"The earth's regular pulse... may be starting to falter"

Natalie Robinson

Q&A with NIWA's sea ice researcher Natalie Robinson

Q: Last winter saw the first decrease in sea ice extent in nearly 40 years (since satellite measurements began). When the epic 5,800 km2 iceberg broke off the Larsen C iceshelf, it was one of the most dramatic events of our Southern winter. Antarctica itself is “beginning to turn green” – with moss banks proliferating across the north of the continent. How do you, as an Antarctic sea ice researcher, integrate all this information and still keep your cool?

A: Just a clarification – last year wasn’t the first time that Antarctic sea ice extent decreased in a year-on-year sense. But it appears to have been a dramatic switch away from the slight increasing trend that the satellites have recorded for almost 40 years. (Note, I’m continuing to watch the validity of this claim as the new monthly data on sea ice extent come in) But… to answer the question! I don’t see it as my job to save the planet. So, while I see incredible changes happening at an unprecedented pace, I see my responsibility as a scientist as:

  1. Taking notice, finding out, identifying and sharing information about the changes that we as a community see happening;
  2. Collecting data, integrating and collaborating with colleagues, and doing a lot of deep and informed thinking to try to understand what the dominant processes are; how those processes interact and feedback into each other; what the driving forces behind those processes are; how they are likely to change when background, inter-annual and/or climate conditions change; and what downstream effect that might have.
  3. Communicating my thoughts and findings to appropriate audiences – effectively giving them the knowledge they need to make informed decisions. This means different things to different audiences, so it’s always a challenge.

So, yes, while I literally lie awake at night fretting about the state of the planet, and the heritage we are leaving for the next generation, keeping my corner clean and getting on with doing my job with excellence is enough to satisfy me (for now!)

Q: How does understanding sea ice contribute to our knowledge about what’s happening more broadly in Antarctica? How closely is your team (partly funded by the Deep South Challenge) collaborating with other sea ice researchers (either from NZ or internationally)?

A: Sea ice is a complicated beast… The satellites observe sea ice from space as ‘white stuff’ in a sea of black. What I mean is that if you’re far enough away, the distinctive characters of different types or styles of sea ice formation get lost, and it comes down to a measure of how much of the surface is black, how much is white, and a consequential spatial concentration from which area and extent are calculated.

However, working right at the ice surface, we know that this thing called ‘sea ice’ that the satellites see as an amorphous white blanket, is the result of a whole mix of different formation processes. This means there are potentially big variations in thickness, floe size, topography, profile, rigidity/flexibility, strength. internal structure etc. – even within a relatively small region (e.g. Terra Nova Bay). And every time you change even one of those aspects, there’s an impact on how the ice physically interacts with the ocean; what sort of habitat the ice provides for the local ecosystem; how heat, salt, momentum and nutrients are exchanged with the ocean; how long the ice might take to melt away (thus exposing dark, liquid ocean in place of bright ice and snow); and the reflection of heat and light back into the atmosphere. Hence, we really need to develop a flexible idea of what sea ice is in terms of predicting how it (and the environment it exists in) might evolve, develop or change over timescales from hours and days to seasons, years and decades.

The type of sea ice we observe can provide us with clues about the water it has formed from, and the journey that water has been on. Sea ice is a highly dynamic and responsive entity, effectively integrating the history of what it has been exposed to over the previous winter (or longer in some cases). This means that by paying enough attention to its composition, and how that changes year to year, it is possible to contribute to a picture of all aspects of the local/regional environment, beyond the ice itself.

Field work in and around Antarctica is difficult, expensive, and often limited by tight seasonal timelines. Therefore, aligning people and projects that occupy the same physical or academic space but which have distinct scientific objectives represents a significant opportunity for efficiency gains. For example, this coming season, my team and I will share our time between our Deep South Challenge project and a Marsden-funded project. The two projects will benefit from use of the same infrastructure and scientific instruments provided by NIWA, logistical support from Antarctica New Zealand, and collaborations with international colleagues. The same model is applied to Antarctic science more generally with a much freer sharing of ideas, data and time than can exist in other sectors.

Q: The Deep South Challenge is trying to “close the loop” – we’re trying to make sure decision makers on dry land in Aotearoa can use our science to begin adapting to our changing climate. Do you feel like you’re part of that loop? If there was one thing you’d like a decision maker to understand about Antarctic sea ice, what would it be? If there’s one thing you’d want to understand about climate policy creation or decision making, what would it be?

A: Sea ice is the biggest annual change on the surface of the planet. It plays huge roles in:

  1. Diving ocean flow, including ventilating the deep ocean and delivering heat around the globe
  2. Influencing atmospheric circulation, including the position and intensity of the storm tracks
  3. Protecting and supporting the vast and prolific southern ocean ecosystem.

It is the engine of the climate system – the Earth’s regular pulse that both responds to, and drives, large-scale climate variation. Its influence stretches into the daily lives of every citizen on the planet – even though many will never think about it and the vast majority will never experience it first-hand. And this steady beat may be starting to falter. It has certainly been trending in a direction that our state-of-the-art climate simulators have failed to capture or explain, and its recent year-on-year behaviour has become more erratic.

For these reasons, as someone who is immersed in the physical science of sea ice, I feel I ought to be part of the conversation. But with so many stakeholders at one end, and so few observational scientists at the other, a lot depends on the link the Earth System Model is intended to provide. It remains to be seen whether the ESM can facilitate the dialogue between the lives of New Zealanders and the complex, frozen system at the bottom of the world, which, for the most part, goes unseen and unnoticed.

Date posted: 03/10/2017

News type: Blog

Programme type: Earth Systems Modelling and Prediction Processes and Observations

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