Until now, it has been quite difficult to get an accurate picture of the extent of the melting up to 130 years ago, as the technological tools of today were not available.
However, researchers have used aerial photos and satellite images from the Danish National Archives dating back to the 1930s, when Denmark began to thoroughly document the coast of Greenland in order to create maps. This archive has never been used before and provides a unique insight.
Out of Greenland's 22,000 glaciers, researchers have manually scrutinised over 1000 of them using 200,000 old photos. This is the largest ever mapping based on such sources.
Anders Bjørk, Assistant Professor at the Department of Geosciences and Natural Resource Management and one of the researchers behind the article says the following:
"Just over 1,000 glaciers is a huge number to study, but we did it because we simply wanted to make sure we had a complete picture of the development over the last 130 years."
The new knowledge generated by this study has two important functions. Firstly, the documentation itself. The researchers can now state with great certainty that the glaciers are in a new phase, where even the northernmost glaciers along the coast are melting extremely fast.
In addition, the documentation will have an important job as data for climate models that project what will happen, for example, to sea levels in the future as the glaciers melt and become part of the oceans.
Such models become better and more accurate the better the documentation that forms the basis of the calculations.