Climate of the polar realms - The Global Climate System: Patterns, Processes, and Teleconnections - page 134

century, in which time a climatic warming has been observed (Giovinetto and
Bentley 1985 ).
The ice that has been accumulating over hundreds of thousands of years
in interior Antarctica flows slowly towards the coastline. In so-called ''ice
streams,'' speeds of up to 500 m/year have been measured. When it reaches
the ocean, it can form ice shelves, the Ross and the Filchner Ice Shelves being
the largest, each with an area in excess of 500 000 km 2 ; these ice shelves
make up 44% of the coastline of Antarctica. In other areas glacier tongues
penetrate into the ocean, as for example the Lambert and Mertz Glacier
Tongues in East Antarctica, or the Drygalski Ice Tongue in the Ross Sea.
These can extend into the sea for tens of kilometers. The ice that breaks
off from these glaciers forms the spectacular and fairly common icebergs
(Figure 5.3a ), and large tabular icebergs are formed when parts of shelves
break off, which appears to have occurred more frequently in the last decade.
These latter ones can last for long time periods. For example, a large tabular
iceberg (B9) was formed in 1989 by the Ross Ice Shelf; later, it broke in half.
One of the parts drifted north (B9A), where it eventually melted. The other
half is presently still well preserved (B9B), after having drifted eastwards for
1200 km, and getting grounded off the Ad´lie Coast. The remainder of the
coastline is often rocky, and this is the area where ablation takes place in
summer. These areas together with the nunataks, or mountaintops, which
penetrate the ice sheet, represent the relatively limited area not covered by
snow and ice permanently.
It should also be pointed out that modern technology has increased
our knowledge of Antarctic climatology substantially. Some 20 years ago,
automatic weather stations (AWS), reporting via satellites, were originally
installed at numerous locations by the USA and Australia, but now are
operated by many nations. Antarctica was an ideal location for these, as it
is so expensive to run year-round manned stations. A book reporting on some
of the results from US stations was edited by Bromwich and Stearns ( 1993 ),
while Allison et al.( 1993 ) reported results for East Antarctica.
5.2.2 Climatology
Surface observations
Antarctica has a very low surface temperature and represents one of the
two heat sinks on Earth. It is part of the global energy cycle, and closely
tied to global climate and its variations. Teleconnections between Antarctica
and the subtropics have been found with various time lags. For example,
the Southern Oscillation Index (SOI, Section 2.8 ) is correlated to various
Antarctic climate parameters (Simmonds and Jacka 1995 ; Turner 2004 ), as
shown in Section 5.6 .