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Kaitlin Naughten is an ocean-ice modeller at the British Antarctic Survey in Cambridge.

Increasing melting of West Antarctic ice shelves may be unavoidable – new research

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Evgeny Kovalev SPB/Shutterstock

Kaitlin Naughten, British Antarctic Survey; Jan De Rydt, Northumbria University, Newcastle, and Paul Holland, British Antarctic Survey

Originally published at The Conversation based on research published in Nature Climate Change

The rate at which the warming Southern Ocean melts the West Antarctic ice sheet will speed up rapidly over the course of this century, regardless of how much emissions fall in coming decades, our new research suggests. This ocean-driven melting is expected to increase sea-level rise, with consequences for coastal communities around the world.

The Antarctic ice sheet, the world’s largest volume of land-based ice, is a system of interconnected glaciers comprised of snowfall that remains year-round. Coastal ice shelves are the floating edges of this ice sheet which stabilise the glaciers behind them. The ocean melts these ice shelves from below, and if melting increases and an ice shelf thins, the speed at which these glaciers discharge fresh water into the ocean increases too and sea levels rise.

In West Antarctica, particularly the Amundsen Sea, this process has been underway for decades. Ice shelves are thinning, glaciers are flowing faster towards the ocean and the ice sheet is shrinking. While ocean temperature measurements in this region are limited, modelling suggests it may have warmed as a result of climate change.

We chose to model the Amundsen Sea because it is the most vulnerable sector of the ice sheet. We used a regional ocean model to find out how ice-shelf melting will change here between now and 2100. How much melting can be prevented by reducing carbon emissions and slowing the rate of climate change – and how much is now unavoidable, no matter what we do?

Rapid change is locked in

We used the UK’s national supercomputer ARCHER2 to run many different simulations of the 21st century, totalling over 4,000 years of ocean warming and ice-shelf melting in the Amundsen Sea.

We considered different trajectories for fossil fuel burning, from the best-case scenario where global warming is limited to 1.5°C in line with the Paris Agreement, to the worst, in which coal, oil and gas use is uncontrolled. We also considered the influence of natural variations in the climate, such as the timing of events such as El Niño.

The results are worrying. In all simulations there is a rapid increase over the course of this century in the rate of ocean warming and ice-shelf melting. Even the best-case scenario in which warming halts at 1.5°C, something that is considered ambitious by many experts, entails a threefold increase in the historical rate of warming and melting.

Simulated ocean warming (red) and ice-shelf melting (orange) under global warming of 2°C. Naughten et al./Nature Climate Change

What’s more, there is little to no difference between the scenarios up to 2045. Ocean warming and ice-shelf melting in the 1.5°C scenario is statistically the same as in a mid-range scenario, which is closer to what existing pledges to reduce fossil fuel use over the coming decades would produce.

The worst-case scenario shows more melting than the others, but only from around mid-century onwards, and many experts think this amount of future fossil fuel burning is unrealistic anyway.

The results imply that we are now committed to rapid ocean warming in the Amundsen Sea until at least 2100, regardless of international policies on fossil fuels.

Four different scenarios of ocean warming in the Amundsen Sea, ranging from ambitious mitigation to extreme fossil fuel use. Naughten et al./Nature Climate Change

The increases in warming and melting are the result of ocean currents strengthening and driving more warm water from the deep ocean towards the shallower ice shelves along the coast. Other studies have suggested this process is behind the ice shelf thinning measured by satellites.

How much will the sea level rise?

Melting ice shelves are a major cause of sea-level rise, but not the whole story. We can’t put a number on how much sea levels will rise without also simulating the flow of Antarctic glaciers and the rate of snow accumulating on the ice sheet, which our model didn’t include.

But we have every reason to believe that increased ice-shelf melting in this region will cause the rate at which sea levels are rising to speed up.

The West Antarctic ice sheet is already contributing substantially to global sea-level rise and is losing about 80 billion tonnes of ice a year. It contains enough ice to cause up to 5 metres of sea-level rise, but we don’t know how much of it will melt, and how quickly. Our colleagues around the world are working hard to answer this question.

Courage and hope

There are some consequences of climate change that can no longer be avoided, no matter how much fossil fuel use falls. Substantial melting of West Antarctica up to 2100 may now be one of them.

How do you tell a bad news story? The conventional wisdom is that you’re supposed to give people hope: to say that there’s a disaster behind one door, but we can avoid it if only we choose a different one. What do you do when your science tells you that all doors lead to the same disaster?

Kate Marvel, an atmospheric scientist, said that when it comes to climate change, “we need courage, not hope … Courage is the resolve to do well without the assurance of a happy ending”. In this case, courage means shifting our attention to the longer term.

