The Changing Antarctic and Southern Ocean and Pathway to Policy

The Southern Ocean plays a major role in global climate. What happens in this fast-changing region will have huge impacts on New Zealand in the coming decades. Understanding the transformations taking place in the Southern Ocean and ensuring this knowledge is reflected in government policy are of major importance in New Zealand’s response to the climate crisis.

These concerns of course extend globally. We are a few months into the UN Decade of Ocean Science for Sustainable Development, which aims to create a common framework to strengthen science-policy connections and enhance the management of coasts and oceans for the benefit of humanity. Even with a pandemic, understanding and containing the changing ocean remains one of our species’ big challenges. Despite its importance, the Southern Ocean is relatively unstudied and there is much we still need to learn about the effects of planetary warming. What can a decade of Antarctic Ocean science bring us, and how does the Antarctic Science Platform fit in? And how can we connect to government policy?

Key Scientific Issues in Understanding the Changing Ocean

One of the overarching indicators for ocean health is Southern Ocean heat content. The oceans store 93% of the extra heat being generated from human-induced climate change. A significant proportion of this is going into the Southern Ocean. New Zealand holds jurisdiction over a large area of the Southern Ocean and so there are important policy considerations that emerge from this research.

Heat content of the oceans might seem like an abstract quantity, but it underpins life on this planet. If all the excess heat from climate change had gone into the atmosphere instead of the oceans, global temperatures would already have jumped by over 50 degrees. Ocean heat hugely affects biological productivity in the ocean which impacts everything from offshore fisheries to coastal ecosystems. It also plays a significant role in our weather and influences damaging events like tropical cyclones, drought and bushfires.

The Southern Ocean is warming at about twice the average rate of the global ocean. While still a relatively cold part of the planet, this large departure from normal temperatures has the potential to rapidly destabilise climatic patterns and increase the melting of Antarctic ice sheets.

As well as absorbing heat, the Southern Ocean is a carbon sink, absorbing carbon dioxide from the atmosphere. Changes in the rate of carbon absorption will impact how quickly the planet warms, if more carbon dioxide ends up in the atmosphere rather than the ocean. More carbon dioxide in the ocean also makes the water more acidic, which affects marine life.

Sea level rise is perhaps the best studied phenomenon by which changes in Antarctica will be transmitted globally, including to Aotearoa New Zealand, by the oceans. There is more we need to understand about ocean interactions with marginal ice around Antarctica and how changing ocean conditions impact on ice melt, in order to reduce uncertainties over sea-level rise to a level useful for policy-making.

The cycle of sea ice extent and thickness is one of the defining features of our planet: an area of floating ice roughly equal to the size of the Antarctic continent forms and melts away each year. Yet there remain major challenges in forecasting sea ice from year to year. It is difficult to model the formation of a material which involves complex physical changes and can be affected by storms thousands of kilometres away. Added to this are the uncertainties that arise from a warming ocean and changing weather patterns, and it is clear that much more data is needed. Enhanced knowledge of sea ice persistence will benefit both science and operations in Antarctica.

Data Transparency and Availability

The changes happening in the Southern Ocean are very complex and involve interactions across the entire ice-ocean-atmosphere system. Making sense of it all requires changes not only in data collection, but also in data transparency and availability. Lack of access to ocean data limits our ability to provide confident answers to stakeholder questions. Remote sampling is improving this situation, as are recent advances in Argo, an international network of floating instruments which measure ocean data. However, challenges still remain at higher latitudes.