Why do lakes and rivers freeze but oceans don ?
Actually, oceans do freeze, although the high salt levels lowers the freezing point to around 28.4°F (-2°C). The polar ice cap that many of us have been hearing about so much lately is, in fact, frozen ocean. The ocean around Alaska freezes in the winter, with sea ice occasionally extending as far south as 60° to 62° N lattitude. The winter is not cold enough for long enough for more of the ocean to freeze, and with the arrival of spring and summer the warmer temperatures causes this ice shelf to melt. However, the parts of the ocean north of Alaska, Canada, and Russia remains frozen all year long although this ice cap is showing signs of shrinkage due to climate change.