The future will not end in 2100, even if most people reading this will no longer be around. Our simulations of the 1.5°C scenario show ice-shelf melting starting to plateau by the end of the century, suggesting that further changes in the 22nd century and beyond may still be preventable. Reducing sea-level rise after 2100, or even slowing it down, could save many coastal cities.

Courage means accepting the need to adapt, protecting coastal communities where it’s possible to do so, and rebuilding or abandoning them where it’s not. By predicting future sea-level rise in advance, we’ll have time to plan for it – rather than wait until the ocean is on our doorstep.

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Kaitlin Naughten, Ocean-Ice Modeller, British Antarctic Survey; Jan De Rydt, Associate Professor of Polar Glaciology and Oceanography, Northumbria University, Newcastle, and Paul Holland, Ocean and Ice Scientist, British Antarctic Survey

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Let’s hear more from the women who leave academia (Part 2)

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After the publication of my previous post, I received an email from Dr Sian Grigg, who decided to leave academia following the completion of her PhD. Read on below to hear her story.

Dear Kaitlin

Thanks for thinking of us who did not continue! I have often thought about this question and still wonder, after 15 years, whether I should have tried harder to pursue a career in academia. And whether I might now try to find a way back in.

I started my PhD on 1 April 2000 and my first child was born on 6 April 2000. 2nd child April 2002. Finished PhD Nov 2005. Moved countries and bought a small hotel with my husband in 2003. At the end of 5 1/2 years of probably too much of everything I think I was just exhausted. And had to decide whether to apply for post-docs or not. The thought of submitting papers from my PhD, moving my family and proving myself in a new position made me wonder about the sanity of it all. Could I rely on my husband to do what needed to be done at home? Could the four of us survive on a post-doc salary? What would my husband do with himself? He’d gone from being a manager at IBM jetting back and forth between Japan and Australia to small hotel owner in the French Pyrenees (where he is from), and I was really uncertain about pushing him to move and whether it would all explode.

And then once you hesitate – it’s all over. I started picking up more slack in the hotel and gave him some space to follow a project of his own. Then you get involved in the day to day of all that and you spend less time working on papers and pushing forward any career opportunities. We had his family around to help with child minding. We lived (and still do) in a really lovely area. Basically the ingredients of a relatively balanced family life were in place.

Academia is such a competitive world – I often compare it to professional sport or the performing arts. It’s hard to make it and you really need to dedicate yourself to it in order to. It isn’t enough to just be good at it because supply greatly outstrips demand. So why would anyone hire you if you are not willing to work crazy hours and push other aspects of your life aside. If I was a man I would have made another decision? I suspect yes. Men are better at being sure what they are doing is THE MOST IMPORTANT THING! The only way! That they will save the world! I had trouble convincing myself that this was truly the case, and that my sacrifice of sane family life would be worth it.

My 18 yr old has just flown off to Australia to start university and my husband is in his second mandate as mayor of our town and various other political functions. I have expanded our hotel business with a tour operator (treks and other things in the Pyrenees) and have worked to continually green our operations. I now think mainly about sustainable tourism projects and how to be more effective in that space. I love running a small business for the freedom it provides. No-one to answer to but myself, generally. As much holiday as I feel like, generally. I wonder whether I would have managed the whole bureaucratic nature of being a scientist in a large institution. I never doubted my ability to do good science but am not sure I would have survived the grant applications and paperwork. I guess you just apply yourself to the task, like everything else.

Most of all I wonder how our family would have survived the constant moving from one post doc to another and how my husband would have managed being dragged around. I can see another life where I was single from age 20-30 and became a scientist. I struggle to really see how it could have worked out with husband and kids in tow. I have no doubt it is also horrid for men who are early career scientists with small children. But the fact is simply that the wives of these men often make it work, messy though it might be. Did I lack faith in my husband that he could do the same? Did I cede when I should have fought? I’m not sure at all. Both are possibilities.

Meanwhile I’ve remained endlessly interested in climate science, economics and the fight for the environment in general. I’ve had time to read widely and often find my science friends simply don’t have time for this. I’ve developed different skills. I lobby my politician husband and influence where I can!

I’m not sure where to from now – now that I am less restricted by both family and to some extent money. Doing a PhD was definitely one of the highlights of my life and has informed it hugely.

I guess, like everything, the issue ends up being diversity. So many women step out of the game – in big business I think there is a huge loss of women who often set up their own business’ or pursue other paths once they have children simply so they have more flexibility and more control over their lives. While this may be the “best” choice for these women and lead to fulfilling lives for them and their families, it may mean that the areas they left are hollowed out and lack diversity of experience and views. This has been flagged in corporate boardrooms. I am not sure whether there is a similar issue in academia.

