On thin ice: Science at the end of the world

Otago Daily Times

3 days ago

A new documentary following climate scientists to Antarctica, explains the physics of our predicament, Tom McKinlay writes.
It's cold in Middlemarch, Pat Langhorn reports when she picks up the phone.
"There's still ice on the puddles."
It's a commonplace enough observation from the Strath Taieri in winter, but the point the professor is making is that the ice has survived late into the day, despite all attentions from the season's admittedly weak sun. Too little energy in it, given the Earth's lean, for it to return the puddle water to liquid.
Emeritus Prof Langhorn knows why.
"We were walking today, as I said, and there was ice on the puddles, and people were poking it and saying, 'oh look, there's still ice'. And I said, 'well, you know, it takes an awful lot of energy to melt ice, and a lot of energy to freeze it as well'."
Physics is the professor's area of expertise. Ice too. Melting a kilogram of ice takes as much energy as it would to raise that same volume of water to 80°C, she explains.
A revealing little truth, neatly explaining Middlemarch's slippery winter reality.
But in Prof Langhorn's world it also has other more existential implications.
For decades now, Prof Langhorn has been studying sea ice. Initially her field work was in the Arctic but, by the second half of the the 1980s, the focus had switched to Antarctica - she's been based at the University of Otago since 1988. At both poles sea ice has been in decline, failing to form or melting more.
That's a worry. Because the sun will continue to send its heat and light, that won't change. But if the sea ice isn't there to meet it, all that energy once consumed by the business of melting is going to do other work instead.
"The thought that suddenly there isn't that ice there taking up all this energy and instead it goes into heating the ocean is a bit frightening, I think," Prof Langhorn says.
The physics lesson about the kilogram of ice, delivered again by Prof Langhorn, appears in a new documentary, Mighty Indeed , which will screen at this year's Doc Edge documentary film festival.
It follows a couple of scientists down to the Antarctic, oceanographer Dr Natalie Robinson and microbiology PhD candidate Jacqui Stewart, representatives of a new generation walking in Prof Langhorne's snowy footsteps.
There's plenty of frightening in Mighty Indeed and frightened people - the scientists - but it also manages to celebrate both women in science and the extraordinary unimagined benefits of blue-skies research, the science for science's sake that ends up making an outsized contribution to the human project.
Prof Langhorne has experienced the highs and lows of both the former and the latter at first hand.
The Scotswoman trained in the UK - Aberdeen then Cambridge's Scott Polar Research Institute - and applied to join the British Antarctic Survey back in the '70s. She made it through the first round, but then the penny dropped that "Pat" was not "Patrick" and her application went no further.
"I mean, things have changed quite dramatically in the area in which I've been involved, in which I've had my career, not just in terms of the science, and, of course, the sea ice has changed dramatically, and that's a very depressing story, but a more uplifting story is that it's now much easier for any gender to be involved in science. Gender is not the issue that it once was in that line of work," she says.
"So now, you know, if you go to a sea ice conference, there will be at least as many women there as men, which is quite a change."
Prof Langhorne is also an advocate for the latter - curiosity and blue-skies science.
"Yes, definitely. And, I mean, again, from my own personal perspective, younger people, as I got towards the end of my career, thought that I had somehow magically seen there was going to be a problem and gone searching to understand this problem, which, of course, was not the truth at all. You know, I was interested in sea ice, and at the time that I started to look at sea ice, it was really considered very sort of flippant and why would you bother?"
It's a demonstration, she says, of the importance of people deciding what they're interested in and doing their very best to follow that line of inquiry.
However, it's no longer a very fashionable idea, she says with regret. That's an obstacle for her young colleagues.
"Blue-skies research is really important, because often it's by exploring things that we don't know that we find out things that we didn't know we were going to find out. We didn't know we didn't know them."
She has observed the building expectation that science should always be at the service of some calculable, bankable output - should be innovating towards a particular application.
"That's just not going to get you the best science," she says.
"You can't innovate by thinking, 'well, this morning I'm going to get up and be innovative'. It's not usually the way it goes. So, yeah, I think exploration is really important."
Prof Langhorne can't remember the moment when her physicist's "flippant" interest in sea ice became climate science and vitally important to the future of civilisation as we know it.
Indeed, back when she started, if anyone outside the academy was giving sea ice any thought at all, it was likely to be as an impediment to drilling for oil. Not that fossil fuel was ever part of her interest. And even Prof Langhorne's first trip to the southern continent had a focus on relatively quotidian matters - on ice as a platform for vehicles and for aircraft to land on.
"So there was a fairly gradual transition, I would say, from thinking about it in terms of 'here is something that's an impediment that we need to move in order to get at the oil that's inconveniently underneath the sea ice', to, goodness me, 'this sea ice is really, really important to climate, and we need to understand why it's disappearing'."
