Ice-Outs Over the Years
When you think about ice, it consists of two common atoms: hydrogen and oxygen. Hydrogen (H2) is the most abundant element in the universe, and it is also the fuel that powers all stars, including our own Sun. In massive, continous thermonuclear reactions, the hydrogen is converted to helium plus a release of radiation. When the radiation reaches the Earth, it keeps everything warm and comfy (at least in the summertime). Oxygen (O2) is the gas that makes up 20% of our atmosphere. Without it no animal could exist.
When God combined these two gases, He created water and lots of it. (Visit your nearest ocean to see for yourself.) The unique feature of water is that when it cools to its freezing point (32oF/0oC), the hydrogen bonds start to push the water molecules apart slightly, forming hexagonal-shaped crystals (think of snow flakes) with space in between. Solid water (AKA ice) is about 9% less dense than liquid water, so, voila, it floats.
Thank God for that unique bit of chemistry. It allows us to put our bob houses on the big lake and, in the Spring, watch the ice slowly melt.
Ice-Out on Lake Winnipesaukee is the date when the lake ice melts enough so that the M/S Mount Washington cruise ship can navigate from Alton Bay to Center Harbor, Weirs Beach, Meredith and Wolfeboro.
Ice-Out is considered the traditional start of the Spring season and island residents can once again reach their cottages to set them up for the summer. Records of this date go back over 130 years to 1887. The Ice-Out date and time is non-scientific and is now determined by an airplane observer who files over the lake several times a day. The pilot essentially makes the official call.
The odd aspect of the graph is that the dates keep alternating between late March/early April at the earliest and mid-April to early May at the latest not the kind of trend you can attribute to global warming. In addition, the most frequent date is April 20th which appears 10 times. Recent late March dates (2010, 2012, and 2016) may be outliers compared to other recent dates that fall between early and mid April. Time will tell.
Data for the graph comes from the following tables.
Dates are derived from https://www.winnipesaukee.com/index.php?pageid=iceout