Types of Pack Ice
There are two forms of pack ice in the Arctic. The winter ice pack consists of annual ice, which melts in the spring and freezes again in the fall. Multiyear ice, which remains frozen throughout the summer, forms farther north in two regions: In the central part of the Arctic Ocean, there is the massive permanent polar pack, otherwise known as the Arctic or polar ice cap, that slowly rotates clockwise as a unit. The summer ice pack, which makes up the other region of multiyear ice, surrounds the permanent polar pack, and breaks up in the summer. These broken pieces of ice block many of the channels between the Arctic islands year-round.