Rarely has the sound of dripping water sounded so sweet. But I’m ahead of myself, already.
Just like clouds, love, and life, as Joni Mitchell beautifully explored, in “Both Sides Now” I realise now I don’t know ice at all. Over the years I’ve encountered some special ice forms at Gelli Uchaf – ice vases, beards or hair, and rime come to mind, but over the last week more discoveries have come to light about what is, after all, just frozen water.
The solid state of the more usually, at least in Wales, liquid H₂O.
What follows demonstrates part of life’s rich tapestry, as Dad used to call it, and also the problem with having an enquiring mind. One can observe novel events and marvel, or wonder.
Or try to capture in words what one’s seen. Or use images to do so. Or contemplate just how they came to be. Or maybe all three.
Let’s start with the bowls. We have four, usually water-filled bowls sitting on tables in the garden, which have often been featured individually before on these pages. One is glazed earthenware, with some William Blake words, from “Auguries of Innocence”, etched into the rim. The other three are of blue glass, though I’m going to discount the one with a Sarracenia in a black plastic pot from this discussion, since the heat-absorbing pot clearly altered the physics of what was going on with the water that surrounded it.
After weeks of rain, mild temperatures, and hints of a weather change, finally, the forecasts firmed up for a high-pressure system building, and at last again, the chance of a (slight?) overnight frost. What we weren’t expecting when it arrived was for it to be as severe as it turned out to be. In the morning, sensing how cold it was, I wondered if the conditions might have been sufficiently precise and favourable for an ice spike to have formed – which I’ve discussed before here.
In the end, there were no spikes, but instead, all 3 bowls with their different shapes and depths of water appeared to have frozen nearly completely, but with a significant domed bulging centre. As often is the case, the blue bowls had tiny air bubbles trapped in the mass of ice, but the other striking feature was how all 3 domes had obvious cruciform cracks in the domed section. And moreover from the frequent loud cracking sounds which filled the still air, this was an ongoing process.
I can’t recall ever seeing this before in any, or certainly not in all 3 bowls with such a pronounced convex ice surface, let alone the cracks, so wondered if some curious climatic sequence like the speed of temperature drop might have been responsible. With any remaining liquid water in a trapped, yet still freezing and thus expanding pocket towards the base of the bowl, perhaps the line of least resistance was to force the slab of ice covering it ever upwards, doming and then fracturing it.. I had no luck in tracking down a detailed explanation for this, but I did discover that the typical hexagonal nature of ice crystals which I’ve described before isn’t the only possible form. It’s the normal type of structure around freezing point and atmospheric pressure, but increase the pressure or lower the temperature even more and several different types of ice crystal can develop. Thus normal, hexagonal ice crystals are correctly known as Ice Ih
Pronounced ice one h, and shown above in molecular form with the pattern of arrangement of water molecules in the crystal. Reduce the temperature and increase the atmospheric pressure, and eventually water would freeze as cubic Ice; tweak the temperature and pressure further and you can create Ice II, Ice III all the way up to Ice XV. This required researchers at Oxford to take Ice VI and reduce its temperature down to -143 degrees C before exposing it to pressure 10,000 times greater than the Earth’s own atmosphere. Amazing what experiments people will think of these days, and not something you’re ever likely to see! The image below illustrates how the different forms of H₂O are determined by such temperature and pressure changes. And I (and maybe you) thought water was, well, just water, steam, or ice.
This work follows on from what scientists evidently tried to do in many experiments over hundreds of years – contain water in a really strong sealed structure, and then lower the temperature to see if the water, expanding as it freezes, will always burst out of its constraint. Cannons made of one-inch thick cast iron were filled with water only for them too to split when the water was frozen. Academics in Florence later filled a ball made of one-inch thick brass with water, only for that too to crack when it was frozen. They later worked out that the force required to split the brass was around 28,000 psi (pounds per square inch). Typical tyre pressure is around 35 psi. Click here for more in a great review. And here for more images
(I should add in a curious side passage of the rabbit hole I fell into, that the researcher who discovered ice crystal XII was Professor John Finney of London University. I suspect the same John Finney who until recently owned the small holding, Caermalwas fach which I referenced in my poem Dream Leaper –
What a time it was,
When beeches wept and
Seasons’ memories lay neatly banked and rusting,
Deep beneath Caermalwas Fach’s
Cathedral sheltering boughs.
And who also achieved a memorable victory in a recent Appeal Court case regarding a planned wind turbine near his property. We’ve never met John, and understand that it wasn’t ever his primary home and indeed that his property has now passed to the local Wildlife Trust, but I’d love to ask him if he ever saw any unusual ice structures in his time spent there.)
