Lead Formation
Sea ice is often classified according to whether or not it is attached (or frozen) to the shoreline. If attached, it is called land fast ice. Otherwise, it is called drift ice and is free to move with currents and winds. This is why leads typically belong to the drift ice zone. They are seen as a stress relieving mechanism, in response to divergent current flows or the effects of wind. Leads are cracks or fissures that initiate inside an otherwise continuous sea ice cover, and open up progressively afterward.They are linear features, though generally not rigorously straight, as they may comprise any number of short offsets at an angle with the general trend of the initial crack. This crack may cut right across both thin and thick ice. Because leads are associated with the initial break up of an ice cover, they open the way to various dynamic processes that can take place afterward, involving the interaction between individual floes, such as the formation of pressure ridges. Depending on the state of stress within the drift zone, leads may also close up. As the two sides converge back toward each other, this can lead to finger rafting of the new ice inside the lead.
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