How do wind and water stresses create cracks and pressure ridges in sea ice?

In the Arctic Ocean, wind and water stresses keep the ice pack in nearly constant motion, which is the primary driver for the formation of cracks and pressure ridges.1

Formation of Cracks and Ridges

• Cracks (Leads): As the ice pack drifts, it frequently breaks apart, creating linear fractures known as leads. These features can extend for hundreds of kilometers and vary significantly in width.2
• Pressure Ridges: When ice floes are compressed against one another by wind and water forces, the ice is mechanically thickened through rafting and ridging. A pressure ridge consists of a "sail" projecting above the waterline and a "keel" extending below it.2

The Role of Stress

The transfer of momentum from the atmosphere to the ocean is enhanced by the rough surfaces created by these ridges. Ridges at the surface act like sails, catching the wind and driving the movement of ice floes, while the keels on the underside of the ice transfer energy to the underlying water. This continuous interaction between the atmosphere, the ice, and the ocean ensures the pack ice remains in a state of dynamic change.31