Extreme sea ice motion -- analysis of ice drifter buoy data in the Gulf of Bothnia 

Sea ice and particularly its motion are problematic for vessels and structures in water areas that experience sea ice. For example, several offshore wind farms are planned to be installed in the Gulf of Bothnia, but uncertainty related to extreme sea ice motion is likely to worry potential investors. Winter navigation, particularly in the coastal boundary zone, can be difficult. While climate change is likely to decrease the average ice concentration, extrema may become more severe.  The motion of sea ice is affected by wind, currents and internal dynamics of the ice field, which are highly complex and inadequately understood. In this study we analyze time-series of data from ice drifter buoys deployed in the Gulf of Bothnia, Baltic Sea, during 2012 - 2023. The combination of data from multiple buoys, ice charts as well as other observations and model forecasts on the atmosphere-sea-ice interaction allows for estimating various parameters for the respective ice fields, such as shear, divergence and deformation, as well as temporal and spatial variability.