Well done for fighting your way in the system. If you ever want a climate friendly holiday you can find us at www.hotel-luz.com or www.pyrenees-mountains.com.

Sian Grigg

Let’s hear more from the women who leave academia.

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“On International Women’s Day”, I wrote on 8 March, “why don’t we instead highlight women who left the workforce due to structural barriers? The current approach is a bit “let’s celebrate the women who navigated this broken system to distract from the fact that it’s broken”.”

So far, I have been one of the women who is “celebrated” on days like this, with social media campaigns showcasing the work of women in science. I am happy to do so, as I know first-hand how important it is to have role models who look like you when you’re trying to succeed in science. If I can convince a young researcher that science is no longer a man’s world – and I truly believe the tide is turning – I will take part in as many hashtags as it takes.

But, this does not mean there are no problems. Building a science career is incredibly competitive these days, and that competition tends to disproportionately filter out underrepresented groups. It’s becoming more and more true that the only way to have a stable job in academia is to be an absolute research superstar, with a heavy dose of luck, and a lot of time to spend writing proposals which are usually rejected. I know so many women who are just not interested in playing this game, and I sympathise with them. I am playing the game for now, but I do not have infinite patience.

In science, we usually only hear from the small number of people who rise to the top, a form of “survivorship bias”. Then we sit back and wonder why almost all of those people are men. If we truly want to understand what is causing women to leave academia, we need to ask the women who have left, not the women who remain.

Shortly after International Women’s Day, I received an email from an anonymous woman in the UK who decided to leave academia after gaining her PhD. She wanted to share her story publicly, and I wanted to help her do that. Please read on below to find out what she has to say.

I always thought that I would be an academic, because I am so passionate about my topic. However, when I started job hunting after my PhD, I realised that staying in academia was not feasible, and not what I wanted after all. I saw a tweet today that really resonated with me which says ‘I didn’t leave academia, academia is losing me’ and this is exactly how I feel. This is for two main reasons:

Lack of job opportunities. Before understanding the problems with academia, I did want to stay and I did try for one year. I applied for many post-docs (both locally and abroad), but the positions were too competitive, often going to candidates with many years of post-doc experience. I then looked into obtaining funding myself, but the fellowship opportunities that I was eligible for required a proportion of the funding to be paid by a university – I contacted many universities but none of them had the funds available. During this year, I became aware of the lack of permanent job opportunities in academia. I understood that I would have to do 10+ years of short-term positions, potentially in different regions around the world, before getting a permanent position. How did I not know this before? This lack of job opportunities may make Early Career Researchers question why they even got a PhD and did all of that hard work in the first place. It does not make them feel particularly wanted or needed in academia, and they therefore feel pushed out of the system.

Lack of security and work-life balance to have a family. In addition to the lack of job opportunities, is the lack of security and work-life balance to have a family – which especially affects women. As I am with a long-term partner and we want to start a family in the next few years (as this may not be possible after 10+ years!), I came to the conclusion that staying in academia was not for me, even if I did successfully get a short-term position. For me, the benefits of staying in academia do not outweigh the costs such as the lack of work-life balance (due to the pressures of obtaining funding and publishing), and the lack of security due to the short-term positions (including having to move locations many times and the lack of maternity support). I believe that the lack of jobs, combined with the desire to have a stable position and a work-life balance in order to have a family, is the leak in the pipeline that drives many women out of academia.

I was first heartbroken with my realisation that I could not feasibly stay in academia, because all this time I have been chasing a dream in academia that is not real. The system is broken and so I don’t want to stay. My new job provides me with everything I need to be content where I am now and start a family, which unfortunately academia does not. I hope the system can somehow be fixed in future, as academia is currently losing a lot of diverse talent.

If you are a woman who has left academia and want to share your story, anonymously or otherwise, you are welcome to email me and we’ll have a chat.

Talking, typing, and the social model of disability

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I wrote this article for Redefining Stammering, an excellent blog run by Sam Simpson (a speech therapist) and Patrick Campbell (a doctor and person who stammers). If you have an interest in stammering or disability theory, I encourage you to check out their work, and particularly their recent book Stammering Pride and Prejudice.

When I was in primary school, I had a teacher who was over-enthusiastic about the virtues of touch-typing. Over the years, he slowly collected disused desktop computers, building up his collection until there was one for every student in his class. They lined the perimeter of the classroom, balanced on assorted desks and tables. He was the Computer Man in the school, and any student lucky enough to be in his class would surely enjoy unfettered access to the technology of the new millennium.

