Safewin 2011 airborne EM sea ice thickness measurements in the Baltic Sea

This report summarizes the results of airborne electromagnetic (EM) ice thickness surveys undertaken during the SafeWin winter field campaign in 2011, using a helicopter‐towed EM Bird. Surveys were flown during and after the RV Aranda sea ice cruise in the Sea and Bay of Bothnia, between March 2 and 7, 2011. Due to severe ice conditions, RV Aranda arrived late at her final destination in the Bay of Bothnia. Therefore, and due to further delays related to technical problems with the helicopter and contaminated fuel, surveys from the ship could only be performed on two days, before the ship had to return south. However, we decided to keep the EM Bird on land in Kokkola, and after some careful training by Alec Casey, Mikko Lensu was able to perform surveys on four more days. In total, 11 flights were performed, covering large parts of the Bay of Bothnia, the Quarken, and the northern Sea of Bothnia. While some flights were designed to provide the best overview of the regional ice thickness distribution, several flights were performed over the buoy array in the region surrounding the ship, to observe thickness changes resulting from changes in ice deformation. Surveys were carried out by the University of Alberta (UofA), Edmonton, Canada, who was a sub-contractor of FMI. UofA participants were Alec Casey, John Lobach, and Christian Haas. The EU SafeWin project aimed to improve the safety of winter navigation in the ice‐covered Baltic Sea and other polar seas. It includes modeling and observational studies. As part of the latter, two winter field campaigns have been performed to provide data for the development and improvement of models and ship‐in‐ice studies, and for their validation. Ice thickness is one of the key parameters governing navigation in ice. Therefore, extensive ground‐based, shipborne, underwater, and airborne ice thickness surveys have been performed.