SEA ICE

Australian Geographic - - Geo Buzz -

Frazil ice <1mm thick

Sea wa­ter freezes at –1.8°C, form­ing tiny crys­tals that calm the sur­face of the wa­ter.

They grow into tiny platelets and spikes, then in­ter­lace to be­come frazil ice.

Pan­cake ice 1–10cm thick

Frazil ice col­lects into tiny floes, which bond to­gether in pans. The pans bump against each other, form­ing a sheet of discs with raised edges like pan­cakes.

Pack ice 1–10m thick

Pan­cake ice co­a­lesces into pack ice, whose area varies sea­son­ally. Even in winter, wind and cur­rents main­tain open ar­eas of wa­ter called polynyas.

Fast ice 1–2m thick

Along coastal mar­gins and in pro­tected bays, ar­eas of mostly per­ma­nent float­ing ‘fast’ ice pro­vide a bridge between pack ice and land. It eas­ily sup­ports ve­hi­cles.

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