The Sun and Us

Climate change is rarely out of the headlines at the moment, and one very visible manifestation of warmer temperatures is the accelerating retreat of glaciers, which currently cover about 10 per cent of the planet. But it turns out there’s a double sting in the tail here, because scientists have discovered that, as glaciers scour their way down a valley, they scrape off the underlying rock and release minerals and metals in the process, including toxic mercury. This flows in the meltwater into the sea. And if the glaciers speed up their retreat, the delivery of that mercury into the food chain accelerates too, as Charlotte Birkmanis heard about this work, published in Nature Geoscience, from Florida State University’s Jon Hawkings...

Jon - There's certainly very high concentrations of mercury as well, which is concerning. Something doesn't really add up here. The concentrations on the surface of the ice, where all the melt-water is coming from are very low, but the concentrations in the rivers that are coming out of the ice or from beneath the ice that we were sampling were very high. So there's a missing mass in there somewhere.

Charlotte - Could you tell us exactly how you did this study? How many sites did you go and take these water quality samples from?

Jon - So we sampled three places in Southwest Greenland and two fjords that those glacial melt-waters run into. Taking water quality samples and taking them back to the lab and analysing them in that lab.

Charlotte - And you found a bit more than you bargained for, I think?

Jon - What we actually found was that some of these meltwaters had very high concentrations of mercury, and we think these concentrations of mercury are quite concerning for the export of this toxic element from ice sheets to the ocean.

Charlotte - So how do you think the mercury got there? Did it come from the glaciers and the melt-water, or did it come from somewhere else?

Jon - We think it's very likely that this mercury is coming from the bedrock beneath the sheets. Glaciers are these natural bulldozers. They move very slowly, but as they move over the bedrock, they crush it and grind it up. And they're really efficient agents of erosion. So if you put a glacier over a landscape, you can increase the amount of physical erosion in that landscape considerably. And there's also a lot of water at the base of glacier's ice/rock interface. And it's delivered there by the surface, by pipes through the ice, and crevasses through the ice from the surface to the bed of the glacier. And it also just sits there as kind of like a storage aquifer. It can sit there for quite a long time, some of the water, without freezing. And so there's interaction between the liquid water coming in from the surface of the ice and the liquid water that's stored beneath the ice, plus all this physical erosion. We think that those two, kind of, releases this mercury into the water, which is then flushed from underneath the glacier into these big glacial melt-water rivers.

Charlotte - And with this flushing, do you think it could go off shore a long way? Could it actually impact the food chain?

Jon - We really don't know if this mercury makes it into the food chain. All we do know at the moment is that there are very high concentrations of mercury in the melt-water and that these high concentrations are maintained to a degree in the coastal waters. We sampled some of the surface waters from fjords nearby, and these fjords are mixing zones between the fresh water coming from the ice sheet and the salt water coming from the ocean. And we found high concentrations in those systems that there are environmentally high concentrations in some of these fjords that are fed by these meltwaters. But as I said, we really don't know if this mercury is getting into the food chain or not. And I think that should be a focus of future research.

Charlotte - You mentioned there are high concentrations. I saw that it was comparable to rivers in industrial China. Can you give us an idea of the levels that we're looking at

Jon - Mercury is usually present in very, very low concentrations in any natural waters. So a typical river has about from 1 to 10 nanograms per litre of mercury in dissolved form. And that's like putting a grain of salt into an Olympic swimming pool sized swimming pool. So very small amounts of mercury, and the mercury we're seeing in Greenland is more like 150 to 300 nanograms per litre. So we're talking one to two orders of magnitude higher in these glacial meltwater rivers than in an average river. That's what you would expect to see in heavily contaminated rivers. So these are very high concentrations. I should also say they are still quite low. They are at, or just above, the recommended drinking limits. But the big concern with mercury is that even though it's very low in water, it can bioaccumulate in food webs. And what we mean by that is, as it goes up the trophic levels in a food web, the mercury actually accumulates in the organism and through that process, it can accumulate up to a million times. That's the main concern really

Now moving on to another sticky subject: glue, which, we’re told by the makers, only works on clean dry surfaces. That’s because getting the chemistry right for glues to work in the presence of water is very difficult. But one solution to finding good glues that will work in the wet is to look at how animals that make glues and live in water have solved the problem. The result, for a team of US scientists, is not just any glue, this stuff’s incredibly strong and even sets underwater. Sally Le Page reports...

