Ice and Break Up

Just to keep everyone up to date… School was out for the kids last Thursday and the last work day for teachers was Friday. I have been busy cleaning up for housing check out which still happens even if you are staying into the summer like I am.

The last weeks of school the kids went crazy and so did I. It felt like every minute was an hour but at last we all (teachers included) got to take a deep breath and run free.

We are now (as of May 1st) to the point that most of the snow has melted and many of the muddy puddles have dried up. Last year the slush lasted quite a bit longer but this year it was done in a few weeks. Part of that was because of the low snow conditions we have had.

Now we are on to the next season, break up. Break up is that time of year when the ice gets thin, holes start to form and finally it goes. Two weeks ago people were still out driving on the river. The next week the ice was gone from Kobuk and Ambler however our little section of ice lasted until the 3rd. The picture below shows the last bit before and after. All the ice was gone once you went one turn up or down the river so this ice was at the very upper most part and maybe a mile or 2 down stream it was clear also but this strip stayed. The two pictures were taken 3 days apart.


Last year it went on the 9th and with the relatively mild winter and early warming I was predicting a few days earlier, more in line with the other villages. It is still early though. Some years it does not break until the end of May. Everyone starts making predictions around in March and April as to when it will break and what the weather for the next months will be. Maybe next year I will start a pool.

When the weather starts to warm one of the first dangers is over flow. The melting snow causes the river to swell under the ice which causes cracks that leak water and can create lakes of water and slush on top of the ice. These are dangerous if a snowmobile hits them as it may fish tail or sink if it is deep enough. And is easy to get stuck in and very heavy to shovel out. In cold wether it is also dangerous because of the splash factor. It may also create a thin crust of ice on top of snow which could be a dangerous snag. More importantly it signals a large volume of water moving and pressing under the ice weakening the integrity of the surface ice.

A related effect of the pressure differences is that it can change the contour of the surface ice. It is a mistake to think that ice is flat. If you freeze a cup or bowl of ice you will see it is rounded and uneven. In the cup this has to do with the pressure of the ice expanding. On the river it has to do with currents and streams. Lakes are flatter but if you are imagining your local ice rink then you have over estimated. While some areas may be quite smooth, others suffer from cracks which create a small step effect. There is also pressure, which can create a gentle slope or a dramatic one. In some places there is a clear line where the ice curves down about a foot and in one section I found there was an ice pit in which the ice followed a 45 down slope almost 6 feet. On the other end of the pressure spectrum we came on an ice volcano where the pressure had built up the ice at a similar angle roughly the same amount.

Unfortunately I do not have very many pictures of ice formations. The best time to get pictures is when the ice has been cleared of snow by wind. My phone was dead when I saw the other described pictures and shortly after it snowed 8 inches and that pretty well covered it until it was too thin to drive on. The picture below is of the ice volcano. The tracks in front are from my snowgo and are roughly 3 feet wide.

Ice volcano

Another danger, ice_thickness_sml.jpgaside from the holes in the ice is the thickness. Just as the surface may not be smooth, the bottom may not either. In one place the ice may be thick enough to go out on but just a few yards away it may be quite thin especially in the late spring and early fall. Some places are prone to being thin due to currents or sandbars. Generally speaking it is best to stick to the trails when traveling on the river and to wait for search and rescue to give the ok

When it does get cold the river pretty much freezes over in a day. One day there is ice along the edge and another it is covered. But it is still several months before it is safe to drive on. Once search and rescue gives the ok the rivers become highways between villages and yes, some people do drive highway speeds sometimes.

I have no idea what the maximum thickness is but it must be 4-5 feet in some places. Some of the more shallow lakes and creeks freeze solid or nearly so and when the ice breaks there are large chunks 3-4 feet thick that float down even after having above freezing temperatures for months. It is hard to tell in the pictures below but the fissures in the ice ran 3-6 feet to the bottom as near as we could tell.


This year it broke on May 3rd. My prediction had been the 1st which I felt was pretty close. Last year the ice jammed up in front of the beach and even after there was quite a bit flowing through. People came down to shoot the ice blocks which was lots of fun. The blocks melt in an odd way so that they are basically lots of icicles held loosely together. This makes for excellent targets which explode and shatter if you hit them right. They were fairly good size targets too and often a block would sit on a flat piece offering a good sized target. The one in the featured image at the top is a cube roughly 2 feet in any direction

This year right after it broke. This volume of ice flow only lasted a day.
last years flow. Bigger chunks and more of them. And it jammed which kept them there longer.


Last year.




Another odd phenomena I noticed this year was the water level of the creek. Below are pictures taken in summer and fall (top) and days before the ice broke (bottom left) and the day after it broke (bottom right). Notice the difference in the water level on the bottom two. I can’t understand why it should change so much, all the ice above had already broken and the creek was still frozen further up. But all the way up the creek the water was almost 2 feet higher.

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