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Ice Out on Lake Iroquois

Some Notes on Freezing and Thawing

Water is most dense at 4 degrees Celsius.

In the Spring, as the temperature of the air rises, the temperature of the surface of the ice rises. When the water at the top surface of the ice reaches 4 degrees C., it becomes more dense and it sinks, mixing with the water under the ice. Warmer water rises ("mixing" occurs, or as we used to say, " The lake is working"), as warmer water, with nutrients and material from the bottom of the lake, moves upward. As the surface of the ice melts further, the entire sheet of ice reaches above 0 degrees, and the ice "suddenly" disappears ("ice out").

In the Fall, air temperatures fall, and water on the surface of the lake cools (as we all know!). When the water reaches 4 degrees C. it sinks, and warmer water comes to the surface, to be cooled further (The lake has been "working" again) . When the water at the surface finally reaches 0 degrees, it freezes, in smaller ponds often overnight. In larger water bodies, wind and wave action mix the water on the surface, making freezing slower and less sudden.

It is good that water is most dense at 4 degrees Celsius. If water were to be most dense at its freezing point, 0 degrees C., surface water would sink at 0 degrees, and lakes would freeze from the bottom up! We would then be swimming in water overlying a mass of ice, waiting for it to melt much later in the summer, if ever, and there would be no fish to catch, no osprey or fishermen to watch, but only a mist rising from the cold water into the summer air.

Ice Out Dates, Lake Iroquois

Ice out dates by year
Year Date
1987 April 9
1993 April 17
1994 April 24
1995 March 27
1996 April 7
1997 April 10
1998 April 8
1999 April 4
2000 March 9
2001 April 24
2002 April 1
2003 April 17
2004 April 15-16
2005 April 10
2006 April 1
2007 April 27
2008 April 12
2009 April 2
2010 April 2
2011 April 16
2012 March 17-18
2013 April 7
2014 April 19
2015 April 19
2016 March 17
2017 April 10
2018 April 24
2019 April 17
2020 April 1
Ice out dates by day and year
Day Years
March 9 2000
Mach 17-18 2012, 2016
April 1 2002, 2006, 2020
April 2 2009, 2010
April 3
April 4 1999
April 5
April 6
April 7 1996, 2013
April 8 1998
April 9 1987
April 10 1997, 2005, 2017
April 11
April 12
April 13 2008
April 14
April 15 2004
April 16 2011
April 17 1993, 2003, 2019
April 18
April 19 2014, 2015
April 20
April 21
April 22 1995
April 23
April 24 1994, 2001, 2018
April 25
April 26
April 27 2007