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Ice and snow thickness in the Baltic Sea

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These pages contain visualizations of measured sea ice and snow thickness from FMI internal database. For each station, the current year is compared with the climatology. The climatology data, spanning nearly 30 years, has been interpolated to weekly resolution. It is derived from long-term sea-ice observations with station-specific data availability:

  • in the northern Bothnian Bay, Tornio and Kemi are based on records from 1990/11/13 to 2023/5/15, followed by Hailuoto (1990/11/13–2023/5/15) and Raahe (1990/11/13–2023/4/17);
  • moving southward along the Bothnian Sea, Kalajoki (1990/11/13–2023/4/17), Kokkola (1990/11/13–2023/2/27), Pietarsaari (1990/11/13–2023/4/10), Vaasa (2014/2/17–2023/4/10) and Vallgrund (1990/11/13–2023/4/17) are included, followed by Kaskinen (1990/11/13–2023/4/17) and Rauma (1997/10/21–2023/4/17);
  • in the Archipelago Sea and Gulf of Finland, Turku is based on observations from 2009/1/19 to 2023/4/3, Hanko from 1990/11/13 to 2023/2/27, Helsinki from 1990/11/13 to 2023/3/13, Porkkala from 1998/10/27 to 2023/4/10, Loviisa from 1990/11/13 to 2012/4/2, and Kotka from 1990/11/13 to 2023/4/17.

The two maps show comparisons between the current year and the long-term climatology for sea ice thickness (left) and snow thickness (right), based on observations from the FMI internal HAV database. Stations are colour-coded according to whether the current ice/snow thickness value is above the 90th percentile (blue), within the range of 10th–90th percentiles (green), below the 10th percentile (red), or not available (grey), relative to climatology mean. Label boxes display the latest ice/snow thickness and its anomaly (in brackets), calculated as the difference between the latest observation and the climatological mean for the corresponding day of the season. All values are in cm unit.

The figures below include maximum, minimum, mean, 90th percentile, and 10th percentile values for ice (left) and snow (right) thickness. The thickness values have been multiplied by –1 for visualization purposes. The ice and snow season is defined to start from October 1st and end on May 31st.

ObsSea4Clim is funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Executive Agency (REA). Neither the European Union nor the granting authority can be held responsible for them.

© Finnish Meteorological Institute