Flash fish freezing

Jordan Sargent has a remarkable photograph taken by Ingolf Kristiansen off the coast of Norway. Apparently a large number of herring were swimming close to the surface when a gust of cold wind froze the water near the surface, trapping the fish in place. I found this surprising because the phase change from water to ice is not instantaneous and one would think that as it happened the fish would go lower where it remains as water.

Very rapid instantaneous freezing is possible when water is supercooled. i.e., stays in the liquid state below the freezing point. This can happen when the water in a container is undisturbed as the temperature drops. Sudden motion can then cause it to rapidly change its phase into ice. Below is a video that shows it happening for a regular bottle of water.

Note how the water freezes from the top down. I did not think that fish freezing could be caused by supercooled water because the fish were swimming around and the water is being constantly disturbed.

The other possibility I can think of is that the oxygen level in the water lower down was so depleted by the cold that the fish had no choice but to stay near the surface, even as the water froze around them.


  1. says

    When I was a kid visiting in northern Ontario, ages ago, a neighbour arguing with Dad over a snowed-in parking space lost his temper and picked up a bottle of milk from the doorstep. (Yes, this was many years ago, when they still delivered milk.) I was watching from the window as he raised the bottle and waved it threateningly at Dad. The cardboard lid gave way, and the milk poured down over his head and froze instantly, leaving him with a thick white coating on head and shoulders.

    End of argument. Dad dug out the car and moved it somewhere safer.

  2. moarscienceplz says

    It’s hard to tell for certain, but a lot of the fish seem to be on their sides or belly-up. So I don’t think they were flash-frozen. The speculation that a large school was driven to very shallow water by predators and then they became trapped between a rock and a hard place – literally – seems more plausible.

  3. wtfwhateverd00d says

    How thick is that herring ball and how quickly did the water freeze? The fish on top may have had nowhere to go.

    Wiki claims a sardine ball in open seas may reach 10 meters in depth:

    > For example, sardines group together when they are threatened. This instinctual behaviour is a defense mechanism, as lone individuals are more likely to be eaten than large groups. Sardine bait balls can be 10–20 metres in diameter and extend to a depth of 10 metres. The bait balls are short lived and seldom last longer than 10 minutes.

    Why is the water bottle freezing top down?

    a) pressure increases with depth?
    b) it’s not freezing top down, it’s just an optical illusion caused by ice crystals floating up and accumulating at the top?
    c) the supercooled water is most disrupted by splashing at the top?

  4. wtfwhateverd00d says

    The description at sploid indicates this was rather shallow water and the herring had been “chased” into the bay, so there likely was no place to descend.

    (Also consider fish that when threatened by birds that can sort of swim, try to out swim them on the surface and not just dive deeper).

  5. bwells says

    Just an hypothesis, but right across Lake Erie from Mano here in SW Ontario, where the water is quite shallow, there is a well known phenomenon causing a mass fish death every decade or so. We call it “lake inversion”.

    In summer and winter, the shallow water stratifies by temperature with the warmer water staying at the surface in summer, and in winter it is at the bottom. Oxygen is most abundant in these warmer layers and that is where the fish stay. If the system experiences a rapid cooling, the density of the surface layer increases and it will sink to the bottom in minutes, and so the layers switch. Suddenly, the fish are surrounded by water with very little oxygen and they die within seconds.

    Our last one occurred in summer 2012. When that occurred, the fish were floating along in clusters from currents, similar in appearance to the photo.

    I think moarscienceplz was on the right track that the fish appeared to have already been dead and that is why they were belly up and frozen at the surface.

  6. dmcclean says

    Doesn’t colder water have the ability to hold more oxygen than does warmer water? Or does this effect reverse below a certain temperature? The chart I found only went down to 0 degC.

  7. Kilian Hekhuis says

    @dmcclean: yes, it has, but that doesn’t mean it needs to have. Water at the bottom of ponds and lakes may be oxygen depleted, while water at the top has enough oxygen because of its air contact.

  8. Jared A says

    I doubt that the surface sea ice could have ever been supercooled. The water needs to be very clean in order to be supercooled. IIRC, organic particulates are especially good nucleation points for ice crystals, so if there are any critters living in there, ice crystals should form readily.

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