Winds Open Antarctic Ice Holes — Then Waves Shatter Them From the Inside Out

A recent Nature Communications paper by Joey J. Voermans (University of Melbourne) and colleagues shows that locally generated waves in Antarctic coastal polynyas can break up surrounding sea ice from the inside outward.

Coastal polynyas are recurring open- water areas within sea ice that act as “sea- ice factories”, producing large volumes of new ice. Their formation and persistence have long been attributed mainly to strong offshore (katabatic or synoptic) winds that advect ice away from the coast. The role of waves has been largely unexplored due to the scarcity of in situ observations.

Using rare wave- buoy data from the Vincennes Bay Polynya (East Antarctica, near Casey Station), the researchers found that strong winds generate energetic, short- period wind waves within the open water.

These waves grow across the polynya’s fetch and are steep enough to fracture the surrounding ice cover starting at the polynya edge and propagating outward. This “inside- outward” breakup contrasts with the more familiar “outside- inward” process driven by long- period Southern Ocean swells that approach the ice edge from the open ocean.

The buoy records (from deployments in 2021, 2022, 2024, and 2025) showed sharp increases in wave energy with relatively short dominant wavelengths once the instruments entered the polynya, consistent with fetch- limited local wind- wave growth rather than distant swell (which is strongly attenuated by intervening pack ice).

Analysis of satellite sea- ice concentration records (2003- 2022) showed that extreme wave- induced breakup events are associated with substantial, persistent reductions in sea- ice concentration lasting at least one week, along with increased transitions to active frazil ice (the loose crystals that form in turbulent, supercooled water).

This creates feedback: waves enlarge and help sustain the open- water area, promoting further heat loss, supercooling, and new ice production.

The results highlight a previously overlooked mechanism in polynya dynamics. As Antarctic coastal polynyas change under a warming climate, wave activity may become increasingly important in shaping sea- ice conditions, dense-water formation, and related processes in the polar ocean.

Paper: Voermans, J. J., et al. (2026). “Inside-outward breakup of sea ice by locally generated waves in the Vincennes Bay Polynya.” Nature Communications. DOI: 10.1038/s41467-026-77979-y.

Katabatic winds are downslope winds driven by gravity acting on denser (usually colder) air.

Cold air near the surface becomes denser than the surrounding air. On elevated terrain, such as a plateau, ice sheet, or mountain slope, this dense air flows downhill under gravity. The term comes from the Greek katabasis (“descent” or “going down”).

Key characteristics:

• They are typically cold and dry.
• Speeds can range from gentle breezes to gale-force or stronger, especially where the terrain funnels or steepens the flow.
• They often intensify at night or in winter when radiative cooling is strongest.

Katabatic winds are common in polar regions and high mountain areas:

• Antarctica: Extremely important. Cold air over the high interior ice sheet drains toward the coast, sometimes reaching very high speeds. These winds help create and maintain coastal polynyas by blowing newly formed sea ice offshore.
• Greenland: Similar drainage flows off the ice sheet.
• Other locations: Alpine valleys, the Adriatic coast (bora winds have a katabatic component), and various mountainous regions worldwide.

In short, katabatic winds are gravity- driven downslope flows of dense cold air, and they play a major role in polar climate and sea-ice dynamics.

Inside-outward breakup of sea ice by locally generated waves in the Vincennes Bay Polynya

Strong offshore winds (including katabatic winds) in the Vincennes Bay Polynya (East Antarctica) generate energetic local wind waves inside the open water. These waves are steep enough to fracture the surrounding sea ice from the inside outward, the opposite of the usual process in which Southern Ocean swells break ice from the outside inward.

Key evidence

• Rare in- situ measurements from four drifting wave buoys (deployed near Casey Station in 2021, 2022, 2024 and 2025) recorded a sharp rise in wave energy with short dominant periods once the buoys entered the polynya, consistent with fetch- limited local wind- wave growth rather than distant swell.
• Southern Ocean swell was strongly attenuated by the intervening pack ice and contributed little to the measured wave energy.
• Satellite records (2003- 2022) show that extreme wave- breakup events coincide with substantial, persistent drops in sea- ice concentration lasting at least one week, plus increased production of active frazil ice.

Coastal polynyas are major “sea- ice factories” and sites of dense- water formation. The study shows that locally generated waves are an important, previously overlooked feedback that helps reshape and sustain these polynyas. As Antarctic conditions change, wave activity may become increasingly significant.

The paper directly links the strong katabatic and synoptic winds that keep the polynya open to the generation of the waves that then break the surrounding ice.

Journal: Nature Communications, 17, Article number: 11224 (2026)

DOI: 10.1038/s41467-026-77979-y

Published: 29 September 2026, Open access

Authors: Joey J. Voermans,
Qingxiang Liu,
Lang Cao,
Josh Kousal,
Petra Heil,
Alexander D. Fraser,
Clarence O. Collins,
Jean Rabault &
Alexander V. Babanin

Abstract

Coastal polynyas are recurring regions of open water within sea ice that serve as sea-ice factories, producing vast amounts of new ice relative to nearby sea-ice-covered regions. Their formation and persistence are commonly attributed to strong offshore winds, while the influence of waves on polynya dynamics remains largely unexplored. Using rare wave-buoy observations from the Vincennes Bay Polynya, we show that strong winds generate energetic waves capable of breaking surrounding sea ice from the inside-outward, contrasting with outside-inward breakup caused by Southern Ocean swells. Satellite records from 2003–2022 reveal that extreme wave-induced breakup events coincide with substantial reductions in sea-ice concentration that persist for at least one week, accompanied by increased transitions to active frazil ice. These findings demonstrate that locally generated waves impact polynya dynamics and reshape surrounding sea-ice conditions. As Antarctic coastal polynyas evolve under a changing climate, wave activity may become increasingly important in shaping their sea-ice conditions and evolution.