The air temperature has an effect on ocean chemistry, salinity, density and height of sea level. Just like with air, when water warms it expands. Water only expands slightly as compared to air expansion but that slight difference makes a huge difference through the depth of the water column. The ocean is warmed by sunlight and from warmer air above it. Increasing these variables causes ocean water to thermally expand. Thus, warmer ocean water will lead to sea level rising.

Sea level can also be increased by the melting of continental glaciers. Enormous amounts of ice are located on Antarctica and Greenland. Warming temperatures will cause more ice to melt than will be deposited on the glacier. This leads to glacier retreat. The ice from the glacier melts and adds its volume to the ocean. Another way this ice can melt is for chunks of it to break off the main glacier and float out to sea. Once out in sea the ice will gradually melt over time. If snow is not occurring on the glacierís source region at a great enough rate to make up for the meltage then it will contribute to cause sea level rise.

The addition of fresh water into the ocean will also contribute to changing the salinity of the ocean water especially at the immediate source region where the fresh water is entering the ocean. Fresh water is less dense than ocean water thus fresh water will tend to first float on the sea water before mixing with in gradually over time. It is interesting to note that colder water can absorb more carbon dioxide than warmer water (think of carbonated soda). Thus, warmer ocean waters overall can have the impact of releasing more carbon dioxide into the air. In contrast, cold ocean waters are able to withdraw large amounts of carbon dioxide since cold water can contain much more carbon dioxide before saturated with carbon dioxide. The oceans are a huge absorber of carbon dioxide. However, when the oceans warm, some of that carbon dioxide could be given back to the air. Studies are investigating how much carbon dioxide is given up when ocean water temperature warms. This is important to investigate due to the impacts of rising levels of carbon dioxide in the atmosphere.