Sally - Imagine this. You're on a warm sunny beach looking out to sea with the call of herring gulls piercing through the sound of kids clamouring over the barnacle encrusted rock pools. The waves crash, and you struggle to pull free a handful of silvery-blue mussels that are stuck firmly to the wet rock faces to cook for dinner. And perhaps you think to yourself, I should go back to the lab and invented a glue half as good as this that also works underwater. Or perhaps not, but Tufts university engineer, Fiorenzo Omenetto did begin to wonder.

Fiorenzo - If we think about adhesion, we look at some of the problems that exist in the real world, like barnacles that stick on the side of boats and are really, really hard to get off. Or muscles that are on rocks and that are very, very tightly bound to the rocks that they stick on in spite of waves and in spite of the people that go and want to get them to eat.

Sally - Indeed, barnacles and mussels manage to stick themselves tightly to submerged rocks and jetties, and even withstand being battered by waves. Mussels do it by secreting molecules that cross-link strongly with surfaces, anchoring themselves in place. Barnacles, on the other hand, produce a waterproof protein cement that provides a large surface area for maximum stickiness. Human-made synthetic glues also rely on similar forms of chemistry to do the same heavy lifting. They create molecular bonds between surfaces that make them hard to pull apart. But in many cases, water molecules can interfere with those bonds, making it much harder for glues to work underwater.

Fiorenzo - The water gets in the way and changes the way that the bonds occur. So it changes the way ultimately that the materials stick.

Sally - So how did the Tufts team solve the problem? One of Fiorenzo's research interests is silk that comes from silkworms. And when he looked closely at the barnacle cement, he spotted something surprisingly familiar.

Fiorenzo - These proteins assemble in a geometry that is very particular. And this particular geometry is very similar to the way that silk assembles.

Sally - But barnacle proteins are hard to extract, whereas we already know how to mass produce silk. So could you, he wondered, substitute silk proteins for barnacle proteins to produce a glue that still works underwater?

Fiorenzo - So mussels and barnacles have evolved strategies to create these bonds in wet environments. And so the thought was very simple. If we could get the chemical part that is used by the mussels, and we have silk that maybe provides the function that barnacles do, well let's mix the two and see what happens and see if we can get the advantages of both.

Sally - By combining silk proteins and the sticky molecules from mussels, they've created a new hybrid glue that is the strongest non-toxic underwater adhesive ever made. Underwater glues are incredibly useful, from the obvious cases, such as sticking pipes together to the less obvious, like sealing up wounds during surgeries without having to use stitches. And this mussel-silk hybrid doesn't have to use any strong solvents that, apart from sometimes being poisonous, also tend to smell terrible. So where can we get some? Well, don't hold your breath, except maybe if you're underwater, because if you are hoping to see a tube of this stuff in the shops, anytime soon, the bad news is that according to Fiorenzo, it's going to be a while.

Fiorenzo - It's not going to be within the next six months. It might be within the next six years. And anything in between is fair.

The importance of the Sun didn’t disappear when we stopped using sundials. It’s extremely important to our health, both physical and mental. Chris Smith spoke to science journalist Linda Geddes, author of the book Chasing the Sun about the impact the Sun has on our health...

Linda - Well, sunlight affects us in various ways. There's Vitamin D as you mentioned, but there's also its effects on our circadian rhythms. So in every cell of our bodies, we have these (close to, but not exactly) 24 hour rhythms - in everything from when we release hormones, to the chemistry of our brains, to the activity of our immune cells. And the way those rhythms are kept synchronised with the time of day outside is through the action of light hitting this subset of cells at the back of the eye. But also the timing of those clocks is influenced by when we see the light. Most people will identify as either 'owls' or 'larks': people who like to stay up late, or people who like to get up with the sunrise. Now if you see lots of bright light early in the morning, your circadian rhythms are going to be shifted earlier, so you're going to become more lark-like; but if you're seeing light late at night in the evening and overnight, it's going to push you more towards being an owl. Genetics is also involved, so it's not just about light; but light does have this influence.

Chris - There must be an influence, then, of the invention of the light bulb! Because we haven't had artificial light until relatively recently in human existence, in the last hundred years or so. So has there been a big shift then?

