Today I went looking to see if any ice remains on Lake of the Woods. I did find some, south of the Barrier Islands, but it’s just little patches of loose, candled ice.
The photo above is from around 10:00 this morning, and looks south over Allie Island towards the Alneau Peninsula. I’ve circled the area of interest so you’ll know where to zoom in for a better look. At full resolution, that’s clearly ice.
I thought a little patch of weak ice like that wouldn’t last long, so I was looking forward to checking on it on my return in the afternoon.
We came back at about 5:00 and after checking to see that Big Sand Lake, north of Minaki was open, (too far away to photograph, but it is open) I started with a picture of Shoal Lake.
As far as I can tell, Shoal Lake is wide open. Because it’s deep, It often clears about three days later than Lake of the Woods, but this year it cleared earlier.
Next shot, Big Narrows.
Looking south. Left of centre is Wiley Point, with Big Narrows above the middle of the picture. In the distance, is that ice on Little Traverse? It was so hazy I wasn’t sure, but there was ice there the other day.
Next, I checked on that ice south of Allie Island.
In the centre of the picture, you can see it’s falling apart, but it’s not gone.
There was a lot of discussion about Bigstone Bay over the weekend, so I wanted to get a bird’s eye view.
This picture is centred on Scotty Island, with Middle Island and Hay Island stretching away to the right. Bigstone Bay appears to be entirely clear.
Next, a closer look at Bare Point and Pine Portage Bay.
Bare Point Marina and Northern Harbour, on Pine Portage Bay, are key access points for Bigstone Bay and Hay Island. Both are wide open now. I counted about twenty boats in the water at Northern Harbour this afternoon. There might be more, but the bigger boats are easier to see.
So although a small amount of ice persists, the lake is essentially open for boating.
Let’s go to the satellite imagery, Bob.
Aqua‘s image was spoiled by cloud today, but Terra got a pretty good shot. The white circle encompasses Rabbit Lake, Round Lake and Laurenson’s Lake, which are good markers for picking out Kenora. The small red circle is the surviving ice south of Allie Island. The large red circle indicates the area of possible ice on Little Traverse, but the satellite image shows nothing except a streak of cloud.
Fun with Clouds, Part Two: at the top left, our friends the fair-weather cumulus. At the right, in blue, high altitude clouds made of ice crystals. In the lower part of the picture, clouds of vertical development: towering cumulus or nascent thunderclouds, with watery bases and icy tops. When clouds like this become full-grown thunderheads, the vertical movement of water droplets up and down through the freezing level forms hailstones.
Summary: only one tiny patch of weak ice remains on Lake of the Woods today, and it will be gone tomorrow.
That means we’ll be ice free on exactly the same date as last year, which kind of makes sense given how the winters were similar in both duration and coldness.
I say kind of, because although the winters had a lot in common, the springs were quite different. 2018 was a late, cold spring that turned really warm at the end of April. 2019 was a slow, cool spring with few warm days.
Here’s Sean’s updated graph of our temperature progress this spring.
Overall, you can see we had moderate thawing this year, with the blue dots showing that mean daily temperatures added up slowly, especially in late April. When Sean and I first modelled this year’s forecast, we chose a thaw index of 240, because that’s how much heat it took to melt last year’s ice, and the two winters were similar. In the end, although the predicted date for ice-out came close, the actual amount of heat it took to do it was less than we thought, and this graph shows a revised forecast with the expected thaw index reduced to 190.
Basically, we assume that a long cold winter makes lots of ice, and it will take lots of warm days to melt it all. That’s simplifying, and we know it. The brutal winter of 2014 thawed with an index of 194, so 190 is not unreasonable. Perhaps last year’s 240 points was an oddity.
In any event, we didn’t need as many thaw days as we first thought. Sean offers these technical insights:
Sources of error are plenty in this high level statistical analysis. Wind, direct sunlight, rain, ice thickness, snow thickness etc are all variables that the analysis does not take into account.
Our ratio of freezing index to thawing index was right around 10 this year, which is the average for the last 15 years or so. Our initial prediction this year was conservative based off of last years data and went with 7.5 freezing index to thawing index ratio.
If we had ignored last year’s unusual thaw, we would have used a ratio of 10 and gone with an index of 200. That would have been close.
That’s basically it for this year. I’ll do a wrap up post when I can confirm that last patch of ice is gone, and I’ll update the different graphs that show how this spring compares to recent years.
Now that boats are hitting the water, it’s time for my annual reminder that the stretch of Safety Bay from Bush Island west to Norman is a licensed Water Aerodrome: an airport for float planes. Please watch out for them when boating in this area. Think of it as a runway. For safety reasons, float planes have the right of way when taking off or landing. When taxiing, they are supposed to be like any other watercraft, but from experience, I can tell you that they cannot decelerate quickly or turn sharply. Do be careful around them.