Polar ocean currents are entering a new and more energetic phase as sea ice continues to thin and retreat across both hemispheres. With larger stretches of open water now exposed, winds are exerting stronger force on the ocean surface, intensifying sideways mixing that redistributes heat, nutrients and even pollutants near the top layers of the sea. Scientists warn that these shifts could ripple through marine food webs and influence how much heat the Arctic and Southern Oceans release back into the atmosphere.
A research team led by Gyuseok Yi, a doctoral scholar at Pusan National University working with the Institute for Basic Science, used a high-resolution Earth system model to examine how warming is changing the mechanics of polar circulation. Their model can track currents only a few miles wide, revealing how climate change reorganizes the stirring processes that shape polar waters.
Changing Polar Waters
One central process undergoing rapid transformation is mesoscale horizontal stirring, which stretches and moves water masses over tens to hundreds of miles. This mechanism shifts heat, salt, plankton and chemicals across the surface ocean. To measure how quickly water parcels drift apart, the researchers used the finite-size Lyapunov exponent (FSLE). Higher values indicate stronger stirring, and the model produced sharp images of eddies and swirling currents with grid spacing of about six miles.
Arctic sea ice has been shrinking for decades, giving winds greater access to open water. According to the simulations, this exposure transfers more energy into the ocean, strengthening mesoscale currents across the central Arctic. The effect becomes more pronounced when carbon dioxide levels double, and the duration of these intensified flows increases with further warming. Instead of having a predictable seasonal pattern, the model shows more erratic mixing as thick ice disappears.
Signs of Shifting Motion Around Antarctica
Around Antarctica, the simulations show major changes to the Antarctic Slope Current, a westward-moving band of water that circles the continent close to the ice zone. As sea ice retreats and meltwater freshens the surface, the current accelerates. Freshwater lightens the surface layer, sharpening density contrasts that help guide heat toward the ice edge. This strengthened pathway can influence how quickly ice shelves thin from below.
Mapping Changes in Polar Seas
Stronger stirring changes how water crosses boundaries where different masses meet. These altered pathways can affect how nutrients reach phytoplankton, where young fish drift and how ecosystems respond to warming. Faster stirring also influences pollution transport. Microplastics already documented in Arctic waters at levels comparable to crowded oceans farther south may be moved more efficiently into subsurface layers where they persist for years. Winds, sea-ice drift and stronger currents all contribute to how plastic waste spreads across polar regions.
Implications for Climate Policy
The researchers note that while the simulations focus on physical processes and do not yet include full biological systems, the trends point to significant consequences. More vigorous stirring means climate models must better resolve fine-scale currents to capture how physical changes interact with marine life. According to co-author June Yi Lee, understanding these links will be crucial for designing adaptation and climate strategies at both local and national levels.
The study’s central message is clear: as sea ice retreats, the physics of polar oceans are rapidly evolving. The movement of water beneath the ice has the potential to amplify or moderate the effects of global warming—making these remote regions key to understanding future climate shifts.