We all known that the Greenland Ice Sheet is rapidly disappearing, but new research has found that the massive slab is more sensitive to climate change than previously thought.

Scientists worry that with more ice being dumped into the Arctic, it will accelerate rising sea levels and threaten coastal communities around the world.

Covering 1.7 million square kilometers (~660,000 square miles), the Greenland Ice Sheet is the second largest ice sheet in the world. If the entire region were to melt, it has the potential of raising sea levels by more than seven meters (23 feet).

For now, it is raising sea levels only at 0.6 millimeters annually due to surface melt alone. But despite its apparent stability, researchers from the University of Cambridge show that there is a more unpredictable source of sea level rise associated with the Greenland Ice Sheet, and that is net annual ice loss caused by its increased movement. This raises global sea levels three millimeters each year.

"There are two sources of net ice loss: melting on the surface and increased flow of the ice itself, and there is a connection between these two mechanisms which we don't fully understand and isn't taken into account by standard ice sheet models," lead researcher Dr. Marion Bougamont explained in a statement.

So, using a 3-D ice sheet model, and ground-based observations of the ice sheet's sediments, Bougamont and her colleagues were able to accurately reproduce how the ice sheet's seasonal movement changes in response to the amount of surface meltwater being delivered to the ground below.

It turns out that lakes, known as supraglacial lakes, usually form on the surfaces of glaciers during melting season, and can empty in just a matter of hours. According to researchers, as the world warms, these drainage events are expected to become even more frequent.

"Not only is the ice sheet sensitive to a changing climate, but extreme meteorological events, such as heavy rainfall and heat waves, can also have a large effect on the rate of ice loss," added co-author Dr. Poul Christoffersen. "The Greenland Ice Sheet is not nearly as stable as we think."

The findings were published in the journal Nature Communications.