Ice observations are gathered for the Finnish Meteorological Institute´s Ice Service that follows and forecasts the ice situation in the Baltic for shipping, as well as for research.
Finnish Meteorological Institute has about 20 people observing ice along the Finnish coastline. They observe the ice situation visually and measure the thickness of the ice weekly. Also the observations reported by public via WeatherApp are used. It is still difficult to get information about the ice thickness without measuring it on the spot.
Sea ice thickness is measured by drilling a hole to the ice and measuring the thickness with a meter. The thickness of the snow on the ice is also measured, because it impacts how the ice grows underneath. The structure of the ice is observed by sawing a piece of ice and lifting it on the ice. Clear ice in the lower part of the piece is fast ice and white ice in the upper part is snow ice.
Also some vessels, mainly icebreakers, observe and report ice conditions.
Today, the most important source for ice observations are satellites. Satellite images show the ice edges, floe sizes, brash ice barriers and cracks, for example. The quality and amount of images has increased a lot. For example airplane observations are not as important as before, because of good satellite observations. Nevertheless, there are still challenges with satellite data. The time and place satellite is observing is not always good for ice observations. In certain images cloudy weather is problematic. Also the time difference from the moment satellite passes the place to when the image is available to be used might be long. In addition, to interpret the image requires experience.
In addition to ice observations, seawater temperature observations are also used when estimating and forecasting ice conditions. Sea water temperature is measured with buoys, mareographs and stations. There are also some ferries operating regularly in the Baltic, equipped with temperature measurement instruments. In addition some satellites observe sea surface temperature too.