1a n. — Outdoors
the spring thawing of ice on rivers and lakes, especially the point in time when the ice on rivers breaks into pieces that are flushed away by the current.
Type: 3. Semantic Change — Break-up is a noun referring to the melting and "breaking up" of ice on completely frozen rivers and lakes in the spring. The point in time of this event is important as river navigation can resume soon after. Break-up has been recorded by sailors and traders for over a century (see the 1874 quotation) and is most celebrated at Dawson City (see CBC reference), which lies at the intersection between the Yukon and Klondike Rivers (see references to watch a video of the 2013 break-up). Locals bet on the precise minute that the ice begins to crack, often winning a large pool of money if close enough (see the 1949 and 2015 quotations). The Yukon River Breakup website (see reference) lists dates and exact times of each year's break-up as far back as 1896. Use of the verb "break up" in this sense goes back to the early 18th century (see also "break up" v.), while the noun appears around the mid-19th century in the sources.
In addition to its cultural significance, break-up records in conjunction with "freeze-up" dates have provided data for shifting global temperatures and offer evidence for global warming (see Canadian Council of Ministers of the Environment 2003: 17-18). As noted by Sandford (2012: 183-185), shifting break-up times and subsequent flooding and "ice jams" can leave a detrimental ecological impact on Dawson City and across the North.
See also COD-2, s.v. "breakup" (4), which is marked "Cdn" and Gage-3, s.v. "break-up"(1), which is marked "Cdn.".
See also: breaking-up (def. 2) break up v. freeze-up open water (def. 1) spring break-up
1b n. — Outdoors
the melting of the frozen ground and snow in spring; spring thaw.
Type: 3. Semantic Change — Break-up also refers to changes on land as a result of warmer temperatures. See meaning 1a.
See also: breaking-up (def. 1) freeze-up
2 n. — Outdoors
the period of time taken for the ice in rivers and lakes to soften, crack up, and disappear.
Type: 3. Semantic Change — See meaning 1a. This meaning is equivalent to the term break-up period, which is also in use.
See also Gage-3, s.v. "break-up" (2), which is marked "Cdn.".