Sea level
If more ice melts than new ice is created the glaciers will become smaller. The water that was stored in the glaciers over thousands of years will return to the ocean and the sea level will rise.
The picture shows a meltwater river on the Greenland ice sheet.
In the Greenland ice sheet alone there is stored so much water that the oceans would rise by 7.4 m, if all of it should melt. Luckily this will not happen for thousands of years.
Are you curious to see what the world would look like if the sea level rose 7 m, click here.