In practice, this mostly meant touch-typing. Whenever we finished our maths work, we were directed to go to a computer and work through the touch-typing programme “All the Right Type”. I was quick at maths and so I did the entire programme three times that year. I was bored out of my skull.

In retrospect, this was one of the best gifts a teacher has ever given me. I now type at around 110 words per minute, which is almost three times that of the average person, and almost double that of the average professional typist. When I am typing, there is a direct pathway from my brain to the screen. The layout of the keyboard and the movement of my fingers is completely automatic, like a concert pianist sight-reading sheet music. The mental load is almost zero. I think the words and they just appear on the screen.

I suppose this is how fluent people must feel when they speak. The complexities of movement required to produce speech – involving their lips, tongue, cheeks, teeth, jaw, and breath – are completely automatic. They don’t have to consciously remind their bodies how to say an N every time they want to say an N. They think the words and they just appear in the air. This is how I feel on the rare occasions when I am fluent: when I talk with my husband, when I talk to the cat, and once – miraculously – in a job interview when all the stars in the universe aligned for me. (If only I’d got the job!)

It took me years to come to terms with the fact that most conversations I partake in will not be like this. For me, in most conversations, the physical and mental effort of producing speech exceeds the effort of choosing what words to say. If I get upset about that fact, or get too wrapped up in chasing fluency, everything becomes much harder. The best strategy is to cultivate a gentle, patient acceptance that speaking is just bloody hard work for me. “These days I think of my stammer as a lodger in my house,” writes author David Mitchell. “Eviction won’t work – the lodger has a right to live here, and a black-belt in karate. But if I treat the lodger with respect – and better yet, with humour and affection – then the lodger respects me back.”

The problem is, I love communication. I am a stammering extrovert, which is a level of irony that must approach oxymoron. If you catch me on a fluent day, you will not be able to shut me up. I love crafting words, and choosing just the right words to express an idea. This is stifled when I am forced to devote a large fraction of my brain to remembering how to say an N.

It’s probably not surprising, then, that writing is my preferred form of communication. I particularly enjoy instant messaging, as my lightning-fast typing allows me to communicate with true fluency. It’s here that I can finally say exactly what I want to say, effortlessly, in real time. Some of the most open and authentic conversations I’ve ever had have been over instant messenger. Several of my closest friends are similarly receptive to this medium, even though they are fluent speakers, and much slower typists. There is widespread condescension towards “millennials who despise phone calls”, but for people like me, this change in young people’s attitudes does wonders for accessibility. In a Finkelstein Village where everybody stammered, all the children would learn to type at 110 words per minute.

And yet, I have been conditioned to feel ashamed that I prefer writing to speaking. Society has decided that the spoken word is the best and most authentic form of communication. Instant messaging is tantamount to “hiding behind your texts”, and the way you speak is far more important than the words you say. Even in this dystopian year of social distancing, phone calls are widely accepted to be preferable to texting. “You can be as clear as possible over the phone,” say relationship experts. “You build a more positive emotional bond on the phone. To truly get to know someone, you need to speak to them.” These are the sorts of conclusions that only fluent people would come up with. They are fraught with fluent privilege.

I love seeing people, and I love talking to people. I’m a stammering extrovert, after all. But it is so exhausting. I deal with the exhaustion. I continue to make phone calls, and to hold meetings over Zoom. I do these things even though I would likely communicate more effectively in writing. I do these things mostly for the benefit of fluent people, who speak more quickly and easily than they type.

If we held meetings over instant messenger, fluent people would feel less comfortable. I would have to wait patiently for them to type out everything they wanted to say. I would be tempted to interrupt them with my lightning-fast typing. The roles would be completely reversed, with the person who stammers enjoying the greater ease of communication. This would feel unfair to me. I am part of a group that makes up 1% of the population, and so I do not question being inconvenienced 100% of the time. What does this signify?

We need your help! Share your views on climate change with us.

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This blog is collaborating with researchers at Wageningen University in the Netherlands, who are conducting a survey of readers of climate blogs. They are investigating audiences’ views on climate change and their blog reading behaviour. Please see below a message from the lead researcher.

Please share your views on climate change and reading blogs by filling out this survey. The data will be used for getting to know the readers of climate change blogs.

What’s in it for you?

  • You have a chance on winning a $20 gift card of Amazon;
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Participation is anonymous, and your answers will be handled confidentially. The data is only used for research purposes.

Your input is highly valued! Please fill out the survey by following this link.

Ice sheet melting: it’s not just about sea level rise

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Originally published at The Science Breaker

Climate change is causing the Greenland and Antarctic Ice Sheets to melt, which releases cold, fresh meltwater into the nearby ocean. This meltwater causes sea level rise, but a lesser-known side effect is the disruption of deep ocean currents and climate patterns worldwide. Our modelling study investigated these processes.

