Geoscience Reference
In-Depth Information
as ice forms records volcanic activity, deposition of extraterrestrial material
and changes in the atmospheric circulation. Climate data are also extracted
from tropical glaciers. For example, in the Quelccaya Ice Cap on the Peruvian
Altiplano, clearly distinguished annual accumulation layers record a 1500-year
chronicle of precipitation.
After glaciers, ground ice is thought to be the next largest reservoir of ice
in the climate system, but estimates of mass and residence times are uncertain.
Sea ice
is ice that forms in the ocean as distinguished from
icebergs
, which
form on glaciers and calve into the ocean. About 15% of the ocean surface is
covered by sea ice for some part of the year. Sea ice forms and grows in the
winter months and melts in the summer, but some regions of the ocean are
always covered with sea ice.
The top two panels in
Figure 2.34
show winter and summer climatologies
of sea ice extent in the Arctic for the period 1979-2000. The total area of
ocean covered by sea ice in this region varies from about 16.5 # 10
6
km
2
in
winter to about 6.5 # 10
6
km
2
in summer. In winter, sea ice extends into the
March
September
March
September
Figure 2.34 Arctic (top) and Antarctic (bottom) sea ice
extent climatology for 1979 to 2000 at the approximate
seasonal maximum and minimum levels based on passive
microwave satellite data. Image provided by National Snow
and Ice Data Center, University of Colorado, Boulder.
