This is a corrected chart and supersedes all previous iterations. Data in the chart has been double-checked again against printed versions of the data available from the Nenana Ice Classic. One or two dates were incorrectly shown in previous versions of my chart through 2018.
The overall trend earlier in those charts remains unchanged, however, and has been reinforced by the record-setting early Ice-Out in 2019 on April 14. This is because of the preponderance of relatively earlier Ice-Outs April 30 through May 7, of which there are forty-five. With or without the record early Ice-Out on April 14, 2019 and the relatively early 2020 Ice-Out on April 27, the median date remains the same: May 4. Half the Ice-Outs occur before that date, half after.
Otherwise from April 14-29 there are 27 early Ice-Outs vs. May 8-20 with 32 late Ice-Outs:
April 14-21: 3
April 22-29: 24
April 30-May 7: 45
May 8-15: 29
May 16-20: 3.
Is "global warming" at work?
If you back out all data from the year 2000 onward, here's what you get:
April 14-21: 2
April 22-29: 14
April 30-May 7: 37
May 8-15: 28
May 16-20: 2.
Median date: May 5.
Obviously the biggest impact since 1999 has been on the week April 22-29, adding ten early Ice-Outs, moving the median date earlier by one day after 20 years.
Another thing it does, however, is balance out the data surrounding April 30-May 7, which otherwise was weighted heavier later, with far more Ice-Outs in the second week of May than the last week of April. It could be that over the long course of history prior to 1917 we're missing a lot of early Ice-Outs which recent warming has only now supplied.
For example, we know early 20th century temperatures were warm enough for Roald Amundsen famously to make it through the Northwest Passage from east to west in his small wooden herring
ship between 1903-1906. He finally traversed the western half of the Canadian island archipelago during 1905 after being ice bound in the heart of it for two winters. In August 1905 he put in at Herschel Island 5 miles off the north coast of Canada due to ice. From there he skied 500 miles south to Eagle, Alaska, in order to send a message by telegraph wire of the news of his singular achievement. The
wire was sent on December 5, 1905. Amundsen spent two months in Eagle before skiing back to his ship and sailing on to Nome in 1906, where his ship then remained until 1972.
Eagle, AK, incidentally, is about 200 miles due east of the Fairbanks Area, which includes Nenana. The mean average temperature for the Fairbanks Area since 1999 is 28.6 vs. 26.3 1904-1999.
The data for Ice-Outs since 1999 is what it is, evidence of warming.
