Walden is two-thirds broken up.

 March 27.

Walden is two-thirds broken up. It will probably be quite open by to-morrow night.

H. D. Thoreau, Journal, March 27, 1851

It will probably be quite open by to-morrow night. See note to March 14, 1860 (" I am surprised to find Walden open. No sooner has the ice of Walden melted than the wind begins to play in dark ripples over the surface of the virgin water. Ice dissolved is the next moment as perfect water as if melted a million years.") See also  April 18, 1856 ("Walden is open entirely to-day for the first time, owing to the rain of yesterday and evening. I have observed its breaking up of different years commencing in ’45, and the average date has been April 4th.") and  A Book of the Seasons, by Henry Thoreau, Ice-out In Thoreau’s records, March 14th was the earliest ice out; April 18th was the latest. From 1995 to 2015, ice out ranged from Jan. 29 (!) to April 12 with the median ice out date March 21.