The second discovery I gleaned from looking into spontaneous ice cracks was that the bulge and cause of the cracks in the bowl ice were possibly similar to those which cause sudden massive, noisy hydro fractures at the base of supraglacial lakes in the ice sheet in Greenland, excellently described and illustrated in this article, by scientists from the Woods Hole Oceanic Institute. Such fractures can lead to huge freshwater lakes disappearing completely down deep crevices in a matter of hours.
The day after the sharp frost, William was due here, and we set off up the hill to try to finish hedge laying and brash clearance, which we managed just before lunch. By this time, despite much sunshine, W.’s latest weather forecast update was showing snow showers moving in by mid-afternoon. We decided to call it a day since he has an hour’s journey to get to home, which was a good call since a heavy snow shower began to fall by 2.30p.m. Hail showers and sleet followed. By the following morning we had a 2-inch covering. All of this is fairly normal for us, given the unreliability of weather forecasts for our particular location. We’ve always tried to clear the worst of the snow from the yard, and the last steep section of track, after first brushing off the PV panels, to mitigate any further (un-forecast) big build up and subsequent freeze. By 10 p.m. that night, the snow was still melting. However, by the morning more hail had fallen, and everything was frozen hard into a curious solid mix of hail, ice, and slush. It took me over an hour to shift the part-frozen light covering from the PV panels, (way longer than ever before), by which time I’d worked out that such cold air temperatures play havoc with aging lungs. N.B. Julian! Remember to wear both balaclava and neck warmer in future, and breathe in slightly moister warmed air in such extreme cold. (We’re talking minus 9 or so).
All began to look lovely in the sunshine and minimal winds of the next 3 days, and this was when I made discovery 2 about ice. The extraordinary feathered ice crystals, (conventional Ice Ih), which began to grow on many surfaces, are known as surface hoar. This is the frozen equivalent of dew, which forms if air moisture falls onto a snow-covered surface, and then begins to crystalise as ice. We’ve certainly seen surface hoar before occasionally, without using this name for it. The images describe the crystals better than I can, but they’re a feature of particularly rare conditions (for us).
What’s needed for surface hoar to form?
- Clear skies, usually at night, which cause the snow surface temperature to decrease rapidly and significantly due to radiative cooling.
- Calm winds, less than 15 km/h. A small amount of wind is necessary to deliver new water vapour supplies as the water vapour deposits onto the surface as ice. This slight air movement can also be provided by subtle downslope flows – a likely cause for us given our location halfway up a mountain. Too much wind will simply damage the fragile structures before they can grow.
- A strong temperature inversion just above the snow surface. This means that the air just above the snow surface is relatively warm, around 10°C warmer or more, compared to the snow (even though the air is often still quite cold!). Hoarfrost can keep forming into the daytime on north-facing slopes that are in the shade because they continue to cool radiatively with little or no heating from the sun.
- Surface hoar forms best on a flat, open surface. If there are trees or rocks close by, this will probably prevent its formation due to radiative warming from these objects. This warming prevents the snow surface from cooling down as much as it would otherwise.
At last, 6 days after the first frost, clouds rolled in overnight, and we were spared a further frost. We managed to break up the surface of the yard using a combination of an ancient inherited rake and mini-fork so that when the Tesco driver arrived after 4 p.m, he was able to turn with no issues. He commented, as delivery drivers often do in these conditions, that we were the only location with ice and snow still lying so heavily. Oh well.
This episode did get me thinking once more about how much energy is required to get all this snow and ice to melt, once it’s sitting there. I covered this topic in some detail, I see, in 2017, without actually coming up with a ballpark figure, after we’d had a heavy ( 30 cm deep) snowfall, but with none of the ice or hail of this recent event. So for the variety of technical issues involved, check out my previous post. But for some estimated maths, and the shocking amount of energy involved to achieve a thaw, here are some back of an envelope figures.
20 mm of hail/sleet and minimal snow (in melted mm of water) fell over 3 days, which had begun to melt, but then froze. That’s 20 litres of water per square metre, or 20 Kg of water, then turned into ice by the low temperatures. Multiply that up to a more easy to visualise area of 10 metres X 10 metres, and you end up with a figure of 2,000 kg of ice! That’s going to take some shifting.
If the ice at its worst is at minus 5 degrees C (actually it reached minus 9 on some nights), then it’s going to need about 20 joules of energy per gm of ice to warm it up to melting point, at 0 degrees C before ice melting can even begin. (4.18 joules per gram per degree C). Or 40 million Joules for our 10 X 10 metres, or 2,000 Kg of ice. But raising the temperature of the ice from minus 5 to 0 degrees C is the easy bit!
