The Baltic Sea ice season in changing climate

The ice pack is an important and highly sensitive component in the climatology of the Baltic Sea, which has been examined with a coupled ice-ocean model. The observed Baltic ice climate variability is well reproduced by the model. Future ice season are simulated as follows: in an average winter in 2050 ice is formed only in the Bay of Bothnia, the Archipelago Sea, the east of Gulf of Finland and on the Estonian west coast. The freezing date has been shifted about 20 days later and the break-up date 10 earlier. The ice thickness is 20 cm thinner. Locally such degrees of change could also be obtained using a simple analytic model. The coupled ice-ocean modeled 30 year’s ice statistics centered on 2050 gives a 30–65 cm range for the annual maximum ice thickness in the Bay of Bothnia. The length of the ice season varied from 3.5–6 months. The latest freezing occurred in January and the ice break-up happened at the earliest in April. Some ice would still be formed in 2100 at Kemi.