By the mid-1990s the interest was squarely on the interaction between ice and ocean and what a warming ocean would mean for the sea ice.
There are lots of reasons to care about sea ice. It reflects sunlight back into space, preventing it heating the dark ocean below. It protects the Antarctic's ice sheets and shelves from the action of the ocean - holding back sea level rise - and it plays a vital role in overturning circulation, the ocean currents that have such an important role in regulating the planet's climate, distributing heat from the poles to the equator.
In another enlightening lesson in physics, delivered again by Prof Langhorne in Mighty Indeed , we learn the freezing of the sea ice leaves the water below saltier, briny, that salty water sinks and helps drive those planet-spanning currents.
"So there's a balancing on the Earth."
In recent years, Prof Langhorne's interest has been at the interface between the ocean and the sea ice and the problem of measuring sea ice thickness remotely - as drilling holes through the ice in Antarctica's testing conditions is no easy task.
"Without knowing how thick it is, you actually don't know how much you have, because, is it a thick slab of butter on your toast, or is it all spread out very thinly? And if you're only looking from above and seeing what the total area is, what the coverage is, then you're not including some of the energy that's tied up with the presence or absence of sea ice, and it's that energy that we really need to care about."
It is the extra heat energy stored in the ocean as a result of greenhouse gas-driven planetary heating that is thought to be behind the decline in Antarctic sea ice - both in terms of the temperatures in the ocean and atmospheric influences.
Concern has ramped up since 2016, when significant decreases began to be recorded. The consistent trend since has been for less sea ice.
The five lowest extents recorded have all been since 2017 and 2025 is thought to be the second consecutive year with a sea ice minimum extent below 2 million km2.
It's change on an epic scale: the sea ice ring around the frozen continent covers an area twice the size of Australia. So going back to Prof Langhorne's kilogram of ice example, it's possible - or possibly impossible - to understand just how much energy is bound up in these processes.
Sobering, the professor says. As long as it's tied up in the sea ice, keeping the sea surface close to 0°C, it's not allowing our temperatures to go bananas, she says.
We've already seen a little of what it could mean.
"There are bigger storms than there used to be and that, unfortunately, that's going to be the main change for us, I think, apart from some sea level rise. The main change is just going to be storm events that get bigger and bigger and bigger and wilder and wilder because all that energy has been sucked out of the ocean and comes to us in storms and flooding events and droughts."
The physicist strikes a note of optimism in the documentary, asserting that in her discipline problems are tractable. Solutions can be found.
However, she concedes that to a very significant extent science has now done its work as far as climate change is concerned. The problem is now clear and we know what the solutions are.
What's left is us.
"I think if we're talking about the problem, in inverted commas, of climate change, and how to mitigate some of the less wanted effects of climate change, then I think the problem is that human beings are in the system too," she says.
"The problem is that it's not a problem in physics; it's a problem in human behaviour, which is much more unpredictable, and much less satisfactory in my view."
But she leans into the belief that human beings are wired for hope and optimism, equipped with an almost indefatigable ability to get up every morning confident that today can be better than yesterday.
"I think that it takes quite a lot to completely dampen people's enthusiasm for life, actually."
That's not to say Prof Langhorne hasn't had her moments.
"When I retired, I thought about what I could do that would be best for the world and the conclusion I quickly came to was that the best thing I could do was die. It would be honestly the best thing I could do," she says. "But I just didn't really want to do that."
Among the challenges we face, she says, is to identify the changes we regard as acceptable, that preserve the life we want to have, while at the same time making the planet a better place.
"But, I mean, that's all sounding very highfalutin. I think that's what most people do, most days, is make judgements like that."
Again, Prof Langhorne sees our present as a more difficult environment than she had to navigate. Young people have more decisions to make than she did, she says. A more difficult future to confront.
"Climate change is physics. And if it is not going to be all right, it is not going to be all right."
Dr Robinson, the oceanographer and next generation sea ice researcher, speaks to that in the documentary, saying she feels like she knows too much and shares her concern for how she talks about climate change around her young children. She is losing sleep over it.
Her children will need different skills for the future they are inheriting, the climate legacy they will inherit, she says. Resilience and an ability to meet challenges among them.
She tries not to think about it too much.
PhD candidate Jacqui Stewart calls working in the field a mental health battle. "Because ... you know." Sometime it gets too much, she says.
She has decided not to have children. For her the ice is already too thin. The film
• Mighty Indeed screens as part of the Doc Edge film festival online from July 28 to August 24.
• docedge.nz/events/mighty-indeed/