Ice melting
A large fraction of Earth’s fresh water is frozen in glaciers and the Antarctic and Greenland ice sheets. When these ice masses melt, they flow into oceans and raise sea levels. NASA’s twin GRACE satellites and the GRACE-Follow On mission have shown that these ice masses are losing mass at an ever faster rate, contributing significantly to global sea level rise.
The loss of these ice masses is caused by heat from the sun and other sources, including wind. However, the most significant factor is the underlying ocean. This warmer ocean is causing the ice to melt, especially in areas that are exposed to sunlight for long periods of time. This includes the edges of ridges, leads and polynyas, as well as surface waters within melt ponds.
These warm surface waters can also cause the keels of the ice to melt. As the ice melts, it can no longer support itself and it may break apart or calve (crack off). This calving contributes to the overall increase in sea level.
The chemistry behind the melting of ice is complex. The ice forms an extremely organized crystal lattice that depends on the hydrogen bonds of water molecules. Different ice melt products, like salts, vary in their ability to enter this structure and disrupt it. They can also have varying effects on the melting point. Sodium chloride, for example, works well in warm temperatures but is less effective in the cold.