ice - Cryosphere...

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Cryosphere ‐part of the earth that is perenially frozen; glaciers & ice sheets (10% of earth), sea ice, frozen ground (20%) Snow ‐snow has a high albedo (reflectance) so when the ground is snow‐covered more of the Sun’s radiation is reflected from the surface, further cooling the Earth surface temperature ‐snow melt contributes to runoff which drains into the ground and overland to streams/rivers ‐in many communities snow melt is integral to municipal water supply ‐ if snowfall is low can cause water restrictions that summer Q: what controls where the snow is when? ‐precip. and temperature ‐the snow line changes both with latitude and with elevation video for snow line retreat ‐snowlines can change year to year depending on weather patterns e.g. if winter snowfall is light and summer temp. high snow fall will move further up in elevation Q: do you think polar regions have high or low amounts of snowfall? ‐actually have low snowfall, it’s just that it’s so cold all of the year so the snow that does accumulate does not melt away ‐the snowline is not at the same elevation everywhere; near the equator, a much taller mountain is required to get snow on it as the snowline increases Glaciers Q: how do glaciers form? ‐snowfall gets compressed and does not melt during summer ‐at the surface of an ice sheet there is snow but as you go deeper the crystals bond together and it becomes ‘firn’ ‐this is compressed by the overlying snow to the density of ice 0.9 kg/m3 ‐as compression increases (as you travel to the deeper parts of the ice sheet) the crystal size grows
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Q: where are glaciers found? ‐we already established that they form in high altitudes and polar regions ‐but we also need precipitation –so lots of glaciers on the West Coast where moisture comes off the pacific ocean ‐in N. hemisphere mountains with lots of peaks glaciers are often found on the north slope of the mountain ‐this is because its in the shade of the mountain peak ‐glaciers are classified into ‘warm’ and ‘cold’ glaciers based on their internal temperature Q: what do you think the temperature of a warm glacier is? ‐it’s right at zero. This is also called a temperate glacier ‐these types of glaciers are common in alpine/mountain environments ‐cold glaciers are below the freezing point for most or all of their thickness ‐the melting point of ice actually changes depending on how much pressure is applied. ‐under high pressure, the melting point decreases…so instead of melting at 0 o C, ice under pressure melts at temperatures below 0 o C.
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Q: what do you think the funnel‐shaped region at the top of these plots represents? ‐changing ice temperature related to seasonal air temperature fluctuations ‐you can see that the warm temps of the summer and cold temps of the winter only penetrate so far into the ice ‐the amount that the temperature penetrates and warms a glacier depends on its thickness….thick
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ice - Cryosphere...

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