‘An Ice Breakup as in the Good Old Days’: Ice Jams in the Aura River, Turku, Southwest Finland, 1739–2024

This study investigates the historical occurrence and impact of ice jams in the
Aura River, Turku, Finland, from 1739 to 2025. Ice jams, which are common
in regions with prolonged river ice cover, can cause significant water level rises
and subsequent flooding. The study analyses historical documents, including
newspaper articles and weather journals, to reconstruct past ice jam events and
their effects. Key findings highlight the role of natural and anthropogenic ob-
stacles, such as bridges and skating rinks, in initiating ice jams. The study further
examines the methods employed to mitigate these events. An ice jam index is
developed to categorise the severity of events over time. The results indicate a
clear change towards fewer severe ice jam events in the twentieth century. This
research contributes to understanding hydrological extremes and their historical
context in Finnish rivers.