You’ve probably heard that climate change is melting the polar ice caps – but what does this actually mean? It refers to the Greenland and Antarctic Ice Sheets, which are large systems of interconnected glaciers, kilometres thick. They are formed by snow falling on land, which compacts into ice and slowly flows downhill towards the ocean. When the ice sheets come into contact with a warming atmosphere or ocean, they begin to melt faster than new ice can form. This releases cold, fresh meltwater into the surrounding ocean. The most well-known consequence of this process is sea-level rise, as the volume of the ocean increases. Unfortunately, there are other side effects beyond sea level rise.

The oceans around Greenland and Antarctica are unusual because they are the only regions of the world’s oceans with significant vertical mixing. Everywhere else, the ocean is stratified, forming layers of water organised by density, with the lightest water at the surface and the heaviest water at the seafloor. The layers don’t interact with each other very much. But in a few locations around the coast of Antarctica, as well as in the North Atlantic Ocean near Greenland, surface water becomes cold and salty enough to sink into the deep ocean. Then it slowly travels around the world for about a thousand years, like a deep-ocean conveyor belt, before resurfacing. This process of “deep water formation”, occurring in just a few regions, affects deep ocean currents which transport heat around the world and influence climate patterns worldwide. But what happens when ice sheet meltwater is released into these deep water formation regions? How are the ocean currents and climate patterns affected?

Our study addressed this question using two different models: an ice sheet model, which simulates the flow of the glaciers making up the Greenland and Antarctic Ice Sheets, and a climate model, which simulates the global atmosphere, ocean, sea ice, and vegetation. Both models run on supercomputers and solve huge numbers of physics equations. Our study was novel because the ice sheet model and the climate model were able to communicate with each other, exchanging information regularly throughout the simulations.

We ran a number of different simulations over the 21st century, using several different scenarios for fossil fuel emissions, which might decline in the future but might continue to grow. In some experiments, the climate model considered the effect of ice sheet meltwater in its calculations; in other experiments, it ignored the meltwater. This allowed us to isolate the impact of ice sheet meltwater on the climate system.

In our simulations, ice sheet melting slowed down the rate of nearby deep water formation. The fresh meltwater reduced the density of the surface ocean, making it more difficult for surface waters to sink. In the North Atlantic, this reduction in deep water formation altered the pathways of nearby ocean currents. The Gulf Stream, which travels up the east coast of North America, and its extension the North Atlantic Drift, which cuts across the Atlantic towards Europe, were redirected such that less heat was transported from North America to Europe. While both locations still warmed (due to climate change), eastern North America experienced a bit of extra warming, while in Europe some of the warmings were canceled out. Furthermore, temperatures became more variable in many regions, indicating a greater prevalence of extreme weather.

Around Antarctica, deep water formation connects the cold atmosphere to the warmer subsurface ocean. This allows the ocean to release heat, warming the atmosphere while cooling the deep ocean. In our simulations, a reduction in deep water formation suppressed this effect, trapping heat beneath the ocean surface. Ice sheet melting, therefore, caused the atmosphere around Antarctica to warm less than it otherwise would have, while the subsurface ocean warmed more dramatically. This result is particularly troubling because the Antarctic Ice Sheet is in contact with these regions of the ocean. It suggests a vicious cycle whereby ice sheet melting causes subsurface ocean warming, which causes more ice sheet melting, and so on.

It is now clear that the effects of ice sheet melting are not just limited to sea-level rise. We can expect ice sheet meltwater to have many more side effects, on ocean currents and weather patterns. But how much will the ice sheets actually melt? That depends on fossil fuel emissions, and how they change in the future. Our study used models, but the same experiment is currently being run in the real world, in real-time.

Original Article:
N. R. Golledge et al., Global environmental consequences of twenty-first-century ice-sheet melt. Nature 566, 65-72 (2019)

How I became a scientist

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For the first fourteen years of my life, I thought science was boring. As far as I could tell, science was a process of memorising facts: the order of the planets, the names of clouds, the parts of a cell. Sometimes science meant building contraptions out of paper and tape to allow an egg to survive a two-metre fall, and I was really terrible at that sort of thing. So instead I spent all my spare time reading and writing, and decided to be a novelist when I grew up.

This all changed in my first year of secondary school, when I met the periodic table. I don’t know what it says about me that my first spark of interest in science boiled down to “This chart is very nicely organised”. (As anyone who has seen my home library will attest, I really like organising things.) The periodic table quickly acted as a gateway drug to basic physics and chemistry. Science still meant memorising facts, but suddenly they were much more interesting facts.

