Breaking the Ice

A couple of days ago, I read a post on Futility Closet about the Nenana Ice Classic. At the beginning of every year, the people of Nenana, Alaska, set a tripod on the frozen Tanana River. They hold a contest to see who can guess the correct date and time that the tripod starts to fall due to the melting ice.

Upon hearing about this, I decided to see if there was a way to statistically predict when the tripod might fall. I found the break up log and started to look at the data.

Since 1917, the ice break has happened sometime between April 20th and May 20th. The average date is May 4th. However, as is pointed out in the Futility Closet post, the National Snow and Ice Data Center record the event to measure climate change, indicating that the date is changing over time.

The graph shows a negative trend, indicating that the date of the ice break has generally been happening earlier in recent years compared to the past. According to the trend line, the estimate for when the ice break should occur has moved forward by a week, from May 9th to May 2nd since 1917. Of course, the R-Squared is rather small, 0.12, meaning that year-to-year changes only account for 12% of the variation in ice break dates.

Of course, one doesn't just win by guessing the right date, they also have to guess the time. I included the time in the previous estimates to get the average dates, so I could just use the time they produce as the estimate. However, I noticed another pattern when looking at just the times.

The ice break rarely happens late at night or early in the morning. It's not even a normal distribution. No ice breaks have ever occurred between 7 and 9 am, but then there have been a lot just after 9. The best explanation is that the ice is most likely to break when the sun is there to warm it up. If the ice doesn't break by sunset, it is unlikely to break that night.

So my prediction for the most statistically probable date and time of the ice break is May 2nd at 2:11pm. Let's see how I do.