Slush under the ice. What causes it?

LAYERS OF PACK ICE THAT GOT BLOWN IN .
THE TOP LAYER FREEZES WHERE THE BOTTOM LAYER IS SLOWLY MELTING BUT STAYS IN THAT SLUSHY STATE BECAUSE ITS COLD ENOUGH .

THATS MY TWO CENTS.
NOT A PRO.

You are right it has nothing to do with warmer temperatures or melting snow. This ice was formed when it was cold and pushed under the other ice. It's called frazil ice. Now frazil ice normally sinks, but this ice did not have time to get heavy enough (unstable) to sink. So after it was pushed under the other ice by wind or current it turned into slush. If it gets colder it will turn into white ice, or it will melt back into the water below the surface. This usually only happens on bigger lakes and not too often. This weird winter created the perfect conditions for this to happen.

ok that's what somebody at work called it, I was telling them how I spent all day clearing the hole after each fish and he said that frazil ice I was dealing with.

Just got in from fishing in the same area that we fished on Sunday - no sign of slush

I did a bit of Googling on frazil ice. I am fascinated with that stuff partly because we see a lot of it floating down the river here in Wasaga on very cold days. Among other things, it's what makes life miserable for float fishermen who want to find on a cold day.

Frazil ice is what forms when the water has too much motion to allow the ice crystals to float to the top and skim over----motion due to currents in the river or wave action on lakes or in the ocean. The ice crystals won't sink as crapeeman suggested but are sometimes described as being 'suspended'. Ice is not very buoyant----remember that icebergs are something like 9/10 tenths submerged.

So I think LS is right(as usual ) about how this occurred---i.e it formed on the lake, got driven under the edge of the ice by the waves and then floated to the surface once under the ice and away from the stirring action of the waves.

One other significance that I noticed Sunday was lots of air bubbles trapped in the "slush" which would agree with your "Frazil" theory.

Good morning. I didn't say it was frazil ice. I said this ice did not have time to get heavy enough (unstable) to sink. Meaning (ineffective buoyancy). Almost all frazil ice sinks eventually as to the allowing factors. The ice in question in the original post was called slush. I agreed with Longshank and his theory. I just explained why it turned to slush, and when it would go away, either by melting or freezing again. You mentioned that ice is not very buoyant. Ice is buoyant, it floats. In fact ice is buoyant because it is less dense than water. And the reason icebergs have so much mass under the surface is because of a long boring math equation on weight versus the buoyant force of seawater. As for the ice you see on the river, some of it is normal floating buoyant ice. And some of it is frazil, (unstable, heavy, ineffective buoyancy) ice.

The ice in my rye and ginger floats...

That's a good one. LOL. People can float in ice water with a bit of help.

That's kind of how I came up with my theory.. was having a drink with shaved ice and sloshed it around in the glass and it kinda layered up on one side way more than the other

Can't be a coincidence that the heaviest slush we find on Simcoe is usually within range of pressure cracks. Must have something to do with the mixing of meltwater and lake water as slush is consistently found near pressure cracks, in my experience.

Frazil ice FLOATING down the river----'nuff sed!

LOL. You are funny, at least I think you are trying to be funny. That is either floating pieces of ice that has broken up off larger sheets of ice. Or it is pancake ice which is formed almost the same as frazile ice but slower and cooler temperatures not quick freeze temperatures. I am definitely not trying to say you are wrong. I am sure you have frazil ice in your river from time to time. If you see frazil ice in a river, it will be bouncing up and down off the bottom, and then to the surface again and again. This depends on how fast the river flows etc. In general 99% of frazil ice sinks. Sorry I did not create the science or the ice, just was letting the original poster know why there was slush under the ice.

I’ve become frazzled reading all this stuff 🙃

LOL.