Session: Last Millennium & Past2K
Author: Eduardo Zorita / email@example.com / Helmholtz-Zentrum Geesthacht, Germany
Co-author: Sebastian Wagner, Helmholtz-Zentrum Geesthacht, Germany;
The land areas surrounding the Mediterranean are prone to naturally occurring multi-year and decadal droughts. Precipitation in this region is concentrated during the winter half years and its variability at inter-annual time scales is strongly controlled by the North Atlantic Oscillation, although this influence is weaker in the Eastern Mediterranean. The mechanisms is the dependence of the North Atlantic storm tracks on the intensity of the North Atlantic Oscillation pattern The analysis of past-millennium simulations of the PMIP3 model suit, however, indicates that decadal drought events are linked by pattern sea-level pressure patterns that are different, and that seem to be more associated with the anomalies of moisture advection by the seasonal mean winds. In the Mediterranean region, these patterns imprint a distinct east-west dipole of precipitation anomalies, which is not clearly present at interannual time scales. This zonal contrast of decadal precipitation variability is consistent with previous analysis of moisture sensitive dendrochronologies.
The decadal drought episodes doe not show an imprint of the external climate forcing, either due to volcanic eruptions nor to the more slowly varying solar irradiance.
At longer time scales than 1000 years, the sea-level-pressure trends caused by the orbital forcing may also have an influence on Mediterranean precipitation, more strongly so in the Eastern Mediterranean, and thus are appear related to trends in the South Asian Monsoon.