Linda - Well, if you send groups of people camping, you notice that their circadian rhythms shift a little bit earlier, so they become more lark-like. But if you go and... when I was researching, chasing the sun, I went and visited an Amish family in America, and they have a much more traditional relationship with light because they're not connected to the electric grid, and they too are much more lark-like. And if you ask... there are some Amish people who will identify as night owls, but if you ask them, "what time would you ideally get up, and what time would you ideally go to bed?" I spoke to one of these people, she said, "ideally, I'd like to stay up until maybe about 10:00 PM? I know it's really, really late, but that would be my choosing." And she'd like to sleep in until 7:00 AM!

Chris - But why is it a problem, then, fighting your clock, becoming more lark-like, or becoming more owl-like? Why is that a problem?

Linda - It's not a problem if you can choose when you get up and go to work. So if you're not feeling sleepy until midnight, 1:00 AM, and you've still got to get up for work or school at 7:00 AM, you're cutting short your sleep. And sleep is important for all sorts of... for your health, for both your physical and mental health.

Chris - So it's the sleep that's paying the price, and the health cost comes because of sleep paying the price, is what you're saying - both in terms of the physiological cost, because we know that people who are sleep deprived have all kinds of physiological problems, high blood pressure, other risks of other things like weight gain and so on - but also mental health, because if you're not sleeping restoratively, you're more likely to suffer in that respect?

Linda - Yes. But there's a second thing, which is that if you're constantly shifting your sleep timing and you're not having that strong light signal in the daytime, and that weak light signal at night, your internal clocks can become desynchronised. So your clock in your heart isn't quite on time and in keeping with the clock in your stomach or the clock in your brain, and you're getting this kind of spreading desynchrony around the body. And that has been shown to have an influence on health independently of sleep as well.

Chris - When you were writing the book, did you also look not just at day-to-day time, but year-to-year time? Because there's also this phenomenon of Seasonal Affective Disorder. I suspect as the Northern Hemisphere goes into summer and we're actually seeing some sunshine, a lot of people will suddenly start to say they feel enormously better for no reason, but it's down to the longer days and sunnier days. Have you looked at Seasonal Affective Disorder as well?

Linda - Yes, I have. And there's an interesting thing about the increasing days though, which is that you assume that the most depressing time of the year is the winter, but when it comes to suicides and especially violent suicide, you get a peak in late spring. And the leading theory for why that is, is that you're getting this increase in serotonin, which is a brain signalling chemical which is produced in response to light as well. That's interesting. But yes, certainly Seasonal Affective Disorder is a real thing. And one of the best cures for it is light therapy, which involves being exposed to bright light, first thing in the morning, and what that is doing is resynchronising your clock to the 24-hour clock outdoors on Earth.

Chris - Have we seen consequences of people being cooped up during lockdown then? And is that part of the reason why people have found it tough - because they've been divorced from that normal, strong solar stimulus to feel good?

Linda - Well, I'm sure it's not the only factor, but one symptom of this kind of this desynchrony and this flattening of the circadian rhythm is that you feel sleepier in the daytime and more awake at night. Independent of the circadian clock actually, those light sensitive cells at the back of the eye also feed into brain areas that control alertness and mood as well. So light is a brain stimulant, but there've been studies that have looked at the effect of exposing people to an hour of relatively low intensity blue light, and being exposed to an hour of that is equivalent to drinking several cups of coffee in terms of the 'alertness boost' it gives you. What I always do is I try and get outdoors first thing in the morning and get some of that bright light first thing, but also try to get outside regularly during the day, just for a kind of light snack.

Sitting on Earth, going through the seasons every year, it can be easy to think the Sun is totally stable and unchanging; but it isn’t: periodically there are storms on the Sun, and if those storms fling material our way, it can cause us serious problems. Chris Smith spoke to Stephanie Yardley, from University College London, who studies these phenomena...

Stephanie - So basically they're huge bubbles of magnetic field and gas that the sun ejects, and they can travel at several million miles an hour through space, and sometimes they hit Earth. And when they reach Earth, in about one to three days on average, then they can interact with the Earth's magnetic field and also the atmosphere.

Chris - Isn't the sun slinging stuff at us all the time? That's called the solar wind, isn't it?

Stephanie - Yes. There's also the solar wind. There's also energetic particles as well. So we're constantly buffeted by the sun's wind.

