http://esseacourses.strategies.org/private/learner.module.php?course_id=276&coursemodule_id= 656&cycle=A&cycle_label=4 http://www.worldclimatereport.com/index.php/2006/10/11/antarctic-ice-sheet-and-the-plotthickens/ http://www.ens-newswire.com/ens/mar2006/2006-03-13-03.asp http://www.newton.dep.anl.gov/askasci/gen01/gen01520.htm University of Copenhagen (2009, September 17). Melting Of The Greenland Ice Sheet Mapped. ScienceDaily. Retrieved September 30, 2009, from http://www.sciencedaily.com /releases/2009/09/090916133508.htm Clement, A.C., Burgman, R., Norris, J.R. (2009) Observational and model evidence for positive low-level cloud feedback. Science 325, 460-464. Hofmann, D.J., Butler, J.H., Tans, P.P. (2009). A new look at atmospheric carbon dioxide. Atmospheric Environment 43(12), 2084-2086 Intergovernmental Panel on Climate Change (IPCC). (2007). Changes in Atmospheric Constituents in Radiative Forcing. Climate Change 2007: The Physical Science Basis. Cambridge University Press: Cambridge, U.K. United States Environmental Protection Agency (EPA). (2009). Frequently asked questions about Global Warming and Climate Change: Back to basics. Retrieved from http://www.epa.gov/climatechange/downloads/Climate_Basics.pdf University Corporation for Atmospheric Research (UCAR). (2007). Climate and global change. Windows to the Universe. Retrieved from http://www.windows.ucar.edu/tour/link=/earth/climate/climate.html H>B>A> E> H> A>L Ice sheets basically originate and form in places where the snow that falls in the winter does not melt entirely over the summer, such as Greenland. Over the years, layers of snow begin to pile up into thick masses of ice. The ice layers grow thicker and become denser as the weight of new ice compresses the old layers. It is believed that because of an increased in global temperatures due to anthropogenic causes, ice sheets could possibly be thickening. In contradiction to scientists who believe that ice sheets will continue to retreat, some scientists believe that the retreat of ice sheets will be offset by increased snowfall. Increases in global temperatures may help new ice sheet growth because ice sheet growth relies more on moisture and very heavy snowfall than colder temperatures (Johnson, secrete of ice ages).Basically, a warmer atmosphere can hold and transfer more water vapor, which will turn to snow when it freezes, than a colder atmosphere. For instance, global climate change modules predict that since the climate is warmer over Antarctica, snow fall should actually increase because the warmer atmosphere can hold more moisture. If snow fall and accumulation increases, then it is assumed that ice sheets should thicken. This is supported by new research by Joughin and his team of scientists, who discovered that the West Antarctic Ice was actually thickening. Ice sheets are also constantly moving. They slowly flow downhill from the pressure of their own weight. According to the National Snow and Ice Data Center, “Near the coast, most of the ice moves through relatively fast-moving outlets called ice streams, glaciers and ice shelves. As long as an ice sheet accumulates the same mass of snow as it loses to the sea, it remains stable.” Joughin and his team studied the flow of ice streams that run from the middle of the ice sheet to the ocean. Since the water runoff is decreasing, the ice sheet must be holding onto the water, which would thus cause it to thicken. References: http://www.scienceagogo.com/news/20020927213400data_trunc_sys.shtml http://www.aip.org/history/climate/floods.htm http://www.worldclimatereport.com/index.php/2006/10/11/antarctic-ice-sheet-and-the-plotthickens/ http://abcnews.go.com/Technology/story?id=98113&page=1 L>E>L>A>B Some scientists purport that underground geothermal heating may be the cause for ice sheet melting in Greenland. For example, according to van der Veen and other scientist, Greenland valleys have higher than usual geothermal gradients. As a result, it may be geothermal heat rather than global warming that causes some of the Greenland glaciers to have higher than usual flow rates. Many scientists feel that is possible for global sea levels to raise an estimated 20-21feet if all of the ice of Greenland were to melt into the North Atlantic Ocean. The melting of ice and rise in sea levels around Greenland has severely impacted wildlife. For example, although walrus are more of a marine species, they still depend on sea ice for resting. Retreating ice has forced walrus to travel farther to forage, and scientists have noted an alarming increase in abandoned walrus pups which have become separated from their mothers as they travel farther out to sea. These lone pups have almost no chance at survival (Post et al, 2009). Furthermore, as floating ice becomes unavailable, walrus have gathered on rocky shores by the thousands. This conglomeration has lead to increased mortality from trampling (Post et al, 2009). Post, E., Forchhammer, M.C., Bret-Harte, M.S., Callaghan, T.V., Christensen, T.R., Elberling, B., Fox, A.D. (2009). Ecological dynamics across the Arctic associated with recent climate change. Nature 325, 1355-1358. http://icecap.us/images/uploads/OllierPaine-NoIceSheetCollapse-AIGNewsAug.2009.pdf