Such an increase in the volume of fresh water flowing into the Atlantic could interfere with the Atlantic Meridional Overturning Circulation (AMOC), the current that carries warm tropical water to northern Europe. It could also reduce the ocean's ability to store carbon.
The Greenland Ice Sheet has experienced record melting in recent years and is also likely to contribute substantially to sea level rise.
If the entire ice sheet were to melt, global sea levels would rise 23.6 feet. Recently, fears have grown that continued climate change will make the Greenland Ice Sheet cross a threshold where long-term melting of the ice sheet is inevitable. Climate models project that local warming in Greenland will be 3 °C (5.4 °F) to 9 °C (16.2 °F) during this century. Such a rise would inundate almost every major coastal city in the world.
Dumping fresh water into the North Atlantic could weaken the Atlantic Meridional Overturning Circulation (AMOC), the vast "conveyor belt" current that carries warm tropical water to northern Europe. It has been suggested that Europe will get colder as a result, but that is unlikely to happen, at least in the next few decades. "That was all blown out of proportion," says Ruth Curry of the Woods Hole Oceanographic Institution in Massachusetts.
The polar oceans are among the world's most important carbon sinks, taking in carbon dioxide from the air and trapping it in their depths — and that could change as a result of the freshwater flux. Curry says Greenland's fresh water will remain at the surface, since the weakened AMOC will be slow to carry it to the bottom. That also means that once this fresh water has absorbed as much carbon dioxide as it can hold, it will not be replaced at the surface by carbon-dioxide-free water that could absorb more of the gas.
For further information see Greenland Ice Sheet.