April 21, 2024: An Information Vacuum

Sorry about the long gap between posts, but I’ve had no new info to share. I haven’t received a single photo from anyone* lately, and the satellites didn’t get a good shot all week.

It didn’t seem useful to go online and say, “the ice is melting, I assume.”

*I did receive one broken comment that might have been an attempt to send a picture. The comment form can only process text. To submit a photo, use the email address: icecaptain[at]outlook.com.

By the way, please keep in mind that using the comments form is not like sending me a private email. Comments are public, and may be seen by anyone with a web browser. It is not wise to include your email address, phone number, or personal links. You’d be opening yourself up to spam.

You probably remember that we expected the ice to be all gone by today’s date. That was based on us reaching a Cumulative Thawing Index of 100 by now. We have not achieved that yet. We had just got to about 90 when the weather turned cold for the last few days.

NASA’s Aqua satellite finally got a partly cloudy image of Lake of the Woods on Saturday afternoon.

If you click on this picture, you’ll see a full-screen view with some place-names tagged to help you get oriented. (There is no larger image available. NASA launched the MODIS satellites decades ago, and what was designated as MODerate resolution then is rather low-res by today’s standards.)

MODIS image of Lake of the Woods from Aqua satellite, April 20, 2024, in false colour.

In this false-colour image, the pale streaks are cloud. The southern portion of the lake is black, indicating open water all the way from Big Traverse Bay to Big Narrows, although there is still ice in Little Traverse. It’s been windy, and a little wind goes a long way in the Big Traverse, so I’m not surprised to see it clearing first this year.

Shoal Lake and the northern part of Lake of the Woods still seem to be mostly ice-covered. The cloud cover makes it hard to be sure of the proportions, but I’d estimate that the lake is now 60% clear. Unfortunately for seasonal lake-dwellers, the remaining ice covers a lot of cottage country.

Can we use this single satellite image to infer anything about how close we are to ice-out? Let’s hop aboard the way-back machine to look at a matching image from the archives. 2021 was an early thaw following a mild winter. Here’s how things looked on April 22nd that year.

MODIS image of Lake of the Woods from Aqua satellite, April 22, 2021 in false colour.

That’s right, the lake was practically clear. We were using aircraft to hunt down the last vestiges of ice.

That’s what we were expecting to happen this year.

Let’s see if I can find a satellite shot that shows about the same amount of ice as yesterday’s image.

2022 was a year when the lake cleared near Kenora before the ice went out for Warroad or Morson, but here’s a shot from when the lake was about 60% clear.

MODIS image of Lake of the Woods from Aqua satellite, May 10, 2022, in false colour.

The ice was all gone six days later.

In 2019, the lake cleared a little more like this year, with ice persisting in Little Traverse, south of the Barrier Islands and on Shoal Lake.

MODIS image of Lake of the Woods from Aqua satellite, May 7, 2019, in false colour.

The lake was ice-free one week later. Keep in mind that in a late thaw, things tend to go faster, because May weather is usually warmer than April.

What does the weather forecast say for the next week or two? Will we get some May-like heat, or April variability? Can we get back on track to reach a CTI (Cumulative Thawing Index) of 100?

At the moment, the forecast looks like a mixed bag. Monday warm, Tuesday cold, then warm and sunny, then mild and wet.

I’m not sure exactly how Sean Cockrem uses the forecast to predict the daily mean temperature, but Tuesday’s forecast of a high of 6ºC followed by an overnight low of -5ºC seems like we’d get a daily mean close to zero, adding nothing to our CTI. After that, I think we could reach the target number of 100 by the weekend.

Will it be enough? Despite the mild winter, the ice has been surprisingly stubborn this year. Sean’s method focuses on temperature, but there are many other factors, such as humidity, wind, sunlight and water levels and flow that we don’t really understand.

I feel like the ice should be gone in roughly a week, but if the weather doesn’t play nice, some ice might last to the end of the month.

That would give us a ‘Pancake Graph’ that looks like this.

You can click on the graph to see it full-screen.

Thaw timelines from 2003 to 2024, with the most recent years at the top.

This graph shows each spring thaw as a blue bar that spans the calendar starting on the date of Inflection Point (when the daily mean temperature rises above freezing) and ending when the ice is 100% clear of ice.

I’m disappointed that our mild winter didn’t lead to an earlier ice-out, but it’s still not bad. A typical thaw doesn’t see us ice-free until the first half of May, and it bears repeating that most cottagers don’t need the lake to be entirely clear to reach their camps.