In the next year of secondary school, maths also became interesting. Until then, maths had been easy to the point of tedium. Most of my time in maths had been spent triple-checking my answers. But now maths was streamed into three different courses, and I chose the most difficult one, and it was wonderful. There is nothing quite as exhilarating as being challenged for the first time.

So now I had a dilemma. I wasn’t so interested in being a novelist any more, and I really liked maths and science. But at my school, all the best maths and science students went on to be doctors. Whereas I was so squeamish about medical things that I would hide from the television whenever my older sisters watched ER. I was also something of a hypochondriac. These are not qualities which are prized by the medical profession.

It was very important for a teenager in the early 2000s to know exactly what they wanted to be when they grew up, so I worried about this a lot. For a while I tried to convince myself to be a doctor anyway. I had no interest in dentistry or pharmacy, which were the other options presented to me. I seriously considered becoming an optometrist, but the faint possibility that I might have to deal with an eyeball that had popped out of someone’s head was enough to turn me against the idea. Some of the strong maths and science students at my school had gone on to become engineers, but I thought that probably involved the same sorts of skills as building egg-protecting devices.

At the same time as this inner turmoil, something else was going on: I was becoming interested in the environment. This was mostly a result of peer pressure. There was a very cool group of students, most in the year above mine, who had started an environmental club. Once a week, I came to school extra early in the morning to hang out with them at club meetings. And we had long and fascinating discussions, ranging from the best way to save water in the school’s bathrooms to environmental policy in the Canadian government.

I started to wonder if there was a career path which connected the environment with maths and science. I went on my school’s career-matching website to find out, and filled in the questionnaire. The website recommended I become a chemist who tested water samples from industrial plants to make sure they weren’t polluting the local environment. I wasn’t particularly inspired by this idea. I remember reading over all the other careers on the website, but I don’t remember seeing anything about academia or scientific research. And, I mean, fair enough. Given the massive oversupply of PhDs in the modern world, I understand why schools wouldn’t want to funnel students in that direction.

Meanwhile, back in the environmental club, names were being drawn out of a hat. One of the local universities was holding a climate change conference for secondary school students, and my school had been allocated three places. I was one of the lucky ones, and a few weeks later I rode the bus to the city centre for the conference.

The first presentation was called “The Science of Climate Change” and it was delivered by Danny Blair, a climatologist at the university. He talked about many different things and all of them were fascinating and I scrawled tiny notes in a tiny notebook as quickly as I could. But I particularly remember him explaining how scientists can use ice cores to figure out the temperature from hundreds of thousands of years ago. In short, oxygen has different isotopes, some of which are heavier than others. When the oxygen atoms join H2O molecules, they form “heavy water” and “light water”. Heavy water needs more energy, and therefore a higher temperature, to evaporate from the ocean and eventually fall as precipitation somewhere else. So by measuring the ratio of heavy water to light water in the ice cores, you can figure out what the global temperature was when each layer of snow fell.

Sitting there with my tiny notebook, I thought this was just the most fascinating thing I’d ever heard. This was the very first time I’d seen a practical application of the periodic table which brought me joy and excitement, rather than despair that I might end up testing water samples for the rest of my life. And it slowly dawned on me that this job called “scientist” basically meant you could study whatever you found interesting, and get paid to do so. “Right then,” I thought, “I’ll be a scientist.”

It’s eleven years later and I still haven’t changed my mind. I didn’t become an ice core scientist, but I did end up studying a different part of the climate system which I found even more interesting. Academia is not perfect, but there is no other way I’d rather spend my working life. Far from memorising an endless stream of facts, it turns out that science is full of creativity and solving mysteries. My work is always changing and growing, and I never get bored.

How does the Weddell Polynya affect Antarctic ice shelves?

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The Weddell Polynya is a large hole in the sea ice of the Weddell Sea, near Antarctica. It occurs only very rarely in observations, but is extremely common in ocean models, many of which simulate a near-permanent polynya. My new paper published today in Journal of Climate finds that the Weddell Polynya increases melting beneath the nearby Filchner-Ronne Ice Shelf. This means it’s important to fix the polynya problems in ocean models, if we want to use them to study ice shelves.

The Southern Ocean surrounding Antarctica is cold at the surface – often so cold that it freezes to form sea ice – but warmer below. The deep ocean is about 1°C, which might not sound warm to you, but to Antarctic oceanographers this is positively balmy. If regions of the Southern Ocean start to convect, with strong top-to-bottom mixing, the warm deep water will come to the surface and melt the sea ice.

