by Heather O’Neill, CNN

ILULISSAT, Greenland (CNN) — From the air, Greenland’s ice sheet, the second largest on Earth, appears to be perfectly still.

But below the surface, the ice sheet is in constant motion, as ice built up in the interior pushes toward the coast in the form of massive glaciers. During warmer months, ice from these glaciers melts into the ocean.

It’s an age-old process that scientists say has speeded up in recent decades because of global warming.

The fear is that melting ice from Greenland and other Arctic areas could cause sea levels to rise enough to flood low-lying cities, such as Shanghai, China, and New York City, displacing millions of people in the process.

article highlights:

* Greenland’s ice melt area increased 30% in 30 years, one scientist says
* The island is now losing more ice each year than it gains from new snow
* This melting ice is causing sea levels to rise around the world
* Scientists fear low-lying areas could be flooded if seas continue to rise

Read the entire article at CNN