Flood events in Transylvania during the Medieval Warm Period and the Little Ice Age

Abstract

We present here the first record of past flooding activity from the Carpathian Mountains, Eastern Europe, based on documentary evidence and sedimentary records along one of the main rivers draining this region (Someșul Mic River). Three periods of increased flood activity have occurred in Transylvania during the last millennium: the first at the beginning of the 10th century (the end of the Dark Ages Cold Period and beginning of the Medieval Warm Period (MWP)); the second at the end of the 16th and beginning of 17th century, during the cold Little Ice Age (LIA) and the third at the end of the 19th century. During the early MWP, generally wet summers resulted in a high incidence of floods and/or high discharges, while the cluster of floods at the end of 16th and beginning of the 17th centuries occurred mostly at flash floods generated during heavy summer thunderstorms. Increasing winter temperatures and spring precipitations probably caused the high incidence of floods at the end of the 19th century. The predominantly wet conditions during the MWP are likely to have resulted from northward penetration of Mediterranean cyclones during a (mostly) positive phase of the North Atlantic Oscillation (NAO), while wet conditions during the LIA arose as a combination of increases in local storminess and moisture transport from the North Atlantic along more southerly positioned westerlies associated with a negative phase of the NAO.