Environmental Engineering Reference
In-Depth Information
Figure 9.4
Sea surface temperatures, ice extent (blue stipple)
and ice elevation for southern winter, 18,000 years ago, with
sea level at -85 m.
Source: After CLIMAP Project (1976).
THE POSTGLACIAL PERIOD
The climatic amelioration following the last glacial maximum was rapid though not
without fluctuations. In the southern Lake District of Britain, organic mud was being
deposited by 14,500 BP, indicating that the ice sheet was beginning to thin rapidly or had
disappeared from the area. The rate of warming was so sudden that in many cases the
vegetation was out of equilibrium with the climate, as can be deduced by comparing
vegetation and insect evidence. It takes years for trees to spread from their refuge areas,
but animals and insects can move more quickly in response to a change in climate as long
as their food supply moves too. By about 12,200 BP, it is believed, the climate of Britain
was similar to that at present (Figure 9.5).
This warmth did not last. A
Heinrich event
took place in what is termed the Younger
Dryas period. As far as we can tell, a significant ice advance appears to have
