Climate of the polar realms - The Global Climate System: Patterns, Processes, and Teleconnections - page 141

name). Hence, climate change in Antarctica will affect the production of such
high-density water, and with it the climate of Earth on a century time scale.
Other meteorological parameters
As the water vapor saturation pressure is a logarithmic function of tempera-
ture and decreases to about half its value for each 5 8C decrease, precipitation
is, in general, light at high latitudes. The Antarctic Peninsula is an exception,
however. Melchior (65.38 S, 63.08W), located close to sea level, recorded a
mean annual value of 1189 mm. Otherwise, coastal stations in Antarctica
record values around 500mm. In windy areas it is not possible to measure
precipitation due to blowing snow, and, for example at Dumont d'Urville,
no amount but only the frequency of precipitation events is recorded. The
precipitation amount decreases steeply when going inland; less than 100 km
from the coast, values under 200mm are observed. Further inland and on the
high Antarctic Plateau values of less than 30mm annually are observed. Here
all precipitation falls in solid form; frequently clear sky precipitation is
observed. No clouds are present, but in the cooling air mass, ice crystals are
formed, which float slowly to the surface and can result in impressive optical
phenomena such as halos and parhelia (sun dogs). The snow accumulates
over time and by analyzing ice cores, the past climate can be reconstructed
(see Chapter 6 ). The most famous ice core is from Vostok and dates back
more than 300 000 years. It was the analysis of such ice cores that supported
the Milankovitch theory being accepted in science. The theory says that the
climate on Earth varies with three parameters of the Earth's rotation (changes
in eccentricity, in axial tilt and in axial precession), having different time
periods of tens of thousand of years, and affecting the solar radiation and with
it the temperature.
In the coastal region of Antarctica, the total mean annual cloud cover is
about 50%; it decreases slightly in winter. When going inland, the amount of
total cloud cover decreases strongly, which is in agreement with the decrease
in precipitation and the frequency of occurrence of active weather systems.
Further, the annual course in cloudiness is more pronounced inland.
The global sea level has been rising annually by about 2mm, and for a long
time the question has been asked if Antarctica is contributing to this sea level
rise. The question is not trivial, as warming will result in more ablation in the
coastal areas of Antarctica, and also most likely in an increase of precipita-
tion. If the snowfall occurs somewhat inland, where no ablation takes place,
more snow might be stored in these areas. The sum could be either positive or
negative. While studies using both direct glaciological methods and atmo-
spheric methods to calculate the moisture fluxes across the Antarctic Circle
have been carried out, the results are still inconclusive. However, satellite-
derived altimetry should solve this problem. In 1997, the Canadian satellite