Icebergs and sea ice melt during the southern hemisphere summer.
—Credit: Ted Scambos and Rob Bauer, NSIDC

Processes that affect the growth and melt of sea ice are referred to as thermodynamics. In the simplest sense, when the temperature of the ocean reaches the freezing point for salt water (-1.8 degrees Celsius, 28.8 degrees Fahrenheit), ice begins to grow. When the temperature rises above the freezing point, ice begins to melt.

In reality, however, the amount and rates of growth and melt depend on the way heat is exchanged within the sea ice, as well as between the top and bottom of the ice. The following sections describe these processes in more detail.