|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||||
|
|
|
|
|
|
|
|
|
||
2. Ice Masses
Ice masses offer storage of H2O (Figure 10 ) on time scales ranging from a few months for continental seasonal snow pack to thousands of years for the Antarctic ice mass. They all contribute to the albedo (reflectivity) of solar radiation. In the 1970s when the prospect of global cooling was being studied, calculations were made of how much warming would be introduced by spreading carbon black on polar ice masses.
The Antarctic continent, because of its circularly symmetrical shape, high elevation, and extreme
cold temperatures, leads to the formation of stationary and persistent
stratospheric clouds that supply the
conditions for ozone depletion. Like the global ocean, the Antarctic ice mass introduces thermal inertia
into the climate system.The Antarctic ice sheet is a massive expanse of permanent ice whose high reflectance causes this
region of the planet to lose more radiant energy through infrared radiation than it gains through
illumination by the sun. This excess loss is made up by energy continually being supplied to the
Antarctic region from lower latitudes by the atmosphere and ocean. Ice forms at high elevation on the
Antarctic continent and slides downslope to the sea to create large floating icebergs that drift away
from the polar ice mass. The ocean surface area covered by these icebergs reduces the amount of open
ocean and reduces total evaporation and loss of heat energy from polar regions. This important fact
only recently is being included in global climate models.
The Greenland ice sheet (Figure 12) is far less
massive than the Antarctic ice field and is not nearly as cold. The consequences of this are discussed
under the unit on Sea-Level Rise.
Having parts of its ice mass near the melting point, the Greenland ice field is more vulnerable to
decrease in size than is the Antarctic ice sheet, and so its time scale for change is shorter than that
of the Antarctic ice sheet.
Mountain glaciers contribute only a small amount of H2O to the global total, but their
locations closer to population centers make them targets for urban and agricultural water supplies. They
can experience noticeable change over periods of decades and, indeed, serve as independent indicators of
global warming as can be seen in the accompanying plot of changes in glacier termini (Figure 13).
Arctic ice is not anchored to land as is Antarctic ice. As floating ice, it governs the evaporation and
heat loss from ocean water and having thickness far less than Antarctic or Greenland ice, it covers a
relatively large surface area despite its relatively small volume. Being
of lower elevation and being surrounded by asymmetric distributions of
land and ocean, the North Pole does not provide an ideal location for persistent polar stratospheric
clouds, although some ozone loss has been detected in this region.
3. Continental Seasonal Snow
Continental seasonal snow also provides recharge for reservoirs used for urban and agricultural purposes. These areas frequently also serve as important recreational sites.
NEXT: --Surface and Subsurface Water
