The previous official record was associated with the exceptional conditions in El Niño-affected winter of 1939-1940, when the ice went out on April 20th 1940. Though since 1940 was a leap year, that was actually a little later (relative to the vernal equinox) than the ice out date in 1998 (which wasn’t a leap year).
Other records are also tumbling in the region, for instance the ice out data at Bethel, Alaska:
The Kuskokwim River at Bethel has gone out. This is, by far, the earliest breakup in the 90+ years of breakup data. This follows the warmest February and warmest March on record. @kuskoiceclassic @Climatologist49 @AlaskaWx pic.twitter.com/auEfe0YQ7J— IARC Fairbanks (@IARC_Alaska) April 13, 2019
While the trend at Nenana since 1908 has been towards earlier ice-out dates (by about 7 days a century on average), the interannual variability is high. This is consistent with the winter warming in this region over that period of about 2.5ºC. Recent winters have got close (2012/14/15/16) (3 to 4 days past the record), but this year’s April 14th date is an impressive jump (and with no leap year to help calendrically).
As usual, I plot both the raw date data and the version adjusted to relative to the vernal equinox (the official time of breakup was ~12:21am).
[As usual, I predict that there will be no interest from the our favorite contrarians in this]