2 WHAT IS AN ICE SHEET?An ice sheet is a mass of glacial land ice extending more than 20,000 square miles.
3 HOW DO ICE SHEETS FORMIce sheets form in areas where snow fall in the winter doesn't completely melt during the summer. Layers and layers build up and grow thicker and denser over thousands of years.Ice sheets are constantly in motion. Moving under their own weight.As long as the the sheet accumulates as much snow as it loses to the ocean it remains stable.
4 WHY ARE ICE SHEETS IMPORTANT? Ice sheets contains huge quantities of frozen water.Influence weather and climate.
5 GREENLAND'S ICE SHEET Over 110,000 years old Covers about 80% of Greenland660,000 square milesSecond largest ice sheet in the worldIt is between miles thickContains 10% of the worlds fresh waterThe weight of the ice sheet is so great that it has pushed the center of Greenland 1000 feet below sea level.
7 THE MELTING ICE SHEETThe Greenland Ice Sheet is located in the Arctic. The arctic climate is warming.The sheet has experienced record melting.The melting has increased by 16% fromRoger J. Braithwaite, The University of Manchester, UK. Image Source: NASA..
8 THE MELTING ICE SHEET'Fears have grown that continued climate change will make the Greenland Ice Sheet cross a threshold where long-term melting of the ice sheet is inevitable. Climate models project that local warming in Greenland will be 5 °F to 16 °F during this century.''Ice sheet models project that such a warming would initiate the long- term melting of the ice sheet, leading to a complete melting of the ice sheet.'
9 DYNAMIC THINNING-'The ice sheet is losing volume from its edges. Glaciers appear to be losing ice at a much faster rate than predicted, and the sides of the ice sheet are losing mass much more quickly than it can accumulate in the interior. This loss is partially due to the increase in runoff from melting caused by warm-weather events, a process called dynamic thinning. Dynamic thinning does not affect all glaciers equally— glaciers lying on top of bedrock that smoothly slopes toward the sea are most strongly affected.'-'Dynamic thinning is, in a way, a positive feedback loop. When it gets warm enough, the surface snow and ice begin to thaw. The melted water either pools or flows in rivers along the surface, or begins flowing under the snow that covers the ice of the sheet. In the process, it flows into small cracks, enlarging them as it moves towards the bottom of the ice sheet.'-'The streams bring surface heat in the form of water down through the glacier to the bottom of the ice sheet. Once the water reaches the bottom of the glacier, it acts as lubrication for the glacier, which then gains speed as it flows downhill towards the sea. Thus, a little melting can have a large effect.'
10 WHY DOES IT MATTER? There are 4 Reasons Sea Level Ocean Circulation Global Heat TransferRegional Atmospheric Circulation
11 SEA LEVEL As the ice sheet melts the sea levels are rising. If the entire ice sheet were to melt it would raise sea levels by 23 feet.This could be a global catastrophe, depending on how fast this occurs.About a third of the World's population live on coastlines.
12 SEA LEVEL CONT.If ocean levels were to rise 2- 3 feet (very possible to happen in the next 20 years) serious global problems would arise.Coastal ErosionLoss of islands, sand bars and reefsIncrease Storm SurgeOcean levels usually rise between 3 and 4 millimeters a year.
13 OCEAN CIRCULATIONIf the Greenland Ice Sheet were to melt at a faster rate it would change the circulation of the ocean.As the freshwater would run off it would collect on top of heavier salt water in the North Atlantic.This would change the salinity in the water which could depress the Gulf Stream.Features/Greenland/greenla nd_sidebar.phpIf the Gulf Stream depresses this could cause a change in the North Atlantic circulation patterns.These circulation patterns is what controls the weather patterns in Europe.Salinity: is the saltiness or dissolved salt content of a body of water
14 GLOBAL HEAT TRANSFERLoss of ice affects the Global Heat TransferHeat transfer is driven by temperature change. The larger the difference the faster the heat flows.'As the polar regions warm, the temperature difference between the equator and the poles is reduced, altering global atmospheric circulation patterns by reducing the force that drives equatorial heat energy toward the poles.'' Much of the world’s current pattern of rainfall would be altered.'s/Greenland/greenland_sidebar.ph p
15 REGIONAL ATMOSPHERIC CIRCULATION On average the top of Greenland (8,400 feet) is ice.This physical mass of ice affects the regional atmospheric circulation patterns.As the ice melts the patterns will change.