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A circle of thinned ice on the southern end of Lake Baikal (Russia, April 2009), from the International Space Station.  The circle has a diameter of 4.4km.

Usually 5 – 7km in diameter, these mysterious ice circles were first reported in April 1999 near Cape Krestovsky, and assumed to be caused by methane emissions from the basin of the lake.  The circles appeared again in April 2003, 2005 and 2008 in the same place, as well as near the settlement of Turka in 2008.

The circles appear in the same locations, often near the Syvatoy Nos peninsula.  Here, anticyclonic eddies often occur, with warm water in their centre.  This causes the ice to become thinner.  The ice is then saturated with water, and sags a little.  Cracks appear. and the structure of the ice changes near the circle.

mostly-history
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Ice melting on Lake Baikal (May 4th, 2012), taken from the Aqua satellite.

Lake Baikal in Russia is covered by a thick layer of ice for several months every year.  The ice begins to form in late December, and by mid-January it usually covers the whole lake.  In spring [March – May], the ice begins to slowly melt.  Patches of open water appear in the southern part of the lake in early May (shown here), and move progressively northwards.  By late June, the northern part of the lake is finally clear of ice.

This image shows ice breaking up in the central part of the lake. Drifting ice and large patches of open water can be seen in the south.  Ice often lasts longer in the extreme south-eastern part of Lake Baikal, as that part of the lake is shallow.

Along the coasts is fast ice.  Fast ice is anchored or fastened to the shore, and doesn’t move with the winds or currents. It usually lasts longer than ice that forms over deeper water.

The village of Listvyanka, on the south-eastern coast of Lake Baikal, has kept records of ice formation and breakup since 1869.  These records show that ice break-up near the village occurs earlier now than in the past.  In the 1870s, thawing would begin around May 10th, but now it begins in late April.  The most rapid change was between 1869 and 1920, and the date of ice break-up has remained fairly constant at Listvyanka – however, ice formation begins later on in the winter than it used to, so the overall ice cover of the lake does not last as long as in the past.

Analysis of satellite data from 1992 to 2004 shows that in the northern and central part of the lake, ice has been breaking up later and lasting longer overall since 1992.  In the southern part of the lake, ice is forming later in the winter, but breaking up at around about the same time, which is consistent with the records from Listvyanka.

There are many factors that can affect how long Lake Baikal’s ice lasts.  These include air temperature, wind patterns, lake currents, clouds, the amount of snowfall, and the volume of river water discharged into the lake.

mostly-history
mostly-history
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The Syvash in the Arabat Spit (Crimea, Ukraine, July 2012).

Also known as the Putrid Sea and the Rotten Sea, the Syvash is a large system of shallow lagoons on Sea of Azov’s west coast.  It almost cuts the Crimean Peninsula off from the mainland, serving as a natural border. With a maximum depth of about 3 metres, the lagoons are very shallow, and the bottom is covered with up to 5 metres of silt.  When the waters heat up and evaporate in summer, they leave a putrid smell, and the remaining water is very salty.

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Sally J. Johnson, from “Limnology: A Memoir,” Black Warrior Review (vol. 43, no. 2, Spring/Summer 2017)
The third color ever recorded in language is red. After, of course, black and white. Ancient language doesn’t show blue because people probably didn’t notice it as a thing.
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