such as "Introduction", "Conclusion"..etc
December 30, 2008 — According to a new doctoral
dissertation at Stockholm University in Sweden, based on analyses of
deposits of pollen grains, it is possible that all of Sweden was
virtually free of ice for long periods during the latest ice age. The
findings show that the glaciation might have started some 20,000 later
than was previously assumed.
“It’s important that we get to the bottom of when the great ice
sheets covered Sweden and how warm it might have been when there was no
ice. At present there are two extremely different hypotheses, which
makes it difficult to study how the ice age climate relates to various
parameters in the climate system, such as the earth’s relation to the
sun,” says Martina Hättestrand, a doctoral candidate at the Department
of Physical Geography and Quaternary Geology, Stockholm University.
In order to understand the climate system of the earth, researchers
today are studying the climatic variations of ice ages. Since we have
the most land forms and geological traces preserved from the latest ice
age, much of the research focuses on that particular period. An
important aspect of the research is to study when the huge continental
ice sheets grew and when they melted away, and to study the environment
and climate of the areas that were free of ice. The size and movement
patterns of the ice sheets can be calculated by studying land forms and
moraine deposits. The ice-free periods can be studied by pollen
analysis, among other methods. Pollen analysis is a method in which
scientists use pollen grains preserved in ancient sediment to create a
picture of what plants once grew in the area and what the climate was
Martina Hättestrand’s dissertation is based on studies of pollen
grains that were deposited more than 40,000 years ago in small lakes
during the ice-free phases of the latest glaciation. During the warm
phases of the Ice Age, high amounts of birch pollen were deposited,
which indicates that summer temperatures were around 10 degrees
centigrade in northern Sweden. During cold ice-free phases, mostly
grass and herbal pollen was deposited.
“The findings from my dissertation indicate that the first icing up
phase of the latest Ice Age may in Scandinavia have started about
95,000 years ago – which is some 20,000 years later than was previously
thought,” says Martina Hättestrand.
According to the previously accepted hypothesis, Sweden was covered
with ice 75,000-20,000 years ago. Martina Hättestrand’s hypothesis, on
the other hand, is that Sweden may have largely been ice-free between
59,000 and 40,000 years ago. If this is true, the last ice sheet of the
Ice Age formed much more rapidly than was previously believed in order
to have reached all the way down to northern Germany during the maximum
phase about 22,000 years ago.
The latest Ice Age is called the Weichselian glacial (glaciation) in
northern Europe. It started roughly 120,000 years ago and ended about
10,000 years ago. The definition of an ice age is that it has a colder
climate than an interglacial period, which is the type of climate we
live in today. The climate varied a great deal during the ice ages.
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