Abstract
The Baltic Sea is partly covered by sea ice in every winter season. Landfast ice (LFI) on the Baltic Sea is a place for recreational activities such as skiing and ice fishing. Over thick LFI ice roads can be established between mainland and islands to speed up transportation compared to the use of ferries. LFI also allows transportation of material to or from islands without piers for large ships. For all these activities, information on LFI extent and sea ice thickness, snow thickness and degree of ice deformation on LFI is very important. We generated new operational products for these LFI parameters based on synthetic aperture radar (SAR) imagery and existing products and prediction models on the Baltic Sea ice properties. The products are generated daily and have a 500 m pixel size. They are visualized in a web-portal titled “Baltic Sea landfast ice extent and thickness (BALFI)” which has free access. The BALFI service was started in February 2019. Before the BALFI service, information on the LFI properties in fine scale (<1 km) was not available from any single source or product. We studied the accuracy and quality of the BALFI products for the ice season 2019–2020 using ice charts and in-situ coastal ice station data. We suggest that the current products give usable information on the Baltic LFI properties for various end-users. We also identify some topics for the further development of the BALFI products.
Highlights
The Baltic Sea is a semi-enclosed brackish sea water basin in Northern Europe
The Baltic Sea ice extent and duration of the ice season depend on the indices of the Arctic Oscillation (AO) and North Atlantic Oscillation (NOA)—e.g., the annual maximum ice extent generally decreases with increasing indices of AO and NAO [2]
The Baltic Sea landfast ice extent and thickness (BALFI) service was started in February 2019, and it is active during the Baltic Sea ice season, typically from November/December to May
Summary
The Baltic Sea is a semi-enclosed brackish sea water basin in Northern Europe. The ice cover in the Baltic Sea usually begins to form in November, and has its largest extent between January and March [1,2,3]. The maximum annual ice cover ranges from 9% to 100% of the whole Baltic Sea area, and the average is 50% [3,4]. The ice in the Baltic Sea occurs as landfast ice (LFI) and drift ice. LFI occurs in the coastal and archipelago areas, and usually extends to the 5–15 m isobath. In the Bay of Bothnia, the annual maximum level ice thickness is typically 0.65–0.80 m, and it reaches 0.3–0.5 m even in mild winters [1,2]. In the Southern Baltic Sea, the coastal areas of Germany and Poland and the Danish Straits, the annual maximum level ice thickness seldom exceeds 0.5 m [5]. The salinity of the Baltic Sea ice is typically from 0.2 to 2% depending on the location, time and weather history [7]
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