It takes a whopping 334 joules to change each gram of ice into water, still at 0 degrees C. Such is the energy needed for water to change its physical state from solid, to liquid – what’s known as the latent heat of fusion/melting. This energy has to come from somewhere (the linked post explains options). Once again multiplied up to our 10 X 10 metre plot or 2,000 kg of ice and it comes in at a staggering 639.2 million joules to get that layer of ice to melt. Add in the 40 million joules to get the ice to zero, and it seems you’ll need about 680 million joules of energy to achieve it.
This is all a bit difficult to visualise, so let’s instead think of a 2 Kilowatt heater sitting in the middle of our 10 X 10 metre plot, trying to do the job, if there were no other energy inputs or losses. That’s quite a powerful heater. Run it for 1 hour and it would have used/emitted 7.2 million joules of energy. This means that to get all the ice to melt, you’d have to run that 2 KW heater continuously for over 94 hours. Or nearly 4 days!
Since we don’t have the landscape littered with such power-guzzling heaters, this vast sum of energy has to be sucked out from the environment, or provided by any input from rain (which we didn’t have), or the sun. Which is fine, briefly, on a sunny day around midday. But if it’s cloudy, you can see how little external energy there is, from the 2 PV inverter readings from 2 nearly consecutive days. The first was sub-zero but sunny, the second day was milder – maybe 3 degrees C – but cloudy. If you study the first PV inverter reading, you’ll see that even this early in the year, the maximum wattage output briefly reached nearly 2.4 KW, so just above my speculated 2 KW heater level. This is almost 65% of the output you might get in high summer, and this from the sun’s energy falling on the roughly 30 square metres of our panels. But you can also see that this high power lasted barely a couple of hours, before tailing off.
All of this maths and physics is designed to illustrate that no matter how a hard frost one experiences, it’s frozen, above-ground precipitation one really needs to worry about for its significant longer-term environmental chilling impact, until it’s all melted.
Before I leave this ice-themed journey, here’s a mystery. As we raked away to roughen up the sheet ice in the yard, I spotted part of a Small Tortoiseshell butterfly wing. How did it get there? Did it seize a moment when the sun appeared to fly out and get snaffled by a hungry bird? Who knows.
I did enjoy a wonderful moment, late morning on one of the freezing but sunny days when walking past one of our Daphne bholua with my beanie pulled down. I was convinced I heard buzzing. Sure enough, I turned and spotted a dark honey bee. Checking on our most hardy honey bee colony nearby, I was amazed to find a huge amount of active foraging/flying activity, just feet from the minus 7 degrees registered on the frozen croquet lawn surface.
The bees clearly have an innate ability to be able to detect and benefit from such insolation. Even past 3 p.m. when the sun was rapidly falling, and not simply be influenced by actual air temperature, when deciding whether to risk a foraging trip from which they might not return to base because of hypothermia. Bear in mind that my 70 KG body was wrapped up in multiple layers to face the weather whilst taking these photos. The bees, roughly 120 mg body weight or about half a million times lighter than me, can manage just a few minutes of honey fuelled flying at most, before their core thoracic temperature of around 34 degrees, (necessary for effective flight muscle activity) will drop away, and they’re doomed.
Our really hardy bees have shown once again that they’re capable of outperforming all the often quoted texts that imply they rarely forage in temperatures below 10 degrees C. See below for a brief video clip.
Whilst up on the croquet lawn, I noticed some fine ice crystals glinting on the edge of the muse stone, so took some photos. And loved the 4 tone linear effect along the edge of the stone. But as with some of my previous photos taken of Poppit beach sand sculptures, I then tried rotating the image. I bet you see a trough in the stone in the third rotated image, towards the left, and not a ridge. It’s another example of the “Crater illusion”, which I discussed here.
This brief video explains what’s behind this optical illusion.
The Thought Box is now complete, and ready to go, when we get any garden visitors from next month. The idea has been trialled with a few family and friends, and I’m intrigued to see what, if anything, happens. I’m also delighted to report that the garden is about to become one which features a “Silent Space”, in which The Thought Box will be placed. This after Liz Ware, the wonderful founder of the charity, agreed to include us. I’ll write a bit more about Liz’s work and vision next time. Watch this space.
Meanwhile, we were left with the off-cut rings of stainless steel/black acrylic which Mark had sent down with the “Ripples” poem. I’d wondered about using them to make some sort of mobile to hang somewhere, and after a regular clear-up of fallen lichen-encrusted twigs and small branches from larch in the copse, I ran the idea past my technical wizard Fiona. What about trying to stick bits of lichen twig onto the dark side of the rings, to add a bit of interest? She reckoned a hot glue gun would be the answer, so after painstakingly shaving off slivers of lichen-encrusted bark with a whittling knife, set to work with the gun.
