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Least sea ice in 800 years
Source: Terra Daily, Date: , 2009
New research, which reconstructs the extent of ice in the sea between
Greenland and Svalbard from the 13th century to the present indicates
that there has never been so little sea ice as there is now. The
research results from the Niels Bohr Institute,at the university of Copenhagen, among others, are
published in the scientific journal, Climate Dynamics.
There are of course neither satellite images nor instrumental records
of the climate all the way back to the 13th century, but nature has its
own 'archive' of the climate in both ice cores and the annual growth
rings of trees and we humans have made records of a great many things
over the years - such as observations in the log books of ships and in
harbour records. Piece all of the information together and you get a
picture of how much sea ice there has been throughout time.
In order to determine how much sea ice there has been, the researchers
needed to turn to data from the logbooks of ships, which whalers and
fisherman kept of their expeditions to the boundary of the sea ice. The
ship logbooks are very precise and go all the way back to the 16th
century.
They relate at which geographical position the ice was found. Another
source of information about the ice are records from harbours in
Iceland, where the severity of the winters have been recorded since the
end of the 18th century.
By combining the curve of the climate with the actual historical
records of the distribution of the ice, researchers have been able to
reconstruct the extent of the sea ice all the way back to the 13th
century. Even though the 13th century was a warm period, the
calculations show that there has never been so little sea ice as in the
20th century.
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