The Medieval Warm Period was significantly warmer than the 20th century in the Barents Arctic region
2.11.2006 9:00
The years since 2000, however, are warmer than any in the last 700 years, says glaciologist Aslak Grinsted in his PhD thesis Advanced methods of glaciological modelling and time series analysis.
Grinsted’s thesis covers a wide range of methods and research methods and is broad in scope. The methods are applied to ice core, Antarctic blue ice areas, sea level, and large scale climate variability. Among the key findings is the information which will help to understand the decline of arctic sea ice.
Two new ice core proxies, the melt proxy and the continentality proxy, for continentality and summer melt were developed for the Lomonosovfonna ice core in central Svalbard.
-During warm summers melting of the snow changes the chemical composition of the snow. By looking at the ratio between sea salt ions we were able to reconstruct a record of the melt intensity of the past, Grinsted explains.
The proxies suggest that summers in the Barents region were as warm or warmer than the present during the medieval warm period. A high quality chemical record of environmental changes was proven to be preserved in the core.
-We find that melting in the 12th century was roughly three times more intensive in the 20th century. As melt is strongly related to spring and summer temperatures, we conclude that the summers in the medieval warm period were significantly warmer, Grinsted says.
According to Aslak Grinsted, the difference between summer and winter temperatures is related to the distance to the open ocean. Central Russia, for example, has a much larger seasonal temperature range than England. In Svalbard the distance to open water depends on the Barents Sea Ice extent.
-By using oxygen isotopes we created a record of the seasonal temperature range of the past. By relating the changes in the seasonal temperature record to changes in the record of summer melt we find interesting details about the end of the Little Ice Age, 1880-1910, winter temperatures rose 20-30 years before spring and summer temperatures. This information will help understand the present arctic sea ice decline, Grinsted explains.
Grinsted’s research was conducted at the Arctic Centre, University of Lapland and the Division of Geophysics, University of Oulu. The work was financially supported by the Thule Institute, Academy of Finland, the Maj & Tor Nessling Foundation and the Finnish Antarctic Research Programme (FINNARP).
Danish Aslak Grinsted was born in 1973 in Copenhagen, Danmark. He received his masters degree in geophysics specializing in glaciers and climate from The University of Copenhagen in 2002. The same year Grinsted moved to Finland. Right after defending his thesis, Aslak Grinsted will travel to Antarctica for four months to do fieldwork.
Aslak Grinsted’s academic dissertation Advanced methods of glaciological modeling and time series analysis will be presented for public discussion in Arktikum House (Aurorasali), Rovaniemi, on November 3rd, at 12 noon.
For additional information, please contact:
Aslak Grinsted
Email: firstname.lastname@ulapland.fi
Telephone: 016 341 2713
www.arcticcentre.org
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