All looked good, but it still needed an old coffin ledger weight, some ex-fishing split shot, swivels, and monofilament nylon line, and we were ready to give it a go. But where to put it? I spent a bit of time assessing locations where similar lichens were already growing on trees in part shade, and in the end plumped for the lowest option. A good decision, since very quickly sections of the stuck-on lichen parted company with the ring, so it’s had to be re-worked with Superglue, and in due course some fine stainless steel wire.
However, already the installed rings are exceeding expectations in terms of visual interest, moving independently of each other, and at least when the sun shone, individual rings will occasionally flash most dramatically. Only time will tell how it copes with stronger winds. But it did mean I delved into the biology of lichens in a bit more detail, for the first time. And, typically, was amazed at what I found out.
Aside from the perennial conundrum of how you pronounce lichen – liken or litchen?
I’ve always been a liken man.
All lichens are examples of a special symbiotic association of two completely different forms of life. In fact, it’s recently become clear that this is probably far too simplistic a categorisation, since yeast and bacterial DNA material can often be isolated from the lichen structure. However the normal components are firstly a phototropic organism – usually a species of alga or cyanobacteria, both of which can capture the sunlight and generate carbohydrates through photosynthesis. And secondly a fungus, which provides a lot of the structure of the lichen and protects the phototroph at its core.
There’s an excellent review of lichen morphology and biology, and a consideration of how such symbiotic associations ever came into being, and indeed still develop and reproduce, “Evolutionary biology of lichen symbioses”, which you can read here.
For a quick summary, the fungal symbionts of lichens are among a very small percentage of fungi in which the entire mycelium is perennially exposed to ambient air. Most fungal mycelia can’t survive this sort of exposure since they’ll dry out and die. Lichen symbionts have no means of internal water regulation and thus hydrate and desiccate with daily and seasonal water and temperature conditions. Lichens not only tolerate, but require regular cycles of wetting and drying for them to survive.
Lichens are found in nearly all terrestrial ecosystems on earth, from tropical rainforests to polar environments. Their survival capabilities are extraordinary – some survive in dry valleys in Antarctica with less than 50 mm of precipitation a year, and temperatures dropping to minus 50 degrees C. In warm deserts they can survive temperatures up to 70 degrees C, and extreme light. They have survived conditions in space for over 18 months. One of their key properties for such resilience is their ability to adapt via anhydrosis – coping with prolonged periods with no access to water. The phototroph part of the lichen does this by what’s known as vitrification, turning itself into a glass like state. The fungal part achieves this by appearing to collapse its cells, and can remain apparently dormant for long periods when conditions are harsh. Thus many lichens grow incredibly slowly, and only when conditions are favourable for them to do so. A millimetre per year is typical for many species!
It seems that whilst the phototroph gains a protected environment from the relationship, the fungus gains by receiving complex carbohydrates from the phototroph, which probably have both a nutritional/energy advantage for the fungus, but also help in its ability to cope with anhydrosis.
One of the fascinating facts about lichens is that the body plan of the lichen is distinct and fundamentally different from that of the co-operating fungus on its own, and indeed its phototroph partner. Just how is this structure created given the two very different co-operating organisms’ genomes? Nobody really seems to know. They often survive on inanimate structures like metals, (above) or stone, (below), from which they may derive some mineral nutrients. Where they grow on plants it’s generally considered that they do no harm at all to their host organism, just using it as an anchor on which to begin to develop.
This is all interesting stuff, at least to me, but the other aspect of lichen is their beautiful variety and the surfaces on which they will establish. This, together with a realisation that they are potentially so long lived, and so slow growing, is what drew me to giving our storm damaged, lichen-encrusted broken twigs a chance to live on for a little longer, on our mobile/sculpture.
However, perhaps there’s even more potential for thinking about lichen in a different way, as this article, by Sarah Westcott explores. I’ll leave you with this reference from American author and poet Forrest Gander who, to quote Sarah:
“suggests that the concept of lichen as a synergistic collaboration between fungus and algae is simplified and that the original organisms are ‘utterly changed in the compact’ and cannot go back to what they were.
‘The thought of two things that come together and alter each other collaboratively – two things becoming one thing that does not age – roused me toward considering lichen a kind of model and metaphor for the intricacies of intimacy,’ ”
Gander, an American Pullitzer prize winner (2019) has written a recent work of poetry, “Twice Alive” exploring his thoughts, and knowledge about lichen, which he reads from in this first public interview after the book’s release. Well worth making time to listen to.