Researchers record the melting of sea ice in Botnion Bay in the northern Baltic Sea

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Researchers record the melting of sea ice in Botnion Bay in the northern Baltic Sea

These images are on April 19, 2021, by Landsat Obtained by Operational Land Imager (OLI) on 8th, it shows the northwest side of Botnion Bay in natural color. The bay is located at the northernmost point of the Baltic Sea, adjacent to Sweden (west) and Finland (east of this image).

Researchers record the melting of sea ice in Botnion Bay in the northern Baltic Sea(1)

The image shows a lot of ice Still attached to the coast of Sweden. This “land fast ice” is fixed on the shore and will not drift. Farther in the bay, drift ice moves freely with wind or currents.

The detailed view shows a close-up view of fast ice on land in the city of Luleå on the northern coast of Sweden. Note that the ice in some places is rust-colored, the most obvious being near Måttsund. This is because water containing sediments has flooded the surface of the ice at some point. This situation may occur when the water level rises, but the ice layer anchored on the land cannot rise with it.

When this image was taken on April 19, the fast ice layer was still mostly intact. As of May 1, the ice map of the Finnish Meteorological Institute showed that most of the fast ice was in an advanced state of disintegration or “rotten”. This is a typical situation of fast ice in the Gulf, which usually begins to decline in mid-April and disappears completely in mid-May.

Although it is seasonal, the presence of ice in Botnion Bay every year is very important to the wildlife in the area. For example, seals use icy habitat to give birth to their cubs. People have also found their use in seasonal ice, which can be used to easily access the islands in the bay. Thousands of islands gather on the coasts of Sweden and Finland; some are inhabited, some have seasonal fishing villages, and many are uninhabited. Some linear features on the ice near the coast are likely to be the footprints left by people while playing in these offshore areas.

Other patterns on the ice, especially those farther from the shore, are caused by natural processes. On the ice surface west of Gelman Island, the bright white noodle-like feature is the area where small ice ridges collide with the ice floes, causing broken debris to accumulate on the surface of the sea ice. The ridges can be several meters high and become quite dense on the sea ice, making winter navigation of the ship particularly challenging. Observations by a Finnish icebreaker on April 18-20 show that it is east of this picture. This phenomenon is still quite common in the sea ice area of ​​China.

In a new research paper accepted for publication on the Cryosphere, researchers describe how they use satellite data to improve navigation safety in frozen waters. The research, led by Renée Mie Fredensborg Hansen of the Finnish Meteorological Institute, used high-resolution topographic measurements from NASA’s Ice, Cloud and Land Elevation Satellite 2 (ICESat-2) to estimate the ridges of sea ice in the Gulf of Botnia. Degree of chemistry.

According to the study’s co-author Sinead Farrell of the University of Maryland, the study provides a reason for the rapid, near real-time release of ICESat-2 data for use in the Arctic and other ice-covered waters.