The lower temperature at the poles allows water to remain in the form of ice. Icebergs hold the largest deposits of fresh water on the Earth.
The melting of icebergs due to global warming has many adverse effects on the environment. Icebergs are sheets of ice which has a far greater ability to reflect infra-red radiation than water; this is due to the fact that ice is white in color and also due to the reflectivity of ice to infra-red radiation. The melting of ice further increases the amount of solar radiation that is absorbed by the Earth leading to higher temperatures and the creation of a vicious circle.
As ice melts the water that is created goes into the oceans raising their level. A large percentage of the human population lives on land that is only a few meters above sea level, the rising sea levels can submerge their inhabitation and force an unmanageable displacement of people.
One obvious consequence is that the level of seawater will increase gradually and eventually many small islands might be recovered with water and disappeared.