From his office at NIWA headquarters in Wellington, scientist Craig Stewart gets updates from the Southern Ocean, where climate change is starting to melt the ice shelves.

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I’m a polar oceanographer who has been working in Antarctic science for two decades. My first trip to Antarctica was with the British Antarctic Survey in 2001; since then, I’ve done perhaps a dozen polar trips, with different objectives. But the themes for me have been using radar to measure the thickness of the ice shelf and using moorings to measure the ocean underneath. 

The last time I went down was in the 2021-2022 summer season. We were camping at the far side of the Ross Ice Shelf, 900 km in a straight line from Scott Base. That’s about a four hour flight on a small plane with a landing in the middle to refuel. You don’t get much further from home for that, or from spare parts for that matter. We were establishing a mooring site, drilling through the ice shelf to put instruments in the ocean underneath. Communications have improved since I first went south – we were able to send and receive emails this time, although not attachments.

It’s a huge contrast from my life of commuting into work in Wellington. It’s all the obvious things – you’re totally isolated, you have to be really well prepared. What I do on a weekly basis, going into the office to look at my computer all day, is not that different from a lot of other people. But when I sit in my office I’m thinking about that next season, how we can have everything we need, how we can best do it. How far can we travel in a day on the Ski-Doo? What is all the software and hardware we’ll need? Will the batteries for the instruments last in cold temperatures? It’s easy to underestimate how much preparation is required, but it’s a significant part of the job.

Because it’s so far away and inaccessible, it’s really difficult to fix things when they go wrong. You have to think ahead a lot. For example, I’ve had a few specific problems with instruments not working lately, and you can’t just go and fix them. We can still get information, and Antarctica New Zealand did a great job servicing some of these, but we couldn’t get to all the sites before the helicopter returned to New Zealand for winter. The rest will have to wait for November, when we can next reach the sites. Things are even tougher when the instruments are under the ice shelf. 

One of my projects is to characterise how the basal melting of the Ross Ice Shelf, where warm water melts it from underneath, varies in different seasons. So we’ve installed 12 radar instruments that were custom built to measure the thickness of ice shelves, powered by a solar panel. They take a shot every hour, and it’s remarkable to me that the technology works, that those measurements get emailed to me while I sit at my desk in Wellington. That’s really pleasing, when the technology works well – 15 years ago, that wasn’t something we could do. 

Taking these measurements is important, because the Antarctic ice sheet is thinning. Picture a pile of snow where it’s so heavy in the middle that it slides inwards and out, pushing between mountains and eventually flowing over the sea. These floating fringes, called ice shelves, are incredibly sensitive to changes in the ocean. The areas in Antarctica where the change is most rapid is where warm water is getting in under the floating ice shelf and melting it from underneath. Measurements help us to understand the vagaries of the ocean, helping us improve future predictions of how the Antarctic ice sheet will respond to warming oceans.

I think about climate change all the time; it’s something I’ve been aware of for more than 20 years – I remember mentioning it in my interview before my first trip to Antarctica. It’s one of the things that motivates me to do the work; we know enough that we need to make major changes to our lifestyles. We should be very concerned. There are huge amounts of questions about how climate change will happen that we need to answer, too, which is why this science matters.

I also think about the carbon cost of the fieldwork itself, which can be high. You fly to Antarctica, there’s fuel use from the Ski-Doo and the helicopter. I feel that fuel use is justified in terms of the knowledge we gain through the work, but as scientists, it’s something we should think carefully about.

You do get some great stories. The first time I went to Antarctica, bad weather meant I was stuck in the Falkland Islands for three weeks. Then I spent 11 weeks with only one other person, camping on the ice shelf in a group of two. He had a bit of a reputation; on Christmas I unwrapped two angels that my lovely family had sent and he said “Crikey! I don’t believe in Christmas”. Some of the equipment is the same as what early polar explorers used; the Scott Polar Tents are heavy, but in a howling polar storm you’re pretty happy to be inside one, and with the British Antarctic Survey, we used Primus stoves and wooden Nansen sledges, which haven’t changed much either. 

I have an engineering background, and I studied oceanography for my Masters and PhD. I think what I like most about my job is the variety, that I can do science and write programmes to analyse data, and be involved in hands-on, technical stuff, like sorting out the battery and solar panels on the radar and going to Antarctica to do fieldwork physically. I’m lucky that I get to do lots of types of work – it keeps things interesting! 

– As told to Shanti Mathias