CAS ES 107 Chapter Notes - Chapter 6: Thermokarst, Thermal Conductivity, Ice Crystals
7 Jun 2018
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Chapter 6: The Cryosphere (Part 1)
Primary components of cryosphere:
-continental ice sheets
-ice shelves
-mountain glaciers
-sea ice
-river and lake ice
-snow cover
-permafrost (frozen ground)
-Changes in the distribution of sea ise and snow cover change the albedo and feed back to
regional and global temperatures
-changes in the amount of glacier ice affect global sea levels
-the melting permafrost releases greenhouse gases to the atmosphere
-the process of sea ice formation helps increase the salinity of the surface ocean at high latitudes
**this all affects ocean density, bottom-water formation, and the deep-ocean circulation
-glaciers, ice sheets and sea ice are in constant motion
-Lakes and rivers play a minor role in global-scale processes but a large one in local ecosystems
Formation of Snow
Ice crystals can grow and take a variety of forms, which are largely a function of temp
-the dominant process is deposition→ the ice forms directly from water vapor, rather than from
the freezing of liquid water
-sublimation→ water transforming directly from ice to vapor
-deposition→ vapor to ice without going thru the liquid phase in between
-as pressure decreases, the melting point also decreases
-if pressure is reduced, boiling point is reduced
-triple point: water can exist in all three phases
-at high enough pressures, ice will not melt, even at extremely high temps
-once ice crystals form, it continues to grow primarily by deposition
-there is little cohesion between ice grains on surface and if they are covered by more layers of
snow, they can form unstable layers that can lead to avalanches on slopes
-ice can also grow by agglomeration as ice crystals join together to form larger snowflakes
Snow Cover
-has high albedo
-some of the solar radiation is transmitted through the ice and some is reflected from the surface
-ice crystals absorb and scatter all wavelengths of visible light almost equally, which is what
gives them their white color
-high albedo means most heat is reflected so the snow can persist for long periods if the air temp
remains below freezing
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Document Summary
Changes in the distribution of sea ise and snow cover change the albedo and feed back to regional and global temperatures. Changes in the amount of glacier ice affect global sea levels. The melting permafrost releases greenhouse gases to the atmosphere. The process of sea ice formation helps increase the salinity of the surface ocean at high latitudes. **this all affects ocean density, bottom-water formation, and the deep-ocean circulation. Glaciers, ice sheets and sea ice are in constant motion. Lakes and rivers play a minor role in global-scale processes but a large one in local ecosystems. Ice crystals can grow and take a variety of forms, which are largely a function of temp. The dominant process is deposition the ice forms directly from water vapor, rather than from the freezing of liquid water. Sublimation water transforming directly from ice to vapor. Deposition vapor to ice without going thru the liquid phase in between.
