This is a great question because it strikes right at the heart of what controls the climate on earth. The most direct effect of melting of continental ice caps is that sea level rises. For example, during an inter-glacial period when the earth is ice free, sea level is hundreds of feet higher!!!! The oceans FLOOD THE LAND, and since most of the continental area is at elevations (today) less than a few hundred feet, this means that serious amounts of land get flooded when the ice caps disappear.

But there are other effects that are more subtle but perhaps even more important. A significant fraction of solar light that falls upon the cross section of the earth is REFLECTED DIRECTLY back out into space. This fraction is around 30 percent. This is important because the more reflected away the less energy is available for heating, and the lower the average earth temperature becomes; now here is where it gets interesting. Ice has a high reflectivity...snow too!!! So, if the planet was COVERED in ice, then its reflectivity would increase and the temp of the Earth’s atmosphere would be LOWER, since less energy is available (it has been sent out to space!)!

On the other hand, if the Earth heats up due to greenhouse warming, then ice melts and the reflectivity goes down, which makes the Earth warmer, which causes more ice to melt, which makes the Earth warmer STILL, which melts even MORE ICE, which makes it warmer, and warmer!!!!!

THIS IS A POSITIVE FEEDBACK LOOP! Eventually the system comes to equilibrium and the Earth will have a constant mean temperature; but that value will be HIGHER (warmer) than when we had a lot of ice to reflect all that sunlight.

In this sense, we can say that melting of the ice caps decreases the reflectivity of the Earth and hence more solar energy is available. This leads to a higher average temperature of the Earth atmosphere.

Well, for one, ice is not melting at the South Pole. Ice is melting at the North Pole.

The Earth's main ice-covered landmass is Antarctica at the South Pole, with about 90 percent of the world's ice (and 70 percent of its fresh water). Antarctica is covered with ice an average of 2,133 meters (7,000 feet) thick. If all of the Antarctic ice melted, sea levels around the world would rise about 61 meters (200 feet). But the average temperature in Antarctica is -37°C, so the ice there is in no danger of melting. In fact, in most parts of the continent it never gets above freezing.

At the other end of the world, the North Pole, the ice is not nearly as thick as at the South Pole. The ice floats on the Arctic Ocean. If it melted, sea levels would not be affected.

There is a significant amount of ice covering Greenland, which would add another 7 meters (20 feet) to the oceans if it melted. Because Greenland is closer to the equator than Antarctica, the temperatures there are higher, so the ice is more likely to melt. Scientists from the Universities of London and Edinburgh say that ice loss in Antarctica and Greenland together contribute approximately 12 percent of the rise in sea levels.

But there might be a less dramatic reason than polar ice melting for the higher ocean level -- the higher temperature of the water. Water is most dense at 4 degrees Celsius. Above and below this temperature, the density of water decreases (the same weight of water occupies a bigger space). So as the overall temperature of the water increases it naturally expands a little bit making the oceans rise.