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Why don't the glaciers just melt?

  1. Aug 14, 2010 #1
    So I was looking at a map of my country (Norway), and we have a couple of glaciers. Now, I understand that when they're at high altitude they don't melt, but I saw some of them reaching down as low as 300 meters above sea level. How come they don't just melt...? It's 20 C for like 5-6 months!
     
  2. jcsd
  3. Aug 14, 2010 #2
    They are continuously replenished through rain and snow.
     
  4. Aug 14, 2010 #3
    I get that, but down to 300 meters....? I figured it would melt much more than what comes down...
     
  5. Aug 14, 2010 #4

    Astronuc

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    I think part of it is that the ice reflects a lot of light.

    Is it 20 C at the glaciers? What is the temperature at night? What is the water temperatures in the vicinity of the glaciers?

    There's a lot glacial mass compared to air mass.
     
  6. Aug 16, 2010 #5

    Partly for the same reason snow remains in shaded areas of my backyard that the sun doesn't reach long after the other snow has melted and air temperatures have risen above freezing. It takes a lot of heat to melt snow and ice because water has a higher specific heat than air and most other substances. It takes over 4 times more heat to raise the temperature of a gram of water than is needed to raise the temperature of a gram of air. The exact amount varies with air pressure and the water content of the air. Thus a lot of warm air is required to melt ice.

    Another factor is that glaciers could be described as "living". They may continually gain and lose ice. Ice forms on the top as moisture accumulates from snow or freezing rain. the added weight causes the glacier to move downhill where the terrain allows such movement. Even if the ice at the low end melts, more ice can form on the top giving the appearance that ice at the low end is not melting.

    If melting ice evaporates it rises and then refreezes if it passes over the glacier.
     
  7. Aug 23, 2010 #6
    Glacial Ice often forms hundreds of years ago at higher elevation and slides down the channels toward the ocean in SLOW motion. It will melt in the ocean or on its way downhill.

    Your glaciers probably are melting towards higher elevations. 300m could be 400m or higher above sea level in 2 to 20 years.

    There is also the downdraft effect. A glacier is a patch of ice that gets so big that it creates its own weather pattern. The melt energy taken from the air around a glacier creates cool air outflow, causing low pressure that can pull downdrafts out of the cold upper layers of the atmosphere. It can cause condensation and cloud formation. It can cause snow that will increase its growth.

    As was mentioned by others the Ice is highly reflective so even if it doesn't cover itself in clouds it will still be almost unaffected by sunlight. Once it gets dirty from dust and soot or from grinding its way down a mountain valley, that all changes and solar heat trapped in darker glacial mix will carve through the ice.
     
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