Baltic Sea Ice Extent Grows Under High-Pressure Weather

Compared to the same time last year, the difference in ice extent is large. Last year, the ice extent was 67,000 square kilometers at the same time. Oskar Åslund, an oceanographer at SMHI's ice service, explained the contrast: 'The weather situation this year compared to last year has been quite different.

Last year was milder and windier with regular rounds of southwesterly winds that compressed the ice in the north toward the Finnish side. ' In the far north, sea ice formed in bays in mid-November and grew at a calm pace until the turn of the year. The largest ice extent in December was on New Year's Eve with 11,000 square kilometers.

Growth continued during the first half of January, but it was only with a shift to high-pressure-dominated weather in mid-January, when colder air temperatures further cooled water temperatures, that the ice extent accelerated. Based on the season's largest recorded ice extent so far, the season could be classified as a normal ice winter, according to Åslund. He noted, 'That means the maximum ice extent has been between 115,000 and 230,000 square kilometers.

This also means we are still a bit away from having a severe ice winter. ' The unusually low water levels in the Baltic Sea could open up for a larger inflow of cold and oxygen-rich water from the North Sea now that a low-pressure system has moved in.