In observations, this doesn’t happen very often, and it only seems to happen in one region: the Weddell Sea, in the Atlantic sector of the Southern Ocean. Satellites spotted a large polynya (about the size of the UK) for three winters in a row, from 1974-1976. But then the Weddell Polynya disappeared until 2017, when a much smaller polynya (about a tenth of the size) showed up for a few months in the spring. We haven’t seen it since.

holland_polynya_1975

The Weddell Polynya in the winter of 1975. (Holland et al., 2001)

nsidc_polynya_2017

The Weddell Polynya in the spring of 2017. (NSIDC)

By contrast, models of the Southern Ocean simulate Weddell Polynyas very enthusiastically. In many ocean models, it’s a near-permanent feature of the Weddell Sea, and is often much larger than the observed polynya from the 1970s. This can happen very easily if the model’s surface waters are slightly too salty, which makes them dense enough to sink, triggering top-to-bottom convection. We also think it might have something to do with imperfect vertical mixing schemes.

It’s a rite of passage for Southern Ocean modellers that sooner or later you will work with a model that forms massive polynyas, all the time, and you can’t make them go away. I spent months and months on this during my PhD, and eventually I gave up and did “surface salinity restoring” to prevent the salty bias from forming. Basically, I killed it with freshwater. If you throw enough freshwater at this problem, the problem will go away.

So when the little Weddell Polynya of 2017 showed up, I was paying attention. And when the worldwide oceanography community jumped on the idea and started publishing lots of papers about the Weddell Polynya, I was paying attention. But soon I noticed that there was an important question nobody was trying to answer: what does the Weddell Polynya mean for Antarctic ice shelves?

Ice shelves are the floating edges of the Antarctic Ice Sheet. They’re in direct contact with the ocean, and they slow down the flow of the glaciers behind them. Ice shelves are what stand between us and massive sea level rise, so we should give them our respect. But ocean modellers have largely neglected them until now, because ice shelf cavities – the pockets of ocean between the ice shelf and the seafloor – are quite difficult to model. This is changing as supercomputers improve and high resolution becomes more affordable. More and more ocean models are adding ice shelf cavities to their simulations, and calculating melt rates at the ice-ocean interface. So if it turns out that the Weddell Polynya contaminates these ice shelf cavities, it would be even more important to fix the models’ polynya biases. It would also be interesting from an observational perspective, especially if the polynya shows up again soon.

At the time I started wondering about the Weddell Polynya and ice shelves, I was conveniently already setting up a new model of the Weddell Sea, which includes ice shelves. This model doesn’t produce Weddell Polynyas spontaneously, and for that I am eternally grateful. But I found a way to create “idealised” polynyas in the model, by choosing particular regions and forcing the model to convect there, whether or not it wanted to. This way I had control over where the polynyas occurred, how large they were, and how long they stayed open. I could run simulations with polynyas, compare them to a simulation with no polynyas, and see how the ice shelf cavities were affected.

I found that Weddell Polynyas do increase melt rates beneath nearby ice shelves. This happens because the polynyas cause density changes in the ocean, which allows more warm, salty deep water to flow onto the Antarctic continental shelf. The melt rates increase the larger the polynya gets, and the longer it stays open. This is bad news for Southern Ocean models with massive, permanent polynyas.

First I looked at the Filchner-Ronne Ice Shelf (FRIS), the second-largest ice shelf in Antarctica, and the focus of my Weddell Sea research these days. On the continental shelf in front of FRIS, the sea ice formation is so strong that the warm signal from the Weddell Polynya gets wiped out. The water ends up at the surface freezing point anyway, and the extra heat is lost to the atmosphere. But the salty signal is still there, and these salinity changes cause the ocean currents beneath FRIS to speed up. Stronger circulation means stronger ice shelf melting, in this case by up to 30% for the largest Weddell Polynyas.

For smaller ice shelves in the Eastern Weddell Sea, the nearby sea ice formation is weaker. So both the warm signal and the salty signal from the Weddell Polynya are preserved, and the ice shelf cavities are flooded with warmer, saltier water. Melting beneath these ice shelves increases by up to 80%.

The modelled changes are smaller for Weddell Polynyas which match observations, in terms of size as well as duration. So if the Weddell Polynya of the 1970s affected the FRIS cavity, it probably wasn’t by very much. And the effect of the little 2017 polynya was probably so small that we’ll never detect it.

However, these results should send a message to Southern Ocean modellers: you really need to fix your polynya problem if you want to model ice shelf cavities. I’m sorry.

Climate change and compassion fatigue

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19

I’m a climate scientist, and I don’t worry about climate change very much. I think about it every day, but I don’t let it in. To me climate change is a fascinating math problem, a symphony unfolding both slowly and quickly before our very eyes. The consequences of this math problem, for myself and my family and our future, I keep locked in a tiny box in my brain. The box rarely gets opened.

