Sea Ice and IcebergsSea Ice Classification
Sea ice is classified by its thickness and age. It ranges from a soupy mix of crystals to multiyear ice up to 3 meters thick.
When sea ice forms, ice crystals expel salt, which accumulates in pockets of salty brine. These pockets weaken the newly formed ice. Over time the brine escapes and is replaced with summer meltwater, which freezes the following winter. The resulting multiyear ice is much stronger and presents a formidable barrier to icebreakers.