Antarctic sea ice plays a central role in regulating global climate, ocean circulation, and polar ecosystems. For decades, it showed remarkable resilience compared to the Arctic, with large interannual fluctuations but long-term stability around a decadal mean. However, since 2016/2017 Antarctic sea ice has entered a new phase of sharp decline, most prominently in the Weddell Sea. This abrupt and unexpected change contrasts strongly with previous behavior and has raised fundamental concerns about the drivers, feedbacks, and consequences of Antarctic sea ice loss. Understanding these changes is critical, as sea ice strongly influences the Southern Ocean’s freshwater balance, heat exchange, carbon fluxes, and ecosystem productivity.
Key challenges:
- Processes and feedbacks: The dominant drivers of sea ice loss remain unclear, involving complex ocean–atmosphere interactions, the Southern Annular Mode, cyclonic activity, cloud-radiation effects, precipitation, and ocean stratification.
- Regional resilience: Compared to the Arctic, Antarctic sea ice has shown greater resilience, likely linked to divergent ice motion and unique processes such as snow-ice formation and platelet ice, which are poorly understood and modeled.
- Observational gaps: Snow, a critical link between sea ice and atmosphere, remains understudied. Large uncertainties persist in satellite products, highlighting the need for continuous, high-resolution validation datasets.
- Consequences: Rapid sea ice decline has major impacts on ocean circulation, freshwater balance, air-sea heat and gas exchange, turbulence in the marginal ice zone, and ecosystems including phytoplankton and higher trophic levels.
Overarching research questions:
- What are the key processes and feedbacks driving changes in Antarctic sea ice mass, properties, and distribution?
- How do dynamic vs. thermodynamic drivers interact, and how do Antarctic processes compare with those in the Arctic?
- What is the role of snow in sea ice dynamics, energy balance, and variability?
- How does seasonal variability of sea ice affect heat budgets, fluxes, and biogeochemical cycling?
- What are the broader consequences for circulation, carbon fluxes, and ecosystems?
Approach:
Progress requires standardised observations of sea ice and snow, deployment of autonomous platforms, regional airborne surveys, continuous validation datasets for satellites, and refined process representation in models. Interdisciplinary efforts are essential to reduce uncertainties and improve predictions of Antarctic sea ice under climate change.
Find out more in the Science Plan on Theme 2.
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