Paleoclimate of the Southern Adriatic Sea region during the ‘Medieval Climate Anomaly’ reflected by organic walled dinoflagellate cysts

To obtain insight into the character and forcing of southern Italian climate change during the 'Medieval Climate Anomaly' (c. AD 900-1200), marine sediments deposited between ad 990 and 1200 from the Gulf of Taranto have been analyzed for their dinoflagellate cyst content with a 3.5 yr resolution. The reconstructed sea surface temperature (SST) appears to be lower than today. We observe a clear 11.4 yr cyclicity in the reconstructed SST series. Furthermore, there is a good matching between SST and global C-14 anomalies. This suggests that solar activity might have had an important influence on the local climate during Medieval time. Short-term fluctuations in accumulation rates of aerobic degradation resistant species that react sensitively on the trophic state of the upper waters and/or are characteristic for river plume waters indicate that the trophic state of the upper waters is closely linked to river discharge, which in turn is strongly related to precipitation in Italy. We reconstruct low river discharge/precipitations in the Adriatic area synchronous to widespread drought events in other nearby subtropical regions. We attribute this to NAO and ENSO related large-scale ocean-atmosphere circulation shifts during the Medieval period. Furthermore, we suggest that eruptions of southern Italian volcanoes might have influenced the local upper water nutrient conditions as well.