Long-term drought intensification over Europe driven by the weakening trend of the Atlantic Meridional Overturning Circulation

Abstract

Study region: Europe, with a particular focus on the Czech Republic, Poland, Spain, and Norway. Study focus: Long-lasting droughts have become a semi-permanent feature of the European climate, especially over the last two decades. These prolonged droughts are usually driven by persistent sea surface temperature anomalies over the Pacific and Atlantic basins. By employing complex statistical methods (i.e., Canonical Correlation Analysis and Convergent Cross-Mapping) in this study we make a comprehensive assessment of the observed drying trend over the central and southern parts of Europe and its underlying drivers. New hydrological insights: Building upon the potential relationship between drought variability and large-scale oceanic and atmospheric circulation, we show that the observed drying trend in the central and southern parts of Europe has been driven by a long-term slowdown of the Atlantic Meridional Overturning Circulation (AMOC), via changes in the large-scale atmospheric circulation. A weakening of AMOC leads to an increase in the frequency of atmospheric-blocking like circulation over the central part of Europe, which in turn inhibits precipitation and favors long-term drying. Since climate projections indicate a slowdown of the AMOC in the future, we suggest that this will potentially lead to an increase in the frequency of dry years, especially over the central and southern parts of Europe (e.g., the eastern part of Germany, the Czech Republic, Poland, Spain and Portugal).

Keywords

• Drought
• AMOC
• CCA
• Cross-Mapping
• Europe