Baltic Sea Ice
Tuesday, 6. May 2008, 18:37:01
As a long-term average the Baltic Sea is ice covered for about 45% of its surface area at maximum annually. The ice-covered area during such a typical winter includes the Gulf of Bothnia, the Gulf of Finland, Gulf of Riga and Väinameri in the Estonian archipelago. The remainder of the Baltic itself does not freeze during a normal winter, with the exception of sheltered bays and shallow lagoons such as the Curonian Lagoon. The ice reaches its maximum extent in February or March; typical ice thickness in the northernmost areas in the Bothnian Bay, the northern basin of the Gulf of Bothnia, is about 70 cm for landfast sea ice. The thickness decreases further south.From Wikipedia.
Freezing begins in the northern coast of Gulf of Bothnia typically in middle of November, reaching the open waters of Bothnian Bay in early January. The Bothnian Sea, the basin south of it, freezes on average in late February. The Gulf of Finland and the Gulf of Riga freeze typically in late January.
The ice extent depends on whether the winter is mild, moderate or severe. Severe winters can lead to ice formation around Denmark and southern Sweden, and on rare occasions the whole sea is frozen, such as in 1942 and 1966. In 1987, some 96% of the Baltic Sea was ice-covered, leaving only a small patch of open water in the south-west around Bornholm. However, in milder winters only restricted parts of the Bay of Bothnia and Gulf of Finland are ice covered, in addition to coastal fringes in more southerly locations such as the Gulf of Riga. In recent years a typical winter produces only ice in the northern and eastern extremities of the Sea. In 2007 there was almost no ice formation except for a short period in March.
The extent of ice covering the Baltic sea this winter (2007/2008) reached an all-time low. New figures from Sweden's meteorological agency (SMHI) indicate the lowest levels since measurements began more than a century ago. Overall, 49,000 km2 of the Baltic sea were covered in ice compared to the usual 180,000 km2. That was just over a quarter of the normal level, and the ice season had ended two weeks early. The highest levels of ice cover in the Baltic came in the winter of 1986 and 1987 when 420,000 km2 of its waters were covered.
The ringed seal had to change its usual habits and give birth much closer to land.
I would like to stress than one warm winter in a local area like the Baltic Sea proves nothing about global warming. Global warming is about a trend in climate change over many years. At the same time I would like to stress that Americans should NOT take their cold winter that same winter 2007/2008 as a sign that this global warming trend has suddenly stopped.
• http://www.thelocal.se/11526/20080503/
• http://www.terradaily.com/reports/Baltic_sea_ice_cover_hits_an_all-time_low_meteorologists_999.html
More in Swedish from SMHI at
http://www.smhi.se/cmp/jsp/polopoly.jsp?d=103&a=34774&l=sv
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