The network of 523 rivers and streams flowing on top of the Greenland ice sheet is draining vast amounts of meltwater through sinkholes.
The problem is that cheap oil is running out. Here enters the concept of 'peak oil'. This doesn't mean that oil itself has run out (though oil being a finite resource it will eventually run out if we continue to deplete it indefinitely). It means that we have depleted over half of all the oil in the world.