A new study led by Bryan Shaddy, who was once an undergraduate at the University of California, Riverside (UCR), and is now at the University of Southern California, along with UCR researchers Alex Greaney and Bhargav Rallabandi, reveals that the movement of Arctic sea ice may be explained by simple collisions between individual pieces of ice. This insight could help scientists better predict how sea ice will move as the Arctic continues to warm. Published in Physical Review Letters, the study suggests that Arctic sea ice is made up of individual slabs, known as floes, which range in size from several meters to a few kilometers. Winds push these floes across the ocean, causing them to drift and spread apart. While scientists know that wind is a major force behind ice movement, the behavior of the ice is more complex than wind alone would suggest. For example, the speed at which the ice moves varies unpredictably, and it spreads much more slowly than simple wind-driven models predict. To better understand this phenomenon, the researchers created a computer simulation that treated the ice floes somewhat like grains of sand moving through a silo, except these "grains" float on water and are pushed by turbulent winds. The model included factors like the drag from the ocean and the collisions between floes. The team tested their model using data from the Fram Strait, a narrow passage between Greenland and the Svalbard archipelago, where Arctic ice flows toward the Atlantic Ocean. Using real-world measurements of wind and ice conditions, the model successfully predicted three previously confusing observations: how quickly the ice spreads, the distribution of floe speeds, and how ice movement changes over different time scales, from hours to days. The reason collisions have such a significant effect is that Arctic ice can be densely packed. In these concentrated ice fields, floes frequently bump into each other, which dissipates some of the energy from the wind and limits how far a floe can travel before hitting another piece of ice. The amount of ice coverage and the size of individual floes influence how often these collisions occur, which in turn affects how quickly the ice spreads. This study provides a physical framework for connecting small-scale interactions—like collisions between floes—to the movement of ice over large distances. While the study does not predict exactly how future warming will change the movement of Arctic ice, it offers a valuable tool for researchers. The framework could help scientists explore whether changes in ice conditions allow floes to disperse more easily and reach warmer waters, where they might melt faster. This could be particularly useful for climate modeling, as global models cannot track each individual floe due to their sheer number and small size. A physics-based description of how these floes behave collectively could help model processes that are otherwise difficult to observe. For Rallabandi, the study highlights how a simple process, like collisions, can explain complex real-world motion. The underlying physics used in the research may also apply to other systems involving many objects moving in unpredictable environments, such as avalanches, landslides, materials science, and even particle-filled inks used in 3D printing.