New study maps how submesoscale ocean flows shape Antarctic sea-ice change

Sea ice plays a crucial role in regulating Earth’s climate. By acting as a barrier between the ocean and atmosphere, it controls how heat and gases such as carbon dioxide move between them. Accurately predicting sea-ice thickness and extent is therefore essential for improving weather forecasts and long-term climate projections.

Yet, modelling sea ice remains one of the toughest challenges in climate science. This is, in part, because sea ice is affected by small, fast-moving ocean flows known as submesoscale currents (1–10 km across), which are not captured by global climate models. Despite their size, they generate powerful vertical movements that transport heat and salt through the upper ocean, influencing how and where sea ice grows or melts.

Now, researchers have helped uncover new insights into these hidden processes beneath the Antarctic sea ice. Their findings, published in Nature Communications, reveal that submesoscale dynamics vary dramatically across the Southern Ocean, with three distinct regimes of behaviour that shape how heat moves between the deep ocean and the surface.

Because the sea ice zone is difficult to access, researchers turned to an unconventional observing platform: seals fitted with ocean sensors. As part of the Marine Mammals Exploring the Oceans Pole to Pole (MEOP) programme, the seals collected over 233,000 temperature and salinity profiles while diving beneath the ice. These unique observations allowed scientists to map submesoscale activity across the Southern Ocean’s seasonal ice zone, an area where data are extremely sparse.

The analysis revealed three distinct patterns of behaviour:

• Dense shelf regions experience deep mixing during winter, when cold winds and sea-ice formation stir the upper ocean down to hundreds of metres. As spring arrives and the surface warms, small-scale currents bring heat upwards, potentially slowing sea-ice growth.
• Warm shelf regions show the opposite effect. Here large inputs of meltwater from ice shelves create sharp contrasts in density, leading to a downward movement of heat which encourages new sea ice to form.
• Open ocean and East Antarctic regions show much weaker vertical heat transport overall. In these areas, fresh meltwater from sea ice strengthens the layering of the ocean, supressing vertical mixing and limiting heat exchange between surface and deep waters.

These findings highlight that the Antarctic sea-ice zone cannot be treated as a single uniform system, and that local ocean conditions strongly influence how heat is exchanged between the ocean and atmosphere.

Current global climate models do not resolve these small-scale flows, meaning key heat and salt exchanges beneath sea ice are often misrepresented. By identifying where and how submesoscale dynamics operate, the study provides crucial information to improve how polar oceans are represented in future climate models.

Understanding these small-scale processes is essential to predicting changes in the Antarctic, which in turn affects global ocean circulation and climate stability.

Prend, C.J., Swart, S., Stewart, A.L. et al. Observed regimes of submesoscale dynamics in the Southern Ocean seasonal ice zone. Nat Commun 16, 8344 (2025). https://doi.org/10.1038/s41467-025-63775-7

Channing Prend University of Edinburgh Research Explorer Profile

Marine Mammals Exploring the Oceans Pole to Pole (MEOP) programme