Chris - But in terms of the intensity, you're saying one of these cosmic burps is far more powerful than just the normal wind that wafts our way off of the sun?

Stephanie - It depends on the conditions and that's why it makes it so difficult to predict, but generally the eruptions cause the spectacular displays of the Aurora. But that doesn't mean that we can't get effects from the solar wind as well or energetic particles.

Chris - Do we know why they happen and why the sun does this?

Stephanie - Yeah. So it's all to do with the magnetic field. So the sun has strong magnetic fields and if you imagine almost like an elastic band that twists and stretches, if you do that, then the elastic band will eventually break. And the same happens with the magnetic field. So it's essentially the sun storing energy in these magnetic fields and then it being released when they snap.

Chris - Do we therefore have a way of spotting when that elastic band is getting over tightened?

Stephanie - Yes. So we look at these regions on the sun of strong magnetic fields and essentially the way we predict what we call "space weather" - so just weather in space - is by looking at these regions and seeing when an eruption occurs. So we sit and stare at the sun and generally we look in wavelengths such as what we spoke about already, so ultraviolet radiation, and also visible light.

Chris - When this material arrives at Earth, what might it be able to do? We've talked about the health of our bodies being hit by sunlight and material from the sun such as UV radiation. But what about when these storms fling this debris our way, what impact does it have?

Stephanie - So as I've already mentioned, we have the spectacular displays of the Aurora, but you can also really affect our technology. Obviously we're very reliant on our technology nowadays and it can affect things like the power grids that we've already spoken about. So we can have power outages and the transformers can be severely damaged. They can affect things like the railway networks. Space flights - so astronauts on space walks, they can receive radiation, or even if you're on a passenger plane, if you're a passenger or crew on an airline aircraft, and also it can affect the actual electronics itself. So it can affect the aircraft itself or satellites and therefore affect communications and things like GPS.

Chris - How does it do that because this is just material coming from the sun, so how can it cause trains to go off kilter and electricity grids to melt down?

Stephanie - Well, it's all to do with the communication. So you can get things like signalling errors, for example, if the timings don't add up and that's all to do with communications going down. The power grids -  you get currents induced in the ground from the changing of the magnetic field, of the Earth's magnetic field, so this can affect the power grids. And you can have power outages for hours but sometimes, if it's strong enough, then you can damage the transformers and they can take even several years to fix them.

Chris - So this has actually happened, it has a documented history of happening, and this is not just speculation -  we've got this down, we know this happens?

Stephanie - Yeah. So one of the more recent events was in 1989, actually, where 6 million people went without power for nine hours in Quebec. And so this cost probably millions or billions of pounds. The biggest event we know of is called the Carrington event, quite a few people have heard of this, which was back in 1859. And we weren't so reliant on technology then so it only really affected the telegraphs and the telegraph operators were receiving shocks. But we had a near miss in 2012 -  we call this the Near Miss Event, and it was during the Olympics. And so this eruption was actually not Earth directed, but if it was, maybe we might've lost the coverage of the Olympics. So who knows we're, you know, sitting and waiting for the next event to occur.

Chris - Perish the thought! So are we watching closely though? Do we have a way to do as good a forecasting for what the sun is doing as we can really forecast for weather on some parts of the surface now? Is there actually a physical program in place to do that?

Stephanie - Yeah. So we're sitting and staring at the sun and we're predicting all the time. Essentially what happens is an eruption will occur at the sun and we will then put this into models and model when it will arrive at Earth, but it's a bit harder than weather prediction so it's still quite difficult to do. And also, for example, the power grid or the national grid, they'll want five days of warning and we can't necessarily give them that lead time. So ideally scientists such as myself look at the regions that these eruptions come from to try and predict them before they happen, rather than once they've occurred. And even then things can go awry. And the eruption doesn't cause as much disruption as we thought, or it doesn't hit us head on, so obviously things evolve as they travel through space.

Chris - Is there anything we can do about this if you do detect an Earth bound storm coming our way?

Stephanie - So the main things, for example, for the power grids you can spread out the power, so you're less likely to get damaged. Or for example, if you're in an aircraft, you can fly at lower altitudes or I guess in a really extreme case you can ground the flights, but obviously doing stuff like this costs money. So we have to be sure that these events are going to happen and are going to affect us.