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| Titel |
The climate in the Baltic Sea region during the last millennium simulated with a regional climate model |
| VerfasserIn |
S. Schimanke, H. E. M. Meier, E. Kjellström, G. Strandberg, R. Hordoir |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 5 ; Nr. 8, no. 5 (2012-09-07), S.1419-1433 |
| Datensatznummer |
250005832
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| Publikation (Nr.) |
 copernicus.org/cp-8-1419-2012.pdf |
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| Zusammenfassung |
| Variability and long-term climate change in the Baltic Sea region is investigated for the
pre-industrial period of the last millennium. For the first time dynamical downscaling covering
the complete millennium is conducted with a regional climate model in this area. As a result of
changing external forcing conditions, the model simulation shows warm conditions in the first
centuries followed by a gradual cooling until ca. 1700 before temperature increases in the last
centuries. This long-term evolution, with a Medieval Climate Anomaly (MCA) and a Little Ice Age
(LIA), is in broad agreement with proxy-based reconstructions. However, the timing of warm and
cold events is not captured at all times. We show that the regional response to the global climate
anomalies is to a strong degree modified by the large-scale circulation in the model. In
particular, we find that a positive phase of the North Atlantic Oscillation (NAO) simulated during MCA contributes to enhancing
winter temperatures and precipitation in the region while a negative NAO index in the LIA reduces
them. In a second step, the regional ocean model (RCO-SCOBI) is used to investigate the impact of
atmospheric changes onto the Baltic Sea for two 100 yr time slices representing the MCA and the
LIA. Besides the warming of the Baltic Sea, the water becomes fresher at all levels during the
MCA. This is induced by increased runoff and stronger westerly winds. Moreover, the oxygen
concentrations in the deep layers are slightly reduced during the MCA. Additional sensitivity
studies are conducted to investigate the impact of even higher temperatures and increased nutrient
loads. The presented experiments suggest that changing nutrient loads may be more important
determining oxygen depletion than changes in temperature or dynamic feedbacks. |
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