According to Gregory the Great, water miracles were common in Italy during the sixth century. In his Dialogues, written during the 590s, he describes how Saint Fridianus, a sixth-century bishop, changed the course of the Serchio River, preventing the Tuscan town of Lucca from flooding.
Meanwhile, Saint Benedict came to the aid of monks living at a parched mountaintop monastery in Campania, by summoning springs to bubble up near the summit. Water miracles make up omore than one-fifth of the text in Dialogues, but new evidence points to a more earthly explanation.
Robert Wiśniewski, from the University of Warsaw, and colleagues analysed a stalagmite from a cave near the town of Lucca. Oxygen isotope ratios within the stalagmite layers revealed how wet or dry it was when the stalagmite formed, while uranium and thorium isotopes allow the layers to be dated.
The stalagmite provided nearly 1,000 years of data and the results, published in Climatic Change, reveal that the sixth century was especially wet. The stalagmite’s isotopic fingerprint indicates that the excess moisture during the sixth century was caused by a negative phase of the North Atlantic Oscillation, driving winter weather patterns that transport moisture from the Atlantic to the Mediterranean, in this case resulting in decades of wet winters for central Italy.