The latest IPCC special report tells the world what I and all of my colleagues have known for years: we’re seriously running out of time. In order to keep climate change in the category of “expensive inconvenience” rather than “civilisation destroyer”, we’re going to have to decarbonise the global economy in less time than many of the people reading this have been alive. But given the priorities of most of the world’s governments, it seems uncomfortably plausible that we’ll be facing the sort of post-apocalyptic wasteland I’ve only ever seen in movies. Will the rich and privileged countries be able to buy their way out of this crisis? Maybe. But maybe not.

I know all this. I’ve known it for years and it’s why I chose the career that I did. It’s the backdrop to my every working day. But I can’t seem to imagine my future intersecting with this future. I can’t picture myself or my family as part of the movie, only as part of the audience. It feels deeply intangible, like my own death.

Instead I surround myself with the comforting minutia of academic life. I worry about small things, like how I’m going to fix the latest problem with my model, and slightly larger things, like what I’m going to do when my contract runs out and whether I will ever get a permanent job. But mostly I just really enjoy studying the disaster. An ice sheet which is falling apart is far more interesting than a stable ice sheet, and I feel privileged to have access to such a good math problem. So I work until my brain feels like it might turn into liquid and slide out of my ears, then I cycle home in the mist and eat Cornish pasties on the couch with my husband while watching the BBC. In so many ways, I love this life. And I don’t worry about climate change, I don’t open that box, for months at a time.

“Compassion fatigue” is a term used to describe healthcare professionals who become desensitised to tragedy and suffering, and lose the ability to empathise with their patients. It begins as a coping strategy, because fully absorbing the emotional impact of such harrowing work would eventually make it impossible to get up in the morning. I think I have compassion fatigue with climate change. The more I study it, the less I actually think about it. The scarier it gets, the less I seem to care.

And maybe this is okay. Maybe compartmentalisation is the healthiest response for those of us close to the issue. Accept the problem, fully let it in, and decide what you’re going to do to help. Then lock up that box in your brain and get on with your piece of the fight. Find joy in this wherever you can. Open up the box once in a while, to remind yourself of your motivation. But for the most part ignore the big picture and keep yourself healthy and happy so that you can keep going. Even if this, in and of itself, is a form of denial.

The silver lining of fake news

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10

What exciting times we live in! The UK is stockpiling food and medicine as it charges willingly into a catastrophe of its own choosing. The next Australian prime minister is likely to be a man who has committed crimes against humanity. And America has descended so far into dystopia that it can’t even be summed up in one pithy sentence.

I spend a lot of time wondering how future generations will look back upon this period in history. Will there be memorial museums on Nauru and at the US-Mexican border, pledging Never Again? Will the UK’s years in the European Union be heralded as a golden age for the country? And what will the history books say about Donald Trump?

When I imagine these future historians, giving their seminars and writing their books and assigning their students essays, there is one overarching theme I’m sure they will focus on. One puzzling phenomenon is at the root of so much of the madness we face today. Our future historian might title such a seminar “Widespread public rejection of facts in the early 21st century”. Or, if you wish to be so crass, “Fake News”. A distrust of experts, and of the very idea of facts, now permeates almost every part of public life – from science to economics to medicine to politics.

Climate change used to be the sole target of this. I’ve been wrestling with fake news on climate change for more than ten years now. And I used to get so frustrated, because my friends and family would read dodgy articles in respectable newspapers written by fossil fuel executives and believe them. Or at least, consider them. Reasonable people heard debate on this issue and assumed there must be some merit to it. “Both sides of the climate change debate have good points to make,” they would reasonably say.

It’s different now. Denialism has spread into so many topics, and received so much attention, that reasonable people are now well aware of its existence. “You guys, did you know that there are people who don’t believe in facts?!” is the gist of so many dinner conversations around the world these days. And the exhausted climate scientists sit back, twirl their spaghetti around their fork, and say “Yes, yes we know. So you’ve finally caught on.”

This is the weird silver lining of fake news: reasonable people now take climate change more seriously. When they read bogus stories about global cooling and natural cycles and scientific conspiracies, they just say “Aha! These are the people who don’t believe in facts.” It’s like the dystopia of 2018 has inoculated many of us against denialism. More and more people now understand and accept the science of climate change, even while those who don’t grow louder and more desperate. Climate change deniers still exist, but it seems that their audience is shrinking.

(Of course, this doesn’t mean we’re actually doing anything about climate change.)

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PS I am now Twittering